JP2014183377A - Communication system, communication apparatus, communication method, and communication program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve radio communication quality.SOLUTION: In a communication system having a calling side communication device capable of using a plurality of radio access networks and an incoming side communication device capable of using at least one radio access network among the plurality of radio access networks, the calling side communication device sets a first radio access network among the plurality of radio access networks to a radio access network to be used for communication and notifies the incoming side communication device of the first radio access network as a radio access network to be used for communication, the incoming side communication device receives notification of the first radio access network from the calling side communication device, determines whether or not the setting of the radio access network to be used can be switched to the first radio access network, and switches the setting of the radio access network to be used to the first radio access network when it is possible to switch the radio access network to the first radio access network.

Description

  The present invention relates to a communication system, a communication device, a communication method, and a communication program.

There are mobile terminals that can use a plurality of operator networks and wireless access networks. A user of such a mobile terminal can automatically or manually select an operator network or a radio access network that is desired to be connected. Examples of the radio access network include LTE (Long Term Evolution), 3G (3rd generation mobile communication system: 3rd Generation), 2G (2nd generation mobile communication system: 2nd Generation), WiMAX (Worldwide Interoperability for Microwave Access), and the like. There is.

On the other hand, in the LTE service, it is expected that end-to-end type services in which terminals directly communicate with each other will increase with the diversification of services. End-to-end services include, for example, voice IP (VoLTE: Voice over LTE) using IMS (IP Multimedia Subsystem), sharing of multimedia information such as files and videos during voice communication, and the like.

JP 2005-64877 A

  However, if the radio access network suitable for the service content is not selected in each of the two mobile terminals that perform communication, the communication quality between the terminals cannot be ensured, and end-to-end service can be enjoyed. It may not be possible.

  Further, for example, when one mobile terminal uses LTE and the other mobile terminal uses 3G as a radio access network, the communication quality cannot be guaranteed due to a speed difference. The communication quality is, for example, that the call is not interrupted and that the sound quality is good in a voice call.

  An object of one embodiment of the present invention is to provide a communication system, a communication apparatus, a communication method, and a communication program that improve communication quality.

One aspect of the present invention is:
A communication system comprising: an originating communication device that can use a plurality of radio access networks; and an incoming communication device that can use at least one of the plurality of radio access networks,
The calling-side communication device includes a storage device and a processor,
The processor is
A first radio access network of the plurality of radio access networks is set as a radio access network used for communication,
Notifying the first communication device as the wireless access network used for the communication,
The called communication device includes a storage device and a processor,
The processor is
Receiving a notification of the first radio access network from the originating communication device;
Determining whether the setting of the radio access network used by the called communication device can be switched to the first radio access network;
When switching to the first radio access network is possible, the setting of the radio access network used by the destination communication device is switched to the first radio access network;
It is a communication system.

  Another aspect of the present invention is a communication device as a transmission side communication device and a communication device as a reception side communication device in the communication system described above. Another aspect of the present invention is a communication method that is executed by a transmission-side communication device and a reception-side communication device in the communication system described above. In addition, another aspect of the present invention can include a communication program that causes a computer to function as a transmission-side communication device or a reception-side device in the communication system described above, and a computer-readable recording medium that records the program. In addition, another aspect of the present invention can include a communication program that causes a computer to function as an incoming communication device in the communication system described above, and a computer-readable recording medium that records the program. The computer-readable recording medium refers to a recording medium in which information such as data and programs is accumulated by electrical, magnetic, optical, mechanical, or chemical action and can be read from the computer or the like.

  According to the disclosed communication system, communication apparatus, communication method, and communication program, communication quality can be improved.

It is a figure which shows an example of the communication system of 1st Embodiment. It is a figure which shows an example of the hardware constitutions of a mobile terminal. It is a figure which shows an example of the functional block of a mobile terminal. It is a figure which shows an example of the SMS message for a RAT switching request. It is an example of the flowchart of the process of the transmission side terminal in 1st Embodiment. It is an example of the flowchart of the process of the receiving side terminal in 1st Embodiment. It is a figure which shows an example of the sequence of the process between the transmission side terminal and receiving side terminal from the input of the transmission request to a transmission side terminal to communication establishment. It is a figure which shows an example of the SMS message for a switching response. It is an example of the flowchart of the process of the transmission side terminal 1A in 2nd Embodiment. It is an example of the flowchart of the process of the receiving side terminal 1B in 2nd Embodiment. It is a figure which shows an example of the sequence of the process between the transmission side terminal and receiving side terminal from the input of the transmission request to a transmission side terminal to communication establishment. It is a figure which shows an example of the sequence of the process between the transmission side terminal and receiving side terminal from the input of the transmission request to a transmission side terminal to communication establishment. It is an example of a RAT switching inquiry screen. It is an example of the flowchart of the process of the receiving side terminal in 3rd Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The configuration of the following embodiment is an exemplification, and the present invention is not limited to the configuration of the embodiment.

<First Embodiment>
FIG. 1 is a diagram illustrating an example of a communication system according to the first embodiment. The communication system 100 includes mobile terminals 1A and 1B. The mobile terminals 1A and 1B can use a plurality of radio access networks such as 2G, 3G, and LTE, for example. The mobile terminal 1A is located in LTE. The mobile terminal 1B is located in 3G. Note that the mobile terminal is located in the radio access network means that in the first embodiment, the mobile terminal is waiting for an incoming call from the radio access network and communicates by the mobile terminal. Indicates that the radio access network to be used is selected. Note that the state of waiting for an incoming call from the radio access network indicates a state where the paging channel is intermittently received in the base station cell of the radio access network. The radio access network in which the mobile terminals 1A and 1B are located is selected from radio networks in which the mobile terminals 1A and 1B detect radio waves, for example, by radio wave intensity, user settings, and the like.

For example, when the mobile terminal 1A makes a transmission request to the mobile terminal 1B, the processing performed in the communication system 100 in the first embodiment is as follows.
(1) Prior to the transmission request, the mobile terminal 1A notifies the mobile terminal 1B of the radio access network (LTE) in which it is located. This notification is performed using, for example, SMS (Short Message Service).
(2) When the mobile terminal 1B receives the notification of the radio access network (LTE) from the mobile terminal 1A, the mobile terminal 1B switches the existing radio access network from 3G to LTE.
(3) The mobile terminal 1A makes a call request to the mobile terminal 1B using LTE, and communication is established between the mobile terminal 1A and the mobile terminal 1B using the same radio access network (LTE).

  As described above, in the first embodiment, the mobile terminal 1A on the transmission side notifies the mobile terminal 1B on the reception side of the wireless access network in the area, so that the mobile terminals on the transmission side and the reception side are the same. Communication can be established over a wireless access network.

  Note that SMS is a service that can send a control message directly to a partner terminal by a telephone number using a signaling channel. The SMS message is transmitted and received through the signaling channel of the radio access network in which the mobile terminals 1A and 1B are located.

  Hereinafter, the mobile terminal 1A on the transmission side is referred to as the transmission side terminal 1A. The mobile terminal 1B on the incoming side is referred to as the incoming terminal 1B. Further, when the calling side terminal 1A and the receiving side terminal 1B are not distinguished, they are simply referred to as the mobile terminal 1.

(Configuration of mobile terminal)
FIG. 2 is a diagram illustrating an example of a hardware configuration of the mobile terminal 1. The mobile terminal 1 is, for example, a smartphone or a mobile tablet terminal. In FIG. 2, a hardware configuration of a smartphone is shown as an example of the mobile terminal 1. The mobile terminal 1 includes an application control unit 10 and a communication control unit 20. The communication control unit 20 includes hardware components related to communication. The application control unit 10 includes hardware components related to processing other than communication.

The application control unit 10 includes a CPU (Central Processing Unit) 101, a power supply control unit 102, a microphone 103, a speaker 104, a touch panel 105, an LCD (Liquid Crystal Display) 106, a ROM (Read Only Memory) / RAM (Random Access Memory) 107. , A message transmitting / receiving unit 108 is included.

  The ROM / RAM 107 is a storage unit including a ROM, a volatile RAM, and a nonvolatile RAM. The volatile RAM includes a memory corresponding to the main memory. The non-volatile RAM stores a communication program, an operation system (OS), and other applications. The communication program is a program for performing a process of notifying the receiving side terminal of the wireless access network in the area prior to establishment of communication with the receiving side terminal as the calling side terminal. The communication program is a program for receiving a notification from the originating terminal as a receiving terminal and switching to the notified radio access network.

  The touch panel 105 is one of position input devices, and inputs the coordinates of the finger contact position corresponding to the screen of the LCD 106. The touch panel 105 may be any system such as a resistive film system, a surface acoustic wave system, an infrared system, an electromagnetic induction system, and a capacitance system. The LCD 106 is one of display devices, and displays screen data in accordance with a signal input from the CPU 101.

  The power control unit 102 is a circuit that executes management of the amount of charge of the battery 208 of the mobile terminal 1 and control of processing related to charging of the battery 208. The microphone 103 is one of voice input devices. The speaker 104 is one of audio output devices. The message transmitting / receiving unit 108 is an interface circuit that connects the CPU 101 and the communication control unit 20 (communication control CPU 201).

  The CPU 101 is a processor that implements various processes by reading a program stored in the ROM / RAM 107, loading it into the main memory, and executing instructions included in the program. The CPU 101 receives inputs from the power control unit 102, the microphone 103, the touch panel 105, and the message transmission / reception unit 108, executes predetermined processing, and performs power supply control unit 102, speaker 104, LCD 106, ROM / RAM 107, message transmission / reception. The processing result is output to the unit 108.

  The communication control unit 20 includes a communication control CPU 201, a voice codec control unit 202, a wireless unit 203, a UIM (User Identity Module) card 207, a battery 208, and a ROM / RAM 209.

The wireless unit 203 is a circuit that is connected to the antenna 300 and receives and transmits a wireless signal through the antenna 300. The wireless unit 203 performs conversion between a wireless signal and an electrical signal, and modulation and demodulation of the electrical signal. The wireless unit 203 includes, for example, the circuits of the LTE processing unit 204, the 3G processing unit 205, and the 2G processing unit 206. By including these circuits, a plurality of LTE, 3G, and 2G wireless access networks can be used. . The 3G processing unit 205 performs, for example, encoding processing, modulation processing, and the like based on WCDMA (Wideband Code Division Multiple Access). The 2G processing unit 206 is, for example, a GSM (Global System for Mobile
Encoding processing, modulation processing, etc. based on Communications) are executed.

  Note that one or more antennas 300 may be provided. When there is one antenna 300, it is shared by the LTE processing unit 204, the 3G processing unit 205, and the 2G processing unit 206. When a plurality of antennas 300 are provided, one antenna is provided for each of the LTE processing unit 204, the 3G processing unit 205, and the 2G processing unit 206.

The audio codec control unit 202 is a circuit that controls processing related to encoding of an audio signal. The UIM card 207 is an IC card that stores information such as a telephone number and a subscriber identification number, and is detachable from the mobile terminal 1. The message transmitting / receiving unit 210 is an interface circuit that connects the communication control CPU 201 and the application control unit 10 (CPU 101).

  The ROM / RAM 209 is a storage unit including a ROM, a volatile RAM, and a nonvolatile RAM. The volatile RAM includes a memory corresponding to the main memory. For example, a program related to communication control is stored in the nonvolatile RAM.

  The communication control CPU 201 is a processor that implements processing related to communication control by loading a program stored in the ROM / RAM 209 into the main memory and executing instructions included in the program.

  Note that the hardware configuration of the mobile terminal 1 is not limited to that shown in FIG. 2, and hardware components can be added, replaced, deleted, and the like as appropriate. The mobile terminal 1 is an example of the “communication device” in the aspect.

When switching the radio access network in which the mobile terminal 1 is located, the mobile terminal 1 switches the LTE processing unit 204, the 3G processing unit 205, and the 2G processing unit 206 that are set to be valid, and switches to the radio access network of the switching destination. A process for enabling intermittent reception of the paging channel from the network is performed. Therefore, switching the radio access network in the area is hereinafter referred to as switching RAT (Radio Access Technology). The radio access network itself is also referred to as RAT. The radio access network in which the mobile terminal 1 is located is hereinafter referred to as a visited RAT.

  FIG. 3 is a diagram illustrating an example of functional blocks of the mobile terminal 1. The application control unit 10 of the mobile terminal 1 includes a user interface processing unit 11, a call control unit 12, a RAT switching control unit 13, and a message transmission / reception unit 14 as functional blocks. The user interface processing unit 11, the call control unit 12, and the RAT switching control unit 13 are realized by the CPU 101 of the application control unit 10 executing programs stored in the ROM / RAM 107, respectively. The message transmission / reception unit 14 corresponds to the message transmission / reception unit 108 of the application control unit 10.

  The user interface processing unit 11 performs processing related to input / output for the user. For example, the user interface processing unit 11 receives a call request from a user through an operation on the touch panel 105 or an input button, and determines whether there is a RAT switching request to the receiving terminal. The presence / absence of the RAT switching request to the receiving terminal is input together with the transmission request by selecting the presence / absence of RAT switching by the user on the transmission screen displayed on the LCD 106, for example. When there is a RAT switching request of the called terminal, the user interface processing unit 11 notifies the call control unit 12.

  The call control unit 12 controls the user interface processing unit 11, the RAT switching control unit 13, and the message transmission / reception unit 14. More specifically, the call control unit 12 exchanges information among the user interface processing unit 11, the RAT switching control unit 13, and the message transmission / reception unit 14, for example. Further, the call control unit 12 makes an SMS message creation request to the RAT switching control unit 13. In addition, the call control unit 12 analyzes the SMS message received from another mobile terminal, and transmits a predetermined SMS message to the RAT switching control unit 13. The call control unit 12 transmits a call origination request.

The RAT switching control unit 13 performs processing related to RAT switching. More specifically, the RAT switching control unit 13 receives an SMS message creation request from the call control unit 12, for example, and receives an SMS message (for RAT switching request) for requesting RAT switching to the called terminal. SMS message). In addition, the RAT switching control unit 13 receives an SMS message for RAT switching request from the originating terminal, makes a RAT switching determination, and makes a RAT switching request to the communication control unit 20.

  The message transmission / reception unit 14 is an interface with the communication control unit 20, and exchanges information between the communication control unit 20 and the call control unit 12 of the application control unit 10.

  Next, the communication control unit 20 of the mobile terminal 1 includes a message transmission / reception unit 21, a call control unit 22, a radio network control unit 23, and a radio communication processing unit 24 as functional blocks. The call control unit 22, the wireless network control unit 23, and the wireless communication processing unit 24 are realized by the communication control CPU 201 of the communication control unit 20 executing programs stored in the ROM / RAM 209. The message transmission / reception unit 21 corresponds to the message transmission / reception unit 210 of the communication control unit 20.

  The message transmission / reception unit 21 is an interface with the application control unit 10, and exchanges information between the application control unit 10 and the call control unit 22 and the wireless network control unit 23 of the communication control unit 20.

  The call control unit 22 exchanges information between the message transmission / reception unit 21 and the wireless communication processing unit 24. When the call control unit 22 receives an incoming call request, the call control unit 22 executes incoming call processing for establishing a call with the originating terminal.

  The wireless network control unit 23 performs RAT switching when a RAT switching request is received from the application control unit 10 (RAT switching control unit 13). More specifically, the radio network control unit 23 switches the effective setting to the RAT processing unit designated by the RAT switching request among the LTE processing unit 204, the 3G processing unit 205, and the 2G processing unit 206. The wireless communication processing unit 24 is an interface with the wireless unit 203.

  FIG. 4 is a diagram illustrating an example of an SMS message for RAT switching request. The SMS message for the RAT switching request is created by the RAT switching control unit 13 when the originating terminal 1A receives the RAT switching request of the receiving terminal 1B together with the originating request from the user.

  The SMS message for RAT switching request includes a switching message flag and RAT information in the header. The switching message flag is a flag for indicating that the SMS message is an RAT switching request SMS message. The switching message flag is 1 bit. For example, when the switching message flag is 0, it is indicated that the message is a normal SMS message. For example, when the switching message flag is 1, it indicates that the SMS message is a RAT switching request.

  The RAT information is information indicating a radio access network in which the mobile terminal 1 that created the SMS message is located. The RAT information is, for example, 2 bits. For example, when the RAT information is 0 (decimal number), it indicates that the serving RAT is LTE. For example, when the RAT information is 1 (decimal number), it is indicated that the serving RAT is 3G. For example, when the RAT information is 2 (decimal number), it indicates that the serving RAT is 2G.

SMS is a service that can directly send a control message to the called terminal 1B using a signaling channel. The SMS message is transmitted from a processing unit (any of the LTE processing unit 204, the 3G processing unit 205, and the 2G processing unit 206) corresponding to the in-service RAT. In the first embodiment, the RAT switching request SMS message notifies the receiving terminal 1B of the RAT switching request to the receiving terminal 1B.

(Processing flow of mobile terminal)
FIG. 5 is an example of a flowchart of processing of the transmission-side terminal 1A in the first embodiment. The flowchart shown in FIG. 5 is a process performed by, for example, starting and executing a communication program when the CPU 101 of the application control unit 10 receives a call request from a user. That is, the flowchart shown in FIG. 5 is started when a call request is input from the user to the caller terminal 1A.

  In S1, the user interface processing unit 11 determines whether or not there is a RAT switching request. The call control unit 12 is notified of the determination result of the presence / absence of the RAT switching request. If there is a RAT switching request (S1: YES), the process proceeds to S2. If there is no RAT switching request (S2: NO), the process proceeds to S4.

  In S2, the RAT switching control unit 13 creates an SMS message for RAT switching request. In the SMS message for RAT switching request, for example, the switching message flag is set to 1 (switching), and the RAT information is set to a value indicating the in-service RAT of the originating terminal 1A. The call control unit 12 makes a request to create an SMS message for RAT switching request. Further, the RAT in the calling terminal 1A is acquired from the radio network control unit 23 of the communication control unit 20 by the call control unit 12, and is notified to the RAT switching control unit 13 together with a request for creating an SMS message for RAT switching request. The

  In S3, the RAT switching control unit 13 transmits an SMS message for RAT switching request. The RAT switching request SMS message is processed by the call control unit 12, the message transmission / reception unit 14, the message transmission / reception unit 21 of the communication control unit 20, the call control unit 22, the wireless communication unit 24, and the processing corresponding to the RAT within the wireless unit 203. To the receiving terminal 1B.

  In S4, the call control unit 12 transmits a call origination request to the called terminal 1B by the serving RAT. The transmission request is transmitted through the message transmission / reception unit 14, the message transmission / reception unit 21 of the communication control unit 20, the call control unit 22, the wireless communication unit 24, and the processing unit of the RAT in the wireless unit 203. For example, when an SMS message for RAT switching request is transmitted, the call control unit 12 may transmit a call request after a predetermined time has elapsed.

FIG. 6 is an example of a flowchart of processing of the receiving terminal 1B in the first embodiment.
The flowchart illustrated in FIG. 6 is a process performed by, for example, starting and executing a communication program when the CPU 101 of the application control unit 10 detects reception of an SMS message. That is, the flowchart shown in FIG. 6 is started when the receiving terminal 1B receives the SMS message. The SMS message is transmitted to the application control unit 10 via the RAT processing unit of the wireless unit 203, the wireless communication processing unit 24, the call control unit 22, the message transmission / reception unit 21, and the message transmission / reception unit 14 of the application control unit 10. Arrives at the call control unit 12.

In S11, the call control unit 12 of the application communication unit 10 determines whether or not the received SMS message is an RAT switching request SMS message. This determination is made based on the value of the switching message flag in the header of the SMS message. For example, when the switching message flag is 0, it is indicated that the message is a normal SMS message. For example, when the switching message flag is 1, it indicates that the SMS message is a RAT switching request. If the SMS message is an RAT switching request SMS message (S11: YES), the process proceeds to S12. When the SMS message is not a RAT switching request message (S11: NO), the processing shown in FIG. 6 is terminated, and the receiving terminal 1B does not switch the visiting RAT and does not switch the visiting RAT. Wait for an incoming request.

  In S12, the call control unit 12 transmits an SMS message for RAT switching request to the RAT switching control unit 13, and the RAT switching control unit 13 switches to the in-service RAT of the originating terminal 1A notified by the RAT switching request. Whether or not is possible is determined. The in-service RAT of the originating terminal 1A is included as RAT information in the SMS message for RAT switching request.

  If switching to the in-service RAT of the calling terminal 1A is possible (S12: YES), the process proceeds to S13. For example, when all the following conditions are satisfied, the RAT switching control unit 13 determines whether switching to the designated RAT is possible. The conditions are: (1) a processing unit corresponding to the designated RAT is provided in the wireless unit 203, (2) a radio wave of the designated RAT is detected, and (3) switching to the designated RAT. (4) The designated RAT is different from the in-zone RAT of the receiving terminal 1B.

  When the switching to the in-service RAT of the originating terminal 1A is impossible (S12: NO), the processing shown in FIG. 6 is terminated, and the receiving-side terminal 1B does not switch the in-service RAT and Wait for an incoming call request at the RAT in the service area. For example, (1) the processing unit corresponding to the designated RAT is not provided in the radio unit 203, (2) the radio wave of the designated RAT is not detected, and (3) switching to the designated RAT is not performed. (4) When the designated RAT and the in-service area RAT of the receiving terminal 1B are the same, the RAT switching control unit 13 determines that switching to the transmitting terminal 1A is impossible. To do.

  In S <b> 13, the RAT switching control unit 13 transmits a RAT switching request to the in-service RAT of the originating terminal 1 </ b> A to the wireless network control unit 23. The RAT switching request reaches the wireless network control unit 23 via the call control unit 12 of the application control unit 10, the message transmission / reception unit 14, and the message transmission / reception unit 21 of the communication control unit 20. When receiving the RAT switching request, the RAT switching control unit 13 performs a switching process to the in-service RAT of the calling terminal 1A. Thereafter, the processing shown in FIG. 6 ends, and the receiving terminal 1B waits for an incoming call request in the in-zone RAT.

(Concrete example)
FIG. 7 is a diagram illustrating an example of a processing sequence between the transmission-side terminal 1A and the reception-side terminal 1B from the input of the transmission request to the transmission-side terminal 1A to the establishment of communication. In the example shown in FIG. 7, the originating terminal 1A and the terminating terminal 1B have LTE, 3G, and 2G functions, and the serving RAT of the originating terminal 1A is the LTE and the serving terminal 1B. Assume that RAT is 3G. Further, it is assumed that the receiving terminal 1B detects LTE radio waves and is permitted to use LTE. Further, it is assumed that the sending terminal 1A and the receiving terminal 1B detect 3G radio waves and can send and receive SMS messages. Below, the processing sequence until communication origination terminal 1A and receiving side terminal 1B establish communication by LTE is demonstrated.

  In OP1, a call origination request and a RAT switching request for the callee terminal 1B are input from the user to the caller terminal 1A (FIG. 5, S1: YES). In OP2, originating terminal 1A creates an SMS message for RAT switching request (FIG. 5, S2). This SMS message is a message for notifying the terminating terminal 1B that the in-service area RAT of the originating terminal 1A is LTE. In the SMS message for RAT switching request, 1 (switching request) is set in the switching message flag, and 0 (LTE) is set in the RAT information. In OP3, the originating terminal 1A transmits an SMS message for RAT switching request to the terminating terminal 1B (FIG. 5, S3).

  In OP4, the receiving terminal 1B receives the SMS message for RAT switching request (FIG. 6, S11: YES), and the receiving terminal 1B can switch the RAT in LTE to the LTE (FIG. 6, S12: YES). ) Switching the serving RAT from 3G to LTE (FIG. 6, S13).

  In OP5, the caller terminal 1A makes a call request to the callee terminal 1B using LTE (FIG. 5, S4). In OP6, the receiving terminal 1B receives the incoming request from the transmitting terminal 1A via LTE, and performs incoming processing. When the incoming call processing is completed, communication between the caller terminal 1A and the callee terminal 1B is established, and the caller terminal 1A and the callee terminal 1B can communicate using the same RAT (LTE). .

(Operational effects of the first embodiment)
In the first embodiment, prior to sending a call request to the callee terminal 1B, the caller terminal 1A uses the SMS message to notify the callee terminal 1B of the in-service area RAT, and the callee terminal 1B is notified. In addition, processing for matching the serving RAT with the serving RAT of the originating terminal 1A is performed. As a result, in end-to-end communication between terminals, the RAT of the calling terminal 1A and the receiving terminal 1B can be matched, and stable communication quality can be maintained.

Second Embodiment
In the second embodiment, the receiving terminal 1B notifies the result of switching the RAT to the RAT notified by the SMS message for RAT switching request, and the calling terminal 1A receives the notification of the result. Transmits a call request to the receiving terminal 1B. In the second embodiment, descriptions overlapping with those in the first embodiment are omitted.

  In the second embodiment, the hardware configuration and functional configuration of the mobile terminal 1 are as shown in FIGS. In the second embodiment, when the RAT switching control unit 13 of the receiving side terminal executes the RAT switching process in response to the reception of the SMS message for the RAT switching request from the calling side terminal, the radio network control unit 23 The RAT switching result is acquired depending on whether or not the RAT switching request has been transmitted. When the RAT switching request has been transmitted to the radio network control unit 23 of the communication control unit 20, the RAT switching control unit 13 determines the RAT switching success as the RAT switching result. The RAT switching control unit 13 determines the RAT switching failure as the RAT switching result when the RAT switching request has not been transmitted to the radio network control unit 23 of the communication control unit 20.

  The RAT switching result is not limited to being acquired by determining whether or not a RAT switching request is transmitted from the RAT switching control unit 13 to the wireless network control unit 23 of the communication control unit 20. For example, after transmitting a RAT switching request to the radio network control unit 23, the RAT switching control unit 13 may inquire and acquire the RAT switching result from the radio network control unit 23.

  When the RAT switching control unit 13 acquires the RAT switching result, the RAT switching control unit 13 creates an SMS message for switching response for notifying the transmitting side terminal of the RAT switching result, and transmits it to the transmitting side terminal. The SMS message for switching response includes information on the RAT switching result and the in-service RAT (details will be described later).

  In addition, when the RAT switching control unit 13 of the calling terminal receives the switching response SMS message from the receiving terminal, the RAT switching control unit 13 extracts the RAT switching result from the SMS message. If the RAT switching result indicates success, the RAT switching control unit 13 notifies the call control unit 12 and the call control unit 12 transmits a call origination request. If the RAT switching result is unsuccessful, the RAT switching control unit 13 extracts the in-service area RAT of the called terminal from the switching response SMS message. The RAT switching control unit 13 determines whether or not the receiving terminal can be switched to the in-service area RAT. If the switching is possible, the RAT switching control unit 13 matches the in-service area terminal with the in-service area RAT. A RAT switching request is transmitted to the wireless network control unit 23 of the communication control unit 20.

  FIG. 8 is a diagram illustrating an example of an SMS message for switching response. The SMS message for switching response is created by the RAT switching control unit 13 when the receiving side terminal 1B receives the SMS message for RAT switching request from the calling side terminal.

  The switching response SMS message includes switching result information and RAT information in the header. The switching result information is information indicating the switching result of the called terminal to the in-service RAT notified by the SMS message for RAT switching request from the calling terminal. The switching result information is, for example, 1 bit. For example, when the switching result information is 0, it indicates successful switching to the in-service RAT of the calling terminal. For example, when the switching result information is 1, the failure of switching to the in-service RAT of the calling terminal is indicated.

  The RAT information is information indicating a radio access network in which the mobile terminal 1 that created the SMS message is located, and has been described with reference to FIG.

(Processing flow of mobile terminal)
FIG. 9 is an example of a flowchart of processing of the calling terminal 1A in the second embodiment. The flowchart shown in FIG. 9 is similar to the flowchart shown in FIG. 5, for example, when the CPU 101 of the application control unit 10 starts and executes a communication program when a call request is input from the user. This is a process to be performed.

  S21 to S23 are the same as the processing of S1 to S3 in FIG. 5 of the first embodiment, respectively. That is, in S21-S23, it is determined whether or not there is a RAT switching request accompanying a call request by a user input (S21). If there is a RAT switching request (S21: YES), an SMS message for RAT switching request is created. (S22) and transmitted to the receiving terminal 1B (S23). If there is no RAT switching request (S21: NO), the process proceeds to S29.

  In S24, when an SMS message for switching response is received from the receiving terminal 1B (S24: YES), the process proceeds to OP25. The SMS message for switching response from the receiving terminal 1B is sent to the RAT processing unit of the wireless unit 203, the call control unit 22 of the communication control unit 20, the message transmission / reception unit 21, and the message transmission / reception unit 14 of the application control unit 10. Then, it is input to the call control unit 12 of the application control unit 10. When the switching result information (see FIG. 8) is included in the SMS message, the call control unit 12 determines that the SMS message is an SMS message for switching response, and transmits the SMS message to the RAT switching control unit 13.

  When the SMS message for switching response is not received from the receiving terminal 1B (S24: NO), the process proceeds to OP29. For example, when the call control unit 12 does not receive the SMS message for switching response even after the elapse of a predetermined time after transmitting the SMS message for RAT switching request, that is, when a timeout occurs, the call control unit 12 performs SMS for switching response. Determine if no message was received.

  For example, in S23, after transmitting the RAT switching request SMS message received from the RAT switching control unit 13, the call control unit 12 includes in the ROM / RAM 107 that it is waiting for a response from the receiving terminal 1B. Record in memory. For example, a flag indicating a response waiting state is used, and when the flag is turned on (set to 1), the response waiting state is recorded. When the SMS message for switching response from the receiving terminal 1B is received or when a timeout occurs, the call control unit 12 turns off the flag (sets it to 0), for example, to receive the memory. The record indicating that the terminal 1B is waiting for a response is deleted.

In S25, the RAT switching control unit 13 determines from the switching response SMS message whether or not the switching process of the in-service area RAT of the receiving terminal 1B is successful. This determination is performed by determining whether the switching result information in the header of the SMS message for switching response is, for example, 0 indicating success of the switching process of the in-service RAT or 1 indicating failure. . If the switching process of the in-service area RAT of the receiving terminal 1B is successful (S25: YES), the process proceeds to S29. If the in-service area RAT switching process of the receiving terminal 1B has failed (S25: NO), the process proceeds to S26.

  In S26, since the switching process of the in-service area RAT in the receiving terminal 1B has failed, the RAT switching control unit 13 adjusts the in-service area RAT of the calling terminal 1A to the receiving terminal 1B. It is determined whether switching to RAT is possible. The in-service area RAT of the receiving terminal 1B is acquired by the RAT information of the SMS message for switching response (see FIG. 8).

  If the incoming terminal 1B can be switched to the in-service RAT (S26: YES), the process proceeds to S27. If switching to the in-service RAT of the receiving terminal 1B is impossible (S26: NO), the transmitting terminal 1A does not switch the in-service RAT, and the process proceeds to S29. The conditions for determining whether or not the RAT can be switched are the same as those described in the first embodiment, for example.

  In S <b> 27, the RAT switching control unit 13 transmits a RAT switching request to the in-service RAT of the receiving terminal 1 </ b> B to the wireless network control unit 23. The RAT switching request reaches the wireless network control unit 23 via the call control unit 12 of the application control unit 10, the message transmission / reception unit 14, and the message transmission / reception unit 21 of the communication control unit 20. Upon receiving the RAT switching request, the wireless network control unit 23 performs a switching process to the in-service RAT of the receiving terminal 1B.

  In S28, the RAT switching control unit 13 acquires the result of the switching process to the in-service RAT of the receiving terminal 1B in S27. This determination is made based on, for example, whether or not the RAT switching control unit 13 has transmitted a RAT switching request to the radio network control unit 23 of the communication control unit 20. Further, for example, the RAT switching control unit 13 may make an inquiry to the wireless network control unit 23 of the communication control unit 20 and acquire the result of the switching process of the in-service RAT. The result of the switching process of the in-service RAT is notified to the call control unit 12.

  In S29, the call control unit 12 transmits a call origination request to the receiving terminal 1B through the visited RAT. The transmission request is transmitted through the message transmission / reception unit 14, the message transmission / reception unit 21 of the communication control unit 20, the call control unit 22, the wireless communication unit 24, and the processing unit of the RAT in the wireless unit 203. When the RAT switching request is not input from the user (S21: NO), or when the SMS message for switching response is not received from the receiving terminal 1B (S24: NO), the switching process of the in-service area RAT of the receiving terminal 1B is successful. In the case (S25: YES), when the switching to the in-service RAT of the receiving terminal 1B is impossible (S26: NO), the switching process to the in-service RAT of the receiving terminal 1B fails (S28). The caller side terminal 1A makes a call request using the RAT at the start of the process shown in FIG. When the switching process to the in-service RAT of the receiving terminal 1B is successful (S28), the transmitting terminal 1A is the in-service RAT after the switching, and the receiving terminal 1B at the start of the process shown in FIG. A call origination request is made by the RAT in the area.

  FIG. 10 is a diagram illustrating an example of a flowchart of processing of the receiving terminal 1B in the second embodiment. The flowchart illustrated in FIG. 10 is a process performed by, for example, starting and executing a communication program when the CPU 101 of the application control unit 10 detects reception of an SMS message.

The processes of S31 to S33 are the same as the processes of S11 to S13 of FIG. 6 of the first embodiment, respectively. In S31-S33, it is determined whether or not the SMS message is a RAT switching request SMS message (S31). If the SMS message is a RAT switching request SMS message (S31: YES), the originating terminal 1A Switching processing to the in-service RAT is executed (S32: YES, S33). When the SMS message is not a RAT switching request message (S31: NO), the processing shown in FIG. 10 is terminated, and the receiving terminal 1B does not switch the visiting RAT and does not switch the visiting RAT. Wait for an incoming request. If the originating terminal 1A cannot switch to the in-service RAT (S32: NO), the receiving terminal 1B does not switch the in-service RAT, and the process proceeds to S35.

  In S34, the RAT switching control unit 13 acquires the result of the switching process to the in-service RAT of the calling terminal 1A. This determination is made based on, for example, whether or not the RAT switching control unit 13 has transmitted a RAT switching request to the radio network control unit 23 of the communication control unit 20. Further, for example, the RAT switching control unit 13 may make an inquiry to the wireless network control unit 23 of the communication control unit 20 and acquire the result of the switching process of the in-service RAT. The result of the switching process of the in-service RAT is notified to the call control unit 12. The call control unit 12 transmits an SMS message creation request for switching response to the RAT switching control unit 13.

  In S35, the RAT switching control unit 13 receives the request for creating the SMS message for switching response from the call control unit 12, and creates the SMS message for switching response. When the switching process of the originating terminal 1A notified by the SMS message for RAT switching request to the in-service RAT is successful, for example, the switching result information of the SMS message for switching response is 0 (success), the RAT information Is set to a value indicating the RAT in the calling terminal 1A. When the switching process to the in-service area RAT of the calling side terminal 1A fails, and when it is determined in S32 that the switching to the in-service area RAT of the calling side terminal 1A is impossible, for example, an SMS message for switching response The switching result information is set to 1 (failure), and the RAT information is set to a value indicating the in-service RAT of the originating terminal 1A.

  In S36, the RAT switching control unit 13 transmits an SMS message for switching response. The switching response SMS message is transmitted through the call control unit 12, the message transmission / reception unit 14, the message transmission / reception unit 21 of the communication control unit 20, the call control unit 22, the wireless communication unit 24, and the in-service RAT processing unit of the wireless unit 203. It is transmitted to the side terminal 1A. Thereafter, the processing shown in FIG. 10 ends, and the receiving terminal 1B waits for an incoming call request in the in-zone RAT.

(Concrete example)
FIG. 11 is a diagram illustrating an example of a processing sequence between the transmission-side terminal 1A and the reception-side terminal 1B from the input of the transmission request to the transmission-side terminal 1A to the establishment of communication. The premise of the example shown in FIG. 11 is the same as the example shown in FIG. Below, the processing sequence until communication origination terminal 1A and receiving side terminal 1B establish communication by LTE is demonstrated.

  In OP11, a transmission request and a RAT switching request for the receiving terminal 1B are input from the user to the transmitting terminal 1A (FIG. 9, S21: YES). In OP12, the originating terminal 1A creates an SMS message for RAT switching request (FIG. 9, S22). This SMS message is a message for notifying the terminating terminal 1B that the in-service area RAT of the originating terminal 1A is LTE. In the SMS message for RAT switching request, 1 (switching request) is set in the switching message flag, and 0 (LTE) is set in the RAT information. In OP13, the originating terminal 1A transmits an SMS message for RAT switching request to the terminating terminal 1B (FIG. 9, S23).

  In OP14, the receiving terminal 1B receives the SMS message for RAT switching request (FIG. 10, S31: YES), and the receiving terminal 1B can switch the RAT in LTE to the LTE (FIG. 10, S32: YES). ) Switching the in-service RAT from 3G to LTE (FIG. 10, S33). The receiving terminal 1B has the LTE function, detects the LTE radio wave, and is permitted to use the LTE, so the switching of the in-service RAT to the LTE is successful (FIG. 10, S34).

  In OP15, the receiving terminal 1B creates a switching response SMS message that notifies the result of the switching process of the RAT to the RAT (LTE) of the calling terminal 1A (FIG. 10, S35). Since switching of the in-service RAT to LTE was successful, the switching response SMS message is set to 0 (successful) and 0 (LTE) to the RAT information in the switching result information. In OP16, the receiving terminal 1B transmits an SMS message for switching response to the transmitting terminal 1A (FIG. 10, S36).

  In OP17, the originating side terminal 1A receives the SMS message for switching response, and the terminating side terminal 1B has successfully switched the in-service RAT to LTE (FIG. 9, S24: YES, S25: YES). A transmission request is transmitted to the side terminal 1B through LTE (FIG. 9, S29).

  In OP18, the receiving terminal 1B receives the incoming request from the transmitting terminal 1A via LTE, and performs incoming processing. When the incoming call processing is completed, communication between the caller terminal 1A and the callee terminal 1B is established, and the caller terminal 1A and the callee terminal 1B can communicate using the same RAT (LTE). .

  FIG. 12 is a diagram illustrating an example of a processing sequence between the transmission-side terminal 1A and the reception-side terminal 1B from the input of the transmission request to the transmission-side terminal 1A to the establishment of communication. In the example shown in FIG. 12, the premise of the transmission side terminal 1 </ b> A is the same as the example shown in FIG. 7. On the other hand, it is assumed that the receiving terminal 1B does not have an LTE function and cannot select LTE as a RAT. It is assumed that the receiving terminal 1B is located in 3G. Further, it is assumed that the sending terminal 1A and the receiving terminal 1B detect 3G radio waves and can send and receive SMS messages. Hereinafter, a processing sequence until communication is established between the caller terminal 1A and the callee terminal 1B when the callee terminal 1B cannot be switched to the in-service RAT of the caller terminal 1A will be described.

  The processing of OP21-OP23 is the same as the processing of OP11-OP13 of FIG.

  In OP24, the receiving side terminal 1B receives the SMS message for RAT switching request from the calling side terminal 1A (FIG. 10, S31: YES), and the receiving side terminal 1B does not have the LTE function. It is determined that the in-service area RAT cannot be switched (FIG. 10, S32: NO).

  In OP25, the receiving terminal 1B creates a switching response SMS message that notifies the result of the switching process of the in-service RAT to the in-service RAT (LTE) of the originating terminal 1A (FIG. 10, S35). Since switching of the in-service RAT to LTE is impossible, 1 (failure) is set in the switching result information and 1 (3G) is set in the RAT information in the SMS message for switching response. In OP26, the receiving terminal 1B transmits an SMS message for switching response to the transmitting terminal 1A (FIG. 10, S36).

  In OP27, the originating terminal 1A receives the switching response SMS message (FIG. 9, S24: YES), and the terminating terminal 1B has failed to switch the RAT in the LTE to the LTE (FIG. 9, S25: NO). ), The in-service RAT is switched to 3G (S26: YES, S27, S28). Here, if the calling side terminal 1A has a 3G function and detects 3G radio waves, the calling side terminal 1A successfully switches the in-service RAT to 3G (FIG. 9, S28). ). In OP28, the calling terminal 1A transmits a call request through 3G to the receiving terminal 1B (S29 in FIG. 9).

  In OP29, the receiving terminal 1B receives the incoming request from the transmitting terminal 1A via 3G, and performs incoming processing. When the incoming call processing is completed, communication between the calling terminal 1A and the called terminal 1B is established, and the calling terminal 1A and the called terminal 1B can communicate using the same RAT (3G). .

(Operational effect of the second embodiment)
In the second embodiment, the receiving terminal 1B notifies the calling terminal 1A of the result of the switching process to the in-service RAT of the calling terminal 1A notified by the SMS message for RAT switching request. As explained in FIG. 11, when the receiving terminal 1B can switch to the visiting RAT of the calling terminal 1A, the receiving terminal 1B changes the visiting RAT to the visiting RAT of the calling terminal 1A. Switch. In addition, the caller terminal 1A transmits a call request to the callee terminal 1B after receiving the notification of the switching result. As a result, the RATs of the calling terminal 1A and the receiving terminal 1B can be matched more reliably.

  In addition, as described with reference to FIG. 12, when the receiving terminal 1B cannot switch to the in-service area RAT of the transmitting side terminal 1A, the initiating terminal 1A receives the notification of the switching result and then returns to the in-service area RAT. Is switched to the in-service area RAT of the receiving terminal 1B, and a call request to the receiving terminal 1B is transmitted. Therefore, according to the second embodiment, even when the receiving terminal 1B cannot switch to the in-service RAT of the calling terminal 1A, the RAT between the calling terminal 1A and the receiving terminal 1B can be matched.

<Third Embodiment>
In the third embodiment, the destination terminal 1B confirms whether or not to switch the parked RAT before the switching process of the parked RAT by the user, and when the switching of the parked RAT is permitted by the user, Is switched. In 3rd Embodiment, the description which overlaps with 1st Embodiment and 2nd Embodiment is abbreviate | omitted.

  Also in the third embodiment, the hardware configuration and functional configuration of the mobile terminal 1 are as shown in FIGS. In the third embodiment, in addition to the processing described in the second embodiment, the RAT switching control unit 13 and the user interface processing unit 11 perform the following processing.

  When the RAT switching control unit 13 of the receiving terminal 1B receives the RAT switching request from the calling terminal 1A, the RAT switching control unit 13 determines whether or not it is necessary to make an inquiry about whether or not RAT switching is possible. For example, the RAT switching control unit 13 determines the execution of the RAT switching inquiry to the user when all of the following conditions are satisfied. The execution conditions of the RAT switching inquiry are, for example, (1) the receiving terminal 1B has a function of the RAT of the calling terminal 1A, and (2) the RAT of the receiving terminal 1B is the calling terminal 1A. Different from the in-zone RAT, (3) the in-zone RAT is fixed to any one RAT. If any one of these conditions is not satisfied, the RAT switching query is not executed. When it is determined that an inquiry about whether or not the user can perform RAT switching is performed, the RAT switching control unit 13 transmits a RAT switching inquiry request to the user interface processing unit 11.

  Upon receiving the RAT switching inquiry request from the RAT switching control unit 13, the user interface processing unit 11 causes the LCD 106 to output a RAT switching inquiry screen. The RAT switching inquiry screen is a screen for allowing the user to select whether or not RAT switching is possible, and is stored in the ROM / RAM 107. The user interface processing unit 11 receives an operation input of the touch panel 105 for the RAT switching inquiry screen from the user, and notifies the RAT switching control unit 13 of whether or not the RAT switching selected by the user is possible.

The RAT switching control unit 13 determines that the in-service RAT switching process is not to be executed when RAT switching rejection is selected by the user.

  FIG. 13 is an example of a RAT switching inquiry screen. The RAT inquiry screen is displayed on the LCD 106 when the receiving terminal 1B receives the SMS reception message for RAT switching request from the calling terminal 1A and, for example, meets the above-mentioned predetermined condition.

  The RAT inquiry screen includes a message for notifying that switching of the in-service RAT is requested from the originating terminal 1A, and a button for selecting whether or not to switch the in-service RAT. For example, in the example shown in FIG. 13, the message “A request to switch the visited network is received from XXX (phone number). Do you want to switch the visited network to LTE?” And the presence of OK and NG A block including a button for selecting whether or not the area RAT can be switched is displayed as a pop-up. When a pressing operation is performed on the OK button, permission to switch the in-service RAT is input. When a pressing operation is performed on the NG button, switching refusal of the in-service RAT is input.

  FIG. 14 is an example of a flowchart of processing of the receiving terminal 1B in the third embodiment. The flowchart illustrated in FIG. 14 is a process performed by, for example, starting and executing a communication program when the CPU 101 of the application control unit 10 detects reception of an SMS message.

  In S41, as in S11 of FIG. 6 of the first embodiment, the call control unit 12 of the application communication unit 10 determines whether or not the received SMS message is an RAT switching request SMS message. If the SMS message is an RAT switching request SMS message (S41: YES), the process proceeds to S42. If the SMS message is not a message for RAT switching request (S41: NO), the processing shown in FIG. 10 ends, and the receiving terminal 1B does not switch the visiting RAT and does not switch the visiting RAT. Wait for an incoming request.

  In S42, the RAT switching control unit 13 determines whether or not a RAT switching inquiry is required for the user. This determination can be made, for example, by (1) the receiving terminal 1B having the function of the RAT in the calling terminal 1A, and (2) the RAT in the receiving terminal 1B being the RAT in the calling terminal 1A. It is different depending on whether or not all (3) the in-service RAT is fixedly set to any one RAT. If it is determined that the RAT switching inquiry is made to the user (S42: YES), the process proceeds to S43. If execution of the RAT switching inquiry to the user is not determined (S42: NO), the process proceeds to S45.

  In S 43, the RAT switching control unit 13 transmits a RAT switching inquiry request to the user interface processing unit 11, and the user interface processing unit 11 outputs a RAT switching inquiry screen to the LCD 106. Thereby, the RAT switching inquiry screen is displayed.

  In S44, when the RAT switching control unit 13 detects an RAT switching permission input from the user (S44: YES), the process proceeds to S45. When the RAT switching control unit 13 detects an RAT switching rejection input from the user (S44: NO), the in-service RAT switching process is not executed, and the process proceeds to S48.

In S45, the RAT switching control unit 13 determines whether or not switching to the in-service RAT of the calling terminal 1A notified by the SMS message for RAT switching request is possible. If the calling terminal 1A can be switched to the in-service RAT (S45: YES), the process proceeds to S46. For example, when all the following conditions are satisfied, the RAT switching control unit 13 determines whether switching to the designated RAT is possible. The conditions are: (1) the radio unit 203 has a processing unit corresponding to the designated RAT, (2) the radio wave of the designated RAT is detected, and (3) the designated R
Switching to AT is permitted by the user. (4) The designated RAT is different from the in-zone RAT of the receiving terminal 1B. Note that (3) the user is permitted to switch to the designated RAT includes that the RAT switching permission is input from the user in S44.

  If switching to the in-service RAT of the originating terminal 1A is impossible (S45: NO), the process proceeds to S48. For example, (1) the processing unit corresponding to the designated RAT is not provided in the radio unit 203, (2) the radio wave of the designated RAT is not detected, and (3) switching to the designated RAT is not performed. (4) When the designated RAT and the in-service area RAT of the receiving terminal 1B are the same, the RAT switching control unit 13 determines that switching to the transmitting terminal 1A is impossible. To do.

  The processing from S46 to S49 is the same as S33 to S36 in FIG. 10 of the second embodiment. In addition, when RAT switching refusal is input from the user in S44 (S44: NO), an SMS message is created as the switching failure of the originating terminal 1A to the in-service RAT. Thereafter, the processing shown in FIG. 14 ends, and the receiving terminal 1B waits for an incoming call request in the in-zone RAT.

<Operational effects of the third embodiment>
In the third embodiment, the receiving terminal 1B confirms whether or not the parked RAT can be switched before the switching process of the visited RAT. As a result, for example, the receiving terminal 1B can switch the serving RAT with the permission of the user even when the serving RAT is fixed to any RAT.

  The execution conditions for the RAT switching inquiry are not limited to those described above, and are set as appropriate according to the operation of the system. For example, regardless of whether there is a fixed RAT user setting in the receiving terminal 1B, every time the RAT switching process is performed by receiving the SMS message for RAT switching request, the user can perform RAT switching. An inquiry about availability may be made.

<Others>
In the first to third embodiments, the SMS message is used for information exchange between the caller terminal 1A and the callee terminal 1B before establishing communication, but the present invention is not limited to this. For example, any protocol that can transmit a control message to the mobile terminal 1 of the communication partner can be used for information exchange between the calling terminal 1A and the receiving terminal 1B before the communication is established. .

  In the first to third embodiments, the RAT used by the originating terminal 1A and the RAT used by the originating terminal 1A to notify the terminating terminal 1B of the located RAT are the same radio. Described as being an access network. Also for the receiving terminal 1B, the in-service RAT and the RAT used for receiving the notification of the in-service RAT from the originating terminal 1A have been described as being the same radio access network. However, the RAT used by the originating terminal 1A and the RAT used by the originating terminal 1A to notify the terminating RAT to the terminating terminal 1B may be different radio access networks. Also for the receiving terminal 1B, the in-service RAT and the RAT used for receiving the notification of the in-service RAT from the transmitting terminal 1A may be different radio access networks.

  In the first to third embodiments, LTE, 3G, and 2G are taken as examples of RATs. However, RATs to which the first to third embodiments are applied are not limited to these, and Wi-Fi, Both the wireless LAN and the RAT that will appear in the future are subject to application of the first to third embodiments.

DESCRIPTION OF SYMBOLS 1 Mobile terminal 10 Application control part 11 User interface processing part 12 Call control part 13 RAT switching control part 14 Message transmission / reception part 20 Communication control part 21 Message transmission / reception part 22 Call control part 23 Wireless network control part 24 Wireless communication processing part

Claims (8)

A communication system comprising: an originating communication device that can use a plurality of radio access networks; and an incoming communication device that can use at least one of the plurality of radio access networks,
The calling-side communication device includes a storage device and a processor,
The processor is
A first radio access network of the plurality of radio access networks is set as a radio access network used for communication;
Notifying the first communication device as the wireless access network used for the communication,
The called communication device includes a storage device and a processor,
The processor is
Receiving a notification of the first radio access network from the originating communication device;
Determining whether the setting of the radio access network used by the called communication device can be switched to the first radio access network;
When switching to the first radio access network is possible, the setting of the radio access network used by the destination communication device is switched to the first radio access network;
Communications system. The processor of the called communication device is:
The communication system according to claim 1, wherein a result of switching to the first radio access network is notified to the originating communication device. The processor of the originating communication device is:
Receiving the switching result notified from the receiving communication device;
When the switching result indicates that switching to the first radio access network is successful, a call origination request to the called communication device is transmitted.
The communication system according to claim 2. The processor of the called communication device is:
When the switching to the first radio access network is impossible, the switching result is that the switching to the first radio access network is impossible, and the receiving communication device uses the communication to communicate with the first radio access network. A second radio access network different from the network,
The processor of the originating communication device is:
When the switching result indicates that switching to the first radio access network is impossible, the setting of the radio access network used for communication is switched to the second radio access network notified by the switching result;
The communication system according to claim 3. A communication device capable of using a plurality of radio access networks,
A storage device and a processor;
The processor is
A first radio access network of the plurality of radio access networks is set as a radio access network used for communication,
Notifying the first wireless access network as the first wireless access network to a communication device of a communication partner;
Communication device. A communication device that can use one or more radio access networks,
A storage device and a processor;
The processor is
Receiving a notification of the first radio access network used for communication by the communication device of the communication partner from the communication device of the communication partner;
Determining whether the setting of the wireless access network to be used can be switched to the first wireless access network;
When switching to the first radio access network is possible, the setting of the radio access network to be used is switched to the first radio access network;
Communication device. In a communication system including a transmission side communication device that can use a plurality of radio access networks and a reception side communication device that can use at least one of the plurality of radio access networks,
The originating communication device is
A first radio access network of the plurality of radio access networks is set as a radio access network used for communication,
Notifying the first communication device as the wireless access network used for the communication,
The called communication device is
Receiving a notification of the first radio access network from the originating communication device;
Determining whether the setting of the radio access network used by the called communication device can be switched to the first radio access network;
When switching to the first radio access network is possible, the setting of the radio access network used by the destination communication device is switched to the first radio access network;
Communication method. In a communication system including a transmission side communication device that can use a plurality of radio access networks and a reception side communication device that can use at least one of the plurality of radio access networks,
In the calling side communication device,
A first radio access network of the plurality of radio access networks is set as a radio access network used for communication;
Let the first communication device be notified of the first wireless access network as a wireless access network used for the communication;
In the incoming communication device,
Receiving a notification of the first radio access network from the originating communication device;
Determining whether the setting of the radio access network used by the called communication device can be switched to the first radio access network;
When switching to the first radio access network is possible, the setting of the radio access network used by the called communication device is switched to the first radio access network.
Communication program for.

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