Terminal device, communication method, and program

Abstract

To prevent interruption of sound.SOLUTION: A terminal device comprises: a communication unit that communicates with another terminal device on the other end of the line; a communication detection unit that detects a communication state of a server device; a communication determination unit that determines whether it is necessary to switch the connection from a first server device to a second server device which is different from the first server device; a switch request unit that, when a determination is made to switch the connection to the second server device, transmits, to the other terminal device, a switch request signal to switch the connection to the second terminal device; and a communication switching unit that, when a switch preparation completion signal indicating that switching the connection to the second server device is ready is received from the other terminal device, stops transmission of sound information to the first server device, and switches the connection from the first server device to the second server device.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a terminal device, a communication method, and a program.

Background Art

[0002] A PoC (Push-To-Talk over Cellular) system is known in which a PoC terminal device and a PoC server device are connected by a wireless network such as LTE (Long Term Evolution) and a wired network such as an optical fiber line (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a PoC system, depending on the usage environment, when the communication quality deteriorates or a delay occurs in a voice call, it may be considered to switch the connected server device and continue the voice call. However, if the server device to be connected is switched during a voice call, it takes time to connect to the new server device and resume the call, and there is a possibility that the voice will be interrupted due to loss or retransmission of voice packets.

[0005] An object of the present invention is to provide a terminal device, a communication method, and a program that can easily switch a server device.

Means for Solving the Problems

[0006] The terminal device of the present invention is a terminal device that communicates with a communication partner's terminal device via a server device, and comprises: a communication unit that communicates with the communication partner's terminal device; a communication detection unit that detects the communication status of the server device; a communication determination unit that determines whether it is necessary to switch the connection target from a first server device to a second server device different from the first server device based on the detection result of the communication detection unit; a switching request unit that, if the communication determination unit determines that it is necessary to switch the connection target to the second server device, transmits a switching request signal to the communication partner's terminal device requesting that it switch the connection target to the second server device; and a communication switching unit that, when it receives a switching readiness complete signal from the communication partner's terminal device indicating that it has finished preparing to switch the connection target to the second server device, stops transmitting voice information to the first server device and switches the connection target from the first server device to the second server device.

[0007] The terminal device of the present invention is a terminal device that communicates with a communication partner's terminal device via a server device, and comprises a connection management unit that generates information relating to connections with a plurality of server devices, and a communication unit that establishes connections with the plurality of server devices and communicates with the communication partner's terminal device, wherein when the connection management unit receives the same voice information transmitted from the communication partner's terminal device to each of the plurality of server devices via the plurality of server devices, it receives a switching request signal transmitted from the communication partner's terminal device via any of the plurality of server devices, determines whether it is possible to switch the server device to be connected, and if it is possible to switch the server device to be connected, it controls the device to receive voice information only from the server device identified based on the switching request signal, and controls the device to transmit a switching readiness signal to the communication partner's terminal device.

[0008] The present invention is a communication method for communicating with a terminal device of a communication partner via a server device, and includes the steps of: communicating with the terminal device of the communication partner; detecting the communication status of the server device; determining, based on the detection result, whether it is necessary to switch the connection target from the first server device to a second server device different from the first server device; if it is determined that it is necessary to switch the connection target to the second server device, sending a switching request signal to the terminal device of the communication partner requesting that the connection target be switched to the second server device; and, upon receiving a switching readiness signal from the terminal device of the communication partner indicating that preparations for switching the connection target to the second server device have been completed, stopping the transmission of voice information to the first server device and switching the connection target from the first server device to the second server device.

[0009] The present invention is a program that causes a computer to execute a program that communicates with a terminal device of a communication partner via a server device, and causes the computer to execute the following steps: communicating with the terminal device of the communication partner; detecting the communication status of the server device; determining, based on the detection result, whether or not it is necessary to switch the connection target from the first server device to a second server device different from the first server device; if it is determined that it is necessary to switch the connection target to the second server device, sending a switching request signal to the terminal device of the communication partner requesting that the connection target be switched to the second server device; and when a switching readiness complete signal is received from the terminal device of the communication partner indicating that preparations for switching the connection target to the second server device have been completed, stopping the transmission of voice information to the first server device and switching the connection target from the first server device to the second server device. [Effects of the Invention]

[0010] According to the present invention, server devices can be easily switched. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 shows an example of the configuration of a communication system according to an embodiment. [Figure 2] Figure 2 is a block diagram showing an example configuration of a terminal device according to an embodiment. [Figure 3] Figure 3 is a block diagram showing an example configuration of a server device according to the embodiment. [Figure 4] Figure 4 is a flowchart showing the processing details of the terminal device according to this embodiment. [Figure 5] Figure 5 is a flowchart showing the processing details of the transmitting terminal device according to this embodiment. [Figure 6] Figure 6 is a sequence diagram showing the processing details of the communication system according to the embodiment. [Modes for carrying out the invention]

[0012] Embodiments of the present invention will be described in detail below with reference to the attached drawings. However, the present invention is not limited by these embodiments, and in the following embodiments, the same parts are denoted by the same reference numerals to omit redundant explanations.

[0013] [Embodiment] An example of the configuration of a communication system according to the embodiment will be described using Figure 1. Figure 1 is a diagram showing an example of the configuration of a communication system according to the embodiment.

[0014] As shown in Figure 1, the communication system 1 includes server device 12-1, server device 12-2, server device 12-3, terminal device 10-1, and terminal device 10-2. Server devices 12-1 to 12-3 are sometimes collectively referred to as server device 12. Terminal devices 10-1 and 10-2 are sometimes collectively referred to as terminal device 10. The communication system 1 includes three server devices 12, from server device 12-1 to server device 12-3, but the present invention is not limited to these. The communication system 1 also includes two terminal devices 10, from terminal device 10-1 to terminal device 10-2, but the present invention is not limited to these.

[0015] Server devices 12-1 to 12-3 are PoC servers. Terminal devices 10-1 and 10-2 are PoC terminals. That is, communication system 1 is a system corresponding to PoC.

[0016] Server devices 12-1 to 12-3 have registered terminal devices 10-1 and 10-2 as terminal devices included in communication system 1, respectively. Server devices 12-1 to 12-3 store the same registration information such as group settings regarding terminal devices 10-1 and 10-2, respectively. Server devices 12-1 to 12-3 do not communicate with other server devices 12. Server devices 12-1 to 12-3 can identify terminal device 10 that is communicating.

[0017] Terminal device 10-1 is connected to server device 12-1 via network N1. Terminal device 10-1 is connected to server device 12-2 via network N2. Terminal device 10-1 is connected to server device 12-3 via network N3. That is, terminal device 10-1 is connected to server devices 12-1 to 12-3 via different networks, respectively. Terminal device 10-1 can maintain communication sessions with each of server devices 12-1 to 12-3.

[0018] Terminal device 10-2 is connected to server device 12-1 via network N4. Terminal device 10-2 is connected to server device 12-2 via network N5. Terminal device 10-3 is connected to server device 12-3 via network N6. That is, terminal device 10-2 is connected to server devices 12-1 to 12-3 via different networks, respectively. Terminal device 10-2 can maintain communication sessions with each of server devices 12-1 to 12-3.

[0019] Networks N1 to N6 are networks including wireless networks and wired networks. When there is no need to distinguish between networks N1 to N6, they may be collectively referred to as network N. Here, in the network connection between terminal devices 10-1 and 10-2 and server device 12, it is desirable that communication sessions be established for networks N1 to N6 as different communication connections and communication paths respectively. The different communication connections and communication paths may be based on physically different communication channels, logically different communication channels, different communication methods, different frequencies, or different time slots. Terminal devices 10-1 and 10-2 may be configured to be connected to such different networks in multiple ways so that multi-session connection is possible.

[0020] Terminal devices 10-1 and 10-2 each store information regarding server device 12 that can be connected to each other.

[0021] (Terminal device) Using FIG. 2, a configuration example of the terminal device according to the embodiment will be described. FIG. 2 is a block diagram showing a configuration example of the terminal device according to the embodiment.

[0022] As shown in FIG. 2, terminal device 10 includes an input unit 20, a display unit 22, a microphone 24, a speaker 26, a storage unit 28, a communication unit 30, and a control unit 32.

[0023] Input unit 20 receives various input operations for terminal device 10. Input unit 20 outputs an operation signal corresponding to the received input operation to control unit 32. Input unit 20 includes, for example, a touch panel, buttons, switches, a PTT (Push-to-Talk) button, etc. When a touch panel is used as input unit 20, input unit 20 is arranged on display unit 22.

[0024] The display unit 22 displays various types of images. The display unit 22 is a display including, for example, a liquid crystal display or an organic EL (Electro-Luminescence) display.

[0025] Microphone 24 is a microphone that detects sounds in the vicinity of the terminal device 10. Microphone 24 detects the voice of the user using the terminal device 10. Microphone 24 converts the detected sound into an audio signal.

[0026] Speaker 26 is a speaker that outputs various types of sound.

[0027] The memory unit 28 stores various types of information. The memory unit 28 stores the calculation contents of the control unit 32 and information such as programs. The memory unit 28 includes, for example, at least one of the following: RAM (Random Access Memory), main memory such as ROM (Read Only Memory), and external memory such as HDD (Hard Disk Drive).

[0028] The communication unit 30 is a communication interface that performs communication between the terminal device 10 and an external device. The communication unit 30 also performs communication between the terminal device 10 and the server device 12.

[0029] The control unit 32 controls each part of the terminal device 10. The control unit 32 includes, for example, an information processing device such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit), and a storage device such as RAM or ROM. The control unit 32 executes a program that controls the operation of the terminal device 10 according to the present invention. The control unit 32 may be implemented by an integrated circuit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array). The control unit 32 may be implemented by a combination of hardware and software.

[0030] The control unit 32 includes a connection management unit 40, a communication detection unit 42, a communication determination unit 44, an audio information transmission unit 46, a switching request unit 48, a communication switching unit 50, an audio information generation unit 52, and a codec unit 54.

[0031] The connection management unit 40 establishes connections with multiple server devices 12 included in the communication system 1. Specifically, the connection management unit 40 establishes connections with multiple server devices 12 by requesting registration from each of the server devices 12.

[0032] The communication detection unit 42 detects the communication status with the server device 12. Specifically, the communication detection unit 42 detects the communication status with the server device 12, which is the current connection target. The communication detection unit 42 may, for example, detect the bitrate as a communication status, but is not limited to this. Based on the communication status, the communication detection unit 42 detects the length of the delay that occurred in the communication with the server device 12, which is the current connection target. The method for detecting the delay that occurred in the communication can be a well-known method and is not limited to this. The server device 12, which is the current connection target, is also called the first server device.

[0033] The communication determination unit 44 determines, based on the communication status detection result by the communication detection unit 42, whether or not it is necessary to switch the connection target from the currently connected server device 12 to another server device 12. For example, the communication determination unit 44 determines to switch the connection target to another server device 12 if the delay in communication with the currently connected server device 12 exceeds a predetermined level. The server device 12 to be switched is also called the second server device.

[0034] The voice information transmission unit 46 generates voice information regarding the voice of the user of the terminal device 10 detected by the microphone 24 to the server device 12 that is currently connected and the server device 12 that is to be switched over, and transmits the generated voice information via the communication unit 30. In other words, the voice information transmission unit 46 transmits the same voice information to the server device 12 that is currently connected and the server device 12 that is to be switched over. The voice information transmission unit 46 may also transmit time information (timestamp) indicating the current time along with the voice information.

[0035] If the communication determination unit 44 determines that it is necessary to switch the connection target to another server device 12, the switching request unit 48 sends a switching request signal to the other server device 12.

[0036] The communication switching unit 50 switches the server device 12 that communicates with the terminal device 10. When the communication switching unit 50 receives a switching readiness signal from the currently connected server device 12 or the server device 12 to be switched, it switches the server device 12 to be connected from the currently connected server device 12 to the server device 12 to be switched. In this case, when the voice information transmission unit 46 switches the server device 12 to which communication is handled, it stops transmitting voice information to the currently connected server device 12.

[0037] The voice information generation unit 52 generates voice information. For example, the voice information generation unit 52 generates voice information to be sent to the server device 12 that is currently connected, based on the voice detected by the microphone 24. For example, the voice information generation unit 52 duplicates the voice information to be sent to the server device 12 that is currently connected, and generates voice information to be sent to the server device 12 that is to be switched over.

[0038] The codec unit 54 compresses audio information for transmission to the server device 12 using an arbitrary compression method. The codec unit 54 then decodes the audio information received from the server device 12.

[0039] An example of the configuration of a server device according to the embodiment will be described using Figure 3. Figure 3 is a block diagram showing an example of the configuration of a server device according to the embodiment.

[0040] As shown in Figure 3, the server device 12 comprises a communication unit 60, a storage unit 62, and a control unit 64.

[0041] The communication unit 60 is a communication interface that performs communication between the server device 12 and an external device. The communication unit 60 also performs communication between the server device 12 and the terminal device 10.

[0042] The memory unit 62 stores various types of information. The memory unit 62 stores the calculation contents of the control unit 64 and information such as programs. The memory unit 62 includes, for example, RAM and at least one of the following: a main memory device such as ROM, or an external memory device such as an HDD.

[0043] The control unit 64 controls each part of the server device 12. The control unit 64 includes, for example, an information processing device such as a CPU or MPU and a storage device such as RAM or ROM. The control unit 64 executes a program that controls the operation of the server device 12 according to the present invention. The control unit 64 may be implemented by an integrated circuit such as an ASIC or FPGA. The control unit 64 may be implemented by a combination of hardware and software.

[0044] The control unit 64 includes a registration management unit 70, a session management unit 72, a terminal information management unit 74, a group information management unit 76, a switching request signal management unit 78, and a switching readiness complete signal management unit 80.

[0045] The registration management unit 70 accepts registrations from each terminal device 10. The registration management unit 70 registers the terminal devices 10 that have accepted registrations as communication-enabled terminal devices 10.

[0046] The session management unit 72 manages the communication session with the terminal device 10. For example, the session management unit 72 transmits voice information received from terminal device 10 to other terminal devices 10.

[0047] The terminal information management unit 74 stores various information about the terminal device 10 that has received registration in the storage unit 62.

[0048] The group information management unit 76 manages group information related to the group to which the terminal device 10, stored in the storage unit 62, belongs.

[0049] The switching request signal management unit 78 manages the switching request signals received from the terminal device 10. The switching request signal management unit 78 transmits the switching request signals received from the terminal device 10 to other terminal devices 10.

[0050] The switching readiness signal management unit 80 manages the switching readiness signal. The switching readiness signal management unit 80 transmits the switching readiness signal received from the receiving terminal device 10 to the transmitting terminal device 10.

[0051] [Processing details] (Processing details of the receiving terminal device) The processing details of the receiving terminal device according to this embodiment will be explained using Figure 4. Figure 4 is a flowchart showing the processing details of the terminal device according to this embodiment.

[0052] In the following example shown in Figure 1, terminal device 10-1 is assumed to be the transmitting terminal device 10, and terminal device 10-2 is assumed to be the receiving terminal device 10. Furthermore, terminal devices 10-1 and 10-2 are assumed to establish sessions with server devices 12-1 and 12-2. Server device 12-1 is assumed to be the server device 12 currently being connected to.

[0053] The connection management unit 40 of terminal device 10-2 performs registration with server devices 12-1 and 12-2 (step S10). Then, the process proceeds to step S12.

[0054] The connection management unit 40 of terminal device 10-2 establishes a session with terminal device 10-1 via server device 12-1 (step S12). Then, the process proceeds to step S14.

[0055] The connection management unit 40 of terminal device 10-2 continuously receives voice information transmitted by terminal device 10-1 from server devices 12-1 and 12-2 respectively (step S14). Then, the process proceeds to step S16.

[0056] The connection management unit 40 of the terminal device 10-2 receives a switching request signal and determines whether or not switching of the server device to be connected is possible based on the switching request signal (step S16). If a switching request signal is received and it is determined that switching of the server device to be connected is possible (step S16; Yes), the process proceeds to step S18. If it is not determined that a switching request signal has been received (step S16; No), the process proceeds to step S14. Here, the determination of whether or not switching of the server device to be connected is possible may be made based on the communication quality of the network connected to the server device that received the switching request signal, and if it is determined that communication is possible, it may be determined that switching of the server device to be connected is possible. Alternatively, the determination of whether or not communication is possible may be made based on the communication status with the server device 12 detected by the communication detection unit 42. For example, if the delay in communication with the server device 12 that is to be switched is not above a predetermined level, it may be determined that communication is possible. Alternatively, for example, if the bit rate in communication with the server device 12 that is to be switched is not below a predetermined level, it may be determined that communication is possible.

[0057] If the answer in step S16 is determined to be Yes, the connection management unit 40 of the terminal device 10-2 receives voice information only from the other server device identified based on the switching request signal (step S18). Here, based on the fact that the switching request signal was received via server device 12-2, the unit may be controlled to receive voice information only from server device 12-2. Also, if the switching request signal contains connection destination information for a new server device 12, the unit may be controlled to receive voice information only from the new server device 12 based on the connection destination information for the new server device 12. Then, the process proceeds to step S20.

[0058] The connection management unit 40 of the terminal device 10-2 sends a switchover readiness signal to the server device 12-2 (step S20). Specifically, the connection management unit 40 of the terminal device 10-2 sends a switchover readiness signal to the server device 12-2 when it has successfully received voice information from the server device 12-2. Then, the process shown in Figure 4 is completed.

[0059] (Processing details of the transmitting terminal device) The processing details of the transmitting terminal device according to this embodiment will be explained using Figure 5. Figure 5 is a flowchart showing the processing details of the transmitting terminal device according to this embodiment.

[0060] The connection management unit 40 of terminal device 10-1 performs registration with server devices 12-1 and 12-2 (step S30). Then, the process proceeds to step S32.

[0061] The connection management unit 40 of terminal device 10-1 establishes a session with terminal device 10-2 via server device 12-1 (step S32). Then, the process proceeds to step S34.

[0062] The communication determination unit 44 of terminal device 10-1 determines whether it is necessary to switch from server device 12-1 to server device 12-2 (step S34). Specifically, the communication determination unit 44 of terminal device 10-1 determines whether it is necessary to switch from server device 12-1 to server device 12-2 based on the result of the communication status detection by the communication detection unit 42 of terminal device 10-1. If it is determined that it is necessary to switch from server device 12-1 to server device 12-2 (step S34; Yes), the process proceeds to step S36. If it is not determined that it is necessary to switch from server device 12-1 to server device 12-2 (step S34; No), the process in step S34 is repeated.

[0063] If the answer in step S34 is determined to be Yes, the connection management unit 40 of terminal device 10-1 establishes a session with terminal device 10-2 via server device 12-2 (step S36). Proceed to step S38.

[0064] The voice information transmission unit 46 of terminal device 10-1 continuously transmits time information indicating the current time and voice information relating to the user's voice on terminal device 10-1 to server devices 12-1 and 12-2 (step S38). Specifically, the voice information transmission unit 46 of terminal device 10-1 continuously transmits the same time information and the same voice information to server devices 12-1 and 12-2. Then, the process proceeds to step S40.

[0065] The switching request unit 48 of terminal device 10-1 sends a switching request signal to server device 12-2 (step S40). Then proceed to step S42.

[0066] The connection management unit 40 of terminal device 10-1 determines whether or not it has received a switching readiness signal (step S42). Specifically, the connection management unit 40 of terminal device 10-1 determines whether or not it has received a switching readiness signal from server device 12-2. If it is determined that a switching readiness signal has been received (step S42; Yes), the process proceeds to step S44. If it is determined that a switching readiness signal has not been received (step S42; No), the process proceeds to step S46.

[0067] If the result in step S42 is determined to be Yes, the voice information transmission unit 46 of the terminal device 10-1 stops transmitting voice to the server device 12-1 (step S44). Then, the process shown in Figure 5 is terminated.

[0068] If the result in step S42 is No, the connection management unit 40 of the terminal device 10-1 determines whether a predetermined time has elapsed since the switching request unit 48 transmitted the switching request signal and whether a timeout has occurred (step S46). If it is determined that a timeout has occurred (step S46; Yes), the process proceeds to step S30. If it is not determined that a timeout has occurred (step S46; No), the process proceeds to step S38.

[0069] (Processing details of the communication system) The processing details of the communication system according to the embodiment will be explained using Figure 6. Figure 6 is a sequence diagram showing the processing details of the communication system according to the embodiment.

[0070] Terminal device 10-1 sends a registration request to server device 12-1 (step S100). Server device 12-1 sends an acknowledgment to terminal device 10-1 indicating that it approves the registration request (proceed to step S102).

[0071] Terminal device 10-2 sends a registration request to server device 12-1 (step S104). Server device 12-1 sends an acknowledgment to terminal device 10-2 indicating that it approves the registration request (proceed to step S106).

[0072] Terminal device 10-1 sends a registration request to server device 12-2 (step S108). Server device 12-2 sends an acknowledgment to terminal device 10-1 indicating that it approves the registration request (proceed to step S110).

[0073] Terminal device 10-2 sends a registration request to server device 12-2 (step S112). Server device 12-2 sends an acknowledgment to terminal device 10-2 indicating that it approves the registration request (proceed to step S114).

[0074] The process from step S100 to step S114 completes the registration of each terminal device 10 to each server device 12.

[0075] Terminal device 10-1 sends a session establishment request to server device 12-1 to establish a session in order to communicate with terminal device 10-2 (step S116). Server device 12-1 sends an acknowledgment to terminal device 10-1 indicating that it permits the establishment of the session (step S118).

[0076] The server device 12-1 transmits the session establishment request received from the terminal device 10-1 to the terminal device 10-2 (step S120). The terminal device 10-2 transmits an acknowledgment to the server device 12-1 indicating that it permits the establishment of the session (step S122).

[0077] Through the processing from step S116 to step S122, a session is established between terminal device 10-1 and terminal device 10-2, enabling communication between terminal device 10-1 and terminal device 10-2.

[0078] Terminal device 10-1 transmits the timestamp and voice information to server device 12-1 (step S124). Server device 12-1 transmits the timestamp and voice information received from terminal device 10-1 to terminal device 10-2 (step S126).

[0079] If terminal device 10-1 determines that it is necessary to switch the connection target from server device 12-1 to server device 12-2, it sends a switching request signal to server device 12-2 (step S128). Server device 12-2 sends the switching request signal received from terminal device 10-1 back to terminal device 10-2 (step S130).

[0080] Terminal device 10-1 transmits a timestamp and voice information to server devices 12-1 and 12-2 (step S132). In step S132, terminal device 10-1 transmits the same information to server devices 12-1 and 12-2.

[0081] The server device 12-1 transmits the timestamp received from terminal device 10-1 and the voice information to terminal device 10-2 (step S134). The server device 12-2 transmits the timestamp received from terminal device 10-1 and the voice information to terminal device 10-2 (step S136). In steps S134 and S136, terminal device 10-2 receives the same information from server device 12-1 and server device 12-2.

[0082] If terminal device 10-2 has successfully received the timestamp and voice information from both server device 12-1 and server device 12-2, it sends a switchover readiness signal to server device 12-2 (step S138). Server device 12-2 sends the switchover readiness signal received from terminal device 10-2 to terminal device 10-1 (step S140).

[0083] As a result of the processing from step S128 to step S140, the server device 12 to be connected to switches from server device 12-1 to server device 12-2.

[0084] Terminal device 10-1 transmits the timestamp and voice information to server device 12-2 (step S142). Server device 12-2 transmits the timestamp and voice information received from terminal device 10-1 back to terminal device 10-2 (step S144). Then, the process shown in Figure 6 is completed.

[0085] As described above, this embodiment can switch the connection target to the target server device while maintaining communication with the currently connected server device. As a result, this embodiment can switch the connection target to the target server device before delays occur in the currently connected server device, thereby reducing the occurrence of delays.

[0086] Each component of the illustrated device is a functional concept and does not necessarily have to be physically configured as shown. In other words, the specific forms of distribution and integration of each device are not limited to those shown, and all or part of them can be functionally or physically distributed and integrated in any unit according to various loads and usage conditions. Furthermore, this distribution and integration configuration may be performed dynamically.

[0087] Although embodiments of the present invention have been described above, the present invention is not limited by the content of these embodiments. Furthermore, the aforementioned components include those that can be easily conceived by those skilled in the art, those that are substantially the same, and those that fall within the so-called equivalent range. Moreover, the aforementioned components can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the components can be made without departing from the gist of the embodiments described above. [Explanation of symbols]

[0088] 1. Communication System 10 Terminal devices 12 Server devices 20 Input section 22 Display section 24 Mike 26 speakers 28, 62 Memory section 30,60 Communications Department 32,64 Control Unit 40 Connection Management Department 42 Communication detection unit 44 Communication determination section 46 Voice Information Transmission Unit 48 Switching Request Section 50 Communication switching unit 52 Voice Information Generation Unit 54 Codec Section 70 Registration Management Department 72 Session Management Department 74 Terminal Information Management Department 76 Group Information Management Department 78 Switching Request Signal Management Unit 80 Switching ready signal management section

Claims

1. A terminal device that communicates with a partner terminal device via a server device, A communication unit that communicates with the terminal device of the communication partner, A communication detection unit for detecting the communication status of the server device, A communication determination unit determines whether it is necessary to switch the connection target from the first server device to a second server device different from the first server device, based on the detection result of the communication detection unit. If the communication determination unit determines that it is necessary to switch the connection target to the second server device, the switching request unit transmits a switching request signal to the communication partner's terminal device requesting that it switch the connection target to the second server device. A communication switching unit that, upon receiving a switching readiness signal from the communication partner's terminal device indicating that preparations to switch the connection target to the second server device have been completed, stops transmitting voice information to the first server device and switches the connection target from the first server device to the second server device, A terminal device equipped with the following features.

2. A terminal device that communicates with a partner terminal device via a server device, A connection management unit that generates information regarding connections with multiple server devices, A communication unit that establishes connections with multiple server devices and communicates with the terminal device of the communication partner, Equipped with, The aforementioned connection management unit, When receiving the same voice information transmitted from the communication partner's terminal device to each of the multiple server devices via the multiple server devices, if a switching request signal is received from the communication partner's terminal device via any of the multiple server devices, it is determined whether switching of the target server device is possible. If switching of the target server device is possible, the system is controlled to receive voice information only from the server device identified based on the switching request signal, and a switching readiness signal is sent to the communication partner's terminal device. Terminal device.

3. The switching request unit determines that the switching completion condition is met when a predetermined period has elapsed after transmitting the switching request signal, or when it has transmitted the switching request signal and received the switching readiness complete signal. The terminal device according to claim 1.

4. A communication method that communicates with a terminal device of a communication partner via a server device, The steps include communicating with the terminal device of the communication partner, The steps include detecting the communication status of the server device, Based on the detection results, the step of determining whether it is necessary to switch the connection target from the first server device to a second server device different from the first server device, If it is determined that it is necessary to switch the connection target to the second server device, the step of sending a switching request signal to the communication partner's terminal device requesting that it switch the connection target to the second server device, When a switching readiness signal is received from the communication partner's terminal device indicating that preparations to switch the connection target to the second server device have been completed, the transmission of voice information to the first server device is stopped, and the connection target is switched from the first server device to the second server device. A communication method that includes this.

5. A program that causes a computer to execute a program that communicates with a terminal device of a communication partner via a server device, The steps include communicating with the terminal device of the communication partner, The steps include detecting the communication status of the server device, Based on the detection results, the step of determining whether it is necessary to switch the connection target from the first server device to a second server device different from the first server device, If it is determined that it is necessary to switch the connection target to the second server device, the step of sending a switching request signal to the communication partner's terminal device requesting that it switch the connection target to the second server device, When a switching readiness signal is received from the communication partner's terminal device indicating that preparations to switch the connection target to the second server device have been completed, the transmission of voice information to the first server device is stopped, and the connection target is switched from the first server device to the second server device. A program that causes the aforementioned computer to execute.

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