Wireless relay equipment and wireless communication terminals

Abstract

To enable communication between wireless communication terminals even when there is no free communication channel.SOLUTION: A wireless relay device includes a relay communication unit that relays a signal using a first communication method, a storage unit that stores location information of a plurality of wireless communication terminals, and a selection unit that selects a relay terminal that performs a relay operation between a communication source wireless communication terminal that has transmitted a relay request and a communication destination wireless communication terminal specified as the communication destination when there is a new relay request in a state in which all communication channels set for the relay communication unit are in use. When the relay terminal has been selected, the selection unit causes the relay communication unit to transmit a transmission instruction signal giving an instruction to transmit on a first backup channel, a reception instruction signal giving an instruction to receive on a second backup channel, and a relay instruction signal that instructs the relay terminal to perform relay operation using the first backup channel and the second backup channel.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a wireless relay device and a wireless communication terminal.

Background Art

[0002] In an ad hoc network in which a mobile communication terminal is connected by wireless communication, a technique for changing a route used for communication is known (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] Normally, a wireless communication terminal communicates with other wireless communication terminals using a communication channel assigned to a wireless relay device (base station device). In this case, when all the communication channels of the wireless relay device are in use and there is no available communication channel, the wireless communication terminal has to wait until a communication channel becomes available in order to communicate.

[0005] An object of the present invention is to provide a wireless relay device and a wireless communication terminal that can enable communication between wireless communication terminals even when there is no available communication channel.

Means for Solving the Problems

[0006] The wireless relay device according to the present invention comprises: a relay communication unit that relays signals using a first communication method; a storage unit that stores location information of a plurality of wireless communication terminals received by the relay communication unit; and a selection unit that, when a new relay request is received while all communication channels set in the relay communication unit are in use, selects a relay terminal to perform relay operations between the source wireless communication terminal that sent the relay request and the destination wireless communication terminal designated as the destination, based on the location information of the plurality of wireless communication terminals stored in the storage unit. When the selection unit selects a relay terminal, it controls the relay communication unit to transmit a transmission instruction signal instructing the source wireless communication terminal to transmit using the first communication method on a first backup channel different from the communication channel set in the relay communication unit; a reception instruction signal instructing the destination wireless communication terminal to receive using the first communication method on a second backup channel different from the communication channel set in the relay communication unit; and a relay instruction signal instructing the relay terminal to perform relay operations using the first backup channel and the second backup channel.

[0007] The wireless communication terminal according to the present invention is a wireless communication terminal that communicates with a wireless relay device according to the present invention, and comprises: a first communication unit that communicates using the first communication method; a second communication unit that communicates using the second communication method; a location information acquisition unit that acquires location information of the wireless communication terminal; a history information storage unit that stores call history information relating to call history communicated by the first communication unit; and a signal relay unit that, when the first communication unit receives a relay instruction signal, forwards and transmits the signals received between the first communication unit and the second communication unit, wherein the first communication unit periodically transmits the location information and the call history information to the wireless relay device, and the signal relay unit transmits the signal received on the first backup channel to the second relay terminal on the connection channel when the relay instruction signal designates the wireless communication terminal as the first relay terminal, and transmits the signal received from the first relay terminal on the connection channel to the second backup channel when the relay instruction signal designates the wireless communication terminal as the second relay terminal. [Effects of the Invention]

[0008] According to the present invention, communication between wireless communication terminals can be enabled even when there are no available communication channels. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 shows an example of the configuration of a wireless communication system according to the first embodiment. [Figure 2] Figure 2 is a diagram illustrating the basic operation of a wireless communication system. [Figure 3] Figure 3 is a diagram illustrating the basic operation of a wireless communication system. [Figure 4] Figure 4 is a block diagram showing an example configuration of a wireless relay device according to the first embodiment. [Figure 5] Figure 5 is a diagram illustrating the call history information according to the first embodiment. [Figure 6] Figure 6 is a block diagram showing an example configuration of a wireless communication terminal according to the first embodiment. [Figure 7] Figure 7 is a flowchart showing the processing flow of the wireless relay device according to the first embodiment. [Figure 8] Figure 8 is a diagram illustrating a method for transmitting a standby signal according to the first embodiment. [Figure 9] Figure 9 is a diagram illustrating a method for selecting the area in which the relay terminal according to the first embodiment is located. [Figure 10] Figure 10 is a diagram illustrating a method for selecting a relay terminal according to the first embodiment. [Figure 11] Figure 11 is a diagram illustrating a method for setting up an alternative channel according to the first embodiment. [Figure 12] Figure 12 illustrates a method for switching a channel to an alternative channel according to the first embodiment. [Figure 13] Figure 13 is a sequence diagram showing the communication flow using the alternative channel according to the first embodiment. [Figure 14]FIG. 14 is a sequence diagram showing the flow of a process for ending communication using an alternative channel according to the first embodiment. [Figure 15] FIG. 15 is a sequence diagram showing the flow of communication using an alternative channel according to the second embodiment. [Figure 16] FIG. 16 is a flowchart showing the flow of the re-selection process of the relay terminal according to the second embodiment.

MODE FOR CARRYING OUT THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that the present invention is not limited by this embodiment, and in the following embodiments, the same parts are denoted by the same reference numerals to omit redundant explanations.

[0011] [First Embodiment] (Wireless Communication System) A configuration example of a wireless communication system according to the first embodiment will be described using FIG. 1. FIG. 1 is a diagram showing a configuration example of a wireless communication system according to the first embodiment.

[0012] As shown in FIG. 1, the wireless communication system 1 includes a plurality of wireless communication terminals 10 and a wireless relay device 12. In the example shown in FIG. 1, the wireless relay device 12 has a control channel CC, a communication channel T1, and a communication channel T2. The transmission frequency of the communication channel T1 is TX1, and the reception frequency is RX1. The transmission frequency of the communication channel T2 is TX2 different from TX1, and the reception frequency is RX2 different from RX1. A plurality of wireless communication terminals 10 are connected to the control channel CC. In the present embodiment, the wireless relay device 12 will be described as having two channels, i.e., the communication channel T1 and the communication channel T2, as communication channels, but the present invention is not limited thereto. As will be described later, in the present embodiment, the wireless relay device 12 has a spare alternative channel T3 as a spare channel different from the communication channels normally used in communication. In the present embodiment, the wireless communication channel will be described as having only one alternative channel T3 as a spare channel, but the present invention is not limited thereto. The number of alternative channels possessed by the wireless relay device 12 may be one or two or more.

[0013] (Basic Operations of Wireless Communication System) Before explaining the operations of the wireless communication system according to the present embodiment, the basic operations of the wireless communication system will be explained. FIGS. 2 and 3 are diagrams for explaining the basic operations of the wireless communication system.

[0014] Figure 2 shows an example of communication between wireless communication terminals 10-1 and 10-2. When the control channel CC of the wireless relay device 12 receives a communication request from wireless communication terminal 10-1 to wireless communication terminal 10-2, it notifies wireless communication terminals 10-1 and 10-2 of the number of an available communication channel. In the example shown in Figure 2, the control channel CC notifies wireless communication terminals 10-1 and 10-2 of the number of communication channel T1. This makes it possible for wireless communication terminals 10-1 and 10-2 to communicate on communication channel T1. In this case, communication channel T1 remains in use until communication between wireless communication terminals 10-1 and 10-2 is completed. Even if the control channel CC receives a communication request from another wireless communication terminal while communication channel T1 is in use, it will not assign communication channel T1 to the other wireless communication terminal.

[0015] As shown in Figure 3, if communication channel T1 is in use and communication channel T2 is free, when control channel CC receives a communication request from wireless communication terminal 10-3 to wireless communication terminal 10-4, it notifies wireless communication terminals 10-3 and 10-4 of the number of communication channel T2. This makes it possible for wireless communication terminals 10-3 and 10-4 to communicate on communication channel T2. Even if control channel CC receives a communication request from another wireless communication terminal while communication channels T1 and T2 are in use, it will not assign communication channels T1 and T2 to the other wireless communication terminal.

[0016] As shown in Figures 2 and 3, if both communication channels T1 and T2 are in use, control channel CC cannot assign a communication channel to another wireless communication terminal. In this case, if another wireless communication terminal wants to communicate, it must wait until either communication channel T1 or communication channel T2 becomes available. In this embodiment, the wireless relay device 12 performs processing that enables other wireless communication terminals to communicate even if communication channels T1 and T2 are in use.

[0017] (Wireless relay device) An example of the configuration of a wireless relay device according to the first embodiment will be explained using Figure 4. Figure 4 is a block diagram showing an example of the configuration of a wireless relay device according to the first embodiment.

[0018] As shown in Figure 4, the wireless relay device 12 comprises a relay communication unit 20, a storage unit 22, and a control unit 24. The wireless relay device 12 is a device that relays communications between wireless communication terminals 10.

[0019] The relay communication unit 20 relays communications from the wireless communication terminal 10. The relay communication unit 20 relays communications from the wireless communication terminal 10 using a first communication method. The first communication method is, for example, a digital business radio communication method such as APCO-P25 (Association of Public Safety Communications Officials International Project 25) and NXDN (registered trademark), but is not limited to these.

[0020] The relay communication unit 20 receives location information and call history information from the wireless communication terminal 10 using the first communication method. The relay communication unit 20 also receives a relay request signal from the wireless communication terminal 10 indicating a relay request using the first communication method.

[0021] The memory unit 22 stores various types of information. For example, the memory unit 22 stores location information of the wireless communication terminal 10 included in the wireless communication system 1. The memory unit 22 also stores information such as the calculation contents of the control unit 24 and programs. The memory unit 22 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). For example, the memory unit 22 stores call history information 22a.

[0022] Figure 5 is a diagram illustrating the call history information according to the first embodiment. As shown in Figure 5, the call history information 22a includes items such as "Unit ID" and "Frequency of Use".

[0023] "Unit ID" is identification information used to uniquely identify the wireless communication terminal 10 included in the wireless communication system 1. Location information is associated with "Unit ID".

[0024] "Usage frequency" indicates information regarding the usage frequency of the corresponding wireless communication terminal 10. "Usage frequency" is expressed as either "high" or "low". For example, "Usage frequency" is "high" if communication has been performed for 20 minutes or more in the last hour, and "low" if it has been performed for less than 20 minutes. In this embodiment, "Usage frequency" is expressed in two types, "high" and "low," but the present invention is not limited thereto.

[0025] The control unit 24 controls each part of the wireless relay device 12. The control unit 24 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 (Random Access Memory) or ROM (Read Only Memory). The control unit 24 executes a program that controls the operation of the wireless relay device 12 according to the present invention. The control unit 24 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 24 may be implemented by a combination of hardware and software.

[0026] The control unit 24 includes an acquisition unit 30, a channel setting unit 32, and a selection unit 34.

[0027] The acquisition unit 30 acquires various types of information. The acquisition unit 30 acquires various types of information from the wireless communication terminal 10 via the relay communication unit 20. The acquisition unit 30 acquires location information and call history information from the wireless communication terminal 10 via the relay communication unit 20. The acquisition unit 30 stores the acquired location information and call history information in the storage unit 22.

[0028] The channel setting unit 32 sets a channel for relaying communication between wireless communication terminals 10 when the relay communication unit 20 receives a relay request. For example, when the relay communication unit 20 receives a relay request, the channel setting unit 32 sets an available channel as the relay channel.

[0029] The selection unit 34 selects another wireless communication terminal 10 to relay the communication of the wireless communication terminal 10 that made the relay request when a new relay request is received while all communication channels set on the relay communication unit 20 are in use. The selection unit 34 selects the other wireless communication terminal 10 based, for example, on location information and call history information of multiple wireless communication terminals 10 stored in the storage unit 22. Details of the selection unit 34 will be described later.

[0030] (Wireless communication terminal) An example of the configuration of a wireless communication terminal according to the first embodiment will be explained using Figure 6. Figure 6 is a block diagram showing an example of the configuration of a wireless communication terminal according to the first embodiment.

[0031] As shown in Figure 6, the wireless communication terminal 10 includes a first communication unit 40, a second communication unit 42, an operation unit 44, a speaker unit 46, a display unit 48, a storage unit 50, a GNSS (Global Navigation Satellite System) 52, and a control unit 54.

[0032] The first communication unit 40 performs communication using a first communication method. The first communication unit 40 performs communication with the wireless relay device 12 using a first communication method, for example. The first communication method is, for example, a digital business radio communication method such as APCO-P25 and NXDN (registered trademark), but is not limited to these.

[0033] The second communication unit 42 performs communication using a second communication method. The second communication method is, for example, short-range wireless communication such as Wi-Fi (registered trademark) and Bluetooth (registered trademark), but is not limited thereto. The second communication unit 42 performs communication with other wireless communication terminals 10 using a second communication method, for example.

[0034] The operation unit 44 receives various input operations for the wireless communication terminal 10. The operation unit 44 outputs an operation signal to the control unit 54 corresponding to the received input operation. The operation unit 44 includes, for example, a touch panel, buttons, switches, a microphone, etc. The operation unit 44 includes, for example, a PTT (Push to Talk) button. When a touch panel is used as the operation unit 44, the operation unit 44 is located on the display unit 48.

[0035] The speaker unit 46 outputs various types of audio. For example, the speaker unit 46 outputs the audio of a user of another wireless communication terminal 10.

[0036] The display unit 48 displays various types of images. The display unit 48 is a display that includes, for example, a liquid crystal display (LCD) or an organic EL (electro-luminescence) display.

[0037] The memory unit 50 stores various types of information. The memory unit 50 stores the calculation contents of the control unit 54 and information such as programs. The memory unit 50 includes, for example, at least one of the following: RAM (Random Access Memory), main memory such as ROM (Read Only Memory), and external storage devices such as HDD (Hard Disk Drive). The memory unit 50 has a history information storage unit 50a.

[0038] The history information storage unit 50a stores history information relating to the communication history of the wireless communication terminal 10. For example, the history information storage unit 50a stores as history information information about the communication time during which the wireless communication terminal 10 performed communication within the most recent hour.

[0039] The GNSS receiving unit 52 consists of a GNSS receiver and the like that receives GNSS signals from GNSS satellites. The GNSS receiving unit 52 outputs the received GNSS signals to the position information acquisition unit 60 of the control unit 54.

[0040] The control unit 54 controls each part of the wireless communication terminal 10. The control unit 54 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 54 executes a program that controls the operation of the wireless communication terminal 10 according to the present invention. The control unit 54 may be implemented by an integrated circuit such as an ASIC or FPGA. The control unit 54 may be implemented by a combination of hardware and software.

[0041] The control unit 54 comprises a location information acquisition unit 60, a signal relay unit 62, an output control unit 64, and a communication control unit 66.

[0042] The location information acquisition unit 60 detects location information related to the current location of the wireless communication terminal 10. The location information acquisition unit 60 acquires location information related to the current location based on the GNSS signal received by the GNSS receiving unit 52, for example.

[0043] The signal relay unit 62 relays communication between one wireless communication terminal 10 and another wireless communication terminal 10. When the first communication unit 40 receives a relay instruction signal from the wireless relay device 12, the signal relay unit 62 forwards the received signal between the first communication unit 40 and the second communication unit 42 and transmits it to the other wireless communication terminal 10.

[0044] The output control unit 64 controls the speaker unit 46 and the display unit 48 to produce output. The output control unit 64 controls the speaker unit 46 to output sound. The output control unit 64 controls the display unit 48 to display the display screen.

[0045] The communication control unit 66 controls the first communication unit 40 and the second communication unit 42 to perform communication with an external device. The communication control unit 66 controls the first communication unit 40 to perform communication with the wireless relay device 12 or the wireless communication terminal 10. The communication control unit 66 controls the second communication unit 42 to perform communication with another wireless communication terminal 10.

[0046] [Processing details] The processing details of the wireless relay device according to the first embodiment will be explained using Figure 7. Figure 7 is a flowchart showing the processing flow of the wireless relay device according to the first embodiment.

[0047] The control unit 24 determines whether or not it has received a communication request signal from the wireless communication terminal 10 to perform communication with another wireless communication terminal 10 (step S10). If it is determined that a communication request signal has been received (step S10; Yes), the process proceeds to step S12. If it is determined that a communication request signal has not been received (step S10; No), the process proceeds to step S10.

[0048] If the result in step S10 is Yes, the channel setting unit 32 determines whether or not there is an available communication channel to be set in the relay communication unit 20 (step S12). If it is determined that there is an available communication channel (step S12; Yes), the process proceeds to step S14. If it is determined that there is no available communication channel (step S12; No), the process proceeds to step S16.

[0049] If the answer in step S12 is determined to be Yes, the channel setting unit 32 sets an available channel to be used as the communication channel for communication by the wireless communication terminal 10 (step S14). This enables communication between wireless communication terminal 10 and other wireless communication terminals 10.

[0050] If the result in step S12 is determined to be No, the control unit 24 sends a standby signal to the wireless communication terminal 10 that sent the communication request (step S16). Figure 8 is a diagram illustrating the method of sending a standby signal according to the first embodiment. In the example shown in Figure 8, assume that communication channel T1 is used by wireless communication terminals 10-1 and 10-2, and communication channel T2 is used by wireless communication terminals 10-3 and 10-4. In this case, assume that the wireless relay device 12 receives a communication request from wireless communication terminal 10-5 while communication channels T1 and T2 are in use. In this case, the control unit 24 identifies the wireless communication terminal 10-6 to be the communication partner based on the communication request received from wireless communication terminal 10-5. The control unit 24 then sends a standby signal 101 to wireless communication terminals 10-5 and 10-6 to indicate that they should be on standby. As a result, a message indicating a standby instruction is displayed on the display units 48 of wireless communication terminals 10-5 and 10-6. Then, proceed to step S18.

[0051] The selection unit 34 selects an area where a wireless communication terminal 10 that will act as a relay terminal for relaying communication between wireless communication terminals 10 is located (step S18). The wireless communication terminal 10 that performs relay operations is called a relay terminal. Figure 9 is a diagram illustrating the method for selecting an area where a relay terminal is located according to the first embodiment. As shown in Figure 9, the selection unit 34 selects an area where the relay terminal is located based on the communication range, which is the area in which the first communication units 40 of wireless communication terminals 10-5 and 10-6 can communicate. Communication range R1 indicates the communication range to which the radio waves of the first communication unit 40 of wireless communication terminal 10-5 can reach. Communication range R2 indicates the communication range to which the radio waves of the first communication unit 40 of wireless communication terminal 10-6 can reach. Communication range R3 indicates the common communication range to which the radio waves of the first communication units 40 of wireless communication terminals 10-5 and 10-6 can reach. The selection unit 34 selects an area where the relay terminal is located from within the communication range R3. The selection unit 34 divides the communication range R3 into predetermined areas and selects the area where the most wireless communication terminals 10 are located. Here, the predetermined area is, for example, a 100m square area, but is not limited to this. For example, in the example shown in Figure 9, the areas within the communication range R3 include areas R31, R32, and R33. In this case, the selection unit 34 selects area R32 as the area where the most wireless communication terminals 10 are located.

[0052] The selection unit 34 selects a relay terminal to relay communication between the wireless communication terminals 10 (step S20). Figure 10 is a diagram illustrating the method for selecting a relay terminal according to the first embodiment. Figure 10 shows the wireless communication terminals 10 located within the region R32 selected in Figure 9. As shown in Figure 10, the region R32 is assumed to contain wireless communication terminals 10-10, 10-20, 10-30, 10-40, 10-50, 10-60, 10-70, 10-80, 10-90, and 10-100. The "Unit IDs" of wireless communication terminals 10-10 to 10-100 are assumed to be "Unit ID 10" to "Unit ID 100" as shown in Figure 5, respectively. The selection unit 34 selects terminals with low usage frequency based on the call history information 22a (see Figure 5) stored in the storage unit 22. In the example shown in Figure 10, the selection unit 34 selects wireless communication terminals 10-20, 10-40, 10-50, 10-60, 10-70, 10-90, and 10-100 as terminals with low usage frequency.

[0053] The selection unit 34 selects a wireless communication terminal 10 that is not frequently used and in which one or more other wireless communication terminals 10 are located within the communication range (hereinafter referred to as the communication range) of the second communication unit 42. Communication range R20 is the communication range of the second communication unit 42 of wireless communication terminals 10-20. Communication range R40 is the communication range of the second communication unit 42 of wireless communication terminals 10-40. Communication range R50 is the communication range of the second communication unit 42 of wireless communication terminals 10-50. Communication range R60 is the communication range of the second communication unit 42 of wireless communication terminal 10-60. Communication range R70 is the communication range of the second communication unit 42 of wireless communication terminal 10-70. Communication range R90 is the communication range of the second communication unit 42 of wireless communication terminal 10-90. Communication range R100 is the communication range of the second communication unit 42 of wireless communication terminal 10-100. The selection unit 34 selects wireless communication terminals 10-20, 10-50, 10-60, 10-70, 10-90, and 10-100 based on the communication range of the second communication unit 42 of each wireless communication terminal 10 that is used infrequently.

[0054] The selection unit 34 selects a communication range in which the most other wireless communication terminals 10 are located within the communication range of the second communication unit 42, and which has a low frequency of use. The selection unit 34 selects the communication range R90 in which the most wireless communication terminals 10 are located. The selection unit 34 selects wireless communication terminals 10-20, 10-50, 10-60, and 10-90, which are included in the communication range R90.

[0055] The selection unit 34 selects the two wireless communication terminals 10-20, 10-50, 10-60, and 10-90 that are closest to each other as relay terminals. In the example shown in Figure 10, the selection unit 34 selects wireless communication terminals 10-60 and 10-90 as relay terminals.

[0056] The selection unit 34 sets an alternative channel using a relay terminal (step S22). Figure 11 is a diagram illustrating the method for setting an alternative channel according to the first embodiment. As shown in Figure 11, the selection unit 34 transmits a relay instruction signal 102 to the wireless communication terminals 10-60 and 10-90 selected in step S20 via the relay communication unit 20, instructing them to create an alternative channel T3 to replace the communication channel. Upon receiving the relay instruction signal 102, wireless communication terminals 10-60 and 10-90 are connected by short-range wireless communication 110 via the second communication unit 42. At this time, RX3 is set as the receiving frequency for the alternative channel T3 in the first communication unit 40 of wireless communication terminal 10-60, and TX3 is set as the transmitting frequency for the alternative channel T3 in the first communication unit 40 of wireless communication terminal 10-90. The channel with frequency RX3 is sometimes called the first backup channel, and the channel with frequency TX3 is sometimes called the second backup channel. As a result, wireless communication terminals 10-60 and 10-90 form a pseudo-alternative channel T3.

[0057] The selection unit 34 transmits a channel switching signal to the wireless communication terminal 10 that sent the communication request and to the wireless communication terminal 10 designated as the communication destination, indicating an instruction to switch the channel to an alternative channel (step S24). Figure 12 is a diagram illustrating the method of switching the channel to an alternative channel according to the first embodiment. As shown in Figure 12, the selection unit 34 transmits a channel switching signal 103 to wireless communication terminals 10-5 and 10-6 via the relay communication unit 20, indicating an instruction to switch the channel to an alternative channel. The channel switching signal 103 is also called a receive instruction signal or a transmit instruction signal. As a result, the first communication unit 40 of wireless communication terminal 10-5 and the first communication unit 40 of wireless communication terminal 10-6 switch their receiving frequency to RX3, which is the receiving frequency for the alternative channel T3, and their transmitting frequency switches to TX3, which is the transmitting frequency for the alternative channel T3. As a result, wireless communication terminals 10-5 and 10-6 can communicate via wireless communication terminals 10-60 and 10-90. Then, the process proceeds to step S24.

[0058] Here, we will explain the communication flow using the alternative channel according to the first embodiment using Figure 13. Figure 13 is a sequence diagram showing the communication flow using the alternative channel according to the first embodiment.

[0059] When the PTT button included in the operation unit 44 of the wireless communication terminal 10-5 is pressed (step S100), the communication control unit 66 controls the first communication unit 40 to transmit an audio signal to the wireless communication terminal 10-60 (step S102).

[0060] The communication control unit 66 of the wireless communication terminal 10-60 controls the first communication unit 40 to receive the voice signal from the wireless communication terminal 10-5 (step S104). The signal relay unit 62 of the wireless communication terminal 10-60 controls the second communication unit 42 to transfer the voice signal received from the wireless communication terminal 10-5 to the wireless communication terminal 10-90 (step S106).

[0061] The signal relay unit 62 of the wireless communication terminal 10-90 controls the second communication unit 42 to receive the voice signal from wireless communication terminal 10-60 (step S108). The communication control unit 66 of the wireless communication terminal 10-90 controls the first communication unit 40 to transmit the voice signal received from wireless communication terminal 10-60 to wireless communication terminal 10-6 (step S110).

[0062] The communication control unit 66 of the wireless communication terminal 10-6 controls the first communication unit 40 to receive an audio signal from the wireless communication terminal 10-90 (step S112). When the PTT button included in the operation unit 44 is pressed (step S114), the communication control unit 66 of the wireless communication terminal 10-6 controls the first communication unit 40 to transmit an audio signal to the wireless communication terminal 10-60 (step S116).

[0063] The communication control unit 66 of the wireless communication terminal 10-60 controls the first communication unit 40 to receive an audio signal from wireless communication terminal 10-6 (step S118). The signal relay unit 62 of the wireless communication terminal 10-60 controls the second communication unit 42 to transfer the audio signal received from wireless communication terminal 10-6 to wireless communication terminal 10-90 (step S120).

[0064] The signal relay unit 62 of the wireless communication terminal 10-90 controls the second communication unit 42 to receive the voice signal from wireless communication terminal 10-60 (step S122). The communication control unit 66 of the wireless communication terminal 10-90 controls the first communication unit 40 to transmit the voice signal received from wireless communication terminal 10-60 to wireless communication terminal 10-5 (step S124).

[0065] The communication control unit 66 of the wireless communication terminal 10-5 controls the first communication unit 40 to receive an audio signal from the wireless communication terminal 10-90 (step S126).

[0066] By performing the process shown in Figure 13, wireless communication terminal 10-5 and wireless communication terminal 10-6 can communicate via the alternative channel T3.

[0067] Return to Figure 7. After step S24, the control unit 24 determines whether or not communication using the alternative channel has ended (step S26). Specifically, the control unit 24 determines to terminate processing when it receives a communication termination signal from the relay terminal.

[0068] The process flow for terminating communication using the alternative channel according to the first embodiment will be explained using Figure 14. Figure 14 is a sequence diagram showing the process flow for terminating communication using the alternative channel according to the first embodiment.

[0069] When the communication control unit 66 of the wireless communication terminal 10-5 receives a call termination operation signal from the operation unit 44 (step S140), it controls the first communication unit 40 to transmit a call termination signal to the wireless communication terminal 10-60 (step S142).

[0070] The communication control unit 66 of the wireless communication terminal 10-60 controls the first communication unit 40 to receive the call termination signal from wireless communication terminal 10-5 (step S144). The signal relay unit 62 of the wireless communication terminal 10-60 controls the second communication unit 42 to forward the call termination signal received from wireless communication terminal 10-5 to wireless communication terminal 10-90 (step S146).

[0071] The signal relay unit 62 of the wireless communication terminal 10-90 controls the second communication unit 42 to receive the call termination signal from wireless communication terminal 10-60 (step S148). The communication control unit 66 of the wireless communication terminal 10-90 controls the first communication unit 40 to transmit the call termination signal received from wireless communication terminal 10-60 to wireless communication terminal 10-6 (step S150).

[0072] The communication control unit 66 of the wireless communication terminal 10-6 controls the first communication unit 40 to receive the call termination signal from the wireless communication terminal 10-90 (step S152).

[0073] The communication control units 66 of wireless communication terminals 10-60 and 10-90 control the second communication unit 42 to terminate the short-range wireless connection (step S154).

[0074] The control units 54 of wireless communication terminals 10-5, 10-6, 10-60, and 10-90 set the channel set in the first communication unit 40 to control channel CC (step S158).

[0075] The communication control unit 66 of wireless communication terminals 10-60 controls the first communication unit 40 to transmit a completion signal to the wireless relay device 12 indicating that communication on the alternative channel T3 has been completed (step S160). The communication control unit 66 of wireless communication terminal 10-90 controls the first communication unit 40 to transmit a completion signal to the wireless relay device 12 indicating that communication on the alternative channel T3 has been completed (step S162). When the wireless relay device 12 receives completion signals from wireless communication terminals 10-60 and 10-90, it determines that communication should be terminated.

[0076] Return to Figure 7. If it is determined that communication should be terminated (Step S26; Yes), proceed to Step S28. If it is not determined that communication should be terminated (Step S26; No), repeat the process in Step S26.

[0077] If the result in step S26 is determined to be Yes, the control unit 24 returns the alternate channel T3 that was being used from the active state to the standby state (step S28). Then, the process shown in Figure 7 is terminated.

[0078] As described above, in the first embodiment, if all communication channels of the wireless relay device 12 are in use, an alternative channel can be set using the wireless communication terminal 10. As a result, in the first embodiment, the wireless communication terminal 10 can communicate with other wireless communication terminals 10 even when all communication channels of the wireless relay device 12 are in use.

[0079] [Modified version of the first embodiment] In the first embodiment, two wireless communication terminals were selected to constitute the alternative channel, but the present invention is not limited to this. For example, any wireless communication terminal capable of simultaneously receiving and transmitting signals may be used to constitute the alternative channel.

[0080] Furthermore, in this invention, an alternative channel may be configured using three or more relay terminals. Specifically, an alternative channel may be configured by connecting three or more relay terminals via short-range wireless communication between the source wireless communication terminal and the destination wireless communication terminal. By configuring an alternative channel with three or more relay terminals, the communication range between the source wireless communication terminal and the destination wireless communication terminal can be extended.

[0081] [Second Embodiment] Next, a second embodiment of the present invention will be described. In the second embodiment, if the short-range wireless communication connection between wireless communication terminals constituting the alternative channel weakens or is instantly disconnected due to trouble, the relay terminal is researched.

[0082] The communication flow using the alternative channel according to the second embodiment will be explained using Figure 15. Figure 15 is a sequence diagram showing the communication flow using the alternative channel according to the second embodiment.

[0083] Figure 15 shows the processing flow when the short-range wireless communication connection between relay terminals constituting an alternative channel becomes weaker than predetermined. In the second embodiment, as in the first embodiment, the communication between wireless communication terminal 10-5 and wireless communication terminal 10-6 will be described as being relayed by wireless communication terminals 10-60 and 10-90.

[0084] The control units 54 of wireless communication terminals 10-60 and 10-90 determine that the signal strength of the short-range wireless communication connection by the second communication unit 42 has fallen below a predetermined threshold (step S200). A signal strength below a predetermined threshold means that it becomes difficult to maintain communication due to the distance between wireless communication terminals 10-60 and 10-90 increasing, or due to interference from jamming radio waves. Note that the case where the signal strength falls below the predetermined threshold also includes the case where the connection between wireless communication terminals 10-60 and 10-90 is lost for an instant. Alternatively, the control unit 54 may determine that the bit error rate of the signal has exceeded a predetermined threshold instead of the signal strength.

[0085] The communication control unit 66 of the wireless communication terminal 10-90 controls the first communication unit 40 and sends a standby message to wireless communication terminal 10-5 and wireless communication terminal 10-6 indicating that it should be put into standby mode (steps S202, S204).

[0086] The control units 54 of wireless communication terminals 10-60 and 10-90 release the alternate channel (step S206).

[0087] The communication control unit 66 of wireless communication terminals 10-60 controls the first communication unit 40 to transmit a reselection request to the wireless relay device 12 indicating a request for reselection of the relay terminals constituting the alternative channel (step S208). The communication control unit 66 of wireless communication terminal 10-90 controls the first communication unit 40 to transmit a reselection request to the wireless relay device 12 indicating a request for reselection of the relay terminals constituting the alternative channel (step S210).

[0088] The re-selection process for the relay terminal according to the second embodiment will be explained using Figure 16. Figure 16 is a flowchart showing the flow of the re-selection process for the relay terminal according to the second embodiment.

[0089] The control unit 24 controls the relay communication unit 20 to receive a request for re-selection of the relay terminal from the relay terminal that is configuring the alternative channel (step S40). Then, the process proceeds to step S42.

[0090] The selection unit 34 re-selects relay terminals to configure an alternative channel (step S42). Specifically, the selection unit 34 selects relay terminals based on call history information 22a (see Figure 5) and the communication range of each wireless communication terminal 10 located in a predetermined area (see Figure 10). For example, in the example shown in Figure 10, the selection unit 34 re-selects two relay terminals from among wireless communication terminals 10-20, 10-50, 10-60, and 10-90. Here, the selection unit 34 re-selects wireless communication terminals 10-50 and 10-60 as relay terminals. Then, the process proceeds to step S44.

[0091] The selection unit 34 instructs the system to set an alternative channel (step S44). Specifically, the selection unit 34 instructs the wireless communication terminals 10-50 and 10-60, which were re-selected in step S42, to set an alternative channel. Then, the system proceeds to step S46.

[0092] Of the two wireless communication terminals 10-50 and 10-60, which have newly become alternative channels, the communication control unit 66 of wireless communication terminal 10-60, which is assigned the transmission frequency TX3 for alternative channel T3, controls the first communication unit 40 to send a call resume message (step S46). Specifically, the communication control unit 66 of wireless communication terminal 10-60 controls the first communication unit 40 to send a call resume message to wireless communication terminal 10, which is waiting for communication, indicating that a call is now possible. Then the process shown in Figure 16 is completed.

[0093] As described above, the second embodiment sends a message to the wireless communication terminal making a call instructing it to put the call on hold when the relay terminal's communication is about to be interrupted. Then, when communication becomes possible again, the second embodiment sends a call start message. This improves the convenience of the second embodiment.

[0094] 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.

[0095] 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]

[0096] 10 Wireless communication terminals 12 Wireless relay device 20 Relay Communications Department 22,50 Storage part 24,54 Control Unit 30 Acquisition Department 32 Channel setting section 34 Selection Section 40. First Communications Department 42. Second Communications Department 44 Control section 46 Speaker section 48 Display section 52 GNSS receiver 60 Location information acquisition section 62 Signal relay section 64 Output Control Unit 66 Communication Control Unit

Claims

1. A relay communication unit that relays signals using the first communication method, A storage unit that stores location information of multiple wireless communication terminals received by the relay communication unit, The relay communication unit includes a selection unit that, when a new relay request is received while all communication channels set in the relay communication unit are in use, selects a relay terminal to perform relay operations between the source wireless communication terminal that sent the relay request and the destination wireless communication terminal designated as the communication destination, based on the location information of a plurality of wireless communication terminals stored in the storage unit. The selection unit selects at least a first relay terminal and a second relay terminal as the relay terminals, and controls the relay communication unit. A transmission instruction signal is given to the source wireless communication terminal which instructs it to transmit using the first communication method, on a first backup channel different from the communication channel set in the relay communication unit, A reception instruction signal is given to the wireless communication terminal to which the communication destination is instructed to receive the signal using the first communication method, on a second backup channel different from the communication channel set in the relay communication unit. The relay terminal is instructed to transmit a relay instruction signal that tells it to perform relay operations using the first and second reserve channels. The relay instruction signal includes information for identifying the first relay terminal, the second relay terminal, and the connection channel of the second communication system. Wireless relay device.

2. The storage unit further stores call history information, including the frequency of use of past communications of the multiple wireless communication terminals received by the relay communication unit. The selection unit selects the relay terminal based on the location information and the call history information. The wireless relay device according to claim 1.

3. The selection unit selects, from among the plurality of wireless communication terminals, the wireless communication terminal located within the range from the source wireless communication terminal and the destination wireless communication terminal that can communicate using the first communication method, as the relay terminal. The wireless relay device according to claim 1 or 2.

4. The selection unit divides the range in which communication is possible using the first communication method from the source wireless communication terminal and the destination wireless communication terminal into a plurality of predetermined areas, and selects the wireless communication terminal located in the area with the largest number of wireless communication terminals as the relay terminal. The wireless relay device according to claim 3.

5. The first relay terminal transmits the signal received from the source wireless communication terminal on the first backup channel to the second relay terminal on the connection channel of the second communication method. The second relay terminal transmits the signal received from the first relay terminal on the connection channel to the communication destination wireless communication terminal on the second backup channel. A wireless relay device according to any one of claims 1 to 4.

6. A wireless communication terminal that communicates with the wireless relay device described in claim 5, A first communication unit that communicates using the first communication method described above, A second communication unit that communicates using the second communication method described above, A location information acquisition unit that acquires location information of its own wireless communication terminal, A history information storage unit that stores call history information relating to the call history communicated by the first communication unit, The system includes a signal relay unit that, when the first communication unit receives a relay instruction signal, forwards and transmits the received signal between the first communication unit and the second communication unit. The first communication unit periodically transmits the location information and the call history information to the wireless relay device. The aforementioned signal relay unit is If the relay instruction signal designates the self-wireless communication terminal as the first relay terminal, the signal received on the first backup channel is transmitted to the second relay terminal on the connection channel. If the relay instruction signal designates the local wireless communication terminal as the second relay terminal, the signal received from the first relay terminal on the connection channel is transmitted on the second backup channel. Wireless communication terminal.

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