Base station device, terminal device, control method, and program for efficient connection destination change processing

Abstract

A base station device notifies a connected terminal device of preset setting information for the terminal device to autonomously select and switch a connection destination cell. The preset setting information includes: first information indicating a combination of a first cell that is a candidate of a primary cell as a handover destination and a second cell that is a candidate of a secondary cell when the first cell is used as the primary cell; and a second information indicating, for each cell included as the first cell or the second cell in the first information, a condition for connecting to the cell and a communication parameter to be used when connecting to the cell, the second information indicating, for each cell included as the first cell or the second cell in the first information, a condition for connecting to the cell and a communication parameter to be used when connecting to the cell, and if a common cell exists in different combinations of the primary cell and the secondary cell indicated by the first information. For the cell, only one communication parameter is included in the preset information as second information.

Description

Technical Field

[0001] The present invention relates to a technology for improving the efficiency of connection destination change processing. Background Art

[0002] In a cellular communication system, in order to ensure communication continuity, a handover technology that switches the connection destination of a terminal device in response to the movement of a terminal device, etc. is used. The standard method for handover is: after the communication quality of the wireless link being connected at the terminal device deteriorates, a process such as handover preparation on the core network side is started, and an instruction message is sent from the base station device to the terminal device. However, this method requires a processing time from when the communication quality actually deteriorates to when the handover instruction is sent, which may prolong the time when communication is not feasible or the communication quality is insufficient. In view of this situation, the Third Generation Partnership Project (3GPP (registered trademark)) discussed a method for performing a process such as pre-preparation and switching of a connection destination cell without receiving an instruction message from a base station device when a predetermined condition is met in the terminal device (see non-patent document 1). The predetermined condition includes, for example, when the wireless quality of an adjacent cell becomes better than the wireless quality of a cell being connected by at least a predetermined level, when the wireless quality of a cell being connected in the terminal device drops below a predetermined value, etc. According to this method, the handover preparation is completed on the core network side before the communication quality degradation that may cause the handover occurs. This allows to significantly reduce the time when communication is not possible or the communication quality is insufficient. This kind of handover is called "conditional handover" or "CHO".

[0003] Similarly, in multi-connectivity (MC) and the like, when a terminal device is connected to multiple cells, processing such as preparation may be performed in advance, and when a predetermined condition is met in the terminal device, the terminal device may add or change a secondary cell without receiving an instruction message from the base station device. Hereinafter, such conditional addition or change of a secondary cell may be referred to as "CPAC".

[0004] Prior art literature

[0005] Non-patent literature

[0006] Non-patent document 1: 3GPP TR38.874, V16.0.0, December 2018 Summary of the invention

[0007] Problem that the invention aims to solve

[0008] A secondary cell can only be configured in combination with a primary cell. Therefore, when performing CHO, the secondary cell may also need to be changed. Therefore, it may also be necessary to pre-set the combination of the primary cell and the secondary cell. However, a specific pre-setting method for such a combination of the primary cell and the secondary cell has not yet been considered.

[0009] Means used to solve problems

[0010] The present invention provides a technology for effectively configuring conditional cell change for a combination of a primary cell and a secondary cell.

[0011] According to one aspect of the present invention, a base station device has a notification unit, which notifies a terminal device connected to the base station device of pre-set information for the terminal device to autonomously select and switch a cell as a connection destination, the pre-set information including first information and second information, the first information indicating a combination of a first cell that is a candidate for a main cell of a handover destination and a second cell that is a candidate for a secondary cell when the first cell is used as the main cell, the second information indicating, for each cell included as the first cell or the second cell in the first information, conditions for connecting to the cell and communication parameters to be used when connecting to the cell, and when there is a common cell in different combinations of the main cell and the secondary cell represented by the first information, only one of the communication parameters is included in the pre-set information as the second information for the cell.

[0012] According to one aspect of the present invention, a terminal device has a receiving unit, which receives pre-setting information for the terminal device to autonomously select and switch a cell as a connection destination from a base station device connected to the terminal device, the pre-setting information including first information and second information, the first information indicating a combination of a first cell that is a candidate for a main cell of a handover destination and a second cell that is a candidate for a secondary cell when the first cell is used as the main cell, the second information indicating, for each cell included as the first cell or the second cell in the first information, conditions for connecting to the cell and communication parameters to be used when connecting to the cell, and when there is a common cell in different combinations of the main cell and the secondary cell represented by the first information, only one of the communication parameters is included in the pre-setting information as the second information for the cell.

[0013] Effects of the Invention

[0014] According to the present invention, conditional cell change for a combination of a primary cell and a secondary cell can be efficiently set.

[0015] Other features and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings. Note that throughout the drawings, the same reference numerals represent the same or similar components. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

[0017] Figure 1 is a diagram illustrating a configuration example of a communication system.

[0018] Figure 2 It is a diagram illustrating an example of notifying a terminal device of information used for conditional handover and conditional secondary cell change or addition.

[0019] Figure 3A It is a diagram illustrating an example of notifying a terminal device of information used for conditional handover and conditional secondary cell change or addition.

[0020] Figure 3B The diagram illustrates an example of information notified to a terminal device for conditional handover and conditional secondary cell change or addition.

[0021] Figure 4A It is a diagram illustrating an example of notifying a terminal device of information used for conditional handover and conditional secondary cell change or addition.

[0022] Figure 4B It is a diagram illustrating an example of notifying a terminal device of information used for conditional handover and conditional secondary cell change or addition.

[0023] Figure 5 is a diagram illustrating an example of the hardware configuration of the device.

[0024] Figure 6 is a diagram illustrating an example of a functional configuration of a base station apparatus.

[0025] Figure 7 is a diagram illustrating an example of a functional configuration of a control device.

[0026] Figure 8 It is a diagram illustrating an example of the flow of processing.

[0027] Fig. 9 It is a diagram illustrating an example of the flow of processing.

[0028] Fig.10 It is a diagram illustrating an example of the flow of processing. DETAILED DESCRIPTION

[0029] Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments are not intended to limit the scope of the claimed invention, nor are they intended to limit the invention requiring the combination of all the features described in the embodiments. Two or more of the multiple features described in the embodiments may be appropriately combined. In addition, the same reference numerals are given to the same or similar configurations, and their redundant descriptions are omitted.

[0030] (System Configuration)

[0031] Figure 1 An example of the configuration of a wireless communication system according to the present embodiment is shown. The wireless communication system is, for example, a cellular communication system that complies with a cellular communication standard defined by the Third Generation Partnership Project (3GPP (registered trademark)) such as Long Term Evolution (LTE), Fifth Generation (5G), etc. However, this is merely an example, and the following description may be applied to any system in which a terminal device can continue to communicate while switching a connection destination cell.

[0032] exist Figure 1 In the wireless communication system shown in the figure, the base station device provides wireless communication services to the terminal device 141. Figure 1 In the example of , base station devices 101 and 102 that respectively provide cells 111 and 112 covering relatively wide areas, and base station devices 121 to 124 that respectively provide cells 131 to 134 covering narrower areas are illustrated as base station devices. The terminal device 141 is configured to be provided with wireless communication services by connecting to at least one of these base station devices and sending wireless signals to the base station device as the connection destination and receiving wireless signals from the base station device as the connection destination. The terminal device 141 is connected to the base station device that configures the cell in which the terminal device 141 itself is located, so hereinafter, this may be referred to as "connecting to the cell (provided by the base station device)".

[0033] The terminal device 141 can be connected to two or more cells at the same time. Among the two or more cells, the cell that controls the communication of the terminal device 141 is called a "primary cell", and the cell to which the terminal device 141 is connected under the control of the primary cell is called a "secondary cell". As an example, it is assumed that the terminal device 141 is connected to the cell 111 or the cell 112 as the primary cell, and is connected to the cells 131 to 134 as the secondary cells.

[0034] In an embodiment of the present invention, in response to, for example, the terminal device 141 establishing a connection with one of the cells, or in response to a certain degree of degradation of the radio quality in the cell to which the terminal device 141 is connected, a pre-setting is performed on the terminal device 141 to switch the cell. Here, the state in which the pre-setting has been performed is a state in which the setting of parameters and the like for the terminal device 141 connected to the cell as a candidate for changing the connection is completed, but the terminal device 141 has not actually switched the base station device as the connection destination. The pre-setting includes conditions for connecting to the cell to switch the connection from other cells, adding cells, etc., and after determining that those conditions are met, the terminal device 141 attempts to establish synchronization and connect to the new connection destination cell. Note that when switching the connection destination cell, the terminal device 141 performs processing for disconnecting the connection from the original connected cell. The processing in which such pre-setting is used for the terminal device 141 to autonomously switch the connection destination primary cell according to the conditions met is called "conditional handover" (CHO). Similarly, the processing in which such pre-setting is used for the terminal device 141 to autonomously switch or add a secondary cell according to the conditions met is called "conditional secondary cell addition or change" (CPAC).

[0035] When CHO is performed, the base station device of the main cell in connection sends a handover request message (HANDOVER REQUEST) to other base station devices providing cells that are candidates of the main cell used as the handover destination, and the handover request message contains information such as the parameters currently used by the terminal device 141. Then, the handover destination candidate base station device sends a message (HANDOVER REQUEST ACKNOWLEDGE) in response to the message to the base station device of the main cell currently connected to the terminal device 141, and the message contains information such as the communication parameters to be used in the case of handing over the terminal device 141. Here, the handover destination candidate base station device saves information such as the sent communication parameters as pre-set information. The base station device in connection or the handover destination candidate base station device determines the conditions that should be satisfied for handover to the handover destination candidate base station device. Then, the base station device in connection notifies the terminal device 141 of the pre-set information, which contains information about the communication parameters to be used in the case of handover to the handover destination candidate base station device and the handover conditions. For example, the notification can be made using a radio resource control (RRC) message. In one example, the pre-setting information is notified to the terminal device 141 using an RRC reconfiguration message (RRC Reconfiguration message).

[0036] When CPAC is performed, the base station device of the main cell in the connection sends a secondary cell addition request message (SgNB Addition Request, SgNB AdditionRequest) to other base station devices that provide cells that are candidates for the secondary cell to be added or changed. Note that, for example, the secondary cell addition request can be initiated in response to a notification of a predetermined message (e.g., SgNB Change Required) from the base station device of the secondary cell in which the terminal device 141 is connected to the main cell base station device in the connection. In this case, the base station device of the main cell in the connection may make the secondary cell addition request as described above in response to the received predetermined message. Then, the other base station devices that provide cells that are candidates for the secondary cell to be added or changed (hereinafter may be referred to as "other base station devices as connection destination candidates") send a response message (SgNB Addition Request Acknowledge, SgNB Addition Request Acknowledge) to the message to the base station device of the main cell in which the terminal device 141 is connected, and the message contains information such as communication parameters that should be used when the terminal device 141 adds or changes the secondary cell. Here, the other base station device as a connection destination candidate saves the information of the communication parameters that have been sent as pre-set information. The base station device of the main cell being connected or the other base station device as a connection destination candidate determines the conditions that should be met when adding or changing the secondary cell. Then, the base station device of the main cell being connected notifies the terminal device 141 of the pre-set information, which contains information about the communication parameters that should be used when connecting to the other base station device as a connection destination candidate and adding or changing the secondary cell, and the conditions for making such a connection. For example, a radio resource control (RRC) message can be used for the notification. In one example, the pre-set information is notified to the terminal device 141 using an RRC reconfiguration message (RRC Reconfiguration message).

[0037] After receiving the pre-set information, the terminal device 141 saves the pre-set information and starts monitoring whether the conditions of CHO or CPAC are met. When the conditions are met, processing such as terminating the connection with the base station device in connection and establishing synchronization with the newly connected base station device is performed to actually switch the connection destination. Note that there can be multiple connection destination candidate cells for CHO or CPAC. Therefore, conditions and communication parameters can be set separately for each of one or more connection destination candidate cells for CHO or CPAC. In addition, if a single base station device is configured with multiple cells, conditions and communication parameters can be set separately for multiple cells. The terminal device 141 monitors whether the conditions corresponding to each of the multiple cells are met, and changes the connection destination using the communication parameters corresponding to the met conditions. In this way, the terminal device 141 can complete CHO or CPAC and continue communication even after the cell is changed.

[0038] The secondary cell is set under the control of the primary cell. Therefore, when the primary cell is changed by CHO, it is necessary to reset the secondary cell. On the other hand, after performing CHO, the setting of the secondary cell associated with the primary cell is abandoned before the change, so it is necessary to set the secondary cell under the control of the changed primary cell. Here, if the secondary cell is set by a normal procedure (not CPAC), the time until the secondary cell setting is completed may be extended. Therefore, the pre-setting of the secondary cell for CPAC can be combined with the pre-setting of the primary cell for CHO, and when the primary cell is changed by CHO, the information of the pre-setting secondary cell associated with the changed primary cell can be used to add or change the secondary cell by CPAC. In this case, for example, when a cell that is a candidate for the primary cell is used as the primary cell, the first base station device that provides the cell can obtain the pre-setting information for CPAC from the second base station device that provides a cell that can be used as a secondary cell. Then, when the cell provided by the first base station device itself is used as a primary cell, for each combination of the primary cell and the secondary cell, the first base station device can notify the base station device to which the terminal device 141 is connected of the conditions and communication parameters for CHO and the conditions and communication parameters for CPAC, and the base station device can then notify the terminal device 141 of the information in the notification.

[0039] For example, in Figure 1, when the cell 111 is used as the primary cell, the cells that can be used as the secondary cells are the cells 131 to 133. In this way, for the combination of the cell 111 and the cell 131, the conditions and communication parameters for CHO of the cell 111, and the conditions and communication parameters for CPAC of the cell 131 can be notified to the terminal device 141. In addition, for the combination of the cell 111 and the cell 132, the conditions and communication parameters for CHO of the cell 111, and the conditions and communication parameters for CPAC of the cell 132 can be notified to the terminal device 141, and for the combination of the cell 111 and the cell 133, the conditions and communication parameters for CHO of the cell 111, and the conditions and communication parameters for CPAC of the cell 133 can be notified to the terminal device 141. Similarly, when cell 112 is used as the primary cell, conditions and communication parameters for CHO and conditions and communication parameters for CPAC for the combination of cells 112 and 131, the combination of cells 112 and 132, and the combination of cells 112 and 134 may be notified to terminal device 141. Figure 1 The example diagram in shows an example in which a cell having a geographical range overlapping with the geographical range of the primary cell candidate is used as a candidate for a secondary cell, but the configuration is not limited thereto. For example, depending on the combination of available frequency bands, only cells using frequency bands available in parallel with the frequency bands used in the primary cell can be adopted as secondary cell candidates. In other words, even if the cells have overlapping geographical ranges, cells using frequency bands that cannot be used in combination with the frequency bands used in the primary cell can be excluded from the secondary cell candidates.

[0040] In this notification, for each of the secondary cell candidates, conditions and communication parameters for CHO of the cell 111 or the cell 112 are notified. In this case, for example, the terminal device 141 is notified Figure 2 . However, the shaded portion is overlapping information, which is considered to be an inefficient form of information notification. Therefore, an embodiment of the present invention provides a method for enabling efficient pre-setting by reducing the amount of information notified to the terminal device 141 with respect to the pre-setting information related to the combination of CHO for the primary cell and CPAC for the secondary cell.

[0041] In the embodiment of the present invention, the conditions, communication parameters, etc. related to each cell are notified only once, which avoids the situation where the same information is repeatedly sent. For example, when the cell 111 is used as the primary cell, the terminal device 141 is notified of conditions such as Figure 3AThe information illustrated in the figure is used as pre-set information. In this information, information indicating a combination of a primary cell and a secondary cell, and information on conditions and communication parameters for each cell are notified to the terminal device 141. When the cell 111 is used as the primary cell, the cells 131, 132, and 133 may be set as secondary cells. Therefore, the information of the cells 111 and 131, the cells 111 and 132, and the cells 111 and 133 are notified to the terminal device 141 as information on possible combinations. Because the cells included in these combinations are the cells 111 and cells 131 to 133, the conditions and communication parameters for these cells are notified. When performing operations such as Figure 2 When notifying the information shown in FIG. 1 , the communication parameters for the cell 111 are notified three times in total, once for each combination. Figure 3A In the case of the information shown in the figure, the communication parameters for the cell 111 are notified only once.

[0042] Here, as an example, it is assumed that two bytes are required for notification of a combination of a primary cell and a secondary cell, one byte is required for notification of a condition for a single cell, and one kilobyte is required for notification of a communication parameter for a single cell. Figure 2 When notifying the information of the information illustrated in FIG. 1 , it is not necessary to notify the combination of the primary cell and the secondary cell, but rather the conditions and communication parameters for each of the three combinations (i.e., cell 111 and cell 131, cell 111 and cell 132, and cell 111 and cell 133) are notified. Therefore, the information on the conditions and communication parameters is notified for each of the six cells (three combinations related to two cells), resulting in 6 kilobytes + 6 bytes. On the other hand, in a case such as Figure 3A In the case of the information illustrated in , 6 bytes of information for specifying three combinations, 4 bytes of information indicating conditions for each cell, and 4 kilobytes of information indicating communication parameters for each cell are used, resulting in a total of 4 kilobytes + 10 bytes. In this way, the information notification method according to an embodiment of the present invention can greatly reduce the amount of information set in advance. Similarly, when the cell 111 is used as the primary cell, the terminal device 141 is notified of information such as Figure 3B The information shown in the figure is used as the pre-set information.

[0043] Note that the first base station device providing the primary cell to which the terminal device 141 is currently connected can obtain information such as the following through CHO from the second base station device providing a cell as a candidate for the primary cell as a connection destination. Figure 3A and Figure 3B, and the content thereof can be sent to the terminal device 141. In this case, the second base station device sends a message requesting information about conditions and communication parameters for performing CPAC (e.g., SgNB Addition Request, SgNB Addition Request) to the third base station device that provides a cell that can be used as a secondary cell when the cell provided by the second base station itself is used as a primary cell. The second base station device can then receive a message in response to the request message (e.g., SgNB Addition Request Acknowledge), and obtain information about conditions and communication parameters used when connected to the secondary cell provided by the third base station device contained in the response message. The second base station device then summarizes the information about the candidate secondary cell obtained from the third base station device and the information about the candidate primary cell provided by the second base station device itself, and notifies the first base station device of the summarized information. For example, the base station device 101 forming the cell 111 obtains information about connection conditions and communication parameters used as candidates for the secondary cell from the base station devices 121, 122, and 123 forming the cells 131, 132, and 133, respectively. Then, the base station device 101 can generate a Figure 3A The information shown in the figure is used as the pre-set information, and the information is notified to the base station device that provides the primary cell currently connected to the terminal device 141. Similarly, the base station device 102 that forms the cell 112 can obtain information about the connection conditions and communication parameters used as the secondary cell candidates from the base station devices 121, 122, and 124 that form the cells 131, 132, and 134, respectively, and generate information such as Figure 3B The information illustrated in the figure is used as pre-set information, and the information is notified to the base station device that provides the primary cell to which the terminal device 141 is currently connected.

[0044] In addition, the first base station device that provides the main cell to which the terminal device 141 is currently connected can obtain only information about cells that can be used as secondary cells from the second base station device that provides cells that are candidates for the main cell generated by CHO. In this case, the first base station device can send and receive messages similar to the messages used in the above-mentioned secondary cell addition or change to the third base station device that provides cells that can be used as secondary cells, and directly obtain connection conditions and communication parameters when the third base station device is used as a secondary cell from the third base station device. In other words, in the second base station device that provides cells that are candidates for the main cell, information about the third base station device that provides cells that are candidates for the secondary cell can be summarized, and the summarized information can be notified to the first base station device, or the first base station device can obtain the information directly from the second base station device and the third base station device.

[0045] Note that when Figure 3A The information and Figure 3B When the information shown in the figure should be sent to the terminal device 141 at the same time, the terminal device 141 may be notified Figure 4A The information as a set thereof is shown in the figure as the pre-set information. In other words, Figure 3A and Figure 3B In this way, the base station device that provides the primary cell to which the terminal device 141 is currently connected can summarize the information of the cell combination, further generate pre-set information including only one of the multiple overlapping information about the conditions and communication parameters, and notify the terminal device 141 of the information. For example, the base station device that provides the primary cell to which the terminal device 141 is currently connected can also Figure 3A and Figure 3B The information shown in the figure is connected and the information of the conditions and communication parameters in any connected information is replaced by a reference (pointer) to the same conditions and communication parameters in other information. Figure 4B As illustrated in FIG. 1 , when the primary cell is cell 112, the information of cell 131 and cell 132 can be replaced with pointers to the information of cell 131 and cell 132 when the primary cell is cell 111. Therefore, by replacing the information of the conditions and communication parameters with pointers that provide a sufficient amount of information in a much smaller size, the size of the pre-set information can be significantly suppressed.

[0046] For example, the above describes an example in which the connection conditions and communication parameters of cells 131 and 132 are the same when cell 111 is the primary cell and cell 112 is the primary cell. However, this is merely an example, and connection conditions and communication parameters that are different from each other may be used instead. In this case, the setting may be such that the common portion is omitted, and notifications for different portions are made separately. In one example, when the connection conditions of the secondary cell are different for each primary cell used in combination therewith, the connection conditions are not omitted, and only the portion corresponding to the overlapping communication parameters is omitted, which prevents notification of the same information from being made multiple times. In addition, in one example, predetermined information such as connection conditions may not be omitted regardless of whether the information overlaps.

[0047] After obtaining the information as described above, the terminal device 141 measures the wireless quality of the candidates for the primary cell, and when the wireless quality satisfies the connection condition of any candidate, CHO is started. In addition, if the connection condition of any candidate for the secondary cell is met at this time, the terminal device 141 starts CPAC for the secondary cell. The terminal device 141 performs a random access procedure (RACH processing) on ​​the cell to be connected in CHO and CPAC, and communicates using the communication parameters contained in the pre-set information after the RACH processing is completed. For example, if the terminal device 141 successfully connects to the primary cell but fails to connect to the secondary cell, the terminal device 141 may attempt to connect to a candidate secondary cell that has been notified as being combined with the primary cell. However, if the terminal device 141 successfully connects to the secondary cell but fails to connect to the primary cell, the terminal device 141 attempts to connect to another primary cell candidate, but the primary cell candidate may be a cell that cannot be used in combination with the secondary cell to which the terminal device 141 has successfully connected. In this case, in the CHO for the primary cell candidate, the terminal device 141 needs to be disconnected from the secondary cell to which it has been successfully connected, and after the CHO is completed, the terminal device 142 needs to try to establish a connection with any secondary cell candidate again. Therefore, when entering this state, the terminal device 141 can try to connect through CHO, wherein priority is given to the primary cell candidate that can be used in combination with the secondary cell to which the terminal device 141 has been successfully connected. For example, the terminal device 141 can add a predetermined offset to the measured wireless quality or its threshold for the cell to be prioritized, so that it is easy to select the cell as the target of handover. The terminal device 141 can also measure the wireless quality while giving priority to the cell to be prioritized. Note that the terminal device 141 can avoid trying to establish a connection for a primary cell candidate that cannot be used in combination with a secondary cell that has been successfully connected. In addition, even if other primary cells are primary cell candidates that cannot be used in combination with secondary cells that have been successfully connected, the terminal device 141 can be allowed to try to establish a connection when the wireless quality is sufficiently higher than that of other candidate primary cells. In this case, when attempting to establish a connection with a primary cell candidate, the terminal device 141 may terminate the connection with the secondary cell to which the connection has been successfully made.

[0048] As described above, when CHO for the primary cell and CPAC for the secondary cell are set at the same time, if the wireless quality of any primary cell candidate satisfies the connection condition, and if the connection condition of any secondary cell candidate is satisfied, the terminal device 141 is connected to the primary cell candidate that satisfies the connection condition, and is connected to the secondary cell candidate associated with the primary cell and satisfies the connection condition. In one example, when the wireless quality of the primary cell candidate is better than the wireless quality of the primary cell in the current connection (at least a certain offset value), and the wireless quality of the secondary cell candidate is better than the wireless quality of the secondary cell in the current connection (at least a certain offset value), the terminal device 141 can perform CHO and CPAC. Note that an event for performing such CHO and CPAC can be newly defined. For convenience, this event may be referred to as "event X" here. In this case, for example, the primary cell may notify the terminal device 141 of the event X (for example, and information such as pre-set information) as a condition for performing CHO and CPAC. In another example, when (i) the radio quality of the primary cell in the current connection and the radio quality of the secondary cell in the current connection are both lower than the first predetermined value, and (ii) the radio quality of the primary cell candidate and the radio quality of the secondary cell candidate are both higher than the second predetermined value, the terminal device 141 can perform CHO and CPAC. Note that an event for performing such CHO and CPAC can be newly defined. For convenience, the event can be referred to as "event Y" here. Note that the first predetermined value of the radio quality of the primary cell in the connection can be different from the first predetermined value of the radio quality of the secondary cell in the connection. Similarly, the second predetermined value of the radio quality of the primary cell candidate can be different from the second predetermined value of the radio quality of the secondary cell candidate. In this case, for example, the primary cell can notify the terminal device 141 of the event Y (for example, and information such as pre-set information) as a condition for performing CHO and CPAC. Conventionally, an event in which the radio quality of the candidate of the connection destination cell (primary cell or secondary cell) is better than the radio quality of the cell (primary cell or secondary cell) in the current connection by at least a certain offset value is defined as event A3. In addition, conventionally, an event in which the wireless quality of the cell currently being connected is lower than a first predetermined value and the wireless quality of the candidate of the connection destination cell is higher than a second predetermined value is defined as event A5. Here, when the primary cell satisfies the condition of event A3 and the secondary cell satisfies the condition of event A5, the terminal device 141 can perform CHO and CPAC. In addition, when the primary cell satisfies the condition of event A5 and the secondary cell satisfies the condition of event A3, the terminal device 141 can perform CHO and CPAC.

[0049] For example, when the conditions of the aforementioned event A3 or event A5 regarding the primary cell are met, the terminal device 141 may change the connection destination to the primary cell candidate while maintaining the conditions and pre-set information of the secondary cell candidate associated with the primary cell candidate. After the primary cell is changed, the terminal device 141 continuously determines whether the conditions of the CPAC of the secondary candidate (e.g., event A3 or event A5) are met based on the result of measuring the wireless quality, and when it is determined that the conditions are met, CPAC may be performed. The terminal device 141 may then perform CPAC based on the information related to the maintained secondary cell candidate.

[0050] In addition, if the wireless quality of any primary cell candidate satisfies the connection condition (for example, event A3 or event A5), the terminal device 141 can perform CHO and CPAC at the same time even if the wireless quality of the secondary cell candidate does not satisfy any connection condition. In this case, the terminal device 141 can select, for example, a cell with the best wireless quality from the secondary cell candidates associated with the primary cell candidate to which the connection is to be changed, and determine the cell as the connection destination of the secondary cell through CPAC. Note that among the secondary cell candidates associated with the primary cell candidate to which the connection is to be changed, a candidate to be connected when CPAC is performed in a state where the connection condition is not satisfied can be specified, and the terminal device 141 can connect to the specified candidate cell. In addition, the terminal device 141 can determine the secondary cell candidate whose obtained wireless quality exceeds the wireless quality threshold value of the wireless quality lower than the connection condition as the secondary cell used as the connection destination in CPAC. Note that if multiple primary cell candidates satisfy the connection condition, and none of the secondary cell candidates associated therewith satisfy the connection condition, the terminal device 141 can select a cell with the best wireless quality among the secondary cell candidates associated with each primary cell candidate, and perform CHO with the primary cell associated with the cell as the connection destination. For example, it is assumed that both the first primary cell candidate and the second primary cell candidate satisfy the CHO condition. Here, it is assumed that the first secondary cell candidate is associated with the first primary cell candidate, and the second secondary cell candidate is associated with the second primary cell candidate. At this time, if the wireless quality of the first secondary cell candidate is higher than the wireless quality of the second secondary cell candidate, the terminal device 141 can determine to perform CHO on the first primary cell and perform CPAC on the first secondary cell. In this way, even if CHO is performed in a state where the conditions for CPAC of the secondary cell have not yet been met, it can be assumed that the state is a state in which the secondary cell can be used after the primary cell has been changed. Therefore, after the primary cell is changed by CHO, large-capacity data communication using the secondary cell can be performed immediately.

[0051] In addition, if the wireless quality of any secondary cell candidate satisfies the connection condition (e.g., event A3 or event A5), the terminal device 141 can change the secondary cell through CPAC. In this case, the terminal device 141 can maintain the conditions and pre-set information of the primary cell candidate associated with the changed secondary cell. The terminal device 141 can then determine whether to perform CHO based on the information maintained on the conditions related to the primary cell candidate, and if the conditions for CHO to be performed are met, CHO can be performed to establish a connection with the primary cell candidate.

[0052] In addition, if the wireless quality of any secondary cell candidate satisfies the connection condition (for example, event A3 or event A5), the terminal device 141 can perform CHO and CPAC at the same time even if the wireless quality of the primary cell candidate does not satisfy any connection condition. In this case, the terminal device 141 can select, for example, a cell with the best wireless quality from the primary cell candidates associated with the secondary cell candidates to which the connection is to be changed, and determine the cell as the connection destination of the primary cell through CHO. Note that, among the primary cell candidates associated with the secondary cell candidates to which the connection is to be changed, the candidate to be connected when CHO is performed in a state where the connection condition is not satisfied can be specified, and the terminal device 141 can be connected to the specified candidate cell. In addition, the terminal device 141 can determine the primary cell candidate whose obtained wireless quality exceeds the wireless quality threshold value of the wireless quality lower than the connection condition as the primary cell used as the connection destination in CHO. Note that if multiple secondary cell candidates satisfy the connection condition, and none of the primary cell candidates associated therewith satisfy the connection condition, the terminal device 141 can select the cell with the best wireless quality from the primary cell candidates associated with each secondary cell candidate, and perform CPAC with the secondary cell associated with the cell as the connection destination. In this way, even if CPAC is performed in a state where the CHO condition for the primary cell has not been satisfied, it can be assumed that the state is a state where the primary cell can be used after the secondary cell has been changed.

[0053] In addition, when performing CHO on a given primary cell candidate, the terminal device 141 may preferentially establish a connection with a secondary cell candidate that can be used in combination with the primary cell and can also be used in combination with other primary cell candidates. Figure 1In the example of , when connected to cell 111, terminal device 141 may attempt to establish a connection with secondary cell candidate cells 131 to 133 through CPAC. At this time, cell 133 cannot be used in combination with cell 112, while cells 131 and 132 may be used in combination with cell 112. Therefore, terminal device 141 may attempt to connect to cell 131 or cell 132 as a secondary cell candidate with a higher priority than cell 133. By this, if the connection with the primary cell candidate fails and only the connection with the secondary cell candidate is successful, the connection may be maintained while attempting to connect to other primary cell candidates. If the connection with other primary cell candidates is successful, there is no need to re-set the secondary cell.

[0054] (Device Configuration)

[0055] Figure 5 The figure shows an example of the hardware configuration of a base station device and a terminal device. In one example, the base station device and the terminal device include a processor 501, a ROM 502, a RAM 503, a storage device 504, and a communication circuit 505. The processor 501 is a computer configured to include at least one processing circuit such as a general-purpose CPU (central processing unit), an ASIC (application-specific integrated circuit), and performs the overall processing of the device, the above-mentioned individual processing, etc. by reading out programs stored in ROM 502, the storage device 504, etc. and executing the programs. ROM 502 is a read-only memory that stores programs related to the processing performed by the base station device and the terminal device, information such as various parameters, etc. RAM 503 is used as a workspace when the processor 501 executes the program, and is a random access memory that stores temporary information. The storage device 504 is composed of, for example, a removable external storage device, etc. For example, the communication circuit 505 is composed of a circuit for LTE or 5G wireless communication. Although Figure 5 The middle figure shows one communication circuit 505, but the base station device and the terminal device may each have multiple communication circuits. For example, the base station device and the terminal device may have an antenna shared by wireless communication circuits for LTE and 5G. Note that the base station device and the terminal device may have separate antennas for LTE and 5G. The base station device may also have a wired communication circuit used when communicating with other base station devices, nodes of a core network, etc. The terminal device may have a communication circuit for another wireless communication system such as a wireless LAN. Also note that the base station device and the terminal device may have a separate communication circuit 505 for each of the multiple frequency bands that can be used, or may have a common communication circuit 505 for at least some of these frequency bands.

[0056] Figure 6 The figure shows an example of the functional configuration of the base station device. The base station device has, for example, an information obtaining unit 601, an information summarizing unit 602, and an information notifying unit 603 as functional parts. Note that Figure 6 Only functional components specifically related to the embodiments of the present invention are illustrated, and various other functional components that the base station device may have are not illustrated. For example, the base station device naturally has other functional components that are commonly provided in LTE and 5G base station devices. Figure 6 The functional blocks in are schematically illustrated, and the functional blocks may be implemented as an integrated unit, or may be further subdivided. Figure 6 Each function in the embodiment can be implemented, for example, by the processor 501 executing a program stored in the ROM 502 or the storage device 504, or by the processor in the communication circuit 505 executing predetermined software. Regarding the processing performed by each functional unit, the above processing will not be described in detail here, and only an overview of its general functions will be given.

[0057] First, a case in which the base station device is a base station device that provides a primary cell to which a terminal device is currently connected, that is, a case in which the base station device is a handover source will be described.

[0058] The information obtaining unit 601 obtains information about connection conditions and communication parameters for CHO from the first other base station device that provides a main cell used as a handover destination candidate. At this time, for example, for a cell that can be combined and used as a secondary cell when the cell provided by the first other base station device is used as the main cell, the information obtaining unit 601 can obtain information about connection conditions and communication parameters for CPAC from the first other base station device. For example, the information obtaining unit 601 sends a handover request message (HANDOVER REQUEST message) to the first other base station device, and the handover request message contains information about the communication parameters currently used by the terminal device. Then, the information obtaining unit 601 receives a handover request confirmation message (HANDOVER REQUEST ACKNOWLEDGE message) from the first other base station device, and the handover request confirmation message contains information about the connection conditions and communication parameters for CHO and CPAC. In this case, the information obtaining unit 601 can obtain information such as Figure 3A and Figure 3B For example, the information obtaining unit 601 may also obtain information that has not been summarized, such as Figure 2 The information shown in the figure.

[0059] Note that when a cell provided by a first other base station device is used as a primary cell, the information obtaining unit 601 can obtain information about connection conditions and communication parameters for CHO from the first other base station device, as well as information specifying cells that can be combined and used as secondary cells. In this case, the information obtaining unit 601 can request information about connection conditions and communication parameters for CPAC from a second other base station device that provides the cell, and obtain information about connection conditions and communication parameters as a response to the request. In one example, in this case, SgNB Addition Request and SgNB Addition Request Acknowledge can be used for request and response, respectively. In other words, information about connection conditions and communication parameters of secondary cell candidates can be obtained via a first other base station device that provides a cell used as a primary cell candidate, or can be obtained directly from a second other base station device that provides a cell used as a secondary cell candidate.

[0060] The information summarizing unit 602 summarizes the information obtained by the information obtaining unit 601 and performs processing such as deleting overlapping communication parameters, replacing with pointers, etc. For example, when obtaining information such as Figure 2 When the information aggregation unit 602 generates the unaggregated information shown in FIG. Figure 3A and Figure 3B The information shown in FIG. 1 , where the information is summarized for each primary cell, or may generate, for example, Figure 4A and Figure 4B The information notifying unit 603 notifies the terminal device of the summarized information on the connection conditions and communication parameters for CHO and CPAC generated by the information summarizing unit 602.

[0061] Next, a case will be described in which the base station apparatus is a base station apparatus of a primary cell in which a terminal apparatus provides connection, that is, a case in which it is a base station apparatus of a handover source.

[0062] For example, if the base station device itself is providing a cell used as a primary cell candidate, the information obtaining unit 601 obtains information about the connection conditions and communication parameters for CPAC of the cell used as a secondary cell candidate that can be used in combination with the cell. For example, in response to a request for connection conditions or communication parameters for CHO from a base station device that provides a primary cell in which the terminal device is currently connected, the information obtaining unit 601 can collect information about connection conditions and communication parameters for CPAC. After receiving a handover request (HANDOVER REQUEST) containing information such as communication parameters currently used by the terminal device from a first other base station device that provides a primary cell in which the terminal device is currently connected, the information obtaining unit 601 sends an SgNB addition request (SgNB Addition Request) containing information corresponding to the communication parameters to a second other base station device that provides a cell used as a secondary cell candidate. Then, the information obtaining unit 601 can receive an SgNB addition request confirmation (SgNB Addition RequestAcknowledge) containing information about connection conditions and communication parameters from the second other base station device.

[0063] The information summarizing unit 602 summarizes the information obtained by the information obtaining unit 601. For example, the information summarizing unit 602 of the base station device 101 generates information such as Figure 3A The information notifying unit 603 notifies the base station device that provides the primary cell to which the terminal device is currently connected of the information generated by the information summarizing unit 602. Note that the information obtained by the information obtaining unit 601 may be provided as is to the base station device that provides the primary cell to which the terminal device is currently connected, in which case the information summarizing unit 602 may be omitted.

[0064] Note that the base station apparatus that provides a cell serving as a secondary cell candidate is configured to notify the other base station apparatuses that have requested the connection conditions and communication parameter information of CPAC of this information.

[0065] In one example, each base station device may have some or all of the above capabilities. In other words, the base station device may have all or only some of the functions of a base station device that provides a primary cell to which the terminal device is currently connected, the functions of a base station device that provides a cell that is a candidate for the primary cell, and the functions of a base station device that provides a cell that is a candidate for a secondary cell.

[0066] Figure 7 The figure shows an example of the functional configuration of the terminal device. For example, the terminal device has a pre-setting unit 701, a condition determination unit 702, and a connection processing unit 703 as functional parts. Note that Figure 7Only functional components specifically related to the embodiments of the present invention are illustrated, and various other functional components that the terminal device may have are not illustrated. For example, the terminal device naturally has other functional components that are generally provided in LTE and 5G base station devices. Figure 7 The functional blocks in are schematically illustrated, and the functional blocks may be implemented as an integrated unit, or may be further subdivided. Figure 7 Each function in the embodiment can be implemented, for example, by the processor 501 executing a program stored in the ROM 502 or the storage device 504, or by the processor in the communication circuit 505 executing predetermined software. Regarding the processing performed by each functional unit, the above processing will not be described in detail here, and only an overview of its general functions will be given.

[0067] The pre-setting unit 701 obtains information on connection conditions and communication parameters for CHO and CPAC from the base station device providing the primary cell in the current connection, and performs configuration for CHO and CPAC. For example, the pre-setting unit 701 receives an RRC reconfiguration message (RRC Reconfiguration message) and obtains information such as Figure 3A and Figure 3B information such as the information shown in the figure, or Figure 4A and Figure 4B . Then, the pre-setting unit 701 performs pre-setting of CHO for the primary cell candidate, and performs pre-setting of CPAC for the cell used as the secondary cell candidate that can be used in combination with the primary cell candidate. The condition determination unit 702 determines whether the connection condition is met for each of the primary cell and secondary cell candidates set by the pre-setting unit 701. The connection processing unit 703 performs connection processing on the cell that the condition determination unit 702 has determined to meet the connection condition, using the communication parameters pre-set for the cell. Note that, for example, if the connection processing unit 703 successfully connects to the secondary cell but fails to connect to the primary cell, the condition determination unit 702 can adjust the connection condition so as to try to connect to another primary cell candidate that can be configured together with the successfully connected secondary cell. In addition, for example, the condition determination unit 702 can adjust the connection condition so as to preferentially connect to the secondary cell candidate that can be used in combination with multiple primary cell candidates.

[0068] (Processing Flow)

[0069] Next, an example of the processing flow will be described. Figure 8 The figure shows a sequence for providing information for CHO and CPAC from a base station device (S-MN) providing a primary cell to which the terminal device is currently connected to the terminal device 141. Note that "S-MN" is an abbreviation for "source master node". Here, the base station device providing a primary cell candidate is referred to as a target master node (T-MN). Figure 1 In the example of FIG. 1 , base station apparatus 101 and base station apparatus 102 are T-MNs. A base station apparatus that provides a cell serving as a secondary cell candidate is referred to as a target secondary node (T-SN). Figure 1 In the example of , base station devices 121 to 124 are T-SNs.

[0070] First, the S-MN transmits a handover request (HANDOVER REQUEST) by selecting a base station device whose reception quality of signals transmitted from these base station devices is at least a predetermined value from the base station devices providing cells used as nearby primary cell candidates as the T-MN (S801). Note that, for example, the handover request (HANDOVER REQUEST) contains information capable of determining whether a communication service can be provided with a communication performance corresponding to the communication parameters currently used by the terminal device 141. In addition, the handover request (HANDOVER REQUEST) here may contain information requesting the terminal device 141 to provide information about secondary cell candidates that can communicate with a communication performance corresponding to the communication parameters in the secondary cell currently connected to the terminal device 141. Note that information on the measured value of the wireless quality in the terminal device 141 for each secondary cell candidate may be provided. After receiving this information, the T-MN transmits an SgNB Addition Request to the T-SN, and when the cell provided by the T-MN itself is used as the primary cell, the T-SN provides a cell that can be used as a secondary cell (S802, S804). For example, the SgNB Addition Request here contains information that enables identification of the requested communication performance, etc. If the communication service can be provided with the requested communication performance, the T-SN sends an SgNB Addition Request Acknowledgement (SgNB AdditionRequest Acknowledge) indicating that the connection is allowed and containing the connection conditions and communication parameters of the CPAC to the T-MN (S803, S805). After receiving the connection conditions and communication parameters for the CPAC from the T-SN, the T-MN sends a handover request acknowledgment (HANDOVER REQUEST ACKNOWLEDGE) to the S-MN, which contains the information and information about the connection conditions and communication parameters in the CHO for the T-MN itself (S807). At this time, the T-MN can Figure 3A and Figure 3B As shown in FIG. 8 , the information is summarized ( S806 ) and then sent to the S-MN.

[0071] After receiving the information of CHO and CPAC from T-MN, S-MN notifies the terminal device 141 of an RRC reconfiguration message (RRC Reconfiguration message) containing the information (S809), and the terminal device 141 returns an RRC reconfiguration completion message (RRC Reconfiguration Complete message) (S810) to S-MN, which completes the pre-setting. Note that S-MN can summarize the information received from T-MN (S808) and then provide the information to the terminal device 141. The pre-setting for CHO and CPAC is completed in the terminal device 141 in the above manner.

[0072] Next, we will refer to Fig. 9 and Fig.10 Describe the processing flow performed when the terminal device changes the connection destination. Note that in these examples, it is assumed that T-MN-A to T-MN-C are base station devices that provide primary cell candidates. It is assumed that the primary cell provided by T-MN-A can also be used in combination with the cell provided by T-SN-D as a secondary cell, and it is also assumed that the primary cell provided by T-MN-B and T-MN-C can be used in combination with the cell provided by T-SN-E as a secondary cell. Here, it is assumed that the terminal device has attempted to establish a connection with T-MN-B through CHO, and further attempted to establish a connection with T-SN-E through CPAC, but has not been able to connect to T-MN-B, and has successfully connected to T-SN-E (S901, S902). In this case, the terminal device determines to preferentially connect to T-MN-C, which is able to provide a primary cell that can be used in combination with the secondary cell provided by T-SN-E, thereby maintaining a connection with T-SN-E (S903). Then, the terminal device attempts to establish a connection with T-MN-C while maintaining a connection with T-SN-E (S904). This eliminates the need to connect to the secondary cell again, so the connection can be established efficiently.

[0073] Fig.10The example in is an example in which, before performing a handover, the terminal device preferentially selects a T-MN that provides a primary cell that can be used with a common secondary cell as the T-MN to be connected to. In this example, two T-MNs, namely T-MN-B and T-MN-C, provide a primary cell that can use a cell provided by T-SN-E as a secondary cell. On the other hand, there is only one T-MN, namely T-MN-A, that provides a primary cell that can use a cell provided by T-SN-D as a secondary cell. Therefore, the terminal device determines that the secondary cell associated with a greater number of primary cells is a cell provided by T-SN-E, and determines to preferentially connect to T-MN-B and T-MN-C that provide a primary cell that can be used with the secondary cell (S1001). Then, for example, based on this determination, the terminal device performs CHO on the base station device with better wireless quality in T-MN-B and T-MN-C, and performs CPAC on T-SN-E (S1002, S1003).

[0074] In an embodiment of the present invention, CHO and CPAC can be efficiently performed in this manner. This makes it possible to contribute to Goal 9 of the United Nations-led Sustainable Development Goals (SDGs), namely, "Build resilient infrastructure, promote inclusive and sustainable industrialization, and foster innovation."

[0075] The present invention is not limited to the above-described embodiments, and various changes / alterations are possible within the scope of the spirit of the present invention.

[0076] This application claims priority from Japanese Patent Application No. 2022-099735 filed on June 21, 2022, which is hereby incorporated by reference.

Claims

1. A base station device, wherein: The base station device includes a notification unit that notifies a terminal device connected to the base station device of pre-set information for the terminal device to autonomously select and switch a cell of a connection destination, The pre-set information includes first information and second information, the first information indicating a combination of a first cell that is a candidate for a primary cell of a handover destination and a second cell that is a candidate for a secondary cell when the first cell is used as the primary cell, and the second information indicating, for each cell included as the first cell or the second cell in the first information, a condition for connecting to the cell and a communication parameter to be used when connecting to the cell, When there is a common cell among different combinations of the primary cell and the secondary cell indicated by the first information, only one communication parameter is included in the pre-configuration information as the second information for the cell.

2. The base station device according to claim 1, wherein: When the first information indicates a combination of one of the first cells that are candidates for the primary cell and each of the plurality of the second cells that are candidates for the secondary cell, the second information indicates the communication parameter of the one first cell only once.

3. The base station device according to claim 1, wherein: When the first information indicates a combination of each of the plurality of first cells that are candidates for the primary cell with one of the second cells that are candidates for the secondary cell, the second information indicates the communication parameter of the one second cell only once.

4. The base station device according to claim 3, wherein: The pre-set information includes, for each of the plurality of first cells, a plurality of third information including the first information and the second information. The communication parameter of the one second cell is represented in the second information included in the third information for a specific cell among the plurality of first cells, The second information contained in the third information regarding other cells among the multiple first cells that are different from the specific cell includes information representing a reference to the communication parameters pointing to the one second cell contained in the third information regarding the specific cell, as information related to the communication parameters of the one second cell, without including the communication parameters.

5. The base station device according to claim 1, wherein: The base station device further includes a receiving unit that receives the first information and the second information for the first cell from a first other base station device that provides the first cell.

6. The base station device according to claim 5, wherein: The receiving unit receives the first information and the second information for the first cell provided by the first other base station device by sending a handover request message to the first other base station device.

7. The base station device according to claim 5, wherein: The base station device further includes a generating unit that collects the first information and the second information acquired from a plurality of the first other base station devices to generate the pre-set information.

8. The base station device according to claim 1, wherein: The base station device further includes a providing unit that provides, to a second other base station device that is connected to another terminal device that uses the cell provided by the base station device as a candidate for a primary cell: information indicating a combination of the cell provided by the base station device and other cells that are candidates for secondary cells when the cell is used as the primary cell; And information indicating conditions for connecting to the cell and the other cell and communication parameters to be used when connecting to the cell and the other cell.

9. The base station device according to claim 8, wherein: The base station apparatus further includes a request unit that requests a third other base station apparatus that provides the other cell to obtain a condition for connecting to the other cell and a communication parameter to be used when connecting to the other cell.

10. The base station device according to claim 9, wherein: The requesting unit makes the request by sending an SgNB add request message.

11. The base station device according to claim 1, wherein: The notification unit notifies the terminal device of the pre-configuration information using a radio resource control (RRC) message.

12. A terminal device, wherein: The terminal device includes a receiving unit that receives, from a base station device connected to the terminal device, pre-set information for the terminal device to autonomously select and switch a cell as a connection destination. The pre-set information includes first information and second information, the first information indicating a combination of a first cell that is a candidate for a primary cell of a handover destination and a second cell that is a candidate for a secondary cell when the first cell is used as the primary cell, and the second information indicating, for each cell included as the first cell or the second cell in the first information, a condition for connecting to the cell and a communication parameter to be used when connecting to the cell, When there is a common cell among different combinations of the primary cell and the secondary cell indicated by the first information, only one communication parameter is included in the pre-configuration information as the second information for the cell.

13. The terminal device according to claim 12, wherein: When the first information indicates a combination of one of the first cells that are candidates for the primary cell and each of the plurality of the second cells that are candidates for the secondary cell, the second information indicates the communication parameter of the one first cell only once.

14. The terminal device according to claim 12, wherein: When the first information indicates a combination of each of the plurality of first cells that are candidates for the primary cell with one of the second cells that are candidates for the secondary cell, the second information indicates the communication parameter of the one second cell only once.

15. The terminal device according to claim 14, wherein: The pre-set information includes, for each of the plurality of first cells, a plurality of third information including the first information and the second information. The communication parameter of the one second cell is represented in the second information included in the third information for a specific cell among the plurality of first cells, The second information contained in the third information regarding other cells among the multiple first cells that are different from the specific cell includes information representing a reference to the communication parameters pointing to the one second cell contained in the third information regarding the specific cell, as information related to the communication parameters of the one second cell, without including the communication parameters.

16. The terminal device according to claim 12, wherein: The receiving unit receives the pre-setting information from the base station device through a radio resource control (RRC) message.

17. A control method, executed by a base station device, wherein: The control method includes the step of notifying a terminal device connected to the base station device of pre-set information for the terminal device to autonomously select and switch a cell of a connection destination, The pre-set information includes first information and second information, the first information indicating a combination of a first cell that is a candidate for a primary cell of a handover destination and a second cell that is a candidate for a secondary cell when the first cell is used as the primary cell, and the second information indicating, for each cell included as the first cell or the second cell in the first information, a condition for connecting to the cell and a communication parameter to be used when connecting to the cell, When there is a common cell among different combinations of the primary cell and the secondary cell indicated by the first information, only one communication parameter is included in the pre-configuration information as the second information for the cell.

18. A control method, which is executed by a terminal device, wherein: The control method includes the steps of receiving, from a base station device connected to the terminal device, pre-set information for the terminal device to autonomously select and switch a cell of a connection destination, The pre-set information includes first information and second information, the first information indicating a combination of a first cell that is a candidate for a primary cell of a handover destination and a second cell that is a candidate for a secondary cell when the first cell is used as the primary cell, and the second information indicating, for each cell included as the first cell or the second cell in the first information, a condition for connecting to the cell and a communication parameter to be used when connecting to the cell, When there is a common cell among different combinations of the primary cell and the secondary cell indicated by the first information, only one communication parameter is included in the pre-configuration information as the second information for the cell.

19. A program for causing a computer included in a base station device to notify a terminal device connected to the base station device of pre-set information for the terminal device to autonomously select and switch a cell as a connection destination, The pre-set information includes first information and second information, the first information indicating a combination of a first cell that is a candidate for a primary cell of a handover destination and a second cell that is a candidate for a secondary cell when the first cell is used as the primary cell, and the second information indicating, for each cell included as the first cell or the second cell in the first information, a condition for connecting to the cell and a communication parameter to be used when connecting to the cell, When there is a common cell among different combinations of the primary cell and the secondary cell indicated by the first information, only one communication parameter is included in the pre-configuration information as the second information for the cell.

20. A program for causing a computer included in a terminal device to receive, from a base station device to which the terminal device is connected, pre-set information for the terminal device to autonomously select and switch a cell as a connection destination, The pre-set information includes first information and second information, the first information indicating a combination of a first cell that is a candidate for a primary cell of a handover destination and a second cell that is a candidate for a secondary cell when the first cell is used as the primary cell, and the second information indicating, for each cell included as the first cell or the second cell in the first information, a condition for connecting to the cell and a communication parameter to be used when connecting to the cell, When there is a common cell among different combinations of the primary cell and the secondary cell indicated by the first information, only one communication parameter is included in the pre-configuration information as the second information for the cell.

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