JP7478277B1 - SIM, communication device, switching method, and program - Google Patents

Abstract

[Problem] By using a SIM, carrier networks are automatically switched. [Solution] In a SIM that can be installed in a communication device equipped with a communication unit, the SIM is equipped with a data storage unit that stores connection information used by the communication unit to connect to a carrier network, and a switching control unit that monitors the state of connection to the carrier network by the communication unit and switches the carrier network based on the state. [Selected Figure] Figure 1

Description

The present invention relates to a SIM (Subscriber Identity Module) installed in a communication device.

In order for communication devices such as mobile terminals and IoT terminals to use the lines of a carrier (which may also be called a mobile network operator), the communication devices are equipped with a SIM.

For example, Patent Document 1 discloses a technology that automatically switches between multiple mobile carriers on a single connected terminal by installing multiple SIM cards.

Patent No. 6272268

However, in conventional technologies such as those described in Patent Document 1, automatic switching to another carrier network is not possible unless multiple SIM cards are used.

The present invention has been made in consideration of the above points, and aims to provide a technology that enables automatic switching of carrier networks by using a single SIM card.

According to the disclosed technology, there is provided a SIM that can be mounted in a communication device having a communication unit,
a data storage unit for storing connection information used for connecting the communication unit to a carrier network;
a switching control unit that monitors a state of connection between the communication unit and a first carrier network, and when a problem occurs in the connection to the first carrier network, switches the connected carrier network from the first carrier network to a second carrier network, and when a certain condition is satisfied, attempts to switch back to the first carrier network;
The SIM includes a key management unit that manages key information used as part of the connection information, separate from the switching control unit, and the key management unit and the switching control unit are included in an applet unit in the SIM.
A SIM is provided.

The disclosed technology makes it possible to automatically switch carrier networks even when using a single SIM card.

FIG. 1 is a diagram illustrating an example of the overall configuration of a communication system. FIG. 2 is a diagram illustrating an example of a hardware configuration of a SIM. FIG. 2 is a diagram illustrating an example of a functional configuration of a SIM. FIG. 2 is a state transition diagram for explaining the operation of the communication device. FIG. 2 illustrates an example of a hardware configuration of a communication device.

The following describes an embodiment of the present invention (the present embodiment) with reference to the drawings. The embodiment described below is merely an example, and the embodiment to which the present invention is applied is not limited to the following embodiment. The "number of times" and "time" described below are both examples, and both can be set to any value.

(System configuration example)
Fig. 1 is a diagram showing an example of the overall configuration of a communication system according to the present embodiment. As shown in Fig. 1, the communication system includes a communication device 200 and a plurality of carrier networks. In Fig. 1, a carrier A network, a carrier B network, and a carrier C network are shown as examples of the plurality of carrier networks. The communication device 200 connects to any one of the plurality of carrier networks to perform communication.

In this embodiment, each carrier network is assumed to be a mobile network (e.g., 5G network, LTE network) of a carrier (operator) that provides mobile communication services, but is not limited to this. Carrier networks to which the communication device 200 can connect (switch) using the SIM 100 may include fixed networks, wireless LAN networks, self-operated mobile networks, etc.

The communication device 200 has a SIM 100 and a communication unit 210. The SIM 100 in this embodiment is a card-type SIM that is generally distributed and sold, but is not limited to this. The SIM 100 may also be a chip-type SIM that is fixed inside the communication device 200.

The communication unit 210 is capable of performing communication operations according to commands from a program (called an applet) running on the SIM 100.

The communication device 200 may be any device capable of mounting the SIM 100. For example, the communication device 200 may be an IoT device, a smartphone, a tablet, a PC, a server, a CPE, a machine tool, an automobile, a drone, etc. The SIM in this embodiment may be called an eSIM or an eUICC.

(Example of hardware configuration of SIM 100)
Fig. 2 shows an example of a basic hardware configuration of the SIM 100. As shown in Fig. 2, the SIM 100 has a CPU 1, a memory 2, and an interface 3. The CPU 1 executes a program stored in the memory 2, thereby executing processing of the SIM 100. By executing the program, the SIM 100 notifies the communication unit 210 of an execution command for TCP or UDP packet transmission from the interface 3 at a predetermined timing, for example, thereby causing the communication unit 210 to execute the operation of transmitting a TCP or UDP packet. Note that the execution command is not limited to transmitting a TCP or UDP packet.

The state of the communication unit 210 is notified to the inside of the SIM 100 through the interface 3, and the SIM 100 executes processing according to the state according to the program being executed. In this embodiment, the program executed on the SIM 100 may be called an applet.

The program (applet) in SIM100 can be stored in SIM100 from outside SIM100 via a network, or a program (applet) recorded on a portable recording medium (memory, CD-ROM, etc.) can be stored in SIM100.

(Example of functional configuration of SIM 100)
Fig. 3 shows an example of the functional configuration of SIM 100. As shown in Fig. 3, SIM 100 includes a data storage unit 110 and an applet unit 120. Data storage unit 110 stores information required for communication unit 210 to connect to a carrier network. This information is referred to as "connection information" here. Connection information differs for each carrier network. Specifically, data storage unit 110 is a file that constitutes a file system on SIM 100.

The communication unit 210 can connect to a carrier network by reading connection information for connecting to the carrier network from the data storage unit 110.

The connection information includes, for example, an International Mobile Subscriber Identity (IMSI), a Public Land Mobile Network (PLMN) list, and Ki/OPc. Ki/OPc is authentication information for connecting to the corresponding carrier network. Ki/OPc may also be called key information.

The applet unit 120 includes a switching control unit 121 and a key management unit 122. Both the switching control unit 121 and the key management unit 122 are functional units realized by a program (applet) on the SIM 100. It is also possible to realize the switching control unit 121 and the key management unit 122 as a single applet. In that case, for example, the key management unit 122 is included in the switching control unit 121.

However, by dividing the switching control unit 121 and the key management unit 122 into two applets, a special effect can be obtained. The effect will be described later.

The switching control unit 121 controls switching of the carrier network to which the communication unit 210 is connected. The switching control unit 121 also manages (holds) connection information other than key information for each carrier network to which the communication unit 210 may be connected. The key management unit 122 manages (holds, updates, etc.) key information for each carrier network to which the communication unit 210 may be connected.

When the switching control unit 121 decides to switch carrier networks, it rewrites the connection information stored in the data storage unit 110 to the connection information to be switched to. For connection information other than key information (such as the IMSI), the switching control unit 121 uses the connection information stored in the switching control unit 121 to perform the rewriting, and for key information, the switching control unit 121 obtains key information from the key management unit 122 and performs the rewriting using that key information. Alternatively, the switching control unit 121 instructs the key management unit 122 to rewrite the key information in the data storage unit 110, and the key management unit 122 performs the rewriting according to the instruction.

The effects of separating the switching control unit 121 and the key management unit 122 (effects of having two applets) are as follows (1) and (2).

(1) By separating the switching control unit 121 and the key management unit 122, it becomes possible to freely upgrade the switching control unit 121 (e.g., by replacing programs via OTA, etc.).

As a more detailed example, the key management unit 122 holds a key called ADM2, which is discarded after the SIM is manufactured. This means that the key management unit 122 cannot be upgraded.

If the switching control unit 121 and the key management unit 122 are separated, the switching control unit 121 can take charge of operations other than those of the key management unit 122, and the switching control unit 121 can be equipped with rich functions and can update those functions.

(2) By implementing the key management unit 122 as compactly as possible, it is possible to minimize security risks.

(Example of Operation of Communication Device 200)
Next, an example of the operation of the communication device 200 based on the control of the SIM 100 will be described with reference to the state transition diagram of Fig. 4. Here, as an example, it is assumed that there are two connection candidates for the communication device 200, a carrier A network and a carrier B network.

In this embodiment, basically, if there is no problem with the connection to carrier A network, communication unit 210 of communication device 200 continues the connection to carrier A network, and if a problem occurs with the connection to carrier A network, it connects to carrier B network. If the connection to carrier A network is restored after connecting to carrier B network, communication unit 210 connects to carrier A network. An example of operation will be described in detail below according to the procedure shown in FIG. 4.

The operation procedure shown in FIG. 4 basically corresponds to the processing procedure of the switching control unit 121 in the SIM 100. Also, each state in FIG. 4 indicates the state that the switching control unit 121 is aware of at that time.

More specifically, the switching control unit 121 constantly monitors (understands) the current state, and according to predetermined conditions corresponding to that state, rewrites the connection information stored in the data storage unit 110 to different connection information or sends a command to the communication unit 210. This realizes the operation of the communication unit 210.

<Carrier A network connection status>
In an initial state, such as when the communication device 200 is started (including the start-up of the SIM 100) or when the SIM 100 is inserted (started up), the communication unit 210 connects to the carrier A network. That is, in the initial state, connection information for the carrier A network is stored in the data storage unit 110 of the SIM 100, and the communication unit 210 connects to the carrier A network using the connection information. Note that when the SIM 100 is started up, all timers/counters are reset. However, it is also possible to set the operation so that when the SIM 100 is started up, the connection information before the start-up is used and the timers/counters are not reset (the values before the start-up are used).

In S101, when the communication unit 210 is connected to the carrier A network, the switching control unit 121 monitors whether the connection to the carrier A network is normal by having the communication unit 210 perform a heartbeat.

Regarding the specific method of the heartbeat, any method may be used as long as it can confirm the normality of the connection with Carrier A's network, but in this embodiment, TCP or UDP packets are sent to a predetermined destination at a specified time interval, and the response is monitored to confirm reachability to the destination. Here, two destinations (destination 1 and destination 2) are used. Hereinafter, packet transmission for reachability confirmation is TCP or UDP packet transmission, but is not limited to this. Packet transmission using protocols other than TCP and UDP may also be performed.

More specifically, the switching control unit 121 transmits packets only to destination 1, and if reachability cannot be confirmed for destination 1, it transmits packets to destination 2.

Regarding the operation of transmitting a TCP or UDP packet, for example, the switching control unit 121 instructs the communication unit 210 to transmit a packet after receiving a notification from the communication unit 210 indicating that the connection with the carrier A network is established. If the connection cannot be confirmed (e.g., if the radio signal cannot be picked up), the switching control unit 121 waits until the connection is established. If the connection cannot be detected after waiting a certain period of time (e.g., one minute), the switching control unit 121 may instruct the communication unit 210 to connect to another carrier network.

When the communication unit 210 receives an instruction to send a TCP or UDP packet, it executes packet transmission and notifies the switching control unit 121 of information indicating whether the packet transmission was successful or unsuccessful (whether the reachability check was successful or unsuccessful). From this information, the switching control unit 121 can determine whether the reachability check to the destination was successful or unsuccessful.

The packet transmission time interval (= the time interval at which the switching control unit 121 instructs the communication unit 210 to execute packet transmission) is, for example, one minute for each of the two destinations. The time interval is measured, for example, by a timer.

In addition, instead of measuring a predetermined time interval using a timer as described above, it is also possible to realize periodic packet transmission by using polling from the communication device 200 (here, communication unit 210) to the SIM 100. Note that this polling is generally performed in devices in which a SIM is inserted.

The time interval for the above polling is, for example, 15 seconds. In this case, the switching control unit 121 in the SIM 100 instructs the communication unit 210 to execute packet transmission every time it detects that it has received polling from the communication unit 210 four times (waited four times). This makes it possible to check reachability at one-minute intervals.

Note that the above "1 minute" and "4 polling waits" are just examples, and the packet transmission interval is not limited to "1 minute" and "4 polling waits".

<Carrier B network switching determination state>
For example, when the switching control unit 121 detects that packet transmission to both of the two destinations has failed (reachability confirmation has failed), the switching control unit 121 transitions to a carrier B network switching determination state (S102).

In the carrier B network switching determination state, the switching control unit 121 causes the communication unit 210 to transmit packets at time intervals that are shorter than the packet transmission time interval in the carrier A network connection state. The destinations for the packet transmission are the same two destinations as in the case of packet transmission in the carrier A network connection state.

The packet transmission time interval for each of the two destinations is, for example, 10 seconds. When polling is used, for example, the switching control unit 121 instructs the communication unit 210 to transmit a packet each time polling is received.

In addition, in the carrier B network switching judgment state, the number of times packets can be sent to each of the two destinations is limited. For example, the number is two times. The judgment here is made in the following two cases A and B.

(A) When the switching control unit 121 detects that either of the two packet transmissions to destination 1 and the two packet transmissions to destination 2 has been successful, in S103, it stops switching and returns to the carrier A network connection state. In the carrier A network connection state, the heartbeat operation is performed as described above.

(B) When the switching control unit 121 detects that packet transmission to destination 1 has failed two consecutive times and that packet transmission to destination 2 has also failed two consecutive times, in S104, it executes a transition to a carrier B network connection state.

When transitioning to a carrier B network connection state, the switching control unit 121 first instructs the communication unit 210 to disconnect from the carrier A network. As a result, the communication unit 210 disconnects from the carrier A network.

Then, the switching control unit 121 rewrites the connection information for the carrier A network in the data storage unit 110 to connection information for the carrier B network, and instructs the communication unit 210 to connect to the carrier B network. As a result, the communication unit 210 connects to the carrier B network. When the communication unit 210 connects to the carrier B network, the current state becomes a carrier B network connection state. More specifically, an attach operation is performed during the connection. The retry operation in the event of an attachment failure will be described later.

<Carrier B network connection status>
In S105 in the carrier B network connected state, the switching control unit 121 performs the heartbeat operation in the same manner as S101 in the carrier A network connected state. The two destinations of the packet transmission at this time may be the same as the two destinations in the carrier A network connected state, or may be different. As in S102 in the carrier A network connected state, if packet transmission to both destinations fails during the heartbeat operation, a connection to the carrier A network is made.

In addition, even if the connection to the carrier B network is normal after connection to the carrier B network, if a certain period of time has elapsed, the switching control unit 121 will attempt to switch back to the carrier A network in S106. The "certain period of time" is, for example, one hour. If polling is used, for example, after connection to the carrier B network, a switchback attempt will be made after receiving polling 240 times.

In a switchback attempt, the switching control unit 121 first instructs the communication unit 210 to disconnect from the carrier B network. As a result, the communication unit 210 disconnects from the carrier B network.

Then, the switching control unit 121 rewrites the connection information for the carrier B network in the data storage unit 110 to connection information for the carrier A network, and instructs the communication unit 210 to connect to the carrier A network. As a result, the communication unit 210 connects to the carrier A network. As a result, the current state becomes a carrier A network switchback determination state.

<Carrier A network switch-back determination state>
In the carrier A network switch-back determination state, the switching control unit 121 causes the communication unit 210 to transmit a packet to destination 1, and if the packet transmission is successful, transitions to a carrier A network connection state (S107). If the packet transmission to destination 1 fails, the switching control unit 121 causes the communication unit 210 to transmit a packet to destination 2, and if the packet transmission is successful, transitions to a carrier A network connection state (S107).

When the switching control unit 121 detects that both packet transmission to destination 1 and packet transmission to destination 2 have failed, it stops the switchback. Specifically, the switching control unit 121 rewrites the connection information for the carrier A network in the data storage unit 110 to connection information for the carrier B network, and instructs the communication unit 210 to connect to the carrier B network. As a result, the communication unit 210 connects to the carrier B network. When the communication unit 210 connects to the carrier B network, the current state becomes a carrier B network connection state.

After that, after a certain period of time (e.g., one hour), the switching control unit 121 again attempts to switch back to the carrier A network. Note that the certain period of time for starting a second attempt to switch back to the carrier A network after the first attempt to switch back to the carrier A network fails may be shorter than the initial "certain period of time" (e.g., one hour).

In addition, the switchover from carrier B network to carrier A network may be triggered by the switching control unit 121 receiving a switchover instruction from an external monitoring server.

<How to avoid simultaneous attachment>
As described above, when a packet transmission fails, switching from carrier A network to carrier B network, or switching from carrier B network to carrier A network, is performed.

In this embodiment, it is assumed that there are multiple communication devices 200 (e.g., multiple IoT devices) equipped with SIM 100. If multiple communication devices 200 simultaneously attach (send a connection request signal) to a carrier network, the carrier network may become congested, making it difficult to connect. Furthermore, if each communication device 200 detects an error during attachment, it retries the attachment, but if all communication devices 200 simultaneously retry to the carrier network at the same time, it is possible that the inability to connect may continue.

In this embodiment, therefore, when an error is detected during attachment, the switching control unit 121 randomizes the timing of the retry. An example of operation in this case is described below. Here, the case of switching from carrier A network to carrier B network is described, but the same applies when switching from carrier B network to carrier A network.

When the switching control unit 121 decides to switch from carrier A network to carrier B network, it disconnects from carrier A network and rewrites the connection information in the data storage unit 110 to connection information for carrier B network. Next, the switching control unit 121 instructs the communication unit 210 to attach to carrier B network. Here, it is assumed that the attachment fails, and the switching control unit 121 receives an error notification from the communication unit 210 indicating that the attachment has failed.

After receiving the error notification, the switching control unit 121 waits a predetermined time (here, 60 seconds) plus n seconds, and when it detects that 60+n seconds have elapsed, it attempts to attach to the carrier B network again. If the attachment fails here as well, it waits 60+n seconds and attempts to attach to the carrier B network again.

The above n is, for example, a random value between 0 and 60 seconds. In other words, a randomly selected value of n is used each time a retry is performed.

When using the polling method described above, after an attachment failure, the device waits for m polls before retrying. m is a random value. For example, m is a value between 4 and 8.

In the above example of switching from carrier A network to carrier B network, if retrying to attach to carrier B network fails R times, connection to carrier A network may be performed. R can be set arbitrarily. For example, R may be 1 or a value of 2 or more. The same applies to the case of switching from carrier B network to carrier A network.

(Example of hardware configuration of communication device)
The communication device 200 described in this embodiment can be realized, for example, by causing a computer to execute a program.

That is, communication device 200 can be realized by executing a program corresponding to the processing performed by communication device 200 using hardware resources such as a CPU and memory built into a computer. The program can be recorded on a computer-readable recording medium (such as a portable memory) and stored or distributed. The program can also be provided via a network such as the Internet or email.

Figure 5 is a diagram showing an example of the hardware configuration of the computer. The computer in Figure 5 has a drive device 1000, an auxiliary storage device 1002, a memory device 1003, a CPU 1004, an interface device 1005, a display device 1006, an input device 1007, an output device 1008, etc., all of which are interconnected by a bus BS. Figure 5 also shows an example in which a SIM 100 is inserted.

The program that realizes the processing on the computer is provided by a recording medium 1001, such as a CD-ROM or a memory card. When the recording medium 1001 storing the program is set in the drive device 1000, the program is installed from the recording medium 1001 via the drive device 1000 into the auxiliary storage device 1002. However, the program does not necessarily have to be installed from the recording medium 1001, but may be downloaded from another computer via a network. The auxiliary storage device 1002 stores the installed program as well as necessary files, data, etc.

When an instruction to start a program is received, the memory device 1003 reads out and stores the program from the auxiliary storage device 1002. The CPU 1004 realizes functions related to the communication device 200 in accordance with the program stored in the memory device 1003. The interface device 1005 is used as an interface (communication function) for connecting to a network, etc. The display device 1006 displays a GUI (Graphical User Interface) or the like according to a program. The input device 1007 is composed of a keyboard and mouse, buttons, a touch panel, etc., and is used to input various operation instructions. The output device 1008 outputs the results of calculations.

(Effects of the embodiment)
As described above, the technique according to the present embodiment enables the communication device 200 to automatically switch carrier networks by using the SIM 100.

The following notes are further provided with respect to the above embodiment.

<Additional Notes>
(Additional Note 1)
A SIM that can be installed in a communication device having a communication unit,
a data storage unit for storing connection information used for connecting the communication unit to a carrier network;
and a switching control unit that monitors a state of connection to a carrier network by the communication unit and switches the carrier network based on the state.
(Additional Note 2)
The SIM described in Appendix 1, wherein when switching from a first carrier network to a second carrier network is performed, the switching control unit rewrites the connection information for the first carrier network in the data storage unit to connection information for the second carrier network.
(Additional Note 3)
The SIM according to claim 1 or 2, further comprising a key management unit that manages key information used as part of the connection information, separate from the switching control unit.
(Additional Note 4)
A SIM described in any one of appendix 1 to 3, in which when switching from a first carrier network to a second carrier network, the switching control unit detects a failure to attach to the second carrier network and then performs an attachment retry when a randomly determined time has elapsed.
(Additional Note 5)
5. The communication device comprising the SIM according to any one of claims 1 to 4.
(Additional Note 6)
A switching method performed by a SIM that can be installed in a communication device having a communication unit, comprising:
A switching method comprising: when the communication unit is connected to a carrier network using connection information stored in a data storage unit in the SIM, monitoring a state of connection to the carrier network, and switching the carrier network based on the state.
(Additional Note 7)
A non-transitory storage medium storing a program for causing a SIM to execute the processing of the switching control unit according to any one of appendixes 1 to 4.

Although the present embodiment has been described above, the present invention is not limited to this specific embodiment, and various modifications and variations are possible within the scope of the gist of the present invention as described in the claims.

1 CPU
2 Memory 3 Interface 100 SIM
110 Data storage unit 120 Applet unit 121 Switching control unit 122 Key management unit 200 Communication device 210 Communication unit 1000 Drive device 1001 Recording medium 1002 Auxiliary storage device 1003 Memory device 1004 CPU
1005 Interface device 1006 Display device 1007 Input device 1008 Output device

Claims (8)

A SIM that can be installed in a communication device having a communication unit,
a data storage unit for storing connection information used for connecting the communication unit to a carrier network;
a switching control unit that monitors a state of connection between the communication unit and a first carrier network, and when a problem occurs in the connection to the first carrier network, switches a connection destination carrier network from the first carrier network to a second carrier network, and when a certain condition is satisfied, attempts to switch back to the first carrier network;
The SIM includes a key management unit that manages key information used as part of the connection information, separate from the switching control unit, and the key management unit and the switching control unit are included in an applet unit in the SIM.
SIM. The SIM according to claim 1 , wherein the certain condition is satisfied when a certain time has elapsed since switching to the second carrier network. The SIM according to claim 1 , wherein the switching control unit determines whether or not a problem has occurred in the connection to the first carrier network by confirming reachability using a TCP or UDP packet. The SIM according to claim 1 , wherein when switching from a first carrier network to a second carrier network is performed, the switching control unit rewrites connection information for the first carrier network in the data storage unit to connection information for the second carrier network. The SIM of claim 1, wherein when switching from a first carrier network to a second carrier network is performed, the switching control unit detects a failure to attach to the second carrier network and then performs an attachment retry when a randomly determined time has elapsed. The communication device comprising a SIM according to any one of claims 1 to 5 . A switching method performed by a SIM that can be mounted in a communication device having a communication unit, the SIM including a switching control unit,
When the communication unit is connected to a first carrier network using the connection information stored in a data storage unit in the SIM, the switching control unit monitors a state of connection with the first carrier network, and when a problem occurs with the connection with the first carrier network, switches the connected carrier network from the first carrier network to a second carrier network, and when a certain condition is satisfied, performs an attempt to switch back to the first carrier network;
The SIM includes a key management unit that manages key information used as part of the connection information, separate from the switching control unit, and the key management unit and the switching control unit are included in an applet unit in the SIM.
Switching method. A program for causing a SIM to execute the processes of the key management unit and the switching control unit according to any one of claims 1 to 5 .

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