Terminal and control method of terminal

Abstract

To provide a terminal and the like using two SIMs that can reduce power consumption of the terminal.SOLUTION: A terminal comprises: a first communication unit for communicating via a first communication mode using a first subscriber identity module with a first base station supporting the first subscriber identity module; a second communication unit for communicating via a second communication mode using a second subscriber identity module that is different from the first communication mode with a second base station supporting the second subscriber identity module; and a control unit for enabling a function of the first communication unit and disabling a function of the second communication unit when the first subscriber identity module can communicate with the first base station and toggling a function of the second communication unit to be enabled when the first subscriber identity module becomes unable to communicate with the first base station.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a terminal and a method for controlling the terminal. [Background technology]

[0002] Terminals such as smartphones that can communicate using two SIMs (Subscriber Identity Modules) are in use. For example, Patent Document 1 proposes a technology for establishing a primary card link and a secondary card link based on Dual Subscriber Identity Module (SIM) Dual Standby (DSDS) / Dual SIM Dual Active (DSDA). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2021-150944 Summary of the Invention [Problem to be solved by the invention]

[0004] In a terminal capable of communication using two SIMs, the terminal communicates using one of the two SIMs. In this case, the other unused SIM is in a standby state ready for communication, consuming power for standby. As a result, unnecessary power consumption occurs for the entire terminal while waiting for communication using the unused SIM. Patent Document 1 does not solve this problem.

[0005] In one aspect, an object of the present disclosure is to provide a terminal or the like that can reduce power consumption of a terminal using two SIMs. [Means for solving the problem]

[0006] A terminal according to one embodiment of the present invention comprises a first communication unit that communicates with a first base station corresponding to a first subscriber identity module by a first communication method using the first subscriber identity module, a second communication unit that communicates with a second base station corresponding to the second subscriber identity module by a second communication method different from the first communication method using a second subscriber identity module, and a control unit that enables the function of the first communication unit and disables the function of the second communication unit when the first subscriber identity module can communicate with the first base station, and switches the function of the second communication unit to enable when the first subscriber identity module is unable to communicate with the first base station. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 illustrates an example of a system according to an embodiment. [Figure 2] FIG. 2 illustrates an example of a terminal. [Figure 3] FIG. 2 is a diagram illustrating an example of a first base station and a second base station. [Figure 4] FIG. 10 is a diagram illustrating a first example of the state of two communication units. [Figure 5] FIG. 10 is a diagram illustrating a second example of the states of the two communication units. [Figure 6] FIG. 10 is a sequence diagram illustrating an example of a processing flow of the entire system according to the embodiment. [Figure 7] This is a sequence diagram continuing from FIG. [Figure 8] 10 is a flowchart illustrating an example of a processing flow of a terminal according to an embodiment. [Figure 9] 9 is a flowchart continuing from FIG. 8. [Figure 10] FIG. 10 is a diagram showing a first example of a modified example. [Figure 11] FIG. 10 is a diagram showing a second example of a modified example. [Figure 12] FIG. 10 is a diagram illustrating a third example of a modified example. [Figure 13] FIG. 10 is a diagram showing a fourth example of a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0008] This embodiment will be described below. Fig. 1 is a diagram showing an example of a system 100 according to this embodiment. The system 100 includes a terminal 101, a first base station 102, and a second base station 103. The system 100 may include a plurality of terminals 101, a plurality of first base stations 102, and a plurality of second base stations 103.

[0009] The terminal 101 is a terminal that performs communication in accordance with communication standards such as the 5G standard, LTE (Long Term Evolution), and 4G standard. The terminal 101 is also referred to as UE (User Equipment).

[0010] The terminal 101 of this embodiment will be described as a terminal capable of RedCap (Reduced Capability) communication. RedCap is a standard in which some communication functions are restricted, assuming use in wearable devices, IoT devices, etc. The restricted communication functions are, for example, some communication functions of NR functions such as bandwidth and MIMO.

[0011] The terminal 101 of this embodiment will be described as a wearable device capable of communication with fewer functions than a normal terminal (for example, a smartphone, a tablet terminal, a laptop computer, etc.). The terminal 101 may be, for example, a small sensor configured as an IoT (Internet of Things) device, or may be a smartphone, etc.

[0012] The first base station 102 is, for example, a wireless base station compatible with RedCap communication functions. The first base station 102 constitutes a first cell 102A. The first cell 102A is an area in which RedCap communication can be performed with the first base station 102. A terminal 101 present in the first cell 102A can perform RedCap communication with the first base station 102.

[0013] The second base station 103 is, for example, a radio base station for performing communication using a communication method different from RedCap (non-RedCap communication). The second base station 103 configures a second cell 103A. A terminal 101 located in the second cell 103A can perform non-RedCap communication with the second base station 103.

[0014] On the other hand, non-RedCap is a standard intended for use with, for example, smartphones and tablet devices, and does not have the communication function limitations imposed on RedCap. The second base station 103 compatible with non-RedCap is, for example, a wireless base station operated by a communications carrier such as a mobile communications carrier or a virtual mobile communications carrier.

[0015] RedCap and non-RedCap are communication standards that comply with, for example, the 5G standard, LTE, 4G standard, etc. As described above, RedCap has some of its communication functions reduced. On the other hand, non-RedCap does not have the communication functions reduced like RedCap. Hereinafter, non-RedCap communication will be described as communication based on a communication service provided by the second base station 103 operated by a telecommunications carrier.

[0016] The first cell 102A may be contained within the second cell 103A, or the first cell 102A and the second cell 103A may partially overlap. Although the first cell 102A is described as covering a larger area than the second cell 103A, the first cell 102A may cover the same area as the second cell 103A or a smaller area.

[0017] 2 is a diagram showing an example of a terminal. The terminal 101 includes a control unit 201, a storage unit 202, an output unit 203, an operation unit 204, a first communication unit 205, and a second communication unit 206. The control unit 201 is, for example, a processor such as a CPU. The control unit 201 may be an MCU (Micro Control Unit) or an MPU (Micro Processor Unit).

[0018] The processor of the control unit 201 executes a program to control the terminal 101 of this embodiment. The control unit 201 may be a circuit having a calculation function, such as an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit).

[0019] The storage unit 202 is a device capable of storing programs and data, such as RAM, ROM, cache memory, flash memory, etc. The storage unit 202 stores programs for controlling the terminal 101 and various application programs that the user can use on the terminal 101.

[0020] The output unit 203 is a device that outputs information in a form that can be perceived by the user, such as a display, a lamp, a speaker, a vibrator, etc. The operation unit 204 is a button, switch, key, touch panel, etc. with which the user operates the terminal 101.

[0021] The first communication unit 205 is a communication module used for wireless communication. The communication module is configured with a predetermined circuit. The first communication unit 205 has a first SIM 205A. The first SIM 205A may be a SIM that can be inserted into or removed from the first communication unit 205, or may be a built-in SIM.

[0022] The first SIM 205A is a SIM used for wireless communication according to the first communication method using the first subscriber identity module. In this embodiment, the first SIM 205A is a SIM compatible with RedCap.

[0023] When the function of the first communication unit 205 is enabled, the first communication unit 205 can perform wireless communication with the first base station 102 using RedCap. When the function of the first communication unit 205 is disabled, the first communication unit 205 cannot perform wireless communication with the first base station 102 using RedCap.

[0024] The second communication unit 206 is a communication module used for wireless communication. The communication module is configured with a predetermined circuit. The second communication unit 206 has a second SIM 206A. The second SIM 206A may be a SIM that can be inserted into or removed from the second communication unit 206, or may be a built-in SIM.

[0025] The second SIM 206A is a SIM used for wireless communication according to a second communication method using a second subscriber identity module. The second communication method is a communication method different from the first communication method. In this embodiment, the second SIM 206A is a SIM that supports non-RedCap. In this embodiment, non-RedCap communication is provided by the second base station 103 operated by the above-mentioned telecommunications carrier.

[0026] When the function of the second communication unit 206 is enabled, the second communication unit 206 is capable of non-RedCap wireless communication with the second base station 103. When the function of the second communication unit 206 is disabled, the second communication unit 206 is not capable of non-RedCap wireless communication with the second base station 103.

[0027] As described above, when terminal 101 is capable of communication using either of two SIMs, first SIM 205A and second SIM 206A, terminal 101 is also referred to as a dual SIM-compatible terminal.

[0028] Next, the first base station 102 and the second base station 103 will be described. Fig. 3 is a diagram showing an example of the first base station 102 and the second base station 103. The first base station 102 and the second base station 103 may have the same configuration or different configurations.

[0029] The first base station 102 and the second base station 103 each include a control unit 301, a storage unit 302, and a communication unit 303. The control unit 301 is a processor such as a CPU, MCU, or MPU. The control unit 301 may also be a circuit having a calculation function such as an FPGA or ASIC. The storage unit 302 is a device capable of storing programs and data, such as a ROM, RAM, cache memory, or flash memory.

[0030] The storage unit 302 stores various data such as a control program for controlling the first base station 102 and the second base station 103. The communication unit 303 is a communication module for performing wireless communication via an antenna.

[0031] The communication unit 303 of the first base station 102 performs RedCap communication with the first communication unit 205 of the terminal 101. The communication unit 303 of the second base station 103 performs non-RedCap communication with the second communication unit 206 of the terminal 101.

[0032] 4 is a diagram showing a first example of the states of two communication units. FIG. 4 shows an example in which the terminal 101 is present within the area of ​​a first cell 102A of a first base station 102 and a second cell 103A of a second base station 103. The first base station 102 and the second base station 103 each periodically transmit broadcast information within their own cells. The broadcast information is, for example, an SIB (System Information Block). The broadcast information includes information identifying base stations with which communication is possible. The first SIB includes information that communication with the first base station 102 is possible. The second SIB includes information that communication with the second base station 103 is possible.

[0033] The first base station 102 transmits a first SIB as broadcast information within the area of ​​the first cell 102A. The second base station 103 transmits a second SIB as broadcast information within the area of ​​the second cell 103A.

[0034] 4, the first communication unit 205 of the terminal 101 receives the first SIB, and the second communication unit 206 receives the second SIB. The control unit 201 of the terminal 101 recognizes that the terminal 101 can communicate with the first base station 102 and the second base station 103 based on the reception of the first SIB and the second SIB.

[0035] When the terminal 101 is able to communicate with the first base station 102 and the second base station 103, the control unit 201 sets the function of the first communication unit 205 to an enabled state and sets the function of the second communication unit 206 to an disabled state. As a result, the control unit 201 sets the terminal 101 to a DSSS (Dual SIM Single Standby) mode. Note that the control unit 201 is assumed to have previously set the base station to which the terminal 101 is to connect to prioritize the first base station 102 over the second base station 103. As a result, the terminal 101 is preferentially connected to the first base station 102.

[0036] For example, the control unit 201 may disable the function of the second communication unit 206 by controlling the second communication unit 206 to prohibit the use of a communication service using the second SIM 206A. Also, as an example, the control unit 201 may control the second communication unit 206 not to execute the attach procedure.

[0037] Generally, even if a dual SIM-compatible terminal is set to DSSS mode, each communication unit into which the two SIMs are inserted is set to a standby state to maintain a state in which communication is possible. In the example of Figure 4, even if terminal 101 is set to DSSS mode, if second communication unit 206 is set to a standby state in which communication with second base station 103 is possible, second communication unit 206 will consume unnecessary power.

[0038] Therefore, when terminal 101 is set to the DSSS mode, control unit 201 disables the function of second communication unit 206. When the function of second communication unit 206 is disabled, second communication unit 206 does not need to wait in a communication-enabled state. This reduces the power consumption of second communication unit 206.

[0039] In this embodiment, based on the fact that the first SIB has been received, the control unit 201 disables the function of the second communication unit 206. This reduces unnecessary power consumption by the second communication unit 206.

[0040] 5 is a diagram showing a second example of the states of the two communication units. Fig. 5 shows an example in which the terminal 101 is outside the area of ​​the first cell 102A of the first base station 102 and is within the area of ​​the second cell 103A of the second base station 103.

[0041] Since the terminal 101 is located outside the area of ​​the first cell 102A of the first base station 102, it does not receive the first SIB transmitted by the first base station 102. In this case, the terminal 101 cannot communicate with the first base station 102. On the other hand, since the terminal 101 is located within the area of ​​the second cell 103A of the second base station 103, it receives the second SIB transmitted by the second base station 103. In this case, the terminal 101 can communicate with the second base station 103.

[0042] When the terminal 101 becomes unable to communicate with the first base station 102, the control unit 201 switches the setting of the function of the second communication unit 206 from disabled to enabled. This enables the terminal 101 to communicate with the second base station 103. In this case, the control unit 201 sets the terminal 101 to DSDS (Dual SIM Dual Standby) mode. The DSDS mode may be DSDA (Dual SIM Dual Active) mode or DSDV (Dual SIM Dual VoLTE). The DSDS mode, DSDA mode, and DSDV mode are modes in which the functions of both the first communication unit 205 and the second communication unit 206 are enabled. Modes other than the DSDS mode, DSDA mode, and DSDV mode may be used as long as the functions of both the first communication unit 205 and the second communication unit 206 are enabled. Furthermore, three or more SIMs may be inserted into the terminal 101. In this case, the DSDS mode, DSDA mode, and DSDV mode may be modes in which the functions of the communication units corresponding to each SIM are enabled.

[0043] 5, the terminal 101 is unable to communicate with the first base station 102, but is able to communicate with the second base station 103. Therefore, the terminal 101 can continue communication with either the first base station 102 or the second base station 103.

[0044] In this embodiment, while the terminal 101 is unable to communicate with the first base station 102, the control unit 201 changes the function setting of the second communication unit 206 from disabled to enabled and also enables the function of the first communication unit 205. As a result, the terminal 101 is set to the DSDS mode, the DSDA mode, and the DSDV mode. Furthermore, because the function of the first communication unit 205 remains enabled, when the first communication unit 205 detects the first SIB, the connection destination of the terminal 101 can be quickly restored to the first base station 102. Meanwhile, the control unit 201 may perform processing to disconnect communication with the first base station 102 and disable the function of the first communication unit 205. This reduces unnecessary power consumption by the unused first communication unit 205.

[0045] Next, an example of the processing flow of the system of this embodiment will be described. Fig. 6 is a sequence diagram showing an example of the processing flow of the entire system 100 of this embodiment. In the sequence diagrams of Fig. 6 and Fig. 7, it is assumed that the terminal 101 is initially located within the areas of the first cell 102A and the second cell 103A, as in the example of Fig. 4.

[0046] The control unit 201 recognizes that the first SIM 205A is inserted into the first communication unit 205 and the second SIM 206A is inserted into the second communication unit 206 (step S101).

[0047] If the first SIM 205A and the second SIM 206A are built-in SIMs, the control unit 201 determines whether a profile containing subscriber information and the like that can be used by the first SIM 205A and the second SIM 206A is valid. If the profile is valid, the control unit 201 determines that the first SIM 205A and the second SIM 206A are inserted.

[0048] The first base station 102 transmits a first SIB (step S102). The second base station 103 transmits a second SIB (step S103). The first base station 102 periodically transmits the first SIB into the first cell 102A, and the second base station 103 periodically transmits the second SIB into the second cell 103A.

[0049] Terminal 101 located within the areas of first cell 102A and second cell 103A receives the first SIB and the second SIB (step S104). First communication unit 205 receives the first SIB, and second communication unit 206 receives the second SIB.

[0050] In this embodiment, when the terminal 101 receives the first SIB and the second SIB, the control unit 201 prioritizes RedCap communication using the first communication unit 205 over non-RedCap communication using the second communication unit 206.

[0051] Since the control unit 201 has received the first SIB and the second SIB, the control unit 201 enables the function of the first communication unit 205 (step S105). Furthermore, since the control unit 201 has received the first SIB, the control unit 201 disables the function of the second communication unit 206 (step S106). As a result, the terminal 101 is set to the DSSS mode.

[0052] The control unit 201 performs authentication processing for the first SIM 205A of the first communication unit 205 (step S107). If the authentication processing for the first SIM 205A is successful, the control unit 201 performs authentication processing between the terminal 101 and the first base station 102 via the first communication unit 205 into which the first SIM 205A is inserted (step S108).

[0053] If the authentication process in step S108 is successful, the first base station 102 starts providing a communication service of RedCap communication to the terminal 101. As a result, RedCap communication is performed between the terminal 101 and the first base station 102 (step S109).

[0054] For example, suppose that the terminal 101 moves out of the area of ​​the first cell 102A of the first base station 102. In this case, the terminal 101 will no longer receive the first SIB. Furthermore, if some kind of failure occurs in the first base station 102, the first base station 102 may stop transmitting the first SIB.

[0055] When the first communication unit 205 becomes unable to communicate with the first base station 102, the control unit 201 disconnects communication between the terminal 101 and the first base station 102 (step S110). For example, the control unit 201 may determine that communication with the first base station 102 has become impossible when the first communication unit 205 is no longer able to detect radio waves from the first base station 102. Alternatively, the control unit 201 may determine that communication with the first base station 102 has become impossible when the first communication unit 205 no longer receives the first SIB. Then, for example, the disconnection of communication may be realized by a detach procedure between the terminal 101 and the first base station 102.

[0056] The control unit 201 counts the period from when the first communication unit 205 becomes unable to communicate with the first base station 102. When the period from when the first communication unit 205 becomes unable to communicate with the first base station 102 reaches the first period, the control unit 201 switches the function of the second communication unit 206 from disabled to enabled (step S111).

[0057] By performing the process of step S111, the terminal 101 is set to the DSDS mode, the DSDA mode, or the DSDV mode. The first period can be set to any value. For example, information indicating the first period may be stored in advance in the storage unit 202.

[0058] Even when the terminal 101 is within the area of ​​the first cell 102A, for example, due to an obstruction or the like, the first communication unit 205 may temporarily become unable to communicate with the first base station 102. The control unit 201 does not switch the function of the second communication unit 206 at the time when the first communication unit 205 becomes unable to communicate with the first base station 102, but switches the function of the second communication unit 206 from disabled to enabled after a predetermined first period has elapsed.

[0059] This makes it possible to detect with high accuracy that communication between the first communication unit 205 and the first base station 102 has become impossible and that it is necessary to switch the function of the second communication unit 206 from disabled to enabled. Therefore, it is possible to appropriately control the switching of the function of the second communication unit 206 from disabled to enabled.

[0060] However, the control unit 201 may immediately switch the function of the second communication unit 206 from disabled to enabled when the first communication unit 205 becomes unable to communicate with the first base station 102. Even in this case, the function of the second communication unit 206 can be switched from disabled to enabled in response to the first communication unit 205 becoming unable to communicate with the first base station 102.

[0061] As described above, the second base station 103 periodically transmits the second SIB (step S112). Also, the first base station 102 periodically transmits the first SIB (step S113). The terminal 101 is outside the area of ​​the first cell 102A and is present within the area of ​​the second cell 103A. The second communication unit 206 of the terminal 101 receives the second SIB (step S114). On the other hand, the first communication unit 205 of the terminal 101 does not receive the first SIB.

[0062] The control unit 201 performs authentication processing for the second SIM 206A of the second communication unit 206 (step S115). If the authentication processing for the second SIM 206A is successful, the control unit 201 performs authentication processing between the terminal 101 and the second base station 103 via the second communication unit 206 into which the second SIM 206A is inserted (step S116).

[0063] If the authentication process in step S116 is successful, the second base station 103 starts providing a non-RedCap communication service to the terminal 101. As a result, non-RedCap communication is performed between the terminal 101 and the second base station 103 (step S117).

[0064] As a result, even if terminal 101 moves out of the area of ​​first cell 102A, terminal 101 can communicate with second base station 103, and communication of terminal 101 is continued. The same applies if a failure occurs in first base station 102 while terminal 101 is within the area of ​​first cell 102A.

[0065] Assume that terminal 101 moves and returns to the area of ​​first cell 102A. In this case, terminal 101 becomes able to communicate with first base station 102. Also, assume that a malfunction that occurred in first base station 102 while terminal 101 was within the area of ​​first cell 102A is resolved. In this case, terminal 101 also becomes able to communicate with first base station 102.

[0066] Fig. 7 is a sequence diagram continuing from Fig. 6. As described above, the first base station 102 periodically transmits IB1 (step S118). Also, the second base station 103 periodically transmits the second SIB (step S119).

[0067] When the terminal 101 returns to the area of ​​the first cell 102A, the first communication unit 205 can receive the first SIB and the second SIB. The terminal 101 receives the first SIB and the second SIB (step S120). The same applies when the malfunction that occurred in the first base station 102 is resolved.

[0068] The control unit 201 recognizes that the first communication unit 205 has received the first SIB (step S121). The control unit 201 performs authentication processing for the first SIM 205A of the first communication unit 205 (step S122). If the authentication processing for the first SIM 205A is successful, the control unit 201 performs authentication processing between the terminal 101 and the first base station 102 via the first communication unit 205 into which the first SIM 205A is inserted (step S123).

[0069] If the authentication process in step S123 is successful, the first base station 102 starts providing a communication service of RedCap communication to the terminal 101. As a result, RedCap communication is performed between the terminal 101 and the first base station 102 (step S124).

[0070] When the period since the communication connection with the first base station 102 was established reaches the second period, the control unit 201 switches the function of the second communication unit 206 from enabled to disabled (step S125).

[0071] The second period can be set to any value. For example, information indicating the second period may be stored in advance in the storage unit 202. The second period may be the same as the first period, or may be a different period.

[0072] By performing the process of step S125, the terminal 101 is set to the DSSS mode. The function of the second communication unit 206 is switched from enabled to disabled, thereby reducing unnecessary power consumption. After performing the process of step S125, the control unit 201 disconnects communication between the terminal 101 and the second base station 103 (step S126).

[0073] The above-described processes from step S102 to step S126 are repeated. For example, when a predetermined termination condition, which will be described later, is satisfied, each process in the sequence diagrams of Fig. 6 and Fig. 7 may be terminated.

[0074] Next, an example of the flow of processing executed by terminal 101 will be described. Fig. 8 is a flowchart showing an example of the flow of processing by terminal 101 of this embodiment. It is assumed that terminal 101 is present within the areas of first cell 102A and second cell 103A when the flowchart of Fig. 8 starts.

[0075] The control unit 201 recognizes that the first SIM 205A is inserted into the first communication unit 205 and the second SIM 206A is inserted into the second communication unit 206 (step S201).

[0076] Terminal 101 located within the areas of first cell 102A and second cell 103A receives the first SIB and the second SIB (step S202). Control unit 201 determines whether first communication unit 205 has received the first SIB (step S203). If the first communication unit 205 has not received the first SIB, the control unit 201 determines No in step S203 and proceeds from "A" to step S212 in Fig. 9. If the first communication unit 205 has received the first SIB, the control unit 201 determines Yes in step S203 and proceeds to step S204. In this case, the control unit 201 enables the function of the first communication unit 205 (step S204).

[0077] Furthermore, the control unit 201 disables the function of the second communication unit 206 (step S205). This sets the terminal 101 to the DSSS mode. The control unit 201 then performs authentication processing for the first SIM 205A of the first communication unit 205 (step S206).

[0078] In this embodiment, it is assumed that the first SIM 205A inserted into the first communication unit 205 is correctly recognized and the authentication process in step S206 is successful. If the first SIM 205A is not correctly recognized and the authentication process fails, the control unit 201 may interrupt the flowchart in Fig. 8. In this case, the control unit 201 may output information indicating that the authentication process for the first SIM 205A has failed from the output unit 203.

[0079] The control unit 201 performs authentication processing between the terminal 101 and the first base station 102 via the first communication unit 205 into which the first SIM 205A is inserted (step S208). In this embodiment, the authentication processing in step S208 is also described as being successful. If the authentication processing in step S208 fails, the control unit 201 may output, from the output unit 203, information indicating that the authentication processing with the first base station 102 has failed.

[0080] After the process of step S207, the control unit 201 controls communication between the terminal 101 and the first base station 102 via the first communication unit 205 (step S208). As a result, communication is performed between the terminal 101 and the first base station 102, and the terminal 101 can perform communication based on the RedCap communication service provided by the first base station 102.

[0081] While communication is being performed between the terminal 101 and the first base station 102, the control unit 201 determines whether the first communication unit 205 has become unable to communicate with the first base station 102 (step S209). As described above, the determination in step S209 may be made based on whether the first communication unit 205 has become unable to detect radio waves from the first base station 102, or may be made based on whether the first communication unit 205 has ceased to receive the first SIB. Furthermore, the control unit 201 may perform the determination process in step S209, for example, at predetermined intervals. The above-mentioned predetermined interval may be the same as or different from the above-mentioned first period.

[0082] If the first communication unit 205 is not unable to communicate with the first base station 102, the control unit 201 determines No in step S209 and returns the process to step S208. In this case, communication (RedCap communication) between the terminal 101 and the first base station 102 continues.

[0083] If the first communication unit 205 is unable to communicate with the first base station 102, the control unit 201 determines Yes in step S209 and proceeds to step S209. In this case, it is assumed that the terminal 101 has moved out of the area of ​​the first cell 102A or a failure has occurred in the first base station 102. The control unit 201 also starts counting the period that has elapsed since the determination in step S209 was Yes.

[0084] The control unit 201 disconnects communication between the terminal 101 and the first base station 102 (step S210). Then, the control unit 201 advances the process from "B" to step S211 in Fig. 9. Fig. 9 is a flowchart continued from Fig. 8.

[0085] The control unit 201 determines whether the period from the point in time when the first communication unit 205 became unable to communicate with the first base station 102 has reached the first period (step S211). As described above, the control unit 201 starts counting the period that has elapsed since the determination in step S209 was Yes. The control unit 201 makes the determination in step S211 based on whether the period being counted has reached the first period that has been stored in advance in the storage unit 202.

[0086] If the period from the time when the first communication unit 205 became unable to communicate with the first base station 102 has not reached the first period, the control unit 201 determines No in step S211 and returns the process to step S211. If the period from the time when the first communication unit 205 became unable to communicate with the first base station 102 has reached the first period, the control unit 201 determines Yes in step S211 and proceeds to step S212.

[0087] The control unit 201 switches the function of the second communication unit 206 from disabled to enabled (step S212). By performing the process of step S212, the terminal 101 is set to the DSDS mode, the DSDA mode, or the DSDV mode. Note that the control unit 201 may immediately perform the process of step S212 when it determines Yes in step S209 (when it determines that the first communication unit 205 has become unable to communicate with the first base station 102). In this case, the process of step S211 is omitted.

[0088] The control unit 201 performs authentication processing for the second SIM 206A of the second communication unit 206 (step S213). In this embodiment, the authentication processing in step S213 is assumed to be successful. If the authentication processing in step S213 fails, the control unit 201 may output information indicating that the authentication processing for the second SIM 206A has failed from the output unit 203.

[0089] The control unit 201 performs authentication processing between the terminal 101 and the second base station 103 via the second communication unit 206 into which the second SIM 206A is inserted (step S214). If the authentication processing in step S214 fails, the control unit 201 may output, from the output unit 203, information indicating that the authentication processing with the second base station 103 has failed.

[0090] After the process of step S214, the control unit 201 controls communication between the terminal 101 and the second base station 103 via the second communication unit 206 (step S215). This allows communication between the terminal 101 and the second base station 103, and the terminal 101 can communicate based on a non-RedCap communication service provided by the second base station 103.

[0091] While communication is being performed between the terminal 101 and the second base station 103, the control unit 201 determines whether the first communication unit 205 is receiving the first SIB (step S216). The control unit 201 periodically performs the determination process of step S216, for example, at predetermined intervals. The predetermined intervals may be the same as or different from the second period described above.

[0092] If the first communication unit 205 has not received the first SIB, the control unit 201 determines No in step S216 and returns the process to step S215. In this case, communication (non-RedCap communication) between the terminal 101 and the second base station 103 continues.

[0093] If the first communication unit 205 has received the first SIB, the control unit 201 determines Yes in step S216 and proceeds to step S217. In this case, it is assumed that the terminal 101 has returned to the area of ​​the first cell 102A or the failure that occurred in the first base station 102 has been resolved.

[0094] The control unit 201 performs authentication processing for the first SIM 205A of the first communication unit 205 (step S217). In this embodiment, the authentication processing in step S217 will be described as being successful. The control unit 201 performs authentication processing between the terminal 101 and the first base station 102 via the first communication unit 205 into which the first SIM 205A is inserted (step S218). In this embodiment, the authentication processing in step S218 will be described as being successful.

[0095] After the process of step S218, the control unit 201 controls communication between the terminal 101 and the first base station 102 via the first communication unit 205 (step S219). As a result, communication between the terminal 101 and the first base station 102 is performed, and the terminal 101 can again perform communication based on the RedCap communication service provided by the first base station 102.

[0096] Here, when the process of step S218 is performed, a communication connection is established between the terminal 101 and the first base station 102. The control unit 201 counts the period that has elapsed since the communication connection between the terminal 101 and the first base station 102 was established.

[0097] The control unit 201 determines whether the connection period of communication between the terminal 101 and the first base station 102 has reached the second period (step S220). The control unit 201 makes the determination in step S220 based on whether the counted period has reached the second period.

[0098] If the connection period of communication between the terminal 101 and the first base station 102 has not reached the second period, the control unit 201 determines No in step S220 and returns the process to step S220. If the connection period of communication between the terminal 101 and the first base station 102 has reached the second period, the control unit 201 proceeds to step S221. Note that the control unit 201 may proceed to step S221 immediately when a communication connection between the terminal 101 and the first base station 102 is established. In this case, the process of step S220 is omitted.

[0099] The control unit 201 disconnects communication between the terminal 101 and the second base station 103 (step S221). This ends communication (non-RedCap communication) between the terminal 101 and the second base station 103. Meanwhile, the terminal 101 is communicating with the first base station 102 (RedCap communication).

[0100] The control unit 201 determines whether the terminal processing has ended (step S222). For example, the control unit 201 may determine "Yes" in step S222 when the power supply of the terminal 101 is cut off. In this case, the control unit 201 ends the flowcharts of Fig. 8 and Fig. 9. The determination of whether the terminal processing has ended may be made based on a factor other than the power supply of the terminal 101.

[0101] If the terminal processing has not ended, the control unit 201 determines No in step S222 and proceeds from "C" to step S205 in Fig. 8. In step S205, the control unit 201 disables the function of the second communication unit 206. This sets the terminal 101 to the DSSS mode.

[0102] In this case, the function of the second communication unit 206 is disabled, thereby reducing the power consumption of the second communication unit 206. Furthermore, the terminal 101 can perform RedCap communication with the second base station 103, thereby maintaining continuity of communication.

[0103] <Modification> Next, modified examples will be described. Fig. 10 is a diagram showing a first example of the modified example. In the example of Fig. 10, the configuration other than the water level meter 151 is the same as that of Fig. 1. The water level meter 151 is, for example, a terminal (sensor terminal) that measures the water level of a river, and corresponds to the terminal 101 of the above-mentioned embodiment. The configuration of the water level meter 151 is the same as that of the terminal 101 of Fig. 2.

[0104] The water level indicator 151 is placed at a fixed position. While the terminal 101 in the above-described embodiment moves, the water level indicator 151 does not move. The water level indicator 151 is placed within the area of ​​the first cell 102A of the first base station 102 and within the area of ​​the second cell 103A of the second base station 103.

[0105] The water level meter 151 is an IoT device, and basically performs RedCap communication with the first base station 102. For this reason, when the water level meter 151 can communicate with the first base station 102, it is preferable to disable the function of the second communication unit 206. In other words, it is preferable that the water level meter 151 be set to DSSS mode.

[0106] On the other hand, as described above, if some kind of failure occurs in the first base station 102, the water level meter 151 will be unable to communicate with the first base station 102. For example, if the above-mentioned river floods due to heavy rain, the water level meter 151 will detect that the water level of the river has reached a dangerous water level. In this case, the water level meter 151 needs to notify information indicating that the water level of the river has reached a dangerous water level.

[0107] Now, suppose that some kind of failure occurs in the first base station 102. In this case, the first communication unit 205 of the water level meter 151 does not receive the first SIB. When the period during which the first communication unit 205 does not receive the first SIB reaches the first period, the control unit 201 switches the function of the second communication unit 206 from disabled to enabled. This allows the water level meter 151 to perform non-RedCap communication with the second base station 103.

[0108] As a result, even if some kind of failure occurs in the first base station 102, the water level meter 151 can notify information indicating that the water level of the river has reached a dangerous water level. Therefore, by setting the water level meter 151 to the DSSS mode, power consumption can be reduced, and important information can be notified to the second base station 103 even if some kind of failure occurs in the first base station 102.

[0109] Furthermore, the control unit 201 of the terminal 101 may perform control to switch the function of the second communication unit 206 from disabled to enabled based on multiple failures in attaching to the first base station 102. Fig. 11 is a diagram showing a second example of the modified example.

[0110] The terminal 101 transmits an attach request to the first base station 102. The first base station 102 transmits the attach request from the terminal 101 to a core network connected to the first base station 102. At this time, the core network may not accept the attach request. In this case, the first base station 102 transmits a message to the terminal 101 indicating that the attach request has failed.

[0111] When the first communication unit 205 receives a message indicating that the attach request has failed multiple times, the control unit 201 of the terminal 101 controls to switch the function of the second communication unit 206 from disabled to enabled. As a result, the terminal 101 switches from DSSS mode to DSDS mode. In this case, the control unit 201 makes the determination in step S211 of FIG. 9 based on whether the first communication unit 205 has received a message indicating that the attach request has failed multiple times. Note that the control unit 201 may also control to switch the function of the second communication unit 206 from disabled to enabled when the first communication unit 205 receives a message indicating that the attach request has failed once.

[0112] The control unit 201 of the terminal 101 may perform control to switch the function of the second communication unit 206 from disabled to enabled based on receiving a reject message from the first base station 102. Fig. 12 is a diagram showing a third example of the modified example.

[0113] For example, in the event of a disaster, the first base station 102 imposes a limit on the number of devices that can connect to the first base station 102. Suppose that the first base station 102 receives an attach request from the terminal 101 when the number of devices connected to the first base station 102 has reached the limit. In this case, the first base station 102 transmits the attach request to the core network, but the core network does not accept the attach request. In this case, the core network controls the first base station 102 to transmit a reject message to the terminal 101. As a result, the terminal 101 receives the reject message from the first base station 102.

[0114] When the first communication unit 205 receives the reject message, the control unit 201 of the terminal 101 controls the function of the second communication unit 206 to be switched from disabled to enabled. As a result, the terminal 101 switches from DSSS mode to DSDS mode. In this case, the control unit 201 performs the determination of step S211 in FIG. 9 based on whether the first communication unit 205 has received the reject message.

[0115] In the above-described embodiment, an example has been described in which the terminal 101 switches between RedCap communication and non-RedCap communication. The terminal 101 may also switch between local communication and wide area communication, for example. Fig. 13 is a diagram showing a fourth example of the modified example.

[0116] The system 400 includes a terminal 101, a local base station 402, and a carrier base station 403. The local base station 402 provides a communication service such as local 5G. The local base station 402 covers the area of ​​a first cell 402A. The local base station 402 may provide a communication service such as regional BWA (Broadband Wireless Access) or NPN (Non-public network).

[0117] The operator base station 403 is, for example, a radio base station that provides a mobile communication service operated by a communication carrier such as the above-mentioned mobile communication carrier or virtual mobile communication carrier. The operator base station 403 covers the area of ​​the second cell 403A. In the following description, it is assumed that the local base station 402 is a base station that provides a local 5G communication service, and the operator base station 403 is a base station that provides a 5G communication service provided by the communication carrier.

[0118] It is also assumed that the local base station 402 and the operator base station 403 use different PLMNs (Public Land Mobile Networks).

[0119] When the first communication unit 205 of the terminal 101 can no longer detect radio waves from the PLMN of the local base station 402, the control unit 201 switches the function of the second communication unit 206 from disabled to enabled. As a result, the terminal 101 switches from DSSS mode to DSDS mode. Because the local base station 402 and the carrier base station 403 use different PLMNs, it is easier to determine the timing to switch the function of the second communication unit 206 from disabled to enabled compared to when the same PLMN is used. Furthermore, because the terminal 101 is basically set to DSSS mode, power consumption is reduced.

[0120] 1 may be base stations of different carriers. The terminal 101 is basically set to DSSS mode, which reduces power consumption. If communication with the first base station 102 becomes impossible, the terminal 101 switches to DSDS mode. This allows the terminal 101 to switch to communication with the second base station 103, thereby maintaining communication with the terminal 101.

[0121] In the above-described embodiment, an example has been described in which, when the terminal 101 receives the first SIB and the second SIB, the control unit 201 prioritizes RedCap communication using the first communication unit 205 over non-RedCap communication using the second communication unit 206. For example, when the terminal 101 receives the first SIB and the second SIB, the control unit 201 may prioritize non-RedCap communication using the second communication unit 206 over RedCap communication using the first communication unit 205.

[0122] In the above-described embodiment, an example was described in which the first communication method using the first subscriber identity module is compatible with RedCap and the second communication method using the second subscriber identity module is compatible with non-RedCap, but it is also possible that the first communication method using the first subscriber identity module is compatible with non-RedCap and the second communication method using the second subscriber identity module is compatible with RedCap.

[0123] Furthermore, the above-mentioned operator base station 403 may correspond to the second subscriber identity module, and the local base station 402 may correspond to the first subscriber identity module.

[0124] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment. Furthermore, the order of the processes in the flowcharts described in the above-described embodiments can be changed as much as possible.

[0125] The program that realizes the functions of this embodiment is stored in a non-transitory recording medium such as a semiconductor medium, an optical recording medium, or a magneto-optical recording medium. For example, a non-volatile memory card can be used as the semiconductor medium. For example, a CD (Compact Disc) or a DVD (Digital Versatile Disc) can be used as the optical recording medium or magneto-optical recording medium. The program may also be supplied to a computer via any transmission medium that can transmit the program. [Explanation of symbols]

[0126] 100 System, 101 Terminal, 102 First base station, 103 Second base station, 201 Control unit, 202 Storage unit, 203 Output unit, 204 Operation unit, 205 First communication unit, 205A First SIM, 206 Second communication unit, 206A Second SIM

Claims

1. a first communication unit that communicates with a first base station corresponding to the first subscriber identity module by a first communication method using the first subscriber identity module; a second communication unit that communicates with a second base station corresponding to the second subscriber identity module by a second communication method different from the first communication method using a second subscriber identity module; a control unit that enables a function of the first communication unit and disables a function of the second communication unit when the first subscriber identity module can communicate with the first base station, and that switches the function of the second communication unit to enable when the first subscriber identity module cannot communicate with the first base station; A terminal comprising:

2. The terminal according to claim 1 , wherein the control unit performs control to switch a function of the second communication unit from disabled to enabled when a period during which the first communication unit is unable to communicate with the first base station becomes a first period.

3. The terminal according to claim 1 , wherein the control unit does not disable the function of the first communication unit while the first subscriber identity module is unable to communicate with the first base station.

4. 4. The terminal according to claim 3, wherein the control unit controls the first communication unit to start communication with the first base station when the first communication unit receives notification information from the first base station, and controls the second communication unit to disconnect communication with the second base station when a period during which the first communication unit is communicating with the first base station enters a second period.

5. The terminal according to claim 4 , wherein the control unit performs control to switch a function of the second communication unit from enabled to disabled after communication with the second base station is disconnected.

6. The terminal according to claim 1 , wherein the first communication method performed by the first communication unit has fewer communication functions than the second communication method performed by the second communication unit.

7. the first base station corresponding to the first subscriber identity module is a base station for a mobile communication service operated by a communication carrier; The terminal according to claim 1 , wherein the second base station corresponding to the second subscriber identity module is a local base station independent of the mobile communication service operated by the communication carrier.

8. A method for controlling a terminal having a first communication unit that communicates with a first base station corresponding to a first subscriber identity module by a first communication method using the first subscriber identity module, and a second communication unit that communicates with a second base station corresponding to the second subscriber identity module by a second communication method using a second subscriber identity module that is different from the first communication method, When the first subscriber identity module is able to communicate with the first base station, the function of the first communication unit is enabled and the function of the second communication unit is disabled; When the first subscriber identity module becomes unable to communicate with the first base station, the function of the second communication unit is switched to be valid. A method for controlling a terminal comprising:

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