Communication device and communication method

Abstract

Provided are a communication device and a communication method that make it possible to identify a distance between the communication device and a communication partner device while stably maintaining communicative connection between the devices. A communication device according to the present disclosure comprises: a communication unit that performs wireless communication with another communication device; an acquisition unit that acquires various kinds of information via the communication unit; an output control unit that controls a transmission output value of the communication unit; and a notification unit that notifies a user of an abnormality. The acquisition unit acquires, from the other communication device, a second signal of a second radio wave including first radio wave reception strength information which is a radio wave strength value of a first radio wave that the other communication device has received from the host communication device and second radio wave transmission strength information which is a transmission output value of the second radio wave that is transmitted by the other communication device. The output control unit controls, so that the received first radio wave reception strength is kept constant, a transmission output value of the first radio wave transmitted to the other communication device.

Description

Communication device and communication method

[0001] The present disclosure relates to a communication device and a communication method.

[0002] 2. Description of the Related Art A technique is known in which, between devices equipped with wireless communication capabilities, radio waves transmitted from a target device are received and the received signal strength of the radio waves is measured to estimate the distance to the target device.

[0003] For example, Patent Document 1 listed below discloses a technique in which, in an RFID tag reader, when a transmitting means transmits radio waves with transmission parameters corresponding to predetermined transmission conditions, a receiving means receives a response signal transmitted from the RFID tag in response to the transmitted radio waves, and when a calculating means calculates the received signal strength of the response signal, a distance estimating means estimates the distance to the RFID tag based on the received signal strength and the transmission parameters.

[0004] JP 2016-62160 A

[0005] However, as described in Patent Document 1 above, the technology for estimating the distance between devices based on the received signal strength is unable to maintain a constant communication quality between devices and prevent communication from being interrupted even if the distance between the devices increases, because the received signal strength changes depending on the distance between the devices.

[0006] In view of the above-mentioned problems, the present disclosure aims to provide a communication device and a communication method that can identify the distance between communication devices while maintaining a stable communication connection between the communication devices.

[0007] In order to solve the above-mentioned problems and achieve the objectives, a communication device according to the present disclosure comprises a communication unit that wirelessly communicates with other communication devices, an acquisition unit that acquires various information via the communication unit, and an output control unit that controls the transmission output value of the communication unit, wherein the acquisition unit acquires from the other communication device a second signal of a second radio wave that includes first radio wave reception strength information, which is the radio wave strength value of a first radio wave received by the other communication device from its own communication device, and second radio wave transmission strength information, which is the transmission output value of a second radio wave transmitted by the other communication device, and the output control unit controls the transmission output value of the first radio wave to be transmitted to the other communication device so that the received first radio wave reception strength information is kept constant.

[0008] In order to solve the above-mentioned problems and achieve the objective, the communication method of the present disclosure comprises the steps of: communicating wirelessly with another communication device; acquiring various information in the wireless communication step; and controlling the transmission output value of the wireless communication; wherein in the acquiring step, a second signal of a second radio wave is acquired from the other communication device, the second signal including first radio wave reception strength information, which is the radio wave strength value of a first radio wave received by the other communication device from its own communication device, and second radio wave transmission strength information, which is the transmission output value of a second radio wave transmitted by the other communication device; and in the controlling step, the transmission output value of the first radio wave to be transmitted to the other communication device is controlled so that the received first radio wave reception strength information is kept constant.

[0009] According to the present disclosure, it is possible to provide a communication device and a communication method that can identify the distance between communication devices while maintaining a stable communication connection between the communication devices.

[0010] FIG. 1 is a diagram illustrating an overview of a communication system according to the present disclosure. FIG. 2 is a diagram illustrating a configuration example of a communication system according to the present disclosure. FIG. 3 is a diagram illustrating a configuration example of a communication device according to the present disclosure. FIG. 4 is a diagram illustrating an example of information stored in a connection information storage unit of a communication device according to the present disclosure. FIG. 5 is a diagram illustrating an example of information stored in a setting value storage unit of a communication device according to the present disclosure. FIG. 6 is a diagram illustrating a configuration example of a communicated device according to the present disclosure. FIG. 7 is a flowchart illustrating a flow of a first aspect of a communication method according to the present disclosure. FIG. 8 is a flowchart illustrating a flow of a second aspect of a communication method according to the present disclosure. FIG. 9 is a flowchart illustrating a flow of a first aspect of a communication method of a communication system according to the present disclosure.

[0011] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. However, the present disclosure is not limited to the embodiments described below.

[0012] (Overview of the Communication System) First, a usage scenario of a communication system 1 according to the present disclosure will be described using FIG. 1 . FIG. 1 is a diagram illustrating an overview of the communication system according to the present disclosure. As shown in FIG. 1 , the communication system 1 according to the present disclosure includes a communication device 100 and a communicated device 200 (200A, 200B). The communication device 100 and the communicated device 200 may have different forms, such as a tablet or a wristwatch, but may be communication devices with similar functions. A radio wave W1 is transmitted from the communication device 100 to another communication device, the communicated device 200 (200A, 200B). Furthermore, a radio wave W2a is transmitted from the communicated device 200A to the communication device 100. Furthermore, a radio wave W2b is transmitted from the communicated device 200B to the communication device 100. The signals transmitted by the radio waves W1, W2a, and W2b include an identifier (device ID) that specifies the source and destination of the radio waves, and a device receiving the radio waves recognizes the signal as having been sent to that device if the destination identifier included in the signal matches the identifier of the device itself. For example, the signal transmitted by the communication device 100 to the communicated device 200A by the radio waves W1 includes the identifier of the communication device as the source and an identifier that specifies the communicated device 200A as the destination.

[0013] For example, a user U who is an administrator may carry the communication device 100, and the children C1 and C2 who are under the user U's supervision may carry the communication device 200, and the device may be used to manage the user U and the children C1 and C2 by controlling the transmission output of wireless communication and by sending notifications so that they do not become separated.

[0014] (Configuration of communication system) Next, the configuration of a communication system 1 according to the present disclosure will be described with reference to Fig. 2. Fig. 2 is a diagram showing an example configuration of a communication system according to the present disclosure. As shown in Fig. 2, the communication system 1 according to the present disclosure includes a communication device 100, a communicated device 200, and a network N. Below, a brief description of these configurations will be given.

[0015] The communication device 100 is an information processing device used by a user U. The communication device 100 may be, for example, an information processing device such as a smartphone, a tablet terminal, a wearable terminal, a mobile phone, or a PDA (Personal Digital Assistant). Note that the example shown in FIG. 1 illustrates a case where the communication device 100 is a smartphone.

[0016] The communicated device 200 is an information processing device used by a person under management, such as a child C, who is under the management of a user U. The communicated device 200 may be, for example, an information processing device such as a smartphone, a tablet terminal, a wearable terminal, a mobile phone, or a PDA (Personal Digital Assistant). Note that the example shown in Fig. 1 illustrates a case where the communicated device 200 is a wearable terminal.

[0017] The network N wirelessly connects the communication device 100 and the communicated device 200 so that they can communicate with each other. The network N may be realized by Bluetooth (registered trademark) or a wireless LAN (Local Area Network) defined by IEEE802.11.

[0018] (Configuration of communication device) Next, the configuration of a communication device according to the present disclosure will be described using Fig. 3. Fig. 3 is a diagram showing an example configuration of a communication device according to the present disclosure. As shown in Fig. 3, a communication device 100 according to the present disclosure includes a communication unit 110, a storage unit 120, a control unit 130, a sound output unit 140, and a display unit 150. These components will be described in order below.

[0019] The communication unit 110 connects the inside and outside of the communication device 100 so that they can communicate with each other, and transmits and receives information between the inside and outside of the communication device 100. The communication unit 110 may be realized by, for example, a Bluetooth (registered trademark) module, a wireless LAN (Local Area Network) card, a Wi-Fi (registered trademark) module, an antenna, etc. The communication unit 110 is, for example, wirelessly connected to the communicated device 200, and transmits and receives information to and from the communicated device 200. In other words, it can be said that the communication unit 110 communicates wirelessly with the communicated device 200.

[0020] For example, the communication unit 110 periodically receives a second signal including first radio wave reception strength information, which is the radio wave strength value of the first radio wave received by the communicated device 200 from the communication device 100, and second radio wave transmission strength information (transmission power information), which is the transmission output value of the second radio wave transmitted by the communicated device 200 to the communication device 100. Furthermore, the communication unit 110 periodically transmits to the communicated device 200 a first signal, which includes second radio wave reception strength information, which is the radio wave strength value of the second radio wave received from the communicated device 200 measured by the measurement unit 132, and first radio wave transmission strength information (transmission power information), which is the transmission output value of the first radio wave transmitted by the communication device 100 to the communicated device 200.

[0021] The storage unit 120 is a storage device that stores various types of information. The storage unit 120 includes a main storage device and an auxiliary storage device. The main storage device may be realized by a semiconductor memory element such as a RAM (Random Access Memory), a ROM (Read Only Memory), or a flash memory. The auxiliary storage device may be realized by, for example, a hard disk, an SSD (Solid State Drive), or an optical disk.

[0022] 3, the storage unit 120 includes a connection information storage unit 121 and a setting value storage unit 122. The information stored in these components will be described below.

[0023] (Connection Information Storage Unit 121) The connection information storage unit 121 stores connection information indicating information related to wireless communication connections with other devices. An example of information stored in the connection information storage unit 121 will be described with reference to Fig. 4. Fig. 4 is a diagram illustrating an example of information stored in the connection information storage unit of a communication device according to the present disclosure.

[0024] In the example shown in FIG. 4, the connection information storage unit 121 stores information relating to the items "device ID" and "pairing setting" in association with each other.

[0025] The "device ID" is an identifier for identifying a device that is the target of pairing, which indicates the execution of a key exchange protocol, and is expressed by a character string, a number, etc. The "pairing setting" is information about the setting of pairing with the device identified by the "device ID," such as an exchanged key, a profile, etc.

[0026] 4 shows an example in which connection information for a device identified by a device ID "TID#1" is stored as "PR#1." For example, information on the communicated device 200 is stored.

[0027] The connection information storage unit 121 is not limited to storing information relating to the items "device ID" and "pairing setting", and may store information relating to any other connection information.

[0028] (Regarding the setting value storage unit 122) The setting value storage unit 122 stores information related to various setting values. An example of information stored in the setting value storage unit 122 will be described with reference to Fig. 5. Fig. 5 is a diagram illustrating an example of information stored in the setting value storage unit of the communication device according to the present disclosure.

[0029] In the example shown in FIG. 5, the setting value storage unit 122 stores information relating to the items "setting content" and "setting value" in association with each other.

[0030] The "setting content" is the name of a parameter to which an arbitrary numerical value is set, such as the "transmission output value" or the "amount of change in the transmission output value per unit time." The "setting value" indicates a specific numerical value for the parameter indicated in the "setting content," such as the value of the first threshold value or the second threshold value.

[0031] 5 shows an example in which the setting value of the parameter indicated by the setting content "ST#1" is stored as "STVL#1." For example, information for managing the communicated device 200 is stored.

[0032] The setting value storage unit 122 is not limited to storing information relating to the items "setting content" and "setting value", but may store information relating to any other setting value.

[0033] (Regarding the control unit 130) The control unit 130 is a controller that manages and controls the communication device 100. The control unit 130 is realized by a CPU (Central Processing Unit), an MPU (Micro Processing Unit), or the like executing various programs stored in the storage unit 120 using RAM as a work area. The control unit 130 may also be realized by an integrated circuit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array).

[0034] As shown in FIG. 3 , the control unit 130 includes an acquisition unit 131, a measurement unit 132, a change amount detection unit 133, an output control unit 134, and a notification unit 135. The control unit 130 realizes these functions and executes these processes by reading and executing a program (software) from the storage unit 120. Note that these components of the control unit 130 may be implemented by electronic circuits. Furthermore, the control unit 130 may execute these processes using a single CPU, or may include multiple CPUs that execute these processes in parallel. These components will be described below in order.

[0035] The acquisition unit 131 acquires various types of information via the communication unit 110. Specific examples of the information acquired by the acquisition unit 131 will be described below.

[0036] For example, the acquisition unit 131 acquires from the communicated device 200 a second signal including first radio wave reception strength information, which is the radio wave strength value of the first radio wave received by the communicated device 200 from the communication device 100, and second radio wave transmission strength information, which is the transmission output value of the second radio wave transmitted by the communicated device 200 to the communication device 100. The transmission output value of the radio wave to be transmitted may be a numerical value corresponding to a received signal strength indicator (RSSI) value indicating the radio wave strength value of the received radio wave. The RSSI value is a value indicating the strength of the signal received by the receiver. Alternatively, the transmission output value of the radio wave to be transmitted may be a transmission power value.

[0037] The measurement unit 132 measures the radio wave intensity value of the radio wave received by the communication unit 110. For example, the measurement unit 132 outputs the measured radio wave intensity value of the second radio wave received by the communication unit 110 from the communicated device 200 as second radio wave reception intensity information. That is, the measurement unit 132 outputs an RSSI value as second radio wave reception intensity information that measures the radio wave intensity value of the second radio wave received from the communicated device 200. Specifically, the measurement unit 132 outputs, as the RSSI value, a value proportional to the logarithmic value expressed in dBμV of the input voltage of the received second radio wave.

[0038] The change amount detection unit 133 determines the amount of change per unit time of the second radio wave transmission strength information included in the received second signal. For example, when the acquisition unit 131 acquires the second signal at predetermined intervals and obtains the transmission output value included in the second radio wave transmission strength information, the change amount detection unit 133 may determine the amount of change per unit time of the transmission output value of the second radio wave transmission strength information by dividing the difference from the transmission output value of the second radio wave transmission strength information received before the predetermined period by the predetermined period. The transmission output value of the second radio wave transmission strength information received before the predetermined period is stored in the storage unit 120.

[0039] The output control unit 134 controls the transmission output value of the communication unit 110. A specific example of how the output control unit 134 controls the transmission output will be described below.

[0040] The output control unit 134 controls the transmission output value of the own device when transmitting to the communicated device 200 so that the radio wave intensity value of the first radio wave received by the communicated device 200 is maintained constant. For example, the output control unit 134 can determine the radio wave intensity value of the first radio wave received by the communicated device 200 by referring to the first radio wave reception strength information included in the second signal acquired by the acquisition unit 131. When the output control unit 134 detects that the radio wave intensity of the first radio wave received by the communicated device 200 is decreasing based on the first radio wave reception strength information, it controls to increase the transmission output. Furthermore, when the output control unit 134 detects that the radio wave intensity of the first radio wave received by the communicated device 200 is increasing based on the first radio wave reception strength information, it controls to decrease the transmission output. Note that the increase and decrease amounts of the transmission output may be determined in advance by actually measuring the relationship between the received radio wave intensity value, the transmission output value, and the device-to-device distance, and then controlled so that the radio wave intensity value of the first radio wave received by the communicated device 200 is maintained constant. In this case, the device-to-device distance can be determined from the transmission output value to be transmitted.

[0041] The notification unit 135 notifies the user of an abnormality. For example, the notification unit 135 notifies the user of an abnormality by causing the sound output unit 140 to output a sound message notifying the user of the abnormality. The notification unit 135 also notifies the user of an abnormality by causing the display unit 150 to display a message notifying the user of the abnormality. The processing of the notification unit 135 will be specifically described below.

[0042] When the transmission output value included in the second radio wave reception intensity information included in the second signal acquired by the acquisition unit 131 becomes equal to or greater than a first threshold, the notification unit 135 notifies that the distance between the communication device 100 and the communicated device 200 has increased by more than a predetermined value. The notification unit 135 causes the sound output unit 140 to output an audio message such as, "The distance to the communicated device 200 with the identification number XX is equal to or greater than a predetermined value." The notification unit 135 may also display the message as text on the display unit 150. The notification unit 135 notifies that the distance between the communicated device 200 and the communication device 100 has increased rapidly when the change in the transmission output value of the second radio wave transmission intensity information calculated by the change amount detection unit 133 becomes equal to or greater than a predetermined second threshold. The change in the transmission output value of the second radio wave transmission intensity information refers to the amount of change in the radio wave intensity value per unit time. That is, when the change per unit time in the transmission output value of the second radio wave transmission strength information detected by the change amount detection unit 133 indicates an increase equal to or greater than a predetermined second threshold, the notification unit 135 notifies the user that the distance between the communicated device 200 and the communication device 100 is increasing rapidly. As the distance between the communicated device 200 and the communication device 100 increases, the received radio wave intensity value attenuates. Therefore, in order to maintain the received radio wave intensity value constant, it is necessary to increase the transmission output value transmitted by the communicated device 200. The correspondence between the transmission output value and the distance can be measured using the actual communication device 100 and the communicated device 200, and the result can be stored in the storage unit 120. The notification unit 135 issues a notification when the increase in the transmission output value of the second radio wave transmission strength information exceeds a threshold, indicating that the distance is increasing rapidly. That is, the notification unit 135 causes the sound output unit 140 to output a voice message such as "The distance to the communicated device 200 having the identification number XX is increasing rapidly." The notification unit 135 may also cause the display unit 150 to display the above-mentioned message as text.

[0043] (Sound Output Unit 140) The sound output unit 140 outputs sounds such as voice. For example, the sound output unit 140 outputs a message notified by the notification unit 135 as sound. The sound output unit 140 may be a speaker, which converts an electrical signal into sound using a diaphragm. That is, the speaker vibrates the diaphragm with a predetermined amplitude and frequency based on a control command given by the electrical signal, thereby vibrating the air in contact with the diaphragm and outputting sound.

[0044] (Regarding the Display Unit 150) The display unit 150 displays various types of information to the user. For example, the display unit 150 displays, as text, a message notified by the notification unit 135. The display unit 150 may be realized by, for example, a liquid crystal display, an organic electroluminescence (EL) display, a micro-LED (light-emitting diode) display, or the like.

[0045] (Configuration of Communicated Device) Next, the configuration of the communicated device according to the present disclosure will be described using FIG. 6. FIG. 6 is a diagram showing an example configuration of the communicated device according to the present disclosure. As shown in FIG. 6, the communicated device 200 according to the present disclosure includes a communication unit 210, a storage unit 220, a control unit 230, a sound output unit 240, and a display unit 250. Below, these components will be described in order.

[0046] The communication unit 210 connects the inside and outside of the communicated device 200 so that they can communicate with each other, and transmits and receives information between the inside and outside of the communicated device 200. The communication unit 210 may be realized by, for example, a Bluetooth (registered trademark) module, a wireless LAN card, a Wi-Fi (registered trademark) module, an antenna, etc.

[0047] For example, the communication unit 210 periodically receives a first radio wave of a first signal that includes second radio wave reception strength information, which is the radio wave strength value of the second radio wave received by the communication device 100 from the communicated device 200, and first radio wave transmission strength information (transmission power information), which is the transmission output value of the first radio wave transmitted by the communication device 100 to the communicated device 200. Furthermore, the communication unit 210 periodically transmits to the communication device 100 a second radio wave of a second signal that includes the first radio wave reception strength information, which is the radio wave strength value of the first radio wave received from the communication device 100 measured by the measurement unit 232, and second radio wave transmission strength information (transmission power information), which is the transmission output value of the second radio wave transmitted by the communicated device 200 to the communication device 100.

[0048] The storage unit 220 is a storage device that stores various types of information. The storage unit 220 includes a main storage device and an auxiliary storage device. The main storage device may be realized by semiconductor memory elements such as RAM, ROM, flash memory, etc. The auxiliary storage device may be realized by, for example, a hard disk, SSD, optical disk, etc.

[0049] 6, the storage unit 220 includes a connection information storage unit 221 and a setting value storage unit 222. The information stored in the connection information storage unit 221 and the setting value storage unit 222 is the same as the information stored in the connection information storage unit 121 and the setting value storage unit 122 of the storage unit 120 of the communication device 100, respectively, and therefore a description of the information stored in the connection information storage unit 221 and the setting value storage unit 222 will be omitted.

[0050] The control unit 230 is a controller that manages and controls the communicated device 200. The control unit 230 is realized by a CPU, an MPU, or the like executing various programs stored in the storage unit 220 using the RAM as a work area. The control unit 230 may also be realized by an integrated circuit such as an ASIC or an FPGA.

[0051] As shown in FIG. 6 , the control unit 230 includes an acquisition unit 231, a measurement unit 232, a change amount detection unit 233, an output control unit 234, and a notification unit 235. The control unit 230 realizes these functions and executes these processes by reading and executing a program (software) from the storage unit 220. Note that these components of the control unit 230 may be implemented by electronic circuits. Furthermore, the control unit 230 may execute these processes using a single CPU, or may include multiple CPUs that execute these processes in parallel. These components will be described below in order.

[0052] The acquisition unit 231 acquires various types of information via the communication unit 210. Specific examples of the information acquired by the acquisition unit 231 will be described below.

[0053] For example, the acquisition unit 231 acquires from the communication device 100 a first signal including second radio wave reception strength information, which is the radio wave strength value of the second radio wave received by the communication device 100 from the communicated device 200, and first radio wave transmission strength information, which is the transmission output value of the first radio wave transmitted by the communication device 100 to the communicated device 200. Note that the transmission output value of the transmission may be a value corresponding to the RSSI value.

[0054] Measurement unit 232 measures the radio wave intensity value of the radio wave received by communication unit 210. For example, measurement unit 232 outputs first radio wave reception intensity information obtained by measuring the radio wave intensity value of the first radio wave received by communication unit 210 from communication device 100. That is, measurement unit 232 outputs an RSSI value as first radio wave reception intensity information obtained by measuring the radio wave intensity value of the first radio wave received from communication device 100. Specifically, measurement unit 232 outputs, as the RSSI value, a value proportional to the logarithmic value of the input voltage of the received first radio wave, expressed in units of dBμV.

[0055] The change amount detection unit 233 obtains the amount of change per unit time of the first radio wave transmission strength information included in the received first signal. For example, when the acquisition unit 231 acquires the first signal at predetermined intervals and obtains the transmission output value included in the first radio wave transmission strength information, the change amount detection unit 233 may obtain the amount of change per unit time of the transmission output value of the first radio wave transmission strength information by dividing the difference between the transmission output value of the first radio wave transmission strength information received before the predetermined interval by the predetermined interval.

[0056] The output control unit 234 controls the transmission output value of the communication device 100 when transmitting to the communication device 100 so that the radio wave intensity value of the second radio wave received by the communication device 100 is maintained constant. For example, the radio wave intensity value of the second radio wave received by the communication device 100 can be determined by referring to second radio wave reception intensity information included in the first signal acquired by the acquisition unit 231. When the output control unit 234 detects that the radio wave intensity value of the second radio wave received by the communication device 100 is decreasing based on the second radio wave reception intensity information, the output control unit 234 controls to increase the transmission output. Furthermore, when the output control unit 234 detects that the second radio wave reception intensity is increasing, the output control unit 234 controls to decrease the transmission output. Note that the increase and decrease amounts of the transmission output may be determined in advance by actually measuring the relationship between the received radio wave intensity value, the transmission output value, and the device-to-device distance, and the control may be performed so that the radio wave intensity value of the second radio wave received by the communication device 100 is maintained constant. In this case, the device-to-device distance can be determined from the transmission output value to be transmitted.

[0057] The notification unit 235 notifies the user of an abnormality. For example, the notification unit 235 notifies the user of an abnormality by causing the sound output unit 240 to output a sound message notifying the user of the abnormality. The notification unit 235 also notifies the user of an abnormality by causing the display unit 250 to display a message notifying the user of the abnormality. The processing of the notification unit 235 will be specifically described below.

[0058] When the transmission output value included in the first radio wave transmission strength information included in the first signal acquired by the acquisition unit 231 becomes equal to or greater than a first threshold, the notification unit 235 notifies that the distance between the communicated device 200 and the communication device 100 has increased by more than a predetermined value. The notification unit 235 causes the sound output unit 240 to output an audio message such as, "The distance from the communication device 100 is equal to or greater than a predetermined value." The notification unit 235 may also cause the display unit 250 to display the message as text. The notification unit 235 notifies that the distance between the communication device 100 and the communication device itself has increased rapidly when the change in the transmission output value of the first radio wave transmission strength information calculated by the change amount detection unit 233 becomes equal to or greater than a predetermined second threshold. The change in the first radio wave transmission strength information refers to the amount of attenuation of the transmission output value per unit time. That is, when the change per unit time of the first radio wave transmission strength information detected by the change amount detection unit 233 becomes equal to or greater than a predetermined second threshold, the notification unit 235 notifies the user that the distance between the communication device 100 and the communication target device 200 is rapidly increasing. The correspondence between the transmission output value and the distance can be measured using the actual communication device 100 and the communicated device 200, the result of which can be stored in the memory unit 220, and the distance can be calculated based on the correspondence between the transmission output value and the distance. The notification unit 235 issues a notification when the increase in the transmission output value of the first radio wave transmission strength information exceeds the threshold, indicating that the distance is rapidly increasing. That is, the notification unit 235 causes the sound output unit 240 to output a voice message such as, "The distance from the communication device 100 is rapidly increasing." The notification unit 235 may also cause the display unit 250 to display the message as text.

[0059] The sound output unit 240 outputs sounds such as voice. For example, the sound output unit 240 outputs a message notified by the notification unit 235 as sound. The sound output unit 240 may be a speaker, which converts an electrical signal into sound using a diaphragm. That is, the speaker vibrates the diaphragm with a predetermined amplitude and frequency based on a control command given by the electrical signal, thereby vibrating the air in contact with the diaphragm and outputting sound.

[0060] The display unit 250 displays various types of information to the user. For example, the display unit 250 displays, as text, a message notified by the notification unit 235. The display unit 250 may be realized by, for example, a liquid crystal display, an organic EL display, a micro LED display, or the like.

[0061] (First Aspect of Communication Method) Next, a first aspect of a communication method according to the present disclosure will be described with reference to Fig. 7. Fig. 7 is a flowchart showing the flow of the first aspect of the communication method according to the present disclosure. The first aspect of the communication method according to the present disclosure will be described step by step along the flow shown in Fig. 7.

[0062] First, the communication device 100 receives a second radio wave from the communicated device 200 to acquire a second signal (step S101). Next, the communication device 100 measures the RSSI value of the received second radio wave (step S102). Next, the communication device 100 acquires second radio wave transmission strength information of the communicated device 200 from the second signal (step S103). The communication device 100 estimates the distance to the communicated device 200 from the second radio wave transmission strength information (step S104). Next, the communication device 100 determines whether the distance is equal to or greater than a first threshold (step S105). If the distance is equal to or greater than the threshold (step S105: Yes), the communication device 100 reports that the distance between the communication device 100 and the communicated device 200 is greater than a predetermined value (step S106). Next, the communication device 100 acquires first radio wave reception strength information of the communicated device 200 from the second signal (step S107). Next, the communication device 100 adjusts the transmission output of the communication device 100 based on the first radio wave reception strength information (step S108). Next, the communication device 100 sets the adjusted transmission output of the communication device 100 to the first radio wave transmission strength information (step S109). Next, the communication device 100 sets the measured RSSI value of the second radio wave to the second radio wave reception strength information (step S110). Next, the communication device 100 sets the first radio wave transmission strength information and the second radio wave reception strength information of the communication device 100 to the first signal (step S111). Next, the communication device 100 transmits the first signal as the first radio wave to the communicated device 200 with the adjusted transmission output (step S112).

[0063] If the distance is not equal to or greater than the threshold value in step S105 (step S105: No), the communication device 100 proceeds to step S107 and executes the subsequent processes.

[0064] The first aspect of the communication method described above may be executed by the communication device 100, or may be executed by a program that causes a computer in the control unit 130 of the communication device 100 to execute processing.

[0065] According to this, the communication device 100 can know the RSSI value when the communicated device 200 receives the radio waves transmitted from the communication device 100, and can control the transmission output value of the communication device 100 so that the RSSI value of the radio waves received by the communicated device 200 is kept constant. Therefore, even if the distance between the communication device 100 and the communicated device 200 increases, wireless communication can be continued. Therefore, it is possible to provide a communication method that can continuously maintain the communication connection between the communication device 100 and the communicated device 200.

[0066] (Second Aspect of Communication Method) Next, a second aspect of the communication method according to the present disclosure will be described with reference to Fig. 8. Fig. 8 is a flowchart showing the flow of the second aspect of the communication method according to the present disclosure. The second aspect of the communication method according to the present disclosure will be described step by step along the flow shown in Fig. 8.

[0067] First, the communication device 100 receives a second radio wave from the communicated device 200 to acquire a second signal (step S201). Next, the communication device 100 measures the RSSI value of the received second radio wave (step S202). Next, the communication device 100 acquires second radio wave transmission strength information of the communicated device 200 from the second signal (step S203). Next, the communication device 100 estimates the speed of the distance from the second signal based on the difference between the second radio wave transmission strength information acquired last time and the second radio wave transmission strength information acquired this time and the interval between reception times (step S204). Next, the communication device 100 determines whether the speed is equal to or greater than a second threshold (step S205). If the speed is equal to or greater than the second threshold (step S205: Yes), the communication device 100 reports that the distance between the communication device 100 and the communicated device 200 is rapidly increasing (step S206). Next, the communication device 100 acquires first radio wave reception strength information of the communicated device 200 from the second signal (step S207). Next, the communication device 100 adjusts the transmission output of the communication device 100 based on the first radio wave reception strength information (step S208). Next, the communication device 100 sets the adjusted transmission output of the communication device 100 to the first radio wave transmission strength information (step S209). Next, the communication device 100 sets the measured RSSI value of the second radio wave to the second radio wave reception strength information (step S210). Next, the communication device 100 sets the first radio wave transmission strength information and the second radio wave reception strength information of the communication device 100 to the first signal (step S211). Next, the communication device 100 transmits the first signal as the first radio wave to the communicated device 200 with the adjusted transmission output (step S212).

[0068] If the speed is not equal to or greater than the second threshold value in step S205 (step S205: No), the communication device 100 proceeds to step S207 and executes the subsequent processes.

[0069] According to this, when the speed of the distance increasing is equal to or greater than the second threshold, it is possible to notify the user that the distance between the communication device 100 and the communicated device 200 is increasing rapidly. Furthermore, the communication device 100 can take measures to prevent communication with the communicated device 200 from being interrupted even when the distance between the communication device 100 and the communicated device 200 is increasing rapidly. Therefore, it is possible to provide a communication method that can continuously maintain a communication connection between the communication device 100 and the communicated device 200.

[0070] (Communication method of communication system) Next, a communication method of the communication system 1 according to the present disclosure will be described using Fig. 9. Fig. 9 is a flowchart showing a flow of a first aspect of processing of the communication system according to the present disclosure. The communication method of the communication system 1 according to the present disclosure will be described step by step along the flow shown in Fig. 9.

[0071] First, the communication device 100 (wireless device A) transmits a first signal (first radio wave) including transmitted radio wave strength information (transmitted radio wave strength information As) and received radio wave strength information (received radio wave strength information Br) to the communicated device 200 (wireless device B) (step S301). Next, the communicated device 200 (wireless device B) measures the radio wave strength (received radio wave strength information Ar) of the first radio wave transmitted from the communication device 100 (wireless device A) (step S302). Next, the communicated device 200 determines the distance from the communication device 100 (wireless device A) based on the transmitted radio wave strength information As included in the first signal (step S303). Note that in step S303, the communicated device 200 may notify the communication device 100 of the determined distance. Next, the communicated device 200 controls the transmission output value (transmitted radio wave strength information Bs) of the communicated device 200 based on the received radio wave strength information Br included in the first signal (step S304).

[0072] Next, the communicated device 200 transmits a second signal (second radio wave) including transmitted radio wave strength information (transmitted radio wave strength information Bs) and received radio wave strength information (received radio wave strength information Ar) to the communication device 100 (step S305). Next, the communication device 100 measures the radio wave reception strength (received radio wave strength information Br) of the second radio wave transmitted from the communicated device 200 (step S306). Next, the communication device 100 determines the distance to the communicated device 200 (wireless device B) from the transmission strength information Bs (step S307). Note that in step S307, the communication device 100 may notify the communicated device 200 of the determined distance. Next, the communication device 100 controls the transmission output value (transmission strength information As) of the communication device 100 based on the reception strength information Ar (step S308). Next, the communication device 100 transmits a first signal (first radio wave) including the transmitted radio wave intensity information As and the received radio wave intensity information Br from the communication device 100 to the communicated device 200 (step S309).

[0073] This allows the communication device 100 and the communicated device 200 to mutually transmit and receive transmission power values ​​and received radio wave intensity values. Therefore, the communication device 100 and the communicated device 200 can acquire basic information for controlling the transmission power values ​​of their own devices so that communication between them is not interrupted. The communicated devices 200 may also transmit and receive transmission power values ​​and received radio wave intensity values ​​and report that the distance has increased based on the transmission power values. Using FIG. 1 , the communicated device 200A and the communicated device 200B may communicate, and the communicated device 200A (200B) may report that "The distance to the communication device 200B (200A) is increasing rapidly."

[0074] (Configuration and Effects) A communication device 100 according to the present disclosure comprises a communication unit 110 that wirelessly communicates with other communication devices, an acquisition unit 131 that acquires various information via the communication unit 110, an output control unit 134 that controls the transmission output value of the communication unit 110, and an alarm unit 135 that alerts a user to an abnormality, wherein the acquisition unit 131 acquires from the other communication device a second signal of a second radio wave that includes first radio wave reception strength information, which is the radio wave strength value of a first radio wave received by the other communication device from its own communication device, and second radio wave transmission strength information, which is the transmission output value of a second radio wave transmitted by the other communication device, and the output control unit 134 controls the transmission output value of the first radio wave to be transmitted to the other communication device so that the received first radio wave reception strength is maintained constant.

[0075] According to this configuration, it is possible to control the transmission output value of the communication device 100 so that the first radio wave reception intensity, which is the radio wave intensity value of the radio wave received by the communicated device 200 from the communication device 100, is kept constant. Therefore, it is possible to provide the communication device 100 that can stably maintain the communication connection between the communication device 100 and the communicated device 200.

[0076] The notification unit 135 of the communication device 100 according to the present disclosure notifies that the distance between the other communication device and the communication device itself has increased by more than a predetermined value when the received second radio wave transmission strength information becomes equal to or greater than a predetermined first threshold value.

[0077] According to this configuration, when the second radio wave transmission intensity information received by the communication device 100 becomes equal to or greater than a predetermined threshold, it is possible to notify that the distance between the communication device and another communication device has become equal to or greater than a predetermined value. Furthermore, the communication device 100 can provide a communication device 100 that can continuously maintain a communication connection between the communication device 100 and the communicated device 200 even when the distance between the communication device 100 and the communicated device 200 becomes greater.

[0078] The communication device 100 according to the present disclosure further includes a measurement unit 132 that measures the radio wave intensity value of the radio wave received by the communication unit 110, and the measurement unit 132 outputs the radio wave intensity value of the second radio wave received by the communication unit 110 from another communication device as second radio wave reception intensity information, the output control unit 134 outputs the transmission output value of the first radio wave that the communication unit 110 transmits to the other communication device as first radio wave transmission intensity information, and the communication unit 110 transmits a first signal including the second radio wave reception intensity information and the first radio wave transmission intensity information to the other communication device as the first radio wave.

[0079] According to this configuration, the communication device 100 can transmit a first signal including the second radio wave reception strength information and the first radio wave transmission strength information as a first radio wave to another communication device. Therefore, the other communication device that receives the first signal can control the transmission output value of the communicated device 200 based on the second radio wave reception strength information. Therefore, the communicated device 200 can provide a communicated device 200 that can continuously maintain a communication connection with the communication device 100.

[0080] The communication device 100 according to the present disclosure further includes a change amount detection unit 133 that calculates the amount of change per unit time of the received second radio wave transmission intensity information, the communication unit 110 periodically receives the second signal, and the notification unit 135 notifies that the distance between the communication device and another communication device has suddenly increased when the amount of change becomes equal to or greater than a predetermined second threshold.

[0081] According to this configuration, when the amount of change per unit time in the second radio wave transmission strength received by communication device 100 from communicated device 200 becomes equal to or greater than a predetermined second threshold, it is possible to notify that communicated device 200 is rapidly moving away from communication device 100. Furthermore, communication device 100 can be provided that can continuously maintain the communication connection between communication device 100 and communicated device 200 even when the distance between communication device 100 and communicated device 200 increases.

[0082] The communication method according to the present disclosure includes a step of wirelessly communicating with another communication device, a step of acquiring various information in the wireless communication step, a step of controlling the transmission output value of the wireless communication, and a step of notifying a user of an abnormality. In the acquiring step, a second signal of a second radio wave is acquired from the other communication device, the second signal including first radio wave reception strength information, which is the radio wave strength value of the first radio wave received by the other communication device from the communication device 100, and second radio wave transmission strength information, which is the transmission output value of the second radio wave transmitted by the other communication device. In the controlling step, the transmission output value of the first radio wave to be transmitted to the other communication device is controlled so that the received first radio wave reception strength is maintained constant.

[0083] According to this configuration, it is possible to control the transmission output value of the communication device 100 so that the first radio wave reception intensity, which is the radio wave intensity value of the radio wave received by the communicated device 200 from the communication device 100, is kept constant. Therefore, it is possible to provide a communication method that can stably maintain the communication connection between the communication device 100 and the communicated device 200.

[0084] The communication device 100 and the communicated device 200 may have the same functional configuration, and the transmission output value of the communicated device 200 can be controlled so that the second radio wave reception intensity, which is the radio wave intensity value of the radio waves received by the communication device 100 from the communicated device 200, is kept constant. Therefore, the communication connection between the communicated device 200 and the communication device 100 can be maintained stably.

[0085] Although the embodiments of the present disclosure have been described above, the embodiments are not limited to the contents of these embodiments. Furthermore, the above-described components include those that can be easily imagined by a person skilled in the art, those that are substantially the same, and those that are within the so-called equivalent range. Furthermore, the above-described components can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the components can be made without departing from the spirit of the above-described embodiments.

[0086] This disclosure contributes to the realization of the SDGs (Sustainable Development Goals) goal of "creating sustainable cities and towns" and includes matters that contribute to the safety and security of public facilities.

[0087] The communication device and communication method according to this embodiment can be used, for example, in a communication device and communication method that can determine the distance between communication devices while maintaining a stable communication connection between the communication devices.

[0088] REFERENCE SIGNS LIST 100 Communication device 110 Communication unit 120 Storage unit 121 Connection information storage unit 122 Set value storage unit 130 Control unit 131 Acquisition unit 132 Measurement unit 133 Change amount detection unit 134 Output control unit 135 Notification unit 140 Sound output unit 150 Display unit 200 Communicated device 210 Communication unit 220 Storage unit 221 Connection information storage unit 230 Control unit 231 Acquisition unit 232 Measurement unit 233 Change amount detection unit 234 Output control unit 235 Notification unit 240 Sound output unit 250 Display unit N Network

Claims

1. A communication device comprising: a communication unit that wirelessly communicates with another communication device; an acquisition unit that acquires various information via the communication unit; and an output control unit that controls the transmission output value of the communication unit, wherein the acquisition unit acquires from the other communication device a second signal of the second radio wave, the second signal including first radio wave reception strength information, which is the radio wave strength value of the first radio wave received by the other communication device from its own communication device, and second radio wave transmission strength information, which is the transmission output value of the second radio wave transmitted by the other communication device, and the output control unit controls the transmission output value of the first radio wave to be transmitted to the other communication device so that the received first radio wave reception strength information is kept constant.

2. A communication device as described in claim 1, further comprising an alarm unit that notifies a user of an abnormality, wherein the alarm unit notifies a user that the distance between the other communication device and the communication device itself has increased by more than a predetermined value when the received second radio wave transmission strength information becomes equal to or exceeds a predetermined first threshold.

3. A communication device as described in claim 1 or 2, further comprising a measurement unit that measures the radio wave intensity value of the radio wave received by the communication unit, wherein the measurement unit outputs the radio wave intensity value of the second radio wave received by the communication unit from the other communication device as second radio wave reception intensity information, the output control unit outputs the transmission output value of the first radio wave that the communication unit transmits to the other communication device as first radio wave transmission intensity information, and the communication unit transmits a first signal including the second radio wave reception intensity information and the first radio wave transmission intensity information to the other communication device as the first radio wave.

4. The communication device described in claim 2, further comprising a change amount detection unit that calculates the amount of change per unit time of the received second radio wave transmission strength information, wherein the communication unit periodically receives the second signal, and the notification unit notifies that the distance between the other communication device and the communication device has suddenly increased when the amount of change becomes equal to or greater than a predetermined second threshold.

5. A communication method comprising the steps of: communicating wirelessly with another communication device; acquiring various information in the wireless communication; and controlling a transmission output value of the wireless communication, wherein in the acquiring step, a second signal of the second radio wave is acquired from the other communication device, the second signal including first radio wave reception strength information, which is a radio wave strength value of the first radio wave received by the other communication device from its own communication device, and second radio wave transmission strength information, which is a transmission output value of the second radio wave transmitted by the other communication device, and in the controlling step, the transmission output value of the first radio wave to be transmitted to the other communication device is controlled so that the received first radio wave reception strength information is kept constant.

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