COMMUNICATION DEVICE, COMMUNICATION METHOD, AND COMMUNICATION SYSTEM

Abstract

To provide a communication device, a communication method, and a communication system that make it difficult to increase a communication load between a center device and the communication device.SOLUTION: A communication device 1 includes a communication unit 11 and a control unit 15. The control unit 15 transmits a first telegraphic message D1 to a center device 2, controls the communication unit 11 so as to receive a first response R1 from the center device 2, and acquires first response reception time, which is the time when the communication unit 11 receives the first response R1 from the center device 2. The control unit 15 transmits a second telegraphic message D2 to the center device 2 after the acquisition of the first response reception time, controls the communication unit 11 so as to receive a second response R2 from the center device 2, and acquires second response reception time, which is the time when the communication unit 11 receives the second response R2 from the center device 2. The control unit 15 calculates a transmission interval ΔT, which is a time interval during which the center device 2 can transmit a response R to the communication unit 11 based on the first response reception time and the second response reception time.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to a communication device, a communication method, and a communication system. [Background technology]

[0002] There is known a communication device that transmits the measurement value of a meter such as a water meter or a gas meter to a central device (see, for example, Patent Document 1). Patent Document 1 discloses a communication system in which a plurality of terminals are connected to a server. In the communication system of Patent Document 1, a gas meter is connected to each of the plurality of terminals. Each terminal transmits the measurement value of the gas meter connected to itself to the server.

[0003] In the communication system of Patent Document 1, the server sets communication timing for each terminal so that communications with each terminal do not overlap in time. The communication timing indicates a communication start time and a communication end time. The server stores the set communication timing in each terminal. Each terminal communicates with the server in accordance with the stored communication timing. Also, in the communication system of Patent Document 1, when the server updates the communication timing, the server stores the communication timing in each terminal every time communication is performed with the terminal. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2000-134679 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in a configuration such as the communication system of Patent Document 1, in which the server (center device) stores communication timing in each terminal (each communication device) each time the server communicates with the terminal, the communication load between the server (center device) and each terminal (each communication device) increases.

[0006] The present invention has been made in view of the above problems, and an object of the present invention is to provide a communication device, a communication method, and a communication system in which the communication load between a center device and a communication device is unlikely to increase. [Means for solving the problem]

[0007] According to one aspect of the present invention, a communication device includes a communication unit and a control unit. The communication unit transmits a message to a center device and receives a response from the center device. The control unit calculates a transmission interval, which is a time interval during which the center device can transmit the response to the communication unit. The control unit executes a first process of controlling the communication unit to transmit a first message to the center device and receive a first response from the center device, and acquiring a first response reception time, which is the time when the communication unit receives the first response from the center device. After acquiring the first response reception time, the control unit executes a second process of controlling the communication unit to transmit a second message to the center device and receive a second response from the center device, and acquiring a second response reception time, which is the time when the communication unit receives the second response from the center device. The control unit executes a third process of calculating the transmission interval based on the first response reception time and the second response reception time.

[0008] According to one aspect of the present invention, a communication method includes the steps of: causing a communication unit to transmit a first electronic message to a center device; in response to the communication unit receiving a first response from the center device, acquiring a first response reception time which is the time when the communication unit received the first response; causing the communication unit to transmit a second electronic message to the center device after acquiring the first response reception time; in response to the communication unit receiving a second response from the center device, acquiring a second response reception time which is the time when the communication unit received the second response; and calculating a transmission interval based on the first response reception time and the second response reception time. The transmission interval indicates a time interval during which the center device can transmit a response to the communication unit.

[0009] According to one aspect of the present invention, a communication system includes a center device and a communication device that are communicatively connected to each other. The communication device includes a communication unit and a control unit. The communication unit transmits a message to the center device and receives a response from the center device. The control unit calculates a transmission interval, which is a time interval during which the center device can transmit the response to the communication unit. The control unit executes a first process of transmitting a first message to the center device and controlling the communication unit to receive a first response from the center device, and acquiring a first response reception time, which is a time when the communication unit receives the first response from the center device. After acquiring the first response reception time, the control unit executes a second process of transmitting a second message to the center device and controlling the communication unit to receive a second response from the center device, and acquiring a second response reception time, which is a time when the communication unit receives the second response from the center device. The control unit executes a third process of calculating the transmission interval based on the first response reception time and the second response reception time. Effect of the Invention

[0010] According to the communication device, the communication method, and the communication system of the present invention, the communication load between the center device and the communication device is less likely to increase. [Brief description of the drawings]

[0011] [Figure 1] 1 is a diagram illustrating a communication system according to a first embodiment of the present invention. [Diagram 2] 1 is a block diagram showing a configuration of a communication device according to a first embodiment of the present invention. [Diagram 3] 1 is a block diagram showing a configuration of a communication unit included in a communication device according to a first embodiment of the present invention. [Figure 4] 4 is a diagram showing a process executed by a first control unit included in the communication device according to the first embodiment of the present invention. FIG. [Diagram 5] 4 is a diagram showing a process executed by a first control unit included in the communication device according to the first embodiment of the present invention. FIG. [Figure 6]4 is a diagram showing a process executed by a first control unit included in the communication device according to the first embodiment of the present invention. FIG. [Figure 7] 4 is a diagram showing a process executed by a first control unit included in the communication device according to the first embodiment of the present invention. FIG. [Figure 8] FIG. 4 is a sequence diagram showing an example of an operation of the communication device according to the first embodiment of the present invention. [Figure 9] FIG. 4 is a sequence diagram showing an example of an operation of the communication device according to the first embodiment of the present invention. [Figure 10] FIG. 4 is a sequence diagram showing an example of an operation of the communication device according to the first embodiment of the present invention. [Figure 11] FIG. 4 is a sequence diagram showing an example of an operation of the communication device according to the first embodiment of the present invention. [Figure 12] FIG. 11 is a diagram illustrating a modified example of a fourth process executed by a first control unit included in the communication device according to the first embodiment of the present invention. [Figure 13] FIG. 11 is a diagram illustrating a fourth process executed by a first control unit included in the communication device according to the second embodiment of the present invention. [Figure 14] FIG. 11 is a diagram illustrating a first process executed by a first control unit included in a communication device according to a third embodiment of the present invention. [Figure 15] FIG. 11 is a diagram illustrating a second process executed by a first control unit included in a communication device according to a third embodiment of the present invention. [Figure 16] FIG. 11 is a sequence diagram showing an example of an operation of a communication device according to a third embodiment of the present invention. [Figure 17] FIG. 11 is a sequence diagram showing an example of an operation of a communication device according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, embodiments of the communication device, communication method, and communication system of the present invention will be described with reference to the drawings (FIGS. 1 to 17). However, the present invention is not limited to the following embodiments, and can be embodied in various forms without departing from the spirit of the present invention. Note that where explanations are repeated, they may be omitted as appropriate. Also, in the drawings, the same or equivalent parts are denoted by the same reference symbols, and explanations will not be repeated.

[0013] [Embodiment 1] Hereinafter, a first embodiment of the present invention will be described with reference to Fig. 1 to Fig. 12. First, a communication system 100 of the present embodiment will be described with reference to Fig. 1. Fig. 1 is a diagram showing a communication system 100 of the present embodiment.

[0014] As shown in FIG. 1, the communication system 100 includes a plurality of communication devices 1 and a center device 2. Each of the plurality of communication devices 1 is communicatively connected to the center device 2. In this embodiment, each communication device 1 is communicatively connected to the center device 2 via a base station 4 and a center-side network control device 5. In the communication system 100 shown in FIG. 1, the plurality of communication devices 1 include a first communication device 1A to a third communication device 1C (three communication devices 1). However, the number of communication devices 1 in the communication system 100 is not limited to three. The communication system 100 may include one communication device 1. Alternatively, the communication system 100 may include two, or four or more communication devices 1.

[0015] The base station 4 and the center-side network control device 5 form a wide-area wireless communication network NW. The wide-area wireless communication network NW is, for example, a PHS (Personal Handy-phone System) network, a FOMA (Freedom Of Mobile Multimedia Access) network, an LTE (Long Term Evolution) network, a 4G (4th generation mobile communication system) network, or a 5G (5th generation mobile communication system) network.

[0016] The center device 2 is communicatively connected to the base station 4 via a center-side network control device 5. The base station 4 and the center-side network control device 5 are provided, for example, in a public network of a telecommunications carrier. The center device 2 is connected to the center-side network control device 5 via, for example, an optical fiber cable. The center-side network control device 5 controls communication between the center device 2 and the base station 4.

[0017] Each communication device 1 transmits a message D to the center device 2. Upon receiving the message D from the communication device 1, the center device 2 transmits a response R to the communication device 1 that transmitted the message D.

[0018] More specifically, the timing at which the response R can be transmitted is determined in advance for the center device 2. Hereinafter, the timing at which the response R can be transmitted may be referred to as "transmission timing". The transmission timing indicates the time Ta at which the response R can be transmitted. Hereinafter, the time Ta at which the response R can be transmitted may be referred to as "transmission possible time Ta". After receiving the message D from the communication device 1, the center device 2 transmits the response R to the communication device 1 at the transmission possible time Ta. More specifically, the transmission timing indicates the communication timing. Therefore, communication between the center device 2 and the communication device 1 becomes possible at the transmission timing. In this embodiment, the communication device 1 transmits the message D to the center device 2 immediately before the transmission possible time Ta. Note that the transmission timing may be set for each communication device 1 so that the transmission timing does not overlap between the communication devices 1. In other words, the transmission timing may be different between the communication devices 1.

[0019] Next, the communication system 100 will be further described with reference to Fig. 1. As shown in Fig. 1, the communication system 100 of this embodiment is a telemeter system, and a meter 3 is communicatively connected to each communication device 1. In other words, a communication device 1 is installed for each meter 3. In this embodiment, the communication device 1 is wired to the meter 3 via an electric wire PL. The electric wire PL includes a signal line and a ground line. The meter 3 is an example of an "external device."

[0020] The meter 3 is installed for each consumer, such as a private home, a company, or various facilities. The meter 3 measures the amount of gas, water, electricity, or the like used. The communication device 1 acquires the measurement result (measurement value) from the corresponding meter 3. The communication device 1 transmits a message D indicating the acquired measurement value to the base station 4. As a result, the measurement value of the meter 3 is transmitted to the center device 2.

[0021] The telemeter system is a system that collects measurement values ​​of meters 3. Specifically, the measurement values ​​of each meter 3 are collected by a center device 2. The center device 2 stores the measurement value for each meter 3. In this embodiment, the center device 2 is a server used by a business operator that supplies resources such as gas, water, or electricity.

[0022] The communication device 1 may be communicably connected to the base station 4 via a master unit. Specifically, the communication device 1 communicates with the master unit by, for example, a specific low power radio (special low power radio). The master unit communicates with the center device 2 via a wide area radio communication network NW (base station 4 and center side network control device 5).

[0023] Next, the communication device 1 of the present embodiment will be described with reference to Fig. 2. Fig. 2 is a block diagram showing the configuration of the communication device 1 of the present embodiment. As shown in Fig. 2, the communication device 1 includes a communication unit 11, a connection unit 12, an operation unit 13, a first clock circuit 14, a first control unit 15, and a first storage unit 16.

[0024] The communication unit 11 communicates with the center device 2 described with reference to FIG. 1 via the base station 4, and transmits a message D to the center device 2. Specifically, the communication unit 11 transmits the message D to the base station 4. As a result, as described with reference to FIG. 1, the message D is transmitted to the center device 2. Also, the communication unit 11 receives a response R from the center device 2 as described with reference to FIG. 1. Specifically, as described with reference to FIG. 1, the center device 2 transmits the response R to the center-side network control device 5. As a result, the response R is transmitted from the center-side network control device 5 to the communication unit 11 via the base station 4, and the communication unit 11 receives the response R.

[0025] The connection unit 12 connects to the meter 3. More specifically, the connection unit 12 has at least one port. An electric wire PL is connected to the port of the connection unit 12. The connection unit 12 is wired to the meter 3 via the electric wire PL. The first control unit 15 acquires a measurement value from the meter 3 via the connection unit 12. The measurement value is an example of "information acquired from an external device." When the first control unit 15 acquires the measurement value from the meter 3, it controls the communication unit 11 to transmit a message D indicating the measurement value to the center device 2. As a result, the communication unit 11 transmits the message D indicating the measurement value to the center device 2.

[0026] The operation unit 13 accepts instructions for the communication device 1. The operation unit 13 includes, for example, a dip switch and a push switch. The dip switch accepts, for example, an instruction to switch the operation mode of the communication device 1. The push switch causes, for example, the first control unit 15 to execute the instruction accepted by the dip switch. The operation unit 13 is operated, for example, when the communication device 1 is installed. Specifically, the operation unit 13 accepts, when the communication device 1 is installed, an opening instruction that instructs the execution of an opening process to enable communication between the communication device 1 and the center device 2. When the operation unit 13 accepts the opening instruction, the first control unit 15 executes the opening process which is a process to enable communication between the communication unit 11 and the center device 2.

[0027] The first clock circuit 14 keeps track of time. The first control unit 15 acquires the current time based on the time kept by the first clock circuit 14. The first control unit 15 further acquires the current date and time based on the current time and calendar information. The date and time includes a date and a time. The calendar information is stored in the first storage unit 16.

[0028] The first control unit 15 controls the communication unit 11, the first clock circuit 14, and the first storage unit 16. Specifically, the first control unit 15 synchronizes the time of the first clock circuit 14 with the time of the second clock circuit 112, which will be described later with reference to FIG. 3. The first control unit 15 also controls the communication unit 11 to cause the communication unit 11 to transmit a telegram D. The first control unit 15 also controls the first storage unit 16 to store various data or information in the first storage unit 16. The first control unit 15 also controls the first storage unit 16 to read out various data or information from the first storage unit 16.

[0029] The first control unit 15 has a processor that executes various processes. For example, the first control unit 15 may have a CPU (Central Processing Unit) or an MPU (Micro Processing Unit) as the processor. The processor executes computer programs stored in the first storage unit 16 to execute various processes. The first control unit 15 and the first storage unit 16 may constitute a microcomputer.

[0030] The first storage unit 16 stores various computer programs. The first storage unit 16 also stores various data or information. Specifically, the first storage unit 16 stores calendar information. The first storage unit 16 has, for example, a semiconductor memory. Specifically, the first storage unit 16 may have a ROM (Read Only Memory) and a RAM (Random Access Memory) as the semiconductor memory. The first storage unit 16 may have a non-volatile semiconductor memory to which data can be written and erased. For example, the first storage unit 16 may have an EEPROM (Electrically Erasable Programmable Read-Only Memory) or a flash memory as the non-volatile semiconductor memory.

[0031] Next, the communication device 1 of the present embodiment will be described with reference to Fig. 3. Fig. 3 is a block diagram showing the configuration of a communication unit 11 included in the communication device 1 of the present embodiment. As shown in Fig. 3, the communication unit 11 includes a communication circuit 111, a second clock circuit 112, a second control unit 113, and a second storage unit 114. Furthermore, as shown in Fig. 3, the communication device 1 further includes an antenna 17.

[0032] The communication circuit 111 converts the signal output from the second control unit 113 to the communication circuit 111 into a signal conforming to a predetermined wireless communication method, and transmits the signal to the antenna 17. As a result, a radio wave (wireless signal) conforming to the predetermined wireless communication method is emitted from the antenna 17. In addition, the communication circuit 111 converts the radio wave (wireless signal) received by the antenna 17 into a signal that can be processed by the second control unit 113, and outputs the signal to the second control unit 113.

[0033] Specifically, the second control unit 113 outputs the message D input to the second control unit 113 from the first control unit 15 to the communication circuit 111. As a result, radio waves indicating the message D are emitted from the antenna 17. In addition, the antenna 17 receives radio waves from the base station 4 indicating the response R transmitted from the center device 2. As a result, the response R is output from the communication circuit 111 to the second control unit 113. The second control unit 113 inputs the response R to the first control unit 15.

[0034] The second clock circuit 112 keeps track of time. The second control unit 113 acquires the current time based on the time kept by the second clock circuit 112. The second control unit 113 further acquires the current date and time based on the current time and calendar information. The calendar information is stored in the second storage unit 114.

[0035] The second control unit 113 controls the communication circuit 111, the second clock circuit 112, and the second storage unit 114. Specifically, the second control unit 113 controls the communication circuit 111 to transmit the message D input from the first control unit 15 to the second control unit 113. The second control unit 113 also inputs the response R output from the communication circuit 111 to the first control unit 15. The second control unit 113 controls the second storage unit 114 to store various data or information in the second storage unit 114. The second control unit 113 controls the second storage unit 114 to read out various data or information from the second storage unit 114.

[0036] The second control unit 113 further executes a reset process. The reset process is executed periodically. For example, the reset process may be executed every three days or every seven days. The reset process is a process in which the base station 4 and the communication unit 11 communicate with each other. The base station 4 and the communication unit 11 communicate with each other periodically, thereby stabilizing the communication between the communication unit 11 and the base station 4. The cycle in which the reset process is executed is stored in advance in the second storage unit 114. Hereinafter, the cycle in which the reset process is executed may be referred to as a "reset cycle." The second control unit 113 executes the reset process periodically based on the calendar information and the reset cycle.

[0037] When executing the reset process, the second control unit 113 acquires the network time from the base station 4 and synchronizes the time of the second clock circuit 112 with the network time. When executing the reset process, the second control unit 113 outputs a signal indicating that the reset process is to be executed to the first control unit 15. When executing the reset process, the first control unit 15 acquires the time of the second clock circuit 112 via the second control unit 113 and synchronizes the time of the first clock circuit 14 with the time of the second clock circuit 112. In other words, the first control unit 15 synchronizes the time of the first clock circuit 14 with the network time.

[0038] The second control unit 113 has a processor that executes various processes. For example, the second control unit 113 may have a CPU or an MPU as a processor. The processor executes a computer program stored in the second storage unit 114 to execute various processes. The second control unit 113 and the second storage unit 114 may form a microcomputer.

[0039] The second storage unit 114 stores various computer programs. The second storage unit 114 also stores various data or information. Specifically, the second storage unit 114 stores calendar information and a reset cycle. The second storage unit 114 has, for example, a semiconductor memory. Specifically, the second storage unit 114 may have a ROM and a RAM as the semiconductor memory. The second storage unit 114 may have a non-volatile semiconductor memory to which data can be written and from which data can be erased. For example, the second storage unit 114 may have an EEPROM or a flash memory as the non-volatile semiconductor memory.

[0040] Next, the communication device 1 of this embodiment will be described with reference to Figs. 1 to 4. Fig. 4 is a diagram showing a process executed by a first control unit 15 included in the communication device 1 of this embodiment. Hereinafter, the process shown in Fig. 4 may be referred to as a "first process." In this embodiment, the first process is executed when notifying the center device 2 of the measurement value of the meter 3. In the following description, the process of notifying the center device 2 of the measurement value of the meter 3 may be referred to as a "measurement value notification process."

[0041] When the first control unit 15 acquires the measured value of the meter 3 via the connection unit 12, it outputs a connection instruction to the second control unit 113 to establish a communication connection with the base station 4 (step S1). In response to the connection instruction, the second control unit 113 executes a process to establish a communication connection with the base station 4. As a result, a communication connection is established between the communication unit 11 and the base station 4, and communication between the communication unit 11 and the base station 4 becomes possible.

[0042] After a communication connection is established between the communication unit 11 and the base station 4, the first control unit 15 controls the communication unit 11 to transmit a message D to the center device 2 and receive a response R from the center device 2 (step S2). Here, the message D indicates the measurement value of the meter 3. Hereinafter, the message D in the first process may be referred to as a "first message D1". Also, the response R in the first process may be referred to as a "first response R1".

[0043] Specifically, the first control unit 15 generates a first electronic message D1 indicating the measurement value of the meter 3, and outputs it to the second control unit 113. The second control unit 113 controls the communication circuit 111 to transmit the first electronic message D1. As a result, the first electronic message D1 is transmitted from the communication unit 11 to the base station 4. The base station 4 transmits the first electronic message D1 to the center-side network control device 5, and the center-side network control device 5 transmits the first electronic message D1 to the center device 2.

[0044] After causing the communication unit 11 to transmit the first electronic message D1, the first control unit 15 puts the communication unit 11 into a reception waiting state. A timeout period TP is set in the reception waiting state. The timeout period TP indicates the maximum period for which the reception waiting state is to continue. In this embodiment, the timeout period TP includes a first timeout period TP1 and a second timeout period TP2 that is shorter than the first timeout period TP1. The first timeout period TP1 and the second timeout period TP2 are stored in advance in the first storage unit 16. When the first process is executed, the first timeout period TP1 is set. Hereinafter, the reception waiting state in which the first timeout period TP1 is set may be referred to as a "first reception waiting state."

[0045] After transmitting the first electronic message D1, the first control unit 15 determines whether the communication unit 11 has received the first response R1 (step S3). Specifically, when the communication unit 11 receives the first response R1, the communication unit 11 outputs the first response R1 to the first control unit 15. Thus, the first control unit 15 determines whether the first response R1 has been received from the communication unit 11.

[0046] If the first control unit 15 determines that the communication unit 11 has not received the first response R1 (No in step S3), it determines whether or not the first timeout period TP1 has elapsed since the first telegram D1 was sent (step S5).

[0047] When the first control unit 15 determines that the first timeout period TP1 has not elapsed (No in step S5), the process shown in Fig. 4 returns to step S3. When the first control unit 15 determines that the first timeout period TP1 has elapsed (Yes in step S5), the first process shown in Fig. 4 ends.

[0048] When the first control unit 15 determines that the communication unit 11 has received the first response R1 (Yes in step S3), the first control unit 15 acquires the response reception date and time, which is the date and time when the communication unit 11 received the first response R1 from the center device 2, and stores the response reception date and time in the first storage unit 16 (step S4). Specifically, when the communication unit 11 determines that the communication unit 11 has received the first response R1, the first control unit 15 acquires the current time from the first clock circuit 14, and acquires the response reception date and time based on the current time and calendar information. The response reception date and time is an example of the "response reception time". Hereinafter, the response reception date and time acquired by the first process may be referred to as the "first response reception date and time". The first response reception date and time is an example of the "first response reception time". When the first control unit 15 acquires the first response reception date and time, the first control unit 15 ends the first process shown in FIG. 4.

[0049] If a timeout occurs during execution of the first process, the first control unit 15 executes the first process described with reference to FIG. 4 again the next time the measurement value notification process is executed.

[0050] Next, the communication device 1 of this embodiment will be described with reference to Fig. 1 to Fig. 5. Fig. 5 is a diagram showing a process executed by a first control unit 15 included in the communication device 1 of this embodiment. Hereinafter, the process shown in Fig. 5 may be referred to as a "second process." In this embodiment, the second process is executed when notifying the center device 2 of the measurement value of the meter 3 after the first process is executed.

[0051] When the first control unit 15 acquires the measured value of the meter 3 via the connection unit 12, it outputs a connection instruction to the second control unit 113 (step S11). As a result, a communication connection is established between the communication unit 11 and the base station 4, and communication between the communication unit 11 and the base station 4 becomes possible.

[0052] After a communication connection is established between the communication unit 11 and the base station 4, the first control unit 15 controls the communication unit 11 to transmit a message D to the center device 2 and receive a response R from the center device 2 (step S12). Here, the message D indicates the measurement value of the meter 3. Hereinafter, the message D in the second processing may be referred to as a "second message D2". Also, the response R in the second processing may be referred to as a "second response R2".

[0053] After the first control unit 15 causes the communication unit 11 to transmit the second electronic document D2, the communication unit 11 is put into a waiting state for reception. Specifically, when the second process is executed, a first timeout period TP1 is set. Therefore, the communication unit 11 is put into the first waiting state for reception, similarly to when the first process is executed.

[0054] After transmitting the second electronic message D2, the first control unit 15 determines whether the communication unit 11 has received the second response R2 (step S13). If the first control unit 15 determines that the communication unit 11 has not received the second response R2 (No in step S13), it determines whether the first timeout period TP1 has elapsed since transmitting the second electronic message D2 (step S15).

[0055] When the first control unit 15 determines that the first timeout period TP1 has not elapsed (No in step S15), the process shown in Fig. 5 returns to step S13. When the first control unit 15 determines that the first timeout period TP1 has elapsed (Yes in step S15), the second process shown in Fig. 5 ends.

[0056] When the first control unit 15 determines that the communication unit 11 has received the second response R2 (Yes in step S13), it acquires the response reception date and time, which is the date and time when the communication unit 11 received the second response R2 from the center device 2, and stores it in the first storage unit 16 (step S14). Hereinafter, the response reception date and time acquired by the second process may be referred to as the "second response reception date and time." The second response reception date and time is an example of the "second response reception time." When the first control unit 15 acquires the second response reception date and time, it ends the second process shown in FIG. 5.

[0057] If a timeout occurs during execution of the second process, the first control unit 15 executes the first process described with reference to Fig. 4 again the next time the measurement value notification process is executed. Therefore, the first control unit 15 repeatedly executes the first process and the second process until the second response reception time is acquired.

[0058] Next, the communication device 1 of the present embodiment will be described with reference to Fig. 1 to Fig. 6. Fig. 6 is a diagram showing a process executed by the first control unit 15 included in the communication device 1 of the present embodiment. Hereinafter, the process shown in Fig. 6 may be referred to as a "third process." In this embodiment, the third process is executed after the second response reception date and time is acquired.

[0059] After acquiring the second response reception date and time, the first control unit 15 calculates a transmission interval ΔT based on the first response reception date and time and the second response reception date and time, and stores the calculated transmission interval ΔT in the first storage unit 16 (step S21). The transmission interval ΔT indicates a time interval during which the center device 2 can transmit a response R to the communication unit 11. Specifically, the first control unit 15 may calculate the transmission interval ΔT based on the difference between the second response reception date and time and the first response reception date and time.

[0060] In this embodiment, after calculating the transmission interval ΔT, the first control unit 15 changes the timeout period TP from the first timeout period TP1 to the second timeout period TP2 (step S22), and ends the third process shown in Fig. 6. Note that the second timeout period TP2 is determined taking into consideration network delays and the like. For example, the second timeout period TP2 may be 10 seconds or 20 seconds.

[0061] Next, the communication device 1 of this embodiment will be described with reference to Figs. 1 to 7. Fig. 7 is a diagram showing a process executed by a first control unit 15 included in the communication device 1 of this embodiment. Hereinafter, the process shown in Fig. 7 may be referred to as a "fourth process". In this embodiment, the fourth process is executed when the measurement value of the meter 3 is notified to the center device 2 after the third process shown in Fig. 6 is executed. Specifically, the fourth process is executed every time the measurement value of the meter 3 is notified to the center device 2 after the transmission interval ΔT is calculated.

[0062] When the first control unit 15 acquires the measurement value of the meter 3 via the connection unit 12, it calculates the time Tb to transmit the electronic message D based on the transmission interval ΔT and the second response reception date and time stored in the first storage unit 16, and determines the time Tb to transmit the electronic message D (step S31). Specifically, when the first control unit 15 acquires the measurement value of the meter 3 via the connection unit 12, it acquires the current date and time based on the current time and calendar information acquired from the first clock circuit 14, and calculates the time Tb to transmit the electronic message D based on the current date and time, the transmission interval ΔT, and the second response reception date and time.

[0063] More specifically, the first control unit 15 calculates the time Tb at which to transmit the electronic message D, which is the time immediately before the transmittable time Ta described with reference to Fig. 1. Specifically, the first control unit 15 calculates the time Tb at which to transmit the electronic message D by finding the nearest future transmittable time Ta to the current date and time among the transmittable times Ta that appear at each transmission interval ΔT starting from the second response reception date and time.

[0064] Hereinafter, the electronic message D in the fourth process may be referred to as the “third electronic message D3”, the response R in the fourth process may be referred to as the “third response R3”, and the time Tb at which the third electronic message D3 is transmitted may be referred to as the “scheduled transmission time Tb”. Here, the third electronic message D3 indicates the measurement value of the meter 3.

[0065] When the first control unit 15 determines the scheduled transmission time Tb, it determines whether or not the standby time Tw has elapsed since the measurement value of the meter 3 was obtained (step S32). In detail, the first control unit 15 calculates the standby time Tw based on the current time obtained from the first clock circuit 14 and the scheduled transmission time Tb. The standby time Tw indicates the time interval from the acquisition of the measurement value of the meter 3 to the arrival of the scheduled transmission time Tb. The first control unit 15 has a timer function, and sets the standby time Tw in the timer function to determine whether or not the standby time Tw has elapsed.

[0066] The first control unit 15 waits until the waiting time Tw has elapsed (No in step S32). When the first control unit 15 determines that the waiting time Tw has elapsed (Yes in step S32), it outputs a connection instruction to the second control unit 113 (step S33). As a result, a communication connection is established between the communication unit 11 and the base station 4.

[0067] After a communication connection is established between the communication unit 11 and the base station 4, the first control unit 15 controls the communication unit 11 to send a third message D3 to the center device 2 and receive a third response R3 from the center device 2 (step S34).

[0068] Specifically, the first control unit 15 causes the communication unit 11 to transmit the third electronic message D3, and then causes the communication unit 11 to enter a reception waiting state. Hereinafter, the reception waiting state in the fourth process may be referred to as a "second reception waiting state." At this time, as described with reference to FIG. 6, the timeout period TP is changed from the first timeout period TP1 to the second timeout period TP2.

[0069] After transmitting the third electronic message D3, the first control unit 15 determines whether the communication unit 11 has received the third response R3 (step S35). When the first control unit 15 determines that the communication unit 11 has received the third response R3 (Yes in step S35), the first control unit 15 ends the fourth process shown in FIG.

[0070] If the first control unit 15 determines that the communication unit 11 has not received the third response R3 (No in step S35), it determines whether the second timeout period TP2 has elapsed since the third telegram D3 was sent (step S36).

[0071] When the first control unit 15 determines that the second timeout period TP2 has not elapsed (No in step S36), the process shown in Fig. 7 returns to step S35. When the first control unit 15 determines that the second timeout period TP2 has elapsed (Yes in step S36), the first control unit 15 changes the timeout period TP from the second timeout period TP2 to the first timeout period TP1 (step S37), and ends the fourth process shown in Fig. 7.

[0072] If a timeout occurs during execution of the fourth process, the first control unit 15 executes the first process described with reference to Fig. 4 again when executing the measurement value notification process next time. Therefore, the first control unit 15 repeatedly executes the first process and the second process until the second response reception time is acquired. Then, after executing the third process described with reference to Fig. 6 again to acquire the transmission interval ΔT again, the fourth process shown in Fig. 7 is executed every time the measurement value notification process is executed.

[0073] Next, the communication device 1 of the present embodiment will be described with reference to Fig. 1 to Fig. 8. Fig. 8 is a sequence diagram showing an example of the operation of the communication device 1 of the present embodiment. In detail, Fig. 8 shows an example of the operation of the first control unit 15 and the communication unit 11 when the first process is executed.

[0074] 8, when the first control unit 15 acquires the measured value of the meter 3 via the connection unit 12, it outputs a connection instruction to the communication unit 11. As a result, a communication connection is established between the communication unit 11 and the base station 4.

[0075] The communication unit 11 is in a dormant state until a connection instruction is received from the first control unit 15. When the communication unit 11 is in a dormant state, it consumes almost no power. The communication unit 11 is activated by receiving a connection instruction from the first control unit 15.

[0076] After a communication connection is established between the communication unit 11 and the base station 4, the first control unit 15 generates a first electronic message D1 indicating the measurement value of the meter 3 and outputs it to the communication unit 11. As a result, the communication unit 11 transmits the first electronic message D1 to the base station 4. The base station 4 transmits the first electronic message D1 to the center-side network control device 5, and the center-side network control device 5 transmits the first electronic message D1 to the center device 2. After transmitting the first electronic message D1, the first control unit 15 puts the communication unit 11 into a first reception waiting state.

[0077] After receiving the first electronic message D1, the center device 2 transmits a first response R1 to the center-side network control device 5 at the transmission possible time Ta. As a result, the first response R1 is transmitted from the center-side network control device 5 to the communication unit 11 via the base station 4.

[0078] When the communication unit 11 receives a first response R1 during the first timeout period TP1 after transmitting the first electronic document D1, the communication unit 11 outputs the first response R1 to the first control unit 15 and goes into a pause state. When the first control unit 15 receives the first response R1 from the communication unit 11, it acquires the date and time of the first response reception.

[0079] Next, the communication device 1 of the present embodiment will be described with reference to Fig. 1 to Fig. 9. Fig. 9 is a sequence diagram showing an example of the operation of the communication device 1 of the present embodiment. In detail, Fig. 9 shows an example of the operation of the first control unit 15 and the communication unit 11 when the second process and the third process are executed. However, hereinafter, only matters different from those described with reference to Fig. 8 will be described, and descriptions of matters similar to those described with reference to Fig. 8 will be omitted.

[0080] As shown in FIG. 9, when the first control unit 15 receives the second response R2 from the communication unit 11 and obtains the second response reception date and time, it calculates the transmission interval ΔT and changes the timeout period TP from the first timeout period TP1 to the second timeout period TP2.

[0081] Next, the communication device 1 of the present embodiment will be described with reference to Fig. 1 to Fig. 10. Fig. 10 is a sequence diagram showing an example of the operation of the communication device 1 of the present embodiment. In detail, Fig. 10 shows an example of the operation of the first control unit 15 and the communication unit 11 when a fourth process is executed.

[0082] When the first control unit 15 acquires the measured value of the meter 3 via the connection unit 12, the first control unit 15 calculates the scheduled transmission time Tb based on the transmission interval ΔT and the second response reception date and time stored in the first storage unit 16.

[0083] After calculating the scheduled transmission time Tb, the first control unit 15 goes into a standby state. Then, when the standby time Tw has elapsed and the current time becomes the scheduled transmission time Tb, the first control unit 15 outputs a connection instruction to the communication unit 11. As a result, a communication connection is established between the communication unit 11 and the base station 4. The communication unit 11 is in a pause state until the standby time Tw has elapsed.

[0084] After a communication connection is established between the communication unit 11 and the base station 4, the first control unit 15 generates a third electronic message D3 indicating the measurement value of the meter 3 and outputs it to the communication unit 11. As a result, the third electronic message D3 is transmitted from the communication unit 11 to the base station 4. The base station 4 transmits the third electronic message D3 to the center-side network control device 5, and the center-side network control device 5 transmits the third electronic message D3 to the center device 2. After transmitting the third electronic message D3, the first control unit 15 puts the communication unit 11 into a second reception waiting state.

[0085] After receiving the third electronic message D3, the center device 2 transmits a third response R3 to the center-side network control device 5 at the transmission possible time Ta. As a result, the third response R3 is transmitted from the center-side network control device 5 to the communication unit 11 via the base station 4.

[0086] If the communication unit 11 receives the third response R3 during the period from when the third telegram D3 is sent until the second timeout period TP2 has elapsed, the communication unit 11 outputs the third response R3 to the first control unit 15 and goes into a pause state.

[0087] Next, the communication device 1 of the present embodiment will be described with reference to Fig. 1 to Fig. 11. Fig. 11 is a sequence diagram showing an example of the operation of the communication device 1 of the present embodiment. In detail, Fig. 11 shows another example of the operation of the first control unit 15 and the communication unit 11 when the fourth process is executed. In the following, only matters different from those described with reference to Fig. 10 will be described, and descriptions of the same matters as those described with reference to Fig. 10 will be omitted.

[0088] As shown in FIG. 11, if the communication unit 11 fails to receive the third response R3 from the base station 4 before the second timeout period TP2 has elapsed, for example due to a communication failure, the first control unit 15 changes the timeout period TP from the second timeout period TP2 to the first timeout period TP1.

[0089] The first embodiment of the present invention has been described above with reference to Fig. 1 to Fig. 11. According to this embodiment, the communication device 1 calculates the scheduled transmission time Tb. Therefore, the communication load between the center device 2 and each communication device 1 is less likely to increase, compared to a configuration in which the center device 2 sets the transmission timing for each communication device 1 every time the center device 2 communicates with each communication device 1, for example.

[0090] Furthermore, according to this embodiment, the communication device 1 calculates the transmission interval ΔT. Therefore, for example, the communication load between the center device 2 and each communication device 1 is less likely to increase compared to a configuration in which the center device 2 sets the transmission interval ΔT for each communication device 1 every time the center device 2 changes the transmission interval ΔT.

[0091] Furthermore, according to this embodiment, when the fourth process is executed, the communication unit 11 is in a sleep state until the waiting time Tw has elapsed. Therefore, the period during which the communication unit 11 is in a sleep state can be extended, so that the rate at which the power is consumed by the communication device 1 can be suppressed. In other words, the power consumption of the communication device 1 can be reduced.

[0092] Furthermore, according to this embodiment, the length of the timeout period TP (second timeout period TP2) during execution of the fourth process can be made shorter than that during execution of the first process and the second process (compared to the length of the first timeout period TP1). Therefore, the period during which the communication unit 11 is in a reception waiting state can be shortened, and the power consumption rate of the communication device 1 can be suppressed.

[0093] In the present embodiment, the first control unit 15 calculates the transmission interval ΔT based on two response reception dates and times (the first response reception date and time and the second response reception date and time), but the first control unit 15 may calculate the transmission interval ΔT based on three or more response reception dates and times. For example, the first control unit 15 may acquire a response reception date and time (hereinafter, the third response reception date and time) when notifying the center device 2 of the measurement value of the meter 3 after executing the second process, and calculate the transmission interval ΔT based on the three response reception dates and times. Specifically, the first control unit 15 may calculate the transmission interval ΔT based on the difference between the first response reception date and time and the second response reception date and time and the difference between the first response reception date and time and the third response reception date and time, or may calculate the transmission interval ΔT based on the difference between the first response reception date and time and the second response reception date and time and the difference between the second response reception date and time and the third response reception date and time.

[0094] Next, a modified example of the communication device 1 of the present embodiment will be described with reference to Fig. 12. Fig. 12 is a diagram showing a modified example of the fourth process executed by the first control unit 15 included in the communication device 1 of the present embodiment.

[0095] The fourth process shown in Fig. 12 includes steps S41 to S48. Here, steps S41 to S46 and S48 are similar to steps S31 to S37 shown in Fig. 7, and therefore the description thereof will be omitted.

[0096] 12, when the first control unit 15 determines that the second timeout period TP2 has elapsed (Yes in step S46), it determines whether the number of times that the third response R3 has failed to be received is N or more (step S47), where "N" is an integer equal to or greater than 2.

[0097] When the first control unit 15 determines that the number of times that the third response R3 has failed to be received is N or more (Yes in step S47), it changes the timeout period TP from the second timeout period TP2 to the first timeout period TP1 (step S48) and ends the fourth process shown in Fig. 12. On the other hand, when the first control unit 15 determines that the number of times that the third response R3 has failed to be received is not N or more (No in step S47), it ends the fourth process shown in Fig. 12.

[0098] The communication device 1 described with reference to FIG. 1 to FIG. 11 changes the timeout period TP from the second timeout period TP2 to the first timeout period TP1 when the communication device 1 fails to receive the third response R3 once. Therefore, even if the cause of the failure to receive the third response R3 is a temporary cause, the first process is executed at the time of the next measurement value notification process. In other words, even if the cause of the failure to receive has been eliminated at the time of the next measurement value notification process, the first process is executed. In contrast, according to the modified example described with reference to FIG. 12, when the reception of the third response R3 fails due to a temporary cause, if the cause of the failure to receive has been eliminated, the telegram D can be transmitted by the fourth process at the time of the next measurement value notification process. Therefore, the power consumption rate of the communication device 1 can be suppressed.

[0099] [Embodiment 2] Next, a second embodiment of the present invention will be described with reference to Figs. 1 to 6 and 13. However, differences from the first embodiment will be described, and a description of the same matters as in the first embodiment will be omitted. The second embodiment differs from the first embodiment in the fourth process.

[0100] Fig. 13 is a diagram showing a fourth process executed by the first control unit 15 included in the communication device 1 of this embodiment. The fourth process shown in Fig. 13 includes steps S51 to S60. Here, steps S51 to S57 are similar to steps S31 to S37 shown in Fig. 7, and therefore their description will be omitted.

[0101] 13, when the first control unit 15 determines that the communication unit 11 has received the third response R3 (Yes in step S55), it acquires the response reception date and time (step S58) and updates the first response reception date and time and the second response reception date and time stored in the first storage unit 16 based on the currently acquired response reception date and time (step S59). In detail, the first control unit 15 deletes the first response reception date and time from the first storage unit 16 and changes the second response reception date and time stored in the first storage unit 16 to the first response reception date and time. Then, the first control unit 15 stores the currently acquired response reception date and time in the first storage unit 16 as the second response reception date and time.

[0102] The first control unit 15 updates the first response reception date and time and the second response reception date and time stored in the first storage unit 16, and then calculates the transmission interval ΔT based on the updated first response reception date and time and the second response reception date and time. Then, the first control unit 15 updates the transmission interval ΔT stored in the first storage unit 16 (step S60), and ends the fourth process shown in FIG.

[0103] The second embodiment of the present invention has been described above with reference to Figures 1 to 6 and 13. According to this embodiment, similar to the first embodiment, the communication load between the center device 2 and each communication device 1 is less likely to increase.

[0104] 1 to 12 obtains the response reception date and time only when the first process and the second process are executed, the longer the time that has passed since the second process was executed (the time that has passed since the second response reception date and time was acquired), the greater the possibility that the difference between the scheduled transmission time Tb and the transmittable time Ta will become. In contrast, according to this embodiment, the response reception date and time is acquired and the transmission interval ΔT is updated every time a response R is received from the center device 2, so that the possibility that the difference between the scheduled transmission time Tb and the transmittable time Ta will become large can be reduced.

[0105] In this embodiment, the first control unit 15 calculates the transmission interval ΔT based on two response reception dates and times (the first response reception date and time and the second response reception date and time), but the first control unit 15 may calculate the transmission interval ΔT based on three or more response reception dates and times. For example, the first control unit 15 may store a history of the response reception dates and times (hereinafter, the fourth response reception date and time) acquired when executing the fourth process in the first storage unit 16, and calculate the transmission interval ΔT based on the history information of the fourth response reception date and time.

[0106] [Embodiment 3] Next, a third embodiment of the present invention will be described with reference to Figures 1 to 3, 6, 7, and 14 to 17. However, differences from the first and second embodiments will be described, and descriptions of the same aspects as the first and second embodiments will be omitted. The third embodiment differs from the first embodiment in the first process and the second process.

[0107] 14 is a diagram showing a first process executed by the first control unit 15 included in the communication device 1 of the present embodiment. In the present embodiment, the first process is executed after the reset process described with reference to FIG.

[0108] 14, after executing the reset process, the first control unit 15 controls the communication unit 11 to transmit a first electronic message D1 to the center device 2 and receive a first response R1 from the center device 2 (step S61). Here, the content of the first electronic message D1 may be empty or may be a content commanding the center device 2 to respond. Note that the communication connection between the communication unit 11 and the base station 4 has been established by the reset process.

[0109] After transmitting the first electronic message D1, the first control unit 15 determines whether the communication unit 11 has received the first response R1 (step S62). If the first control unit 15 determines that the communication unit 11 has not received the first response R1 (No in step S62), it causes the communication unit 11 to transmit the first electronic message D1 again (step S61). That is, the communication device 1 transmits the first electronic message D1 intermittently until it receives the first response R1 from the center device 2. Here, the transmission interval of the first electronic message D1 may be, for example, 5 seconds.

[0110] When the first control unit 15 determines that the communication unit 11 has received the first response R1 (Yes in step S62), it acquires the first response reception date and time and stores it in the first storage unit 16 (step S63). As a result, the first process shown in FIG. 14 ends.

[0111] 15 is a diagram showing a second process executed by the first control unit 15 included in the communication device 1 of this embodiment. In this embodiment, the second process is executed after the first response reception date and time is acquired.

[0112] 15, after acquiring the first response reception date and time, the first control unit 15 outputs a connection instruction to the second control unit 113 (step S71). As a result, a communication connection is established between the communication unit 11 and the base station 4.

[0113] After a communication connection is established between the communication unit 11 and the base station 4, the first control unit 15 controls the communication unit 11 to transmit a second electronic message D2 to the center device 2 and receive a second response R2 from the center device 2 (step S72). Here, the content of the second electronic message D2 may be empty or may be a content commanding the center device 2 to respond.

[0114] After transmitting the second electronic message D2, the first control unit 15 determines whether the communication unit 11 has received the second response R2 (step S73). If the first control unit 15 determines that the communication unit 11 has not received the second response R2 (No in step S73), the first control unit 15 causes the communication unit 11 to transmit the second electronic message D2 again (step S72). That is, the communication device 1 transmits the second electronic message D2 intermittently until it receives the second response R2 from the center device 2. Here, the transmission interval of the second electronic message D2 may be, for example, 5 seconds.

[0115] When the first control unit 15 determines that the communication unit 11 has received the second response R2 (Yes in step S73), it acquires the second response reception date and time and stores it in the first storage unit 16 (step S74). As a result, the second process shown in FIG. 15 ends.

[0116] Fig. 16 is a sequence diagram showing an example of the operation of the communication device 1 of this embodiment. In detail, Fig. 16 shows an example of the operation of the first control unit 15 and the communication unit 11 when the first process is executed.

[0117] 16, when the reset process is executed, the communication unit 11 starts up from a hibernation state and establishes a communication connection with the base station 4. At this time, as described with reference to FIG. 3, the communication unit 11 acquires the network time from the base station 4 and synchronizes the time of the second clock circuit 112 with the network time.

[0118] When the communication unit 11 executes the reset process, the first control unit 15 synchronizes the time of the first clock circuit 14 with the time of the second clock circuit 112, thereby synchronizing the time of the first clock circuit 14 with the network time.

[0119] When the first control unit 15 synchronizes the time of the first clock circuit 14 with the network time, it generates a first electronic message D1 and outputs it to the communication unit 11 while a communication connection between the communication unit 11 and the base station 4 is established. When the first electronic message D1 is output to the communication unit 11, the first electronic message D1 is transmitted to the center device 2. In detail, the first control unit 15 causes the communication unit 11 to transmit the first electronic message D1 intermittently until the communication unit 11 receives a first response R1 from the center device 2.

[0120] At the transmission possible time Ta, the center device 2 transmits the first response R1 to the center-side network control device 5. As a result, the first response R1 is transmitted from the center-side network control device 5 to the communication unit 11 via the base station 4.

[0121] When the communication unit 11 receives the first response R1, it outputs the first response R1 to the first control unit 15 and goes into a pause state. When the first control unit 15 receives the first response R1 from the communication unit 11, it obtains the first response reception date and time.

[0122] Fig. 17 is a sequence diagram showing an example of the operation of the communication device 1 of this embodiment. In detail, Fig. 17 shows an example of the operation of the first control unit 15 and the communication unit 11 when the second process and the third process are executed.

[0123] When the first control unit 15 acquires the first response reception date and time as described with reference to Fig. 16, the first control unit 15 outputs a connection instruction to the communication unit 11 as shown in Fig. 17. As a result, a communication connection is established between the communication unit 11 and the base station 4.

[0124] After a communication connection is established between the communication unit 11 and the base station 4, the first control unit 15 generates a second electronic message D2 and outputs it to the communication unit 11. When the second electronic message D2 is output to the communication unit 11, the second electronic message D2 is transmitted to the center device 2. In detail, the first control unit 15 causes the communication unit 11 to transmit the second electronic message D2 intermittently until the communication unit 11 receives a second response R2 from the center device 2.

[0125] At the transmission possible time Ta, the center device 2 transmits the second response R2 to the center-side network control device 5. As a result, the second response R2 is transmitted from the center-side network control device 5 to the communication unit 11 via the base station 4.

[0126] When the communication unit 11 receives the second response R2, it outputs the second response R2 to the first control unit 15 and goes into a pause state. When the first control unit 15 receives the second response R2 from the communication unit 11, it acquires the second response reception date and time.

[0127] When the first control unit 15 acquires the second response reception date and time, it calculates the transmission interval ΔT and changes the timeout period TP from the first timeout period TP1 to the second timeout period TP2.

[0128] The third embodiment of the present invention has been described above with reference to Figures 1 to 3, 6, 7, and 14 to 17. According to this embodiment, similar to the first embodiment, the communication load between the center device 2 and each communication device 1 is less likely to increase.

[0129] 1 to 12, the communication device 1 acquires the response reception date and time during the measurement value notification process, and therefore may execute the second process after one or more transmittable times Ta have elapsed since the first response reception date and time was acquired by the first process. In this case, the transmission interval ΔT calculated by the first control unit 15 is longer than the interval between the transmittable times Ta. In contrast, according to the present embodiment, the second process is executed immediately after the first process, and therefore the interval between the transmittable times Ta can be more reliably acquired as the transmission interval ΔT.

[0130] Furthermore, according to this embodiment, the communication device 1 transmits the first electronic text D1 at short intervals (short cycles), and therefore can reduce the possibility that one or more transmittable times Ta will pass between the transmission of a certain first electronic text D1 and the transmission of the next first electronic text D1. Similarly, the communication device 1 transmits the second electronic text D2 at short intervals (short cycles), and therefore can reduce the possibility that one or more transmittable times Ta will pass between the transmission of a certain second electronic text D2 and the transmission of the next second electronic text D2. Therefore, the interval between the transmittable times Ta can be more reliably obtained as the transmission interval ΔT.

[0131] Furthermore, according to this embodiment, the communication unit 11 executes the first process and the second process to obtain the first response reception date and time and the second response reception date and time each time it executes the reset process, thereby reducing the possibility that the difference between the scheduled transmission time Tb and the transmittable time Ta will become large.

[0132] In this embodiment, the first control unit 15 calculates the transmission interval ΔT based on two response reception dates and times (the first response reception date and time and the second response reception date and time). However, the first control unit 15 may calculate the transmission interval ΔT based on three or more response reception dates and times.

[0133] In addition, in the present embodiment, the first process and the second process are executed immediately after the reset process, but the first process and the second process may be executed immediately after the opening process described with reference to FIG. 2. Alternatively, the first process and the second process may be executed during the measurement value notification process. For example, when the first control unit 15 acquires the measurement value of the meter 3 via the connection unit 12, the first control unit 15 may execute the first process described with reference to FIG. 14, and after the execution of the first process, the second process described with reference to FIG. 5. Alternatively, when the first control unit 15 acquires the measurement value of the meter 3 via the connection unit 12, the first control unit 15 may execute the first process described with reference to FIG. 4, and after the execution of the first process, the second process described with reference to FIG. 15.

[0134] The embodiments of the present invention have been described above with reference to the drawings (FIGS. 1 to 17). However, the present invention is not limited to the above embodiments, and can be implemented in various aspects without departing from the gist of the present invention. In addition, the components disclosed in the above embodiments can be modified as appropriate. For example, a certain component among all the components shown in one embodiment may be added to a component of another embodiment, or some of all the components shown in one embodiment may be deleted from the embodiment.

[0135] The drawings are mainly schematic illustrations of each component to facilitate understanding of the invention, and the thickness, length, number, spacing, etc. of each component shown in the drawings may differ from the actual ones due to the convenience of creating the drawings. Furthermore, the configurations of each component shown in the above embodiment are merely examples and are not particularly limited, and it goes without saying that various modifications are possible within a range that does not substantially deviate from the effects of the present invention.

[0136] For example, in the embodiment described with reference to FIGS. 1 to 17, the communication device 1 is connected to the meter 3 by wire, but the communication device 1 may be connected to the meter 3 by wireless.

[0137] In the embodiment described with reference to Figs. 1 to 17, the communication device 1 is connected to the meter 3, but the external device to which the communication device 1 is connected is not limited to the meter 3. For example, the external device may be a contact device. A contact device is a device that does not comply with the U-bus standard, and detects some state change (for example, a change indicating a short / open switching state of a contact) and notifies on or off information. The on or off information is an example of "information acquired from an external device."

[0138] 1 to 17, the first control unit 15 acquires the response reception date and time, but the first control unit 15 may acquire the time (response reception time) at which the communication unit 11 receives the response R from the center device 2. In this case, the first control unit 15 calculates the scheduled transmission time Tb based on the current time acquired from the first clock circuit 14, the transmission interval ΔT, and the response reception time.

[0139] 1 to 17, the first control unit 15 determines whether the waiting time Tw has elapsed, but the first control unit 15 does not have to determine whether the waiting time Tw has elapsed. For example, the first control unit 15 may determine whether the current date and time obtained from the first clock circuit 14 matches the scheduled transmission time Tb.

[0140] 1 to 17, the timeout period TP is shortened after the transmission interval ΔT is calculated, but the timeout period TP does not have to be shortened after the transmission interval ΔT is calculated. That is, the process of changing the timeout period TP may be omitted. In other words, the length of the timeout period TP may be constant. [Industrial Applicability]

[0141] The present invention is useful for communication devices and has industrial applicability. [Explanation of symbols]

[0142] 1: Communication equipment 2: Center device 11: Communications Department 15: First control section 100:Communication Systems

Claims

1. a communication unit that transmits a message to a center device and receives a response from the center device; a control unit that calculates a transmission interval, which is a time interval during which the center device can transmit the response to the communication unit; Equipped with The control unit is a first process of transmitting a first message to the center device, controlling the communication unit to receive a first response from the center device, and acquiring a first response reception time that is a time when the communication unit receives the first response from the center device; a second process of controlling the communication unit to transmit a second message to the center device after acquiring the first response reception time and to receive a second response from the center device, and acquiring a second response reception time, which is the time when the communication unit receives the second response from the center device; a third process of calculating the transmission interval based on the first response reception time and the second response reception time; A communication device that executes the above.

2. Further comprising a connection section for connecting to an external device, The control unit is The first process is executed when the information acquired from the external device is notified to the center device.

2. The communication device according to claim 1, wherein the second process is executed when notifying the center device of information acquired from the external device after acquiring the first response reception time.

3. The control unit is causing the communication unit to continuously transmit the first telegram until the first response is received during the execution of the first process; The communication device according to claim 1 , wherein, during execution of the second process, the communication unit is caused to continuously transmit the second telegram until the second response is received.

4. the communication unit communicates with the center device via a base station; The communication unit acquires a network time from the base station, The communication device according to claim 3 , wherein the control unit executes the first process and the second process when the communication unit acquires the network time.

5. the communication unit communicates with the center device via a base station; The communication unit periodically communicates with the base station; The communication device according to claim 3 , wherein the control unit executes the first process and the second process when the communication unit communicates with the base station.

6. Further comprising a connection section for connecting to an external device, The communication device according to claim 3 , wherein the control unit executes the first process and the second process when notifying the center device of information acquired from the external device.

7. The control unit causes the communication unit to transmit the message, and then sets the communication unit to a reception waiting state; The communication device according to claim 1 , wherein the control unit is configured to, after calculating the transmission interval, shorten a timeout period that is a maximum period for which the reception waiting state is to continue.

8. 8. The communication device according to claim 7, wherein the control unit, after calculating the transmission interval, determines whether the communication unit has received the response within the timeout period, and if it determines that the communication unit has not received the response within the timeout period, restores a length of the timeout period to its original length.

9. The communication device according to claim 1 , wherein after the calculation of the transmission interval, the control unit determines a time at which the communication unit transmits the message based on the transmission interval.

10. transmitting a first message from a communication unit to a center device; acquiring a first response reception time, which is a time when the communication unit receives the first response, in response to the communication unit receiving the first response from the center device; a step of transmitting a second electronic message from the communication unit to the center device after acquiring the first response reception time; acquiring a second response reception time, which is a time when the communication unit receives the second response, in response to the communication unit receiving the second response from the center device; calculating a transmission interval based on the first response reception time and the second response reception time; Including, The communication method, wherein the transmission interval indicates a time interval during which the center device can transmit a response to the communication unit.

11. A center device and a communication device are connected to each other so as to be able to communicate with each other, The communication device includes: a communication unit that transmits a message to the center device and receives a response from the center device; a control unit that calculates a transmission interval, which is a time interval during which the center device can transmit the response to the communication unit; Equipped with The control unit is a first process of transmitting a first message to the center device, controlling the communication unit to receive a first response from the center device, and acquiring a first response reception time that is a time when the communication unit receives the first response from the center device; a second process of controlling the communication unit to transmit a second message to the center device after acquiring the first response reception time and to receive a second response from the center device, and acquiring a second response reception time, which is the time when the communication unit receives the second response from the center device; a third process of calculating the transmission interval based on the first response reception time and the second response reception time; A communication system that performs the above steps.

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