HK1223486B - Relay device, voice communication system, recording medium, and relay method - Google Patents

Description

Relay device, voice communication system, recording medium, and relay method

Technical Field

The present invention relates to a voice communication system utilizing a network such as a wireless LAN.

Background Art

Conventionally, so-called wireless communication devices, which modulate a high-frequency carrier wave (a continuous-time signal) with an analog or digital signal and transmit it, have been the mainstream for wireless voice communication. While one-to-one communication is the basic function of wireless communication devices, some have also been proposed, featuring group communication capabilities that allow multiple wireless communication devices to communicate simultaneously.

Furthermore, as disclosed in Japanese Patent Application Laid-Open No. 2010-109506, a wireless communication system (trunk radio system) composed of repeaters and the like has been proposed. This system has a priority calling function. Specifically, if a high-priority communication request (call) is received, even a wireless communication device currently in communication (talking) can make a call (communication). In this system, the wireless communication device determines the priority of the communication and switches the communication. Specifically, the communication is switched by switching to the repeater channel corresponding to the high-priority communication request.

Prior art literature

Patent Literature

Patent Document 1: Japanese Patent Application Laid-Open No. 2010-109506

Summary of the Invention

Problems to be solved by the invention

In the aforementioned trunked radio system, when a high-priority communication request arrives, the corresponding repeater channel must be changed, which takes time to complete the communication switch. Furthermore, while this system can implement a priority calling function, it requires multiple repeater channels (radio waves), resulting in poor radio wave efficiency. Furthermore, if all repeater channels are in use, communication switching becomes difficult.

The object of the present invention is to provide a voice communication system and a relay device used in the system, wherein the relay device and a terminal device serving as a communication machine are connected via a communication network, and the communication between the terminal devices is managed based on the priority of the communication on the relay device side, thereby enabling switching to a higher priority communication on the relay device side.

Means for solving problems

The relay device of the present invention comprises: a network communication unit for communicating with a plurality of terminal devices via a communication network, a control unit, and a priority information storage unit. When the control unit receives a call voice signal from a terminal device, it establishes a communication session in which the terminal device and the terminal device of the communication partner specified by the call voice signal participate, and forwards the voice signal between the terminal devices participating in the communication session. The priority information storage unit stores priority information related to the communication session. In addition, the control unit includes: a priority determination unit which, when receiving a call voice signal specifying a terminal device participating in an existing communication session as a communication partner, determines the priority of the existing communication session and the new communication session to be established by this call voice signal based on the priority information. If the priority of the new communication session is higher than the priority of the existing communication session, the control unit removes the terminal device participating in the existing communication session from the existing communication session and causes it to participate in the new communication session.

The program of the present invention causes a computer of a relay device including a network communication unit for communicating with multiple terminal devices via a network and a storage unit for storing priority information of communication sessions participated in by the multiple terminal devices to function as a first unit. Upon receiving a call audio signal from a terminal device, the first unit establishes a communication session involving the terminal device and a terminal device designated as a communication partner by the call audio signal, and mutually forwards audio signals between the terminal devices participating in the communication session. The first unit includes: a second unit that, upon receiving a call audio signal specifying a terminal device participating in an existing communication session as a communication partner, determines the priority of the existing communication session and a new communication session to be established by the current call audio signal based on the priority information; and a third unit that, if the priority of the new communication session is higher than that of the existing communication session, removes the terminal device participating in the existing communication session from the existing communication session and directs it to participate in the new communication session.

In the relay method of the present invention, a control unit of a relay device having a network communication unit for communicating with multiple terminal devices via a network and a storage unit for storing priority information of communication sessions participated in by the multiple terminal devices executes a first process: upon receiving a call audio signal from a terminal device, a communication session is established involving the terminal device and a terminal device designated as a communication partner by the call audio signal, and audio signals are forwarded between the terminal devices participating in the communication session. The first process includes: a second process of determining, based on the priority information, the priority of the existing communication session and the new communication session to be established by the current call audio signal upon receiving a call audio signal designating a terminal device participating in the existing communication session; and a third process of removing the terminal device participating in the existing communication session from the existing communication session and causing it to participate in the new communication session if the priority of the new communication session is higher than that of the existing communication session.

The control unit and the first unit, as well as the first process, can appropriately establish a single communication session in which a terminal device and another terminal device participate, a group communication session in which terminal devices belonging to a predetermined group participate, or a full communication session in which all of the plurality of communicable terminal devices participate. The priority storage unit can store priority information for each type of communication session.

The control section and the first unit may cancel the communication session if no audio signal is received from any terminal device participating in the communication session within a predetermined time period in the first process.

The control unit and the first unit can, in the first process, allow the terminal device removed from the existing communication session to rejoin the existing communication session when the canceled communication session is a new communication session and the existing communication session has not been canceled (is still existing).

The voice communication system of the present invention comprises the aforementioned relay device and a plurality of terminal devices that communicate with each other via a communication network. The terminal devices include a terminal network communication unit that communicates with the relay device via the communication network, and a terminal control unit that transmits a voice signal, including information specifying the terminal device of the communication partner, to the relay device via the terminal network communication unit.

The terminal device may further include a push-to-talk (PTT) circuit, and the terminal network communication unit may transmit a voice signal to the relay device while the PTT switch is on, and receive the voice signal transmitted from the relay device regardless of whether the PTT switch is on or off.

The network may have a plurality of access points of a wireless local area network (LAN), and the terminal network communication unit of the terminal device may be connected to the network via any of the access points.

Effects of the Invention

According to the present invention, by connecting a relay device and a terminal device serving as a communication machine via a communication network, and managing the priority of communication and communication between terminal devices on the relay device side, it is possible to immediately switch to high-priority communication on the relay device side.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a block diagram of a voice communication system according to an embodiment of the present invention.

FIG2 is a block diagram of a transceiver serving as a terminal device.

FIG3 is a diagram showing an example of the structure of a voice data packet.

FIG4 is a block diagram of a server device.

FIG. 5A is a diagram showing a terminal table set in the server device.

FIG5B is a diagram showing a group table set in the server device.

FIG5C is a diagram showing a hybrid table set in the server device.

FIG5D is a diagram showing a priority table set in the server device.

FIG6A is a diagram showing a hybrid table set in the server device.

FIG6B is a diagram showing a hybrid table set in the server device.

FIG6C is a diagram showing a mixing table set in the server device.

FIG6D is a diagram showing a hybrid table set in the server device.

FIG6E is a diagram showing a hybrid table set in the server device.

FIG7 is a flowchart showing the operation of the transceiver.

FIG8A is a flowchart showing the operation of the server device.

FIG8B is a flowchart showing the operation of the server device.

FIG9 is a flowchart showing a registration process executed by the server device.

DETAILED DESCRIPTION

The voice communication system of the present invention will be described with reference to the accompanying drawings. FIG1 is a block diagram of a voice communication system as an embodiment of the present invention. In this voice communication system, a plurality of terminal devices 14 communicate with each other using a wireless LAN (local area network) 16 such as Wi-Fi. The terminal device 14 is in a shape similar to a portable transceiver for wireless communication and has a PTT (push-to-talk) switch 220 as shown in FIG2 . Functionally, the terminal device 14 is a wireless network device that sends and receives voice data packets via a wireless access point (AP) 13. The server device 11, which serves as a relay device, relays the mutual communication of the plurality of terminal devices 14 via the wired network 15 and the wireless LAN 16. In addition, hereinafter, the wired network 15 and the wireless LAN 16 are collectively referred to as the network 17.

The terminal device 14 can perform communication in the form of single communication, group communication, and full communication (full call) via the server device 11. In single communication, the communication partner (other terminal device 14) is specified to communicate on a one-to-one basis. In group communication, communication is performed with the terminal devices 14 belonging to a pre-set group. In full communication, communication is performed with all terminal devices 14 that are connected to the network 17 and can communicate. The user can operate his terminal device 14 to select the desired form from these communication forms. The server device 11 establishes any of the above-mentioned forms of communication sessions based on a call from the terminal device 14. In addition, priorities are set for each form of communication session. Even if a terminal device 14 is participating in a communication session, if a communication session with a higher priority that includes this device is established, the communication session it participates in will be switched to the communication session with the higher priority. Details will be described later.

When the terminal device 14 is connected to the network 17, the server device 11 sends configuration data to the terminal device 14 to enable communication. The configuration data sent by the server device 11 includes, for example, a terminal number that the terminal device 14 can communicate with and an update program.

As the wired network 15, an Ethernet (registered trademark) LAN, the Internet, or the like can be used. When the Internet is included in the wired network 15, secure communication can be achieved by using a VPN (Virtual Private Network). Furthermore, as the wireless LAN 16, a communication method compliant with IEEE802.11, such as Wi-Fi, can be used. The terminal device 14 and the wireless access point 13 communicate using the communication method of the wireless LAN 16.

There are multiple wireless access points 13. Each wireless access point 13 is installed on a different floor or room of a building, for example. Therefore, it is possible to estimate which floor or room a terminal device 14 is located based on which wireless access point 13 the terminal device 14 belongs to.

The management device 12 is connected to the wired network 15. The management device 12 is comprised of a personal computer with a management program installed. Based on the administrator's operation, the management device 12 accesses the server device 11 and sets the tables shown in Figures 5A and 5B on the server device 11. Furthermore, the management device 12 functions as a terminal device and can communicate with other terminal devices 14.

FIG2 is a block diagram of the terminal device 14. As described above, functionally, the terminal device 14 is a wireless network device that transmits and receives voice data packets via the wireless access point (AP) 13 of the wireless LAN. The control unit 20 controls the operation of the terminal device 14 and is composed of a microprocessor. The control unit 20 has a storage unit 21 that stores various data. The setting data downloaded from the server device 11 is stored in the storage unit 21. The control unit 20 is connected to an operation unit 22, a display unit 23, an audio circuit 24, and a wireless LAN communication unit 25. The operation unit 22 includes a push button switch such as a PTT switch 220, and after receiving the user's operation, the operation signal is input to the control unit 20. The display unit 23 includes a liquid crystal display. The liquid crystal display displays the identification number of the communication partner selected by the user's operation, the identification number of the incoming caller, etc.

The audio circuit 24 includes a microphone 240 and a speaker 241. The control unit 20 decodes received audio data packets and inputs them to the audio circuit 24. The audio circuit converts the decoded audio signal into an analog signal and outputs it from the speaker 241. The audio circuit 24 converts the audio signal input from the microphone 240 into a digital signal and inputs it to the control unit 20. The control unit 20 converts the digital audio signal into audio data packets and inputs them to the wireless LAN communication unit 25. The wireless LAN communication unit 25 includes circuitry for wireless communication using a communication method compliant with IEEE 802.11. The wireless LAN communication unit 25 transmits data packets input from the control unit 20 to the wireless access point 13 and inputs data packets received from the wireless access point 13 to the control unit 20.

If the user speaks into the microphone 240 while pressing the PTT switch 220, the terminal device 14 edits the sound signal into a sound data packet and sends it to the server device 11. The sound data packet has the structure shown in Figure 3. The header of the sound data packet contains the destination IP address (destination address) and the source address (sender address). The data body contains the forwarding destination terminal number and the sending source terminal number together with the digitized sound signal. The forwarding destination terminal number is the identification number of the communication partner (target device). The identification number of the communication partner is a terminal number (single communication), a group number (group communication) or a whole number (whole communication). Although the destination of the sound data packet sent from the terminal device 14 is the server device 11, the final destination of the sound signal is the terminal device 14 of the communication partner. If the server device 11 receives the sound data packet, it extracts the data body from the sound data packet and forwards the sound signal (sound data packet) to the terminal device 14 of the communication partner. In the case where the identification number of the communication partner is a group number or a whole number, the sound signal is forwarded to multiple terminal devices 14 that are the communication partners. That is, in the case of group communication, the audio signal is transferred to a plurality of terminal devices 14 belonging to the group. In the case of full communication (full number), the audio signal is transferred to all terminal devices 14 that can communicate.

When forwarding the audio signal, a new audio packet is created with the IP address of the forwarding destination terminal device 14 as the destination address and the IP address of the server 11 as the source address. The forwarding destination terminal number included in the data body of the new packet is the same as the forwarding destination terminal number included in the data body of the audio packet received by the server 11. The source terminal number may be cleared or appended with the same number as the source terminal number in the audio packet received by the server 11.

To summarize the above process, when the PTT switch 220 is turned on, the terminal device 14 does not perform the communication establishment process such as the SIP process, but instead sends a voice data packet to the server device 11, which is a voice signal input from the microphone 240 and has the identification number of the communication partner appended to it. The server device 11 forwards this voice signal to the communication partner identified by the identification number. In this way, in this voice communication system, communication begins by sending a voice data packet (RTP data packet), so the user can start communication almost simultaneously with turning on the PTT switch 220, and can communicate with the same user experience as a conventional wireless communication transceiver. To achieve this user experience, the server device 11 manages the IP address, group, etc. of each terminal device 14, and forwards the voice signal.

The terminal device 14 not only has a PTT switch 220 but also has a VOX circuit. The so-called VOX circuit is a circuit that determines whether a call sound (sound signal) is input based on the input level of the microphone 240 and its duration, and switches the device to the transmission state (PTT switch is turned on) when it is determined that a call sound is input. The terminal device 14 can use a VOX circuit instead of the PTT switch 220, or use the VOX circuit together with the PTT switch 220 to switch the transmission on/off. In addition, a general wireless communication transceiver is a simplex mode that cannot receive wireless signals in the transmission state. On the other hand, since the terminal device 14 transmits and receives sound signals by sound data packet communication via the wireless LAN 16, it is possible to transmit and receive sound data packets in parallel. By using this function, the terminal device 14 can realize full-duplex communication in which sound signals are transmitted and received simultaneously. However, the terminal device 14 edits and transmits the voice data packet only when the target talking voice is input through the PTT switch 220 or the VOX function, so that even in the case of full-duplex communication, silent voice data packets cannot be continuously transmitted.

The server device 11 forwards the audio signal contained in the audio data packet received from the terminal device 14 via the network 17 to the communicating terminal device 14 via the network 17. In group communication, the audio signal is forwarded to multiple terminal devices 14 belonging to the group. In group communication or group communication, multiple users may speak simultaneously, and audio signals may be transmitted simultaneously from multiple terminal devices 14. In such cases, the server device 11 mixes these multiple audio signals, compiles a new audio signal, and forwards this new audio signal as an audio data packet to each terminal device 14. Furthermore, mixing is performed for each terminal device 14, and the audio signal transmitted by the server device 11 is not included in the mixed audio. In other words, the server device 11 forwards a mixed signal of all received audio signals to terminal devices 14 that have not transmitted audio signals. For terminal devices 14 that have transmitted audio signals, the audio signal transmitted by the terminal device 14 is excluded, and the remaining audio signals are mixed and forwarded. This prevents the audio signal transmitted by the server device 11 from echoing back to the terminal device 14 that has transmitted audio signals.

Figure 4 is a block diagram of the server device 11. The server device 11 includes a control unit 30, a storage unit 31, and a network communication unit 32. The storage unit 31, which is composed of, for example, a hard disk or RAM, stores the various tables shown in Figure 5 and configuration data for each terminal device 14. The control unit 30 performs configuration of the terminal devices 14, mixing of audio signals, and other operations. The network communication unit 32 controls communication with the wired network 15.

5A , 5B, 5C, and 5D are diagrams showing tables provided in the storage unit 31 of the server device 11 .

FIG5A is a diagram showing a terminal table 301. The terminal table 301 is a table used by the server device 11 to manage the terminal devices 14. Each terminal device 14 is identified by a uniquely assigned identification number (terminal number). In the terminal table 301, an activation flag and a storage address for setting data are stored for each terminal number. The activation flag is a flag indicating that the terminal device 14 is connected to the network 17 and has accessed the server device 11, and has accepted registration and download of various data from the server device 11. In other words, it is a flag indicating that registration is complete and communication is possible. The activation flag is set by the server device 11 when registration of the terminal device 14 is complete. Setting data includes, for example, program update data (firmware), a phone book that records the group to which the terminal device belongs, and other groups with which communication is permitted.

When the terminal device 14 is connected to the network 17, the server device 11 communicates with the terminal device 14 to register the terminal device 14. Furthermore, at an appropriate time thereafter, the server device 11 communicates with the terminal device 14 to update the registration of the terminal device 14. The appropriate time thereafter is, for example, when the wireless access point 13 to which the terminal device is connected is switched at regular intervals.

When selecting a communication partner, the user operates the terminal device 14 to display candidate communication partner numbers on the display unit 23. The candidate communication partner numbers are the terminal number of the activated terminal device 14 and the group number permitted to communicate.

Figure 5B shows group table 302. Group table 302 is a table used by server device 11 to manage groups. Each group is identified by a uniquely assigned identification number (group number). Group table 302 stores the group number and the terminal numbers of the terminal devices 14 belonging to the group (belonging terminal devices) for each group. The number of terminal devices 14 belonging to a group can be one or more. The administrator operates management device 12 to set these terminal table 301 and group table 302 on server device 11.

Figure 5C shows a hybrid table (session table) 303. Hybrid table 303 is a table used by server device 11 to manage communication sessions. A communication session is the communication status between multiple terminal devices 14 using server device 11 as a relay. Hybrid table 303 has multiple rows, each storing information about a single communication session. When server device 11 receives a voice signal (voice packet) from a terminal device 14, it refers to hybrid table 303 to determine which communication session the voice signal belongs to.

A communication session is handled, for example, according to the following process. The establishment of a communication session, i.e., the setting of the hybrid table 303, is performed when the initial call voice data packet for establishing a communication session is received from the terminal device 14. A single (for example, several seconds) voice sound is divided into short (20 milliseconds in this embodiment) voice data packets for transmission and reception. In addition, in a communication session, a return voice sound for a certain voice sound is sent from other terminal devices. The interval (silent time) between the previous voice sound and the return voice sound is about 0 seconds to several seconds. The holding time of the communication session is set to be greater than the maximum value of the silent time in general communication. In addition, the above-mentioned basic communication session process is common to all forms of individual communication, group communication, and overall communication, but the setting process of the hybrid table 303 is different in each communication form.

In the mixed table 303, for each communication session, items including a session number, a calling terminal number, a participating terminal number, an additional terminal number, an excluded terminal number, and a remaining holding time (T1) are provided. The session number is a number that identifies the communication session. The calling terminal number is the terminal number of the terminal device 14 (calling terminal device) that sent the initial voice data packet (call voice data packet) of the communication session. The session number only needs to be a unique value for each communication session. In this embodiment, the forwarding destination terminal number written in the call voice data packet is used. A communication session in which a terminal number (e.g., "19") is registered as a session number is a communication session for single communication (single communication session). Single communication refers to one-to-one communication between single terminal devices 14. A communication session in which a group number (e.g., "G1") is registered as a session number is a communication session for group communication (group communication session). Group communication refers to communication in which multiple terminal devices 14 (generally three or more) exchange voice signals with each other. Furthermore, a communication session in which a collective number (eg, "A": see FIG6C ) is registered as a session number is a collective communication session (collective communication session). Collective communication refers to communication in which all communicable terminal devices 14 connected to the network 17 exchange voice signals with each other.

The participating terminal numbers are a list of the terminal numbers of the terminal devices 14 participating in the communication session. When a voice packet is transmitted from a terminal device 14 whose terminal number is registered in the participating terminal numbers, the control unit 30 forwards the voice signal of the voice packet to the other terminal devices 14 whose terminal numbers are registered in the participating terminal numbers, thereby enabling mutual communication between the participating terminal devices.

In the case of a group communication session, the participating terminal numbers are the terminal numbers of the calling terminal device and the terminal numbers of the terminal devices 14 belonging to the group designated as the communication partner. However, since terminal devices 14 that belong to the group but are not active, or terminal devices 14 that are currently in other individual communication sessions, cannot participate in the group communication session, the terminal numbers of these terminal devices 14 are excluded from the participating terminal numbers (registered in the excluded terminal number column). In addition, if the calling terminal device is a terminal device 14 that does not belong to the group, that is, if the terminal device 14 calls a group other than the group to which it belongs, the terminal number of this terminal device 14 is also registered as the participating terminal number. At the same time, the terminal numbers of additional terminal devices that have been temporarily registered as members are also registered in the additional terminal number column. In other words, in this group communication session, even if the calling terminal device does not belong to the group, it is treated as a terminal device 14 participating in the communication session (participating terminal device) in the same way as the terminal devices 14 that belong to the group.

In the case of a full communication session, the participating terminal numbers are the terminal number of the calling terminal device and the terminal numbers of all communicable terminal devices 14. The excluded terminal numbers are the same as those in the group communication described above. In addition, no additional terminal numbers are registered.

In the case of a single communication session, the terminal number of the calling terminal device and the terminal number of the communicating party's terminal device 14 are registered as participating terminal numbers. Since it is a one-to-one communication, the additional terminal number and the excluded terminal number are not registered.

Furthermore, the columns for adding or excluding terminal numbers are not essential in the items of the mixed table 303. Table management can be achieved simply by adding or excluding terminal numbers in the column for participating terminal numbers.

The hold time is the time during which the communication session is maintained without canceling it even when no voice data packets are being sent from the participating terminal devices. The hold time for each communication session in the server device 11 is set to 30 seconds, for example. The hold time timer (TS) of the mixed table 303 is a timer that counts the elapse of the hold time when no voice data packets are being sent. In the processing of the control unit 30 (see FIG. 7 ), the hold time timer TS counts down if no voice data packets are being sent, and is reset to 30 seconds if a voice data packet is being sent. If the timer TS expires due to no voice data packets being sent from the participating terminal devices within 30 seconds, the communication session is canceled, and the information about the communication session is deleted from the mixed table 303.

In the above example, in a group communication session, the calling terminal device is registered in addition to the affiliated terminal device in the participating terminal device field of the mixed table 303, while inactive terminal devices 14, even though affiliated terminal devices, and terminal devices 14 currently in other communication sessions are excluded. However, the terminal devices 14 that are additionally registered in the participating terminal device field and the terminal devices 14 that are excluded are not limited to these cases.

If a terminal device 14 participating in a low-priority communication session (e.g., a group communication session) starts another high-priority communication session (e.g., an individual communication session) midway through, it is excluded from the participating terminal devices in the low-priority communication session at that point in time. In other words, the terminal number of the terminal device 14 is moved from the participating terminal number column to the excluded terminal number column.

Furthermore, in order to continue the communication session, each terminal device 14 also needs to measure a hold time. The hold time (T1) of the terminal device 14 is shorter than the hold time (TS = 30 seconds) of the server device 11. For example, timer T1 is set to 5 seconds. If 5 seconds have passed since the user turned off the PTT switch 220, even if the communication session on the server device 11 is maintained, another communication session can be started by a predetermined operation.

In addition, the mixing table 303 can be divided into two tables consisting of an ongoing mixing table and a backoff table. The ongoing mixing table is a table that registers the currently ongoing mixing session and is formed on a high-speed memory. The session whose communication (transmission and reception of voice data packets) is interrupted is transferred to the backoff table in a short time of about 200 milliseconds and is maintained in the backoff table for a holding time (T1). If communication (transmission and reception of voice data packets) occurs again during the holding time, the communication session is transferred to the ongoing mixing table again for the execution of mixing. In this way, the release of each terminal device 14 from the mixing table 303 can be advanced.

5D is a diagram showing a priority table 304. In the priority table 304, the priority of the communication is stored in correspondence with the form (call category) of each communication session. The priority is represented by a numerical value, for example, and the smaller the value, the higher the priority. When there is a request to establish a new communication session for the terminal device 14 in the communication session, the server device 11 uses the priority to determine whether to switch the current communication session of the terminal device 14 to the new communication session. That is, when the priority of the new communication session is higher than the priority of the current communication session, the communication session of the terminal device 14 is switched to the new communication session with a high priority. In addition, the priority table is also set by the administrator of the operation management device 12. The following is explained using the example of the mixed table 303 shown in FIG. 6A, FIG. 6B and FIG. 6C.

For example, let's consider the following scenario: While a group communication session with session number "G1" is already registered, as shown in FIG6A , terminal device 14 with terminal number "20" sends a request (call voice data packet) to server device 11 for a single communication session with terminal device 14 with terminal number "4." Terminal device 14 with terminal number "4" is already participating in the group communication session, as shown in FIG6A . Server device 11 refers to priority table 304 and compares the priority "3" of the current group communication session with the priority "2" of the new single communication session for terminal device 14 with terminal number "4." In this comparison, server device 11 determines that the new communication session (single communication session) has a higher priority and switches the communication session of terminal device 14 with terminal number "4" from a group communication session to a single communication session. As a result, as shown in FIG6B , a new communication session with terminal number "4" as its session number is registered in mixed table 303. Furthermore, in the group communication session with session number "G1," terminal number "4," which was previously registered in the participating terminal entry, is moved to the excluded terminal entry.

In the above group communication session, although the terminal device 14 with terminal number "4" is excluded, multiple terminal devices 14 are still registered as participating terminals. Therefore, the above group communication session can be maintained in the mixed table 303. However, the registration can also be canceled (ending the communication session).

Next, let's take the following scenario as an example: While a group communication session with session number "G1" is already registered, as shown in FIG6A , terminal device 14 with terminal number "10" sends a request (call voice data packet) for a full communication session to server device 11. A full communication session targets all terminal devices 14 capable of communication, so all terminal devices 14 participating in the group communication session with session number "G1" become the targets of this full communication session. Therefore, server device 11 refers to the priority table and compares the current group communication session priority of "3" with the new full communication session priority of "1" for terminal devices 14 with terminal numbers "1," "2," "3," "4," "5," and "23." Server device 11 determines that the full communication session has a higher priority and switches the communication session of the terminal device 14 from the group communication session to the full communication session. That is, as shown in FIG6C , a new communication session with terminal number "A (full number)" as its session number is registered in mixed table 303. Furthermore, the group communication session with session number "G1" is deregistered (group communication session ends) because all participating terminals have been switched to the above-mentioned general communication session. In addition, the terminal device 14 with terminal number "100" is not in the active state (activation flag: OFF) and cannot communicate, so it is registered as an excluded terminal.

Next, let's describe the following scenario: While a single communication session (group conversation) with session number "6" is already registered, as shown in Figure 6D , terminal device 14 with terminal number "5" sends a request (call voice data packet) for a group communication session with group number "G1" to server device 11. Terminal device 14 with terminal number "1" included in group "G1" is already participating in a single communication session, as shown in Figure 6D . Therefore, server device 11 refers to the priority table and compares the priority "2" of the current single communication session with the priority "3" of the new group communication session for terminal device 14 with terminal number "1." Server device 11 determines that the single communication session has a higher priority and maintains the current single communication session for terminal device 14 with terminal number "1." Furthermore, since the other communication partners of the aforementioned group communication session (terminal numbers "2," "3," and "4") are able to communicate (not already in another communication session), the aforementioned group communication session can proceed. Therefore, as shown in Figure 6E , a new communication session with session number "G1" is registered, with terminal number "1" as the excluded terminal.

Furthermore, if the priority of the current communication session is the same as that of the new communication session, the new communication session will not be switched. Switching is performed only when the priority is higher, but it is also possible to switch to the new communication session even when the priorities are the same. Furthermore, the priorities in priority table 304 are not specifically limited to this one; a single communication session may be set to priority 1.

FIG7 is a flowchart illustrating the communication control process executed by the control unit 20 of the terminal device 14. This process is repeated every 20 milliseconds. In this process, the current communication status is estimated based on the on/off state of the PTT switch 220 and the reception of audio packets (RTP packets). The flags and timers used in this flowchart are as follows.

PTT: is an abbreviation of the push-to-talk switch (PTT switch) 220, but is not limited to the on/off of the PTT switch 220, and also includes the on/off of the transmission signal based on the VOX circuit.

NC0: The identification number of the communication partner selected by the user (individual number/group number/all number)

NC1: Session number used, a number for identifying the communication session in progress, and the identification number (individual number/group number/global number) of the communication partner written in the first voice packet establishing the communication session.

FC: Communication session flag (a flag indicating that the terminal device 14 is participating in a communication session)

FT: Communication flag (a flag indicating that a voice packet is being sent or received)

T1: Hold time timer (a timer for counting the hold time (5 seconds) of a communication session)

S10 to S20 are voice data packet transmission management processes. The control unit 20 determines the status of the PTT switch 220 (S10). If the PTT switch 220 is on, the control unit 20 proceeds to S11. If the PTT switch 220 is not on, the control unit 20 proceeds to S20. In the description of this flowchart, turning on the PTT switch includes turning on the VOX transmission function.

In S11, the control unit 20 determines whether the communication session flag FC is set. If the communication session flag FC is not set (No in S11), the voice data packet created by turning on the PTT switch 220 this time is a call voice data packet. The control unit 20 sets the communication session flag FC and the communication flag FT indicating that the voice data packet is being transmitted or received (S12). The control unit 20 transfers the communication partner number NC0 selected by the user to the communication session number NC1 (S13), and transmits the voice data packet with the communication session number NC1 written into the data body along with the voice signal to the server device 11 (S14). By transmitting this call voice data packet, the server device 11 starts a communication session. After resetting the hold time timer T1 to 5 seconds (S15), the control unit 20 advances the processing to the voice data packet reception management processing after S30.

If the communication session flag FC is set in S11 (Yes in S11), the control unit 20 determines whether the communication flag FT is set, that is, whether a voice packet is currently being transmitted or received (S16). If the communication flag FT is not set (No in S16), the control unit 20 sets the communication flag FT (S17). The processing proceeds from S11 to S16 to S17, which means that the transmission of a new voice packet (the user's conversation voice) is started while the already-started communication session is maintained. In S18, it is determined whether to continue the already-started communication session and return the current voice packet to the communication session (No in S18), or to terminate the previous communication session and send the current voice packet to a new communication partner, that is, to establish a new communication session (Yes in S18). This determination can be made, for example, based on whether the user performed an operation, such as selecting the communication partner, immediately before the current PTT switch 220 was turned on. When the user performs an operation of selecting a new communication partner, in the process of S19 , a process of establishing a new communication session with the selected communication partner may be performed.

Furthermore, it is also possible to execute the judgment process of S18 described above, and when the communication session is switched based on priority, return to the communication session immediately before the switch. For example, a re-communication operation can be performed from the operating unit 22 of the terminal device 14, and the user can execute the switching process of returning to the communication session immediately before the switch by performing the re-communication operation. In this case, the terminal device 14 detects that the re-communication operation has been performed, and thus determines that the communication session is updated (yes in S18). In addition, the terminal device 14 detects that the re-communication operation has been performed, and attaches a request signal for returning to the communication session immediately before the switch to the voice data packet and sends it to the server device 11. Then, the server device 11, which receives the voice data packet, executes the process of returning to the communication session immediately before the switch.

If the communication session is to be updated (YES in S18), the control unit 20 transfers the currently selected communication partner number NC0 to the communication session number NC1 (S19) and proceeds to S14. If the communication session that has already started is to be continued (NO in S18), the control unit 20 proceeds directly from S18 to S14.

If the PTT switch 220 is not on in S10 (No in S10), the control unit 20 resets the communication flag FT (S20). If the communication flag FT has already been reset, the status quo can be maintained. The control unit 20 then advances the process to the voice packet reception management process from S30 onwards.

In S30, the control unit 20 determines whether a voice packet has been received via the network 17. If a voice packet has been received, the control unit 20 advances the process to S31. If a voice packet has not been received, the control unit 20 advances the process to S40.

In S31, the control unit 20 determines whether the communication session flag FC is set. If the communication session flag FC is not set (No in S31), it determines that a new communication session has been established and its initial voice packet has been sent. The control unit 20 sets the communication session flag FC and the communication in progress flag FT (S32). The FT flag indicates that a voice packet is currently being transmitted or received. The control unit 20 transfers the communication partner number contained in the voice packet to the communication session number NC1 (S33). The control unit 20 outputs the voice packet to the audio circuit 24 (S34) and resets the hold timer T1 to 5 seconds (S35).

If the communication session flag FC is already set in S31 (YES in S31), the control unit 20 determines whether the communication session number contained in the current voice packet is the same as the communication session number NC1 (S36). If they are the same (YES in S36), the control unit 20 sets the communication active flag FT in response to the reception of the current voice packet (S38). If the communication active flag FT is already set, the current state may be maintained. The control unit 20 then proceeds to S34.

If it is determined in S36 that the communication session numbers are different (No in S36), the control unit 20 transfers the communication session number contained in the current audio data packet to the communication session number NC1 (S37) and advances the process to S38. The process advances from S36 to S37 when the server device 11 switches the communication session based on priority.

If no audio data packet is received in S30 (No in S30), the control unit 20 determines whether the communication session flag FC is set (S40). If the communication session flag FC is set (Yes in S40), the control unit 20 executes the processing from S41 onwards. If the communication session flag FC is not set (No in S40), the control unit 20 immediately terminates the processing.

In S41, the control unit 20 determines whether the communication flag FT is set. If the communication flag FT is set (Yes in S41), the control unit 20 immediately terminates the process. If the communication flag FT is not set (No in S41), that is, if the communication flag FT is reset but the communication session flag FC is set, the control unit 20 decrements the hold time timer T1 by 1 (20 milliseconds) (S42). Then, the control unit 20 determines whether the hold time timer T1 has reached 0 due to this subtraction (S43). If the hold time timer T1 has reached 0 (Yes in S43), the control unit 20 resets the communication session flag FC to cancel the communication session (S44). If the hold time timer T1 is still greater than 0 in S43 (No in S43), the control unit 20 immediately terminates the process.

8A and 8B are flowcharts showing the operation of the server device 11. Fig. 8A shows the processing when receiving a voice packet, and Fig. 8B shows the mixing table management processing.

In FIG8A , upon receiving a voice packet, the control unit 30 determines whether the communication session, identified by the source terminal number and the communication partner number, is already registered in the hybrid table 303 ( S50 ). If the communication session is already registered in the hybrid table 303 ( YES in S50 ), the control unit 30 forwards the voice signal contained in the received voice packet to the terminal device 14 participating in the communication session based on the participating terminal number in the hybrid table 303 ( S56 ). The control unit then resets the hold timer TS for the communication session in the hybrid table 303 to 30 seconds ( S57 ).

If the communication session of the received voice packet is not registered in the mixed table 303 (No in S50), that is, if the voice packet is a call voice packet, a new communication session based on the call voice packet is registered in the mixed table 303 (S51). This registration process is described below using FIG. 9.

Figure 9 is a flowchart showing the registration process performed by the server device 11. This process is performed in S51 of Figure 8A. The control unit 30 selects a terminal device 14 (terminal device number) as a candidate participating terminal for the new communication session based on the session number (individual number/group number/group number) contained in the received call voice data packet (S70). The control unit 30 then determines whether the terminal device 14 is currently in a communication session (S71). Specifically, it determines whether it is included as a participating terminal in the communication sessions registered in the mixed table 303. If it is not currently in communication in S71 (No in S71), the control unit 30 determines that the terminal device 14 is a participating terminal in the new communication session (S72) and advances the process to S75. On the other hand, if it is currently in communication in S71 (Yes in S71), the control unit 30 determines whether the priority of the new communication session is higher than that of the terminal device 14's current communication session (S73). If the priority of the new communication session is high (YES in S73), the control unit 30 advances the process to S72 and determines the terminal device 14 as a participating terminal in the new communication session. On the other hand, if the priority of the new communication session is low in S73 (NO in S73), the control unit 30 determines the terminal device 14 as an excluded terminal in the new communication session (S74) and advances the process to S75. The control unit 30 then repeats the above process until the processes of S70 to S74 have been executed for all terminal devices 14 that are candidates for participating terminals in the new communication session (YES in S75).

In S75, if the above processing for all candidate terminal devices 14 is completed (Yes in S75), the control unit 30 determines whether there is a terminal device 14 determined to be a participating terminal (S76). If there is a terminal device 14 that is a participating terminal (Yes in S76), the control unit 30 registers the new communication session in the mixed table 303 (S77), and ends the processing. In S77, the communication partner number (communication session number) of the call voice packet is registered as the session number, and the terminal number of the terminal device 14 that sent the call voice packet is registered as the calling terminal number. The numbers of the terminal devices 14 determined to be participating terminals and the calling terminal number are registered as participating terminal numbers. In addition, the numbers of the terminal devices 14 determined to be excluded terminals are registered as excluded terminal numbers. In addition, the numbers of inactive terminal devices 14 (activation flag is OFF) are also registered as excluded terminal numbers. If there is no terminal device 14 participating in S76 (No in S76), the control unit 30 regards that a new communication session is not established, does not register a new communication session in the hybrid table 303, and ends the registration process.

The control unit 30 then returns to FIG. 8A and proceeds to S52. In S52, the control unit 30 determines whether the new communication session is registered in the hybrid table. If it is not registered in the hybrid table (No in S52), the control unit 30 deems that a new communication session has not been established and terminates the processing of the received voice packet. On the other hand, if it is registered in the hybrid table in S52 (Yes in S52), the control unit 30 forwards the voice signal of the received voice packet to the terminal device 14 participating in the communication session based on the participating terminal number in the hybrid table 303 (S53).

The control unit 30 determines whether any terminal device has been excluded from the participating terminal devices of the communication session already registered in the hybrid table 303 due to the currently established communication session (S54). Specifically, if a terminal device 14 that participated in a previously established communication session, based on priority, etc., now participates in the newly established communication session, it needs to be removed from the previously established communication session. If such a terminal device 14 exists (Yes in S54), the control unit 30 updates the other communication sessions (S55). Specifically, the terminal number of the terminal device 14 is deleted from the participating terminal number column of the previously established communication session. The excluded terminal number is transferred to the excluded terminal number column. Furthermore, if all terminal numbers of the terminal device 14 have been removed from the participating terminal number columns of the previously established communication session, the communication session is deleted. This optimizes the participating terminal devices of the communication session. If no terminal device has been excluded from the participating terminal devices of the communication session already registered in the hybrid table 303 in S54 (No in S54), the processing of receiving the voice data packet ends.

The hybrid table management process shown in FIG8B is repeated periodically (e.g., every 20 milliseconds). The control unit 30 first specifies the communication session in the first row of the hybrid table 303 (S60). The control unit 30 decrements the hold time timer TS for the specified communication session by 1 (20 milliseconds) (S61) and determines whether the hold time timer TS has reached 0 as a result of this subtraction (S62). If the hold time timer TS has reached 0 (YES in S62), the control unit 30 deems the communication session to have ended and deletes the communication session in that row (S63).

The control unit 30 sequentially executes the above-described processing until the final row of the hybrid table 303 ( S64 , S65 ), thereby managing the hybrid table 303 .

If the communication session is terminated in S63, the terminal device 14 participating in the communication session can be allowed to join another communication session midway. For example, if the communication session that has ended is a high-priority communication session, and one of the terminal devices 14 participating in the communication session is a terminal device that was selected from a previously established low-priority communication session, the terminal device 14 can be allowed to rejoin the original low-priority communication session (of course, this is only limited to the case where the low-priority communication session is still ongoing). In addition, even if the terminal device 14 participating in the ended high-priority communication session belongs to a low-priority communication session (group) established after the previous communication session, the terminal device can be allowed to join the low-priority communication session midway. Such processing can be achieved by searching to see if the terminal number of the terminal device 14 participating in the communication session is registered as an excluded terminal in another ongoing communication session when the communication session is terminated in S63. If the terminal number is registered as an excluded terminal, the terminal number is transferred to a participating terminal.

As described above, in the voice communication system of this embodiment, the relay device (server device 11) and the terminal device 14 as a communication machine are connected via a communication network, and the communication between the terminal devices 14 is managed on the server device 11 side based on the priority of the communication. As a result, it is possible to immediately switch to a communication with a high priority on the server device 11 side. Therefore, the time spent on switching the communication session can be shortened compared to the past. Moreover, the information related to the priority of the communication is managed by the server device 11, so the user can apply the priority desired by the user only by using the management device 12 to update the information related to the priority of the server device 11, so the priority update operation is also relatively easy. In addition, after being switched to the communication with a high priority, the communication is maintained in the same way as other communications, so the content that is desired to be transmitted to the communication partner can be reliably transmitted.

In the above embodiment, priorities are set for individual, group, and group communication communication session types, but this is not particularly limiting. For example, priorities can also be set for the terminal device 14 numbers. For example, a configuration can be employed where the terminal device 14 numbers belonging to a certain position are given a higher priority than the terminal device 14 numbers belonging to other positions. Furthermore, if the terminal device number with the higher priority is the calling terminal number in a new communication session, the calling terminal will be switched to the new communication session even if the calling terminal is already in another communication session.

In addition, in the above embodiment, communication sessions are switched based on a priority table, but this is not particularly limited to this. For example, an emergency call operation can be performed from the operating unit 22 of the terminal device 14, and the communication session in which the user performs the emergency call operation is designated as a high-priority communication session. When the emergency call operation is performed, the call audio data packet is supplemented with information indicating the emergency situation, and the server device 11 receives (stores) this supplementary information to determine the priority.

In the above embodiment, an inactive terminal device is excluded from the communication session as an excluded terminal device. However, the terminal device may be allowed to participate in the communication session midway when the terminal device becomes active.

Furthermore, in the above embodiment, when a portion of participating terminals in a communication session has been disconnected (moved to a new communication session) due to a priority call, the remaining (non-detached) participating terminals in the communication session are not notified of their disconnection. However, notification may be provided. For example, a message notifying the disconnected terminal devices 14 may be synthesized into the audio signal of the audio data packet in the communication session and transmitted. Furthermore, a message notifying the terminal devices 14 that their communication session (affiliation) has changed may be synthesized into the audio signal of the audio data packet in the new communication session and transmitted.

In addition, in the above embodiment, the current communication session is immediately switched to a new communication session with a higher priority, but this is not particularly limited to this. For example, if the current communication session is at a peak in sending voice packets, the switching to the new communication session may be waited until the transmission is completed.

In the above embodiment, a communication session is established in response to a call audio packet transmitted from terminal device 14. However, the trigger for establishing a communication session is not limited to this. For example, an administrator can establish and cancel a conversation group by manipulating hybrid table 303 via management device 12. Furthermore, management device 12 can also establish and cancel extended group communications between groups as described above. This approach also enables comprehensive management and flexible changes to communication sessions.

Explanation of symbols

11 Server device (relay device)

12 Management Device

13 Wireless Access Points

14 Terminal Devices

20 Control unit (of terminal device)

30 Control unit (of the server device)

32 Network Communications Department

220 PTT (Push to Talk) switch

301 Terminal Form

302 Group Table

303 Hybrid Table

304 Priority Table

Claims (15)

1. A relay device, characterized in that it comprises: The network communication unit connects to a communication network and communicates with multiple terminal devices via that communication network; The control unit, upon receiving a call voice signal from the terminal device, establishes a communication session involving the terminal device and the terminal device of the communication counterpart designated by the call voice signal, and forwards the voice signal to each other among the terminal devices participating in the communication session; and The storage unit stores a hybrid table corresponding to the currently established communication sessions and the terminal devices participating in those sessions, as well as a priority table corresponding to the types and priorities of the communication sessions. When the control unit receives a call voice signal designating at least a portion of the terminal devices participating in the original communication session as the communication counterpart, it refers to a mixing table and a priority table to determine the priority of the new communication session and the original communication session. When the priority of the new communication session is lower than that of the original communication session, i) Establish a new communication session; ii) Refer to the terminal devices and the mixing table specified by the new communication session to determine the participating terminal devices of the original communication session included in the terminal devices specified by the new communication session; iii) Remove the terminal devices that participated in the original communication session from the new communication session and designate them as participating terminal devices in the new communication session, and send voice signals to the participating terminal devices in the new communication session. When the new communication session has a higher priority than the existing communication session, i) Establish a new communication session; ii) A terminal device designated by the new communication session that includes a part of the participating terminal devices of the original communication session shall be included as a participating terminal device in the new communication session and shall participate in the new communication session. iii) Referring to the terminal number and the mixing table, determine the participating terminal devices of the new communication session in the original communication session; iv) Refer to the terminal devices and the mixing table specified by the new communication session to determine the participating terminal devices of the new communication session included in the participating terminal devices of the original communication session. v) Remove the participating terminal device of the new communication session from the existing communication session, so that the audio signal of the existing communication session is not sent to the participating terminal device of the new communication session. 2. The relay device according to claim 1, characterized in that, The control unit appropriately establishes a single communication session involving one terminal device and another terminal device, a group communication session involving terminal devices belonging to a pre-defined group, and a collective communication session involving all of the multiple terminal devices capable of communication. The priority storage unit stores priority information for various types of communication sessions. 3. The relay device according to claim 1, characterized in that, If the control unit fails to receive an audio signal from any of the terminal devices participating in the communication session within a given time, the communication session is cancelled. 4. The relay device according to claim 3, characterized in that, If the cancelled communication session is the new communication session and the original communication session has not been cancelled, the control unit causes the terminal device that was removed from the original communication session to rejoin the original communication session. 5. A voice communication system comprising a relay device and multiple terminal devices that communicate with each other via a communication network, characterized in that, The relay device includes: The network communication unit is connected to the communication network and communicates with multiple terminal devices via the communication network; The control unit, upon receiving a call voice signal from the terminal device, establishes a communication session involving the terminal device and the terminal device of the communication counterpart designated by the call voice signal, and forwards the voice signal to each other among the terminal devices participating in the communication session; and The storage unit stores a hybrid table corresponding to the currently established communication sessions and the terminal devices participating in those sessions, as well as a priority table corresponding to the types and priorities of the communication sessions. When the control unit receives a call voice signal designating at least a portion of the terminal devices participating in the original communication session as the communication counterpart, it refers to a mixing table and a priority table to determine the priority of the new communication session and the original communication session. When the priority of the new communication session is lower than that of the original communication session, i) Establish a new communication session; ii) Refer to the terminal devices and the mixing table specified by the new communication session to determine the participating terminal devices of the original communication session included in the terminal devices specified by the new communication session; iii) Remove the terminal devices that participated in the original communication session from the new communication session and designate them as participating terminal devices in the new communication session, and send voice signals to the participating terminal devices in the new communication session. When the new communication session has a higher priority than the existing communication session, i) Establish a new communication session; ii) A terminal device designated by the new communication session that includes a part of the participating terminal devices of the original communication session shall be included as a participating terminal device in the new communication session and shall participate in the new communication session. iii) Referring to the terminal number and the mixing table, determine the participating terminal devices of the new communication session in the original communication session; iv) Refer to the terminal devices and the mixing table specified by the new communication session to determine the participating terminal devices of the new communication session included in the participating terminal devices of the original communication session. v) Remove the participating terminal device of the new communication session from the existing communication session, so that the audio signal of the existing communication session is not sent to the participating terminal device of the new communication session. The terminal device includes: The terminal network communication unit communicates with the relay device via the communication network; and The terminal control unit transmits an audio signal containing information specifying the terminal device of the communication counterpart to the relay device via the terminal network communication unit. 6. The voice communication system according to claim 5, characterized in that, The terminal device also has a one-button circuit. The terminal network communication unit sends the sound signal to the relay device while the keyless connection circuit is connected, and receives the sound signal sent from the relay device regardless of whether the keyless connection circuit is connected or disconnected. 7. The voice communication system according to claim 5, characterized in that, The network has multiple access points for a wireless local area network. The terminal network communication unit of the terminal device connects to the network via any access point. 8. A recording medium containing a computer program, wherein a relay device includes a network communication unit for communicating with multiple terminal devices via a network, and a storage unit for storing a hybrid table corresponding to currently established communication sessions and the terminal devices participating in the communication sessions, and a priority table corresponding to the types and priorities of the communication sessions, wherein the computer program causes the computer of the relay device to perform the following functions: Upon receiving a call voice signal from the terminal device, a communication session is established involving the terminal device and the terminal device of the communication counterpart specified by the call voice signal. The voice signals are then forwarded between the terminal devices participating in the communication session. Upon receiving a call voice signal designating at least a portion of the terminal devices participating in the original communication session as the communication counterpart, the priorities of the new and original communication sessions are determined by referring to a hybrid table and a priority table. When the priority of the new communication session is lower than that of the original communication session, i) Establish a new communication session; ii) Refer to the terminal devices and the mixing table specified by the new communication session to determine the participating terminal devices of the original communication session included in the terminal devices specified by the new communication session; iii) Remove the terminal devices that participated in the original communication session from the new communication session and designate them as participating terminal devices in the new communication session, and send voice signals to the participating terminal devices in the new communication session. When the new communication session has a higher priority than the existing communication session, i) Establish a new communication session; ii) A terminal device designated by the new communication session that includes a part of the participating terminal devices of the original communication session shall be included as a participating terminal device in the new communication session and shall participate in the new communication session. iii) Referring to the terminal number and the mixing table, determine the participating terminal devices of the new communication session in the original communication session; iv) Refer to the terminal devices and the mixing table specified by the new communication session to determine the participating terminal devices of the new communication session included in the participating terminal devices of the original communication session. v) Remove the participating terminal device of the new communication session from the existing communication session, so that the audio signal of the existing communication session is not sent to the participating terminal device of the new communication session. 9. The recording medium according to claim 8, characterized in that, The computer program enables the computer of the relay device to perform the following functions: establish a single communication session involving one terminal device and another terminal device, a group communication session involving terminal devices belonging to a pre-defined group, and a collective communication session involving all of the multiple terminal devices capable of communication. The storage unit stores priority information for various types of communication sessions. 10. The recording medium according to claim 8, characterized in that, The computer program enables the computer of the relay device to also perform the following function: cancel the communication session if no sound signal is received from any of the terminal devices participating in the communication session within a given time. 11. The recording medium according to claim 10, characterized in that, The computer program enables the computer of the relay device to also perform the following function: if the cancelled communication session is the new communication session and the original communication session has not been cancelled, to enable the terminal device that was removed from the original communication session to rejoin the original communication session. 12. A relay method, executed by a control unit of a relay device, the relay device comprising a network communication unit for communicating with multiple terminal devices via a network, and a storage unit for storing a hybrid table corresponding to currently established communication sessions and the terminal devices participating in the communication sessions, and a priority table corresponding to the types and priorities of the communication sessions, characterized in that... Upon receiving a call voice signal from the terminal device, a communication session is established involving the terminal device and the terminal device of the communication counterpart specified by the call voice signal. The voice signals are then forwarded between the terminal devices participating in the communication session. Upon receiving a call voice signal designating at least a portion of the terminal devices participating in the original communication session as the communication counterpart, the priorities of the new and original communication sessions are determined by referring to a hybrid table and a priority table. When the priority of the new communication session is lower than that of the original communication session, i) Establish a new communication session; ii) Refer to the terminal devices and the mixing table specified by the new communication session to determine the participating terminal devices of the original communication session included in the terminal devices specified by the new communication session; iii) Remove the terminal devices that participated in the original communication session from the new communication session and designate them as participating terminal devices in the new communication session, and send voice signals to the participating terminal devices in the new communication session. When the new communication session has a higher priority than the existing communication session, i) Establish a new communication session; ii) A terminal device designated by the new communication session that includes a part of the participating terminal devices of the original communication session shall be included as a participating terminal device in the new communication session and shall participate in the new communication session. iii) Referring to the terminal number and the mixing table, determine the participating terminal devices of the new communication session in the original communication session; iv) Refer to the terminal devices and the mixing table specified by the new communication session to determine the participating terminal devices of the new communication session included in the participating terminal devices of the original communication session. v) Remove the participating terminal device of the new communication session from the existing communication session, so that the audio signal of the existing communication session is not sent to the participating terminal device of the new communication session. 13. The relay method according to claim 12, characterized in that, A single communication session can be established, consisting of one terminal device and another terminal device; a group communication session can be established, consisting of terminal devices belonging to a pre-defined group; and a general communication session can be established, consisting of all of the multiple terminal devices capable of communication. The storage unit stores priority information for various types of communication sessions. 14. The relay method according to claim 12, characterized in that, The communication session is cancelled if no audio signal is received from any of the participating terminal devices within a given time. 15. The relay method according to claim 14, characterized in that, If the cancelled communication session is the new communication session and the original communication session has not been cancelled, the terminal device that was removed from the original communication session may rejoin the original communication session.