Communication base station

Abstract

To provide a communication master unit which can reduce a time required to complete the communication of all communication slave units.SOLUTION: A communication master unit 1 communicates with a plurality of communication slave units 2. The plurality of communication slave units 2 include first and second communication slave units. The first communication slave unit directly communicates with the communication master unit 1. The second communication slave unit communicates with the communication master unit 1 through at least one other communication slave unit out of the plurality of communication slave units 2. Each communication slave unit 2 communicates with the communication master unit 1 through at least one link L having been established with the communication master unit 1. A hop count HP which indicates the number of links L of the first communication slave unit indicates 1. A hop count HP of the second communication slave unit increases corresponding to the number of other communication slave units which intervenes with the communication master unit 1 and the other communication slave units. The communication master unit 1 includes a setting part 15. The setting part 15 sets a communication start time T of each communication slave unit 2, based on the hop count HP of each communication slave unit 2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a communication base unit. [Background technology]

[0002] Patent Document 1 discloses a communication system including a plurality of communication terminal devices, a data accumulation server, and a network. The communication system of Patent Document 1 can avoid congestion by distributing the data transmission times of the communication terminal devices. Specifically, in the communication system of Patent Document 1, each communication terminal device calculates its own delay time relative to a set time common to the communication terminal devices so that the data transmission times of the communication terminal devices are distributed, and determines the data transmission time by adding its own delay time to the set time. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-175481 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the technology disclosed in Patent Document 1, the time intervals between data transmission times of each communication terminal device are uniformly set to the same time intervals. Therefore, as the number of communication terminal devices increases, the time required for all communication terminal devices to complete communication increases in proportion to the number of communication terminal devices.

[0005] The present invention has been made in consideration of the above-mentioned problems, and its purpose is to provide a communication base unit that can shorten the time required for communication to be completed for all communication slave units, compared to a configuration in which the time interval between the communication start times of each communication slave unit is set to the same time interval uniformly. [Means for solving the problem]

[0006] According to one aspect of the present invention, a communication base station communicates with a plurality of communication slave stations. The plurality of communication slave stations include a first communication slave station and a second communication slave station. The first communication slave station communicates directly with the communication base station. The second communication slave station communicates with the communication base station via at least one other communication slave station among the plurality of communication slave stations. Each of the plurality of communication slave stations communicates with the communication base station via at least one link established between the communication base station and the communication base station. A hop count indicating the number of links of the first communication slave station indicates 1. The hop count of the second communication slave station increases in accordance with the number of other communication slave stations intervening between the communication base station and the communication base station. The communication base station includes a setting unit. The setting unit sets the communication start time of each of the plurality of communication slave stations based on the hop count of each of the plurality of communication slave stations. [Effects of the Invention]

[0007] According to the communication base unit of the present invention, the time required for communication to be completed by all communication slave units can be shortened compared to a configuration in which the time interval between the communication start times of each communication slave unit is set to the same time interval. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating a communication system including a communication master unit according to an embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram showing a configuration of a communication master device according to the embodiment of the present invention. [Figure 3] FIG. 2 is a block diagram showing the configuration of a communication slave unit. [Figure 4] 5 is a flowchart illustrating a process executed by a control unit of the communication master device according to the embodiment of the present invention. [Figure 5] 5 is a flowchart illustrating a process executed by a control unit of the communication master device according to the embodiment of the present invention. [Figure 6] FIG. 10 is a diagram illustrating an example of a time interval. [Figure 7] FIG. 10 is a diagram illustrating an example of a communication start time. [Figure 8]FIG. 4 is a sequence diagram illustrating an example of an operation of the communication master device according to the embodiment of the present invention. [Figure 9] FIG. 4 is a sequence diagram illustrating an example of an operation of the communication master device according to the embodiment of the present invention. [Figure 10] FIG. 10 is a sequence diagram illustrating an example of an operation of a communication slave device. [Figure 11] FIG. 10 is a sequence diagram illustrating an example of an operation of a communication slave device. [Figure 12] 5 is a flowchart illustrating a process executed by a control unit of the communication master device according to the embodiment of the present invention. [Figure 13] FIG. 10 is a diagram illustrating an example of communication time. [Figure 14] FIG. 10 is a diagram illustrating an example of an updated communication start time. [Figure 15] FIG. 10 is a sequence diagram illustrating an example of an operation of a communication slave device. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the communication base unit of the present invention will be described with reference to the drawings (FIGS. 1 to 15). However, the present invention is not limited to the following embodiment, and can be implemented in various aspects without departing from the gist of the present invention. Note that where explanations are repeated, they may be omitted as appropriate. Furthermore, in the drawings, the same or equivalent parts are designated by the same reference numerals, and explanations will not be repeated.

[0010] 1 is a diagram showing a communication system 100 including a communication base unit 1 according to this embodiment. In this embodiment, the communication system 100 is a telemetry system in which measurement values ​​of a plurality of meters 3 are collected by a center device 4.

[0011] As shown in Fig. 1, in this embodiment, the communication system 100 includes a communication base unit 1, a plurality of communication slave units 2, a plurality of meters 3, a center device 4, and a center-side network control device 5. Hereinafter, the communication base unit 1 may be referred to as "base unit 1." Also, the communication slave unit 2 may be referred to as "slave unit 2."

[0012] The meter 3 is a measuring device related to resources or energy. The meter 3 measures, for example, gas, water, or electricity. The meter 3 is installed for each consumer, such as a private home, a company, or various facilities. The meter 3 measures, for example, the amount of gas, water, or electricity used, and outputs the measurement value as the measurement result.

[0013] The master unit 1 communicates with a plurality of slave units 2. A slave unit 2 is installed for each meter 3. Each slave unit 2 transmits to the master unit 1 a message indicating the measurement value output from the corresponding meter 3. Specifically, each slave unit 2 performs scheduled meter reading and transmits a message indicating the measurement value to the master unit 1 at a predetermined time. Scheduled meter reading refers to the process of acquiring a measurement value from a meter 3 at a predetermined date and time. For example, each slave unit 2 acquires a measurement value from the corresponding meter 3 at Y hour, Y minute, Y second on Y day of every month. Hereinafter, a message indicating a measurement value may be referred to as a "measurement value message."

[0014] The multiple handset devices 2 include a handset device 2 that communicates directly with the base unit 1 and a handset device 2 that communicates with the base unit 1 via at least one other handset device 2 among the multiple handset devices 2. Hereinafter, a handset device 2 that communicates directly with the base unit 1 may be referred to as a "first handset device 2A." Also, a handset device 2 that communicates with the base unit 1 via at least one other handset device 2 among the multiple handset devices 2 may be referred to as a "second handset device 2B." For example, specified low-power radio communication is used for communication between the base unit 1 and the first handset device 2A, and for communication between the handset devices 2. The frequency band for specified low-power radio communication is, for example, the 920 MHz band.

[0015] Each of the multiple slave devices 2 communicates with the master device 1 via at least one link L established between the master device 1 and the slave device 2 with which it communicates. Hereinafter, the number of links L established between the master device 1 and the slave device 2 with which it communicates may be referred to as the "hop count HP." The hop count HP of the first slave device 2A indicates "1." The hop count HP of the second slave device 2B increases in accordance with the number of other slave devices 2 between the master device 1 and the second slave device 2B.

[0016] In this embodiment, the multiple slave units 2 include five slave units 2a to 2e, and the multiple meters 3 include five meters 3a to 3e. After acquiring the measurement value of meter 3a, slave unit 2a creates a telegram D31 (measurement value telegram D31) indicating the measurement value of meter 3a and transmits it to the master unit 1. Similarly, slave units 2b to 2e transmit telegrams D32 to D35 (measurement value telegrams D32 to D35) indicating the measurement values ​​of meters 3b to 3e, respectively, to the master unit 1.

[0017] Of the five slave devices 2a to 2e, slave device 2a and slave device 2d are first slave devices 2A, and slave device 2b, slave device 2c, and slave device 2e are second slave devices 2B. Therefore, the number of hops HP of slave device 2a and slave device 2d is "1." The number of hops HP of slave device 2b, slave device 2c, and slave device 2e increases in accordance with the number of other slave devices 2 between them and the master device 1.

[0018] Specifically, of the five slave devices 2a to 2e, three slave devices 2a to 2c form a first communication route Rt1. Of the five slave devices 2a to 2e, two slave devices 2d and 2e form a second communication route Rt2. The slave device 2b included in the first communication route Rt1 communicates with the master device 1 via the slave device 2a. The slave device 2c included in the first communication route Rt1 communicates with the master device 1 via the slave devices 2a and 2b. The slave device 2e included in the second communication route Rt2 communicates with the master device 1 via the slave device 2d. Therefore, the number of hops HP of the slave devices 2b and 2e is "2", and the number of hops HP of the slave device 2c is "3".

[0019] When the child device 2a communicates with the base device 1, a first link L1 is formed between the child device 2a and the base device 1. When the child device 2b communicates with the base device 1, a first link L1 and a second link L2 are formed between the child device 2b and the base device 1. The second link L2 is formed between the child device 2b and the child device 2a. When the child device 2c communicates with the base device 1, the first link L1 to the third link L3 are formed between the child device 2c and the base device 1. The third link L3 is formed between the child device 2c and the child device 2b. When the child device 2d communicates with the base device 1, a fourth link L4 is formed between the child device 2d and the base device 1. When the child device 2e communicates with the base device 1, a fourth link L4 and a fifth link L5 are formed between the child device 2e and the base device 1. The fifth link L5 is formed between the child device 2e and the child device 2d.

[0020] An identification code ID is assigned to each of the multiple slave units 2. The identification code ID is, for example, a number. In this embodiment, "N1" is assigned as the identification code ID to the slave unit 2a. Similarly, "N2" to "N5" are assigned as the identification code ID to the slave units 2b to 2e, respectively.

[0021] The master unit 1 sets the communication start time T after the regular meter reading for each slave unit 2. For example, the master unit 1 sets the communication start time T after the regular meter reading for each slave unit 2 when installing the master unit 1 and five slave units 2a to 2e. Alternatively, the master unit 1 sets the communication start time T after the regular meter reading for each slave unit 2 when installing additional slave units 2. Hereinafter, the communication start time T after the regular meter reading may be referred to as the "communication start time T."

[0022] The communication start time T indicates the time at which the slave unit 2 starts communication to transmit the measurement value of the meter 3 to the master unit 1. The master unit 1 sets a different communication start time T for each slave unit 2. As a result, congestion can be avoided.

[0023] When the current time reaches communication start time T, each slave 2 starts communication and transmits a measurement value telegram to master 1. After master 1 receives measurement value telegrams D31 to D35 from slaves 2a to 2e, master 1 transmits telegram D3 indicating the measurement values ​​of meters 3a to 3e to center device 4. Note that master 1 may transmit a telegram indicating the measurement value to center device 4 every time it receives a measurement value telegram from each slave 2.

[0024] Specifically, the base device 1 is connected to a wide area wireless network Ne by wireless communication, and is communicatively connected to a center-side network control device 5 via the wide area wireless network Ne. The center device 4 is communicatively connected to the center-side network control device 5. The wide area wireless network Ne 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 (Fourth Generation Mobile Communication System) network, or a 5G (Fifth Generation Mobile Communication System) network.

[0025] The center-side network control device 5 is provided in, for example, a public network of a telecommunications carrier, and controls communication between the base unit 1 and the center device 4 via the wide-area wireless network Ne.

[0026] For example, if the meter 3 is a gas meter, the center device 4 is managed by a gas supplier. The center device 4 acquires the measured values ​​of the meter 3 from messages received from the base unit 1 via the wide area wireless network Ne and the center-side network control device 5, and stores the measured values ​​for each meter 3. In other words, the center device 4 stores the measured values ​​of the meter 3 for each consumer. The center device 4 includes, for example, a server.

[0027] In this embodiment, the meter 3 is not connected to the master unit 1, but the meter 3 may be connected to the master unit 1.

[0028] Next, the base unit 1 will be described with reference to Figures 1 and 2. Figure 2 is a block diagram showing the configuration of the communication base unit 1 of this embodiment. As shown in Figure 2, the base unit 1 includes a first communication unit 11, a second communication unit 12, a storage unit 13, a clock circuit 14, and a control unit 15.

[0029] The first communication unit 11 is communicatively connected to the center device 4. Specifically, the first communication unit 11 is communicatively connected to the center device 4 via a wide area wireless network Ne and a center-side network control device 5. More specifically, the first communication unit 11 is communicatively connected to the wide area wireless network Ne by wireless communication. Then, the first communication unit 11 transmits and receives messages to and from the center-side network control device 5 via the wide area wireless network Ne. As a result, messages are transmitted and received between the first communication unit 11 and the center device 4. The first communication unit 11 is a communication module capable of wide area communication such as with a PHS network, a FOMA network, an LTE network, a 4G network, and a 5G network.

[0030] The second communication unit 12 performs wireless communication with the handset 2. Specifically, the second communication unit 12 forms a link L with the first handset 2A and transmits and receives messages to and from the first handset 2A. In this embodiment, the second communication unit 12 performs wireless communication with the handset 2a and the handset 2d. The second communication unit 12 includes, for example, a communication module having an RF-LSI for 920 MHz band communication.

[0031] The storage unit 13 stores various computer programs and various data. The various computer programs include, for example, a computer program for setting a communication start time T for each slave device 2. The various data include, for example, data indicating an identification code ID of the host device (base device 1) and each slave device 2, destination information of the host device (base device 1) and each slave device 2, a communication route Rt of each slave device 2, and the number of hops HP of each slave device 2. The storage unit 13 has, for example, a semiconductor memory such as a read-only memory (ROM), a random access memory (RAM), and a flash memory.

[0032] The clock circuit 14 keeps time. The control unit 15 obtains the current time based on the time kept by the clock circuit 14.

[0033] The control unit 15 controls each element of the device. For example, the control unit 15 controls the first communication unit 11, the second communication unit 12, the storage unit 13, and the clock circuit 14. Specifically, the control unit 15 has a processor such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). The processor controls each element of the device by executing a computer program stored in the storage unit 13. The control unit 15 and the storage unit 13 may form a microcomputer.

[0034] The control unit 15 executes various processes. Specifically, a processor executes a computer program stored in the storage unit 13 to execute various processes. For example, the control unit 15 executes a process to set a communication start time T for each slave device 2. Specifically, the control unit 15 sets the communication start time T for each of the multiple slave devices 2 based on the number of hops HP for each of the multiple slave devices 2. The control unit 15 is an example of a "setting unit."

[0035] According to this embodiment, the communication start time T of each slave device 2 is set based on the hop count HP of each slave device 2, which makes it possible to shorten the time required for communication to be completed by all slave devices 2, compared to a configuration in which the same time interval is set for the communication start times T of all slave devices 2. Specifically, by making the time interval X between the communication start time T of a slave device 2 with a small hop count HP and the communication start time T of the slave device 2 that starts communication next shorter than the time interval X between the communication start time T of a slave device 2 with a large hop count HP and the communication start time T of the slave device 2 that starts communication next, it is possible to shorten the time required for communication to be completed by all slave devices 2.

[0036] In this embodiment, the control unit 15 determines, for each of the multiple slave devices 2, a time interval X at which communication with the master device 1 is to start, based on the hop count HP of each of the multiple slave devices 2. Then, based on each time interval X, the control unit 15 sets a communication start time T for each of the multiple slave devices 2. Specifically, the time interval X includes a first time interval X1 and a second time interval X2. The first time interval X1 indicates the time interval X that is set after communication starts for a slave device 2 whose hop count HP is the first hop count. The second time interval X2 indicates the time interval X that is set after communication starts for a slave device 2 whose hop count HP is the second hop count, which is larger than the first hop count. The control unit 15 determines each time interval X so that the second time interval X2 is longer than the first time interval X1.

[0037] For example, the first hop count is "1," and the slave devices 2 having the hop count HP of the first hop count are slave device 2a and slave device 2d. The second hop count is "2," and the slave devices 2 having the hop count HP of the second hop count are slave device 2b and slave device 2e. The control unit 15 determines each time interval X so that the time interval X (second time interval X2) provided after the slave devices 2b and 2e start communication is longer than the time interval X (first time interval X1) provided after the slave devices 2a and 2d start communication.

[0038] More specifically, the parent unit 1 (first communication unit 11) receives a message D1 indicating the execution date and time of the regular meter reading from the center device 4. The control unit 15 extracts the meter reading time t1 from the execution date and time of the regular meter reading. Then, based on the meter reading time t1 and each time interval X, it sets the communication start time T for each of the multiple child units 2. The meter reading time t1 is an example of a "set time." Hereinafter, the message D1 indicating the execution date and time of the regular meter reading may be referred to as a "regular meter reading setting message D1." Furthermore, the execution date and time of the regular meter reading may be referred to as a "regular meter reading date and time."

[0039] Furthermore, when the second communication unit 12 receives a measurement value telegram, the control unit 15 acquires the reception time, which is the time when the measurement value telegram was received, and stores the reception time in the memory unit 13. More specifically, when the second communication unit 12 receives a measurement value telegram, the control unit 15 acquires the current time from the clock circuit 14 and stores the time acquired from the clock circuit 14 in the memory unit 13 as the reception time. The control unit 15 is an example of an "acquisition unit." The control unit 15 receives measurement value telegrams D31 to D35 from all of the slave units 2a to 2e and stores the reception times of all of the measurement value telegrams D31 to D35 in the memory unit 13, and then updates the communication start time T of each slave unit 2 based on the reception times stored in the memory unit 13.

[0040] According to this embodiment, the communication start time T of each slave unit 2 can be updated based on the actual time when the measurement value was received from each slave unit 2, thereby shortening the time required for communication of all slave units 2 to be completed.

[0041] Specifically, the control unit 15 updates the communication start time T of each slave unit 2 so that the slave unit 2 with the largest difference between its communication start time T and its reception time will be the last to start communication with the base unit 1. More specifically, the time interval X set for the slave unit 2 with the largest difference between its communication start time T and its reception time is the longest among the time intervals X set for each slave unit 2. Therefore, by having the slave unit 2 with the largest difference between its communication start time T and its reception time communicate with the base unit 1 last, the waiting time due to the longest time interval X can be eliminated. As a result, the time required for all slave units 2 to complete communication can be further shortened. In this embodiment, the control unit 15 updates the communication start time T of each slave unit 2 so that communication with the base unit 1 is performed in ascending order of the difference between the communication start time T and its reception time.

[0042] Next, the slave unit 2 will be described with reference to Figures 1 to 3. Figure 3 is a block diagram showing the configuration of the communication slave unit 2. As shown in Figure 3, the slave unit 2 includes a connection unit 21, a communication unit 22, a storage unit 23, a clock circuit 24, and a control unit 25.

[0043] The connection unit 21 is connected to the meter 3. Specifically, the connection unit 21 has at least one port. One end of the electric wire PL is connected to the port of the connection unit 21. The electric wire PL includes a signal line and a ground line. The connection unit 21 is wiredly connected to the meter 3 via the electric wire PL. The control unit 25 acquires a measurement value from the meter 3 via the connection unit 21.

[0044] The communication unit 22 performs wireless communication with the base unit 1 or other handset 2. Specifically, the communication unit 22 of the first handset 2A forms a link L with the base unit 1 and transmits and receives messages to and from the base unit 1. The communication unit 22 of the second handset 2B forms a link L with another handset 2 and transmits and receives messages to and from the other handset 2. The communication unit 22 includes, for example, a communication module having an RF-LSI for 920 MHz band communication.

[0045] The storage unit 23 stores various computer programs and various data. The various computer programs include, for example, a computer program for acquiring the measurement value of the meter 3 at the scheduled meter reading date and time, and a computer program for executing wireless communication with the communication partner. The various data include, for example, data indicating the scheduled meter reading date and time, the communication start time T of the own device, the hop count HP of the own device, the identification code ID of the own device, destination information of the own device, and destination information of the communication partner. For example, the storage unit 23 of the slave 2a stores data indicating the destination information of the master 1 and the slave 2b as destination information of the communication partner. The storage unit 23 includes, for example, semiconductor memory such as ROM, RAM, and flash memory.

[0046] The clock circuit 24 keeps track of the time. The control unit 25 acquires the current time based on the time kept by the clock circuit 24. The control unit 25 further acquires the current date and time based on the current time and calendar information. The date and time include the date and time. The calendar information is stored in the storage unit 23.

[0047] The control unit 25 controls each element of the device. For example, the control unit 25 controls the connection unit 21, the communication unit 22, the storage unit 23, and the clock circuit 24. Specifically, the control unit 25 has a processor such as a CPU or an MPU. The processor controls each element of the device by executing a computer program stored in the storage unit 23. The control unit 25 and the storage unit 23 may form a microcomputer.

[0048] The control unit 25 executes various processes. Specifically, the processor executes a computer program stored in the storage unit 23 to execute various processes. For example, at the scheduled meter reading date and time, the control unit 25 acquires the measurement value of the meter 3 and stores it in the storage unit 23. Furthermore, at the communication start time T, the control unit 25 starts processing to transmit a measurement value message to the master unit 1.

[0049] Next, the processing executed by the control unit 25 of the master unit 1 will be described with reference to Figs. 1 to 5. Fig. 4 is a flowchart showing the processing executed by the control unit 25 of the communication master unit 1 of this embodiment. In detail, Fig. 4 shows the processing for setting the regular meter reading date and time and the communication start time T for each slave unit 2. Hereinafter, the processing for setting the regular meter reading date and time and the communication start time T for each slave unit 2 may be referred to as the "process for setting the communication start time, etc." As shown in Fig. 4, the processing for setting the communication start time, etc. includes steps S1 to S4.

[0050] First, the first communication unit 11 of the master unit 1 receives the regular meter reading setting message D1 from the center device 4 (step S1). The center device 4 transmits the regular meter reading setting message D1 to the master unit 1 when the master unit 1 and the five slave units 2a to 2e are installed. The center device 4 also transmits the regular meter reading setting message D1 to the master unit 1 when a slave unit 2 is added.

[0051] When the first communication unit 11 receives the regular meter reading setting message D1, the control unit 15 of the master 1 determines the communication start time T for each slave 2 (step S2). Specifically, the control unit 15 extracts the meter reading time t1 from the regular meter reading setting message D1. The control unit 15 also determines, for each slave 2, the time interval X at which communication with the master 1 is to start, based on the hop count HP of each slave 2. The control unit 15 also determines the communication order of each slave 2 based on the identification code ID of each slave 2. The control unit 15 then determines the communication start time T for each slave 2 based on the meter reading time t1, the time interval X determined for each slave 2, and the communication order of each slave 2.

[0052] After determining the communication start time T for each slave device 2, the control unit 15 of the base device 1 notifies the center device 4 of the communication start time T for each slave device 2 (step S3). Specifically, the control unit 15 transmits a message indicating the communication start time T for each slave device 2 to the center device 4 via the first communication unit 11.

[0053] The control unit 15 of the master unit 1 notifies the center device 4 of the communication start time T of each slave unit 2, and then sets the regular meter reading date and time and the communication start time T to each slave unit 2 (step S4), and ends the communication start time, etc. setting process. Specifically, the control unit 15 of the master unit 1 notifies each slave unit 2 of the regular meter reading date and time and the communication start time T. In more detail, the control unit 15 of the master unit 1 transmits a message D2 indicating the regular meter reading date and time and the communication start time T to each slave unit 2 via the second communication unit 12. Hereinafter, the message D2 indicating the regular meter reading date and time and the communication start time T may be referred to as the "message D2 for setting the communication start time, etc."

[0054] When the communication unit 22 receives the communication start time setting message D2, the control unit 25 of each slave unit 2 extracts the regular meter reading date and time and the communication start time T from the communication start time setting message D2 and stores them in the memory unit 23.

[0055] Fig. 5 is a flowchart showing the processing executed by the control unit 25 of the communication base device 1 of this embodiment. In particular, Fig. 5 shows an example of the details of step S4 of the communication start time setting processing (Fig. 4).

[0056] After notifying the center device 4 of the communication start time T of each slave device 2 (step S3 in FIG. 4), the control unit 15 of the master device 1 determines whether or not the regular meter reading date and time and the communication start time T have been set for all slave devices 2 (step S41). In other words, the control unit 15 determines whether or not there are any slave devices 2 for which the regular meter reading date and time and the communication start time T have not been set. Specifically, the control unit 15 determines whether or not the communication start time setting message D2 has been sent to all slave devices 2.

[0057] If the control unit 15 of the master unit 1 determines that there are any slave units 2 remaining for which the regular meter reading date and time and the communication start time T have not been set (No in step S41), it sets the regular meter reading date and time and the communication start time T for one of the slave units 2 for which the regular meter reading date and time and the communication start time T have not been set (step S42). In other words, the control unit 15 of the master unit 1 transmits a communication start time setting message D2 to one of the slave units 2 for which the regular meter reading date and time and the communication start time T have not been set. As a result, the process returns to step S41. On the other hand, if the control unit 15 determines that the regular meter reading date and time and the communication start time T have been set for all of the slave units 2 (Yes in step S41), the process shown in FIGS. 4 and 5 ends.

[0058] Next, the time interval X and the communication start time T will be described with reference to Fig. 1 to Fig. 7. Fig. 6 is a diagram showing an example of the time interval X, and Fig. 7 is a diagram showing an example of the communication start time T.

[0059] As shown in FIG. 6, the control unit 15 of the master device 1 determines the time interval X for each slave device 2 such that the time interval X between the start times T of communication between the slave device 2 with a larger hop count HP and the next slave device 2 to start communication is larger. In the present embodiment, the control unit 15 of the master device 1 sets the first time interval X1 for the slave devices 2 (slave devices 2a and 2d) with a hop count HP of "1", sets the second time interval X2 for the slave devices 2 (slave devices 2b and 2e) with a hop count HP of "2", and sets the third time interval X3 for the slave device 2 (slave device 2c) with a hop count HP of "3". The first time interval X1 is smaller than the second time interval X2 and the third time interval X3 (X1 < X2, X3). The second time interval X2 is larger than the first time interval X1 and smaller than the third time interval X3 (X1 < X2 < X3). The third time interval X3 is larger than the first time interval X1 and the second time interval X2 (X3 > X1, X2).

[0060] As shown in FIG. 7, the control unit 15 of the master device 1 determines the communication start time T of each slave device 2 based on the needle inspection time t1, the communication order of each slave device 2, and the time interval X set for each slave device 2. In the present embodiment, the communication order of each slave device 2 is in the order of the identification code ID of each slave device 2. That is, the smaller the identification code ID, the earlier the communication order. In the present embodiment, the communication order of the five slave devices 2a to 2e is in the order of slave device 2a, slave device 2b, slave device 2c, slave device 2d, slave device 2e.

[0061] The control unit 15 of the master device 1 sets the communication start time T (t21) of the slave device 2 (slave device 2a) that starts communication first to the needle inspection time t1. The control unit 15 of the master device 1 determines the communication start time T of the slave device 2 (slave device 2b) that starts communication second based on the communication start time T (t21) set for the slave device 2 (slave device 2a) that starts communication first and the time interval X (the first time interval X1). Specifically, the control unit 15 of the master device 1 sets the communication start time T of the slave device 2b to the time t22 that is delayed by the first time interval X1 with respect to the time t21.

[0062] Similarly, control unit 15 of base unit 1 sets communication start time T for handset 2c to time t23, which is delayed by the second time interval X2 from time t22. Control unit 15 of base unit 1 sets communication start time T for handset 2d to time t24, which is delayed by the third time interval X3 from time t23. Control unit 15 of base unit 1 sets communication start time T for handset 2e to time t25, which is delayed by the first time interval X1 from time t24.

[0063] In other words, the communication start time T(t22) of the slave 2b indicates a time delayed from the meter reading time t1 by the first time interval X1 (the time interval X set for the slave 2a). The communication start time T(t23) of the slave 2c indicates a time delayed from the meter reading time t1 by the total time of the first time interval X1 and the second time interval X2 (the time interval X set for the slave 2b). The communication start time T(t24) of the slave 2d indicates a time delayed from the meter reading time t1 by the total time of the first time interval X1, the second time interval X2, and the third time interval X3 (the time interval X set for the slave 2c). The communication start time T(t25) of the slave 2e indicates a time delayed from the meter reading time t1 by the total time of the first time interval X1, the second time interval X2, the third time interval X3, and the first time interval X1 (the time interval X set for the slave 2d).

[0064] Next, the master unit 1 of this 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 master unit 1 of this embodiment. In detail, Fig. 8 shows the operation of the master unit 1 when setting the regular meter reading date and time and the communication start time T for each slave unit 2.

[0065] As shown in Fig. 8, when the master unit 1 receives the regular meter reading setting message D1 from the center device 4, it transmits a response message Re1 to the center device 4. Specifically, the control unit 15 of the master unit 1 creates a message (response message Re1) indicating that the regular meter reading setting message D1 has been received, and transmits the response message Re1 to the center device 4 via the first communication unit 11. Thereafter, the control unit 15 determines the communication start time T for each slave unit 2, as described with reference to Figs. 6 and 7. Then, as described with reference to Fig. 4, it notifies the center device 4 of the communication start time T for each slave unit 2 (step S3 in Fig. 4).

[0066] After notifying the center device 4 of the communication start time T of each slave 2, the master 1 sets the regular meter reading date and time and the communication start time T in succession for each slave 2. Specifically, the master 1 sets the regular meter reading date and time and the communication start time T in succession for slave 2a, slave 2b, slave 2c, slave 2d, and slave 2e.

[0067] In detail, the control unit 15 of the parent unit 1 creates a communication start time setting message D21 indicating the scheduled meter reading date and time and the communication start time t21, and transmits the communication start time setting message D21 to the child unit 2a via the second communication unit 12.

[0068] When the control unit 15 of the parent unit 1 receives a response message Re21 from the child unit 2a indicating that the communication start time setting message D21 has been received, the control unit 15 creates a communication start time setting message D22 indicating the scheduled meter reading date and time and the communication start time t22, and transmits the communication start time setting message D22 to the child unit 2b via the second communication unit 12.

[0069] When the control unit 15 of the parent unit 1 receives a response message Re22 from the child unit 2b indicating that the communication start time setting message D22 has been received, the control unit 15 creates a communication start time setting message D23 indicating the scheduled meter reading date and time and the communication start time t23, and transmits the communication start time setting message D23 to the child unit 2c via the second communication unit 12.

[0070] When the control unit 15 of the parent unit 1 receives a response message Re23 from the child unit 2c indicating that the communication start time setting message D23 has been received, the control unit 15 creates a communication start time setting message D24 indicating the scheduled meter reading date and time and the communication start time t24, and transmits the communication start time setting message D24 to the child unit 2d via the second communication unit 12.

[0071] When the control unit 15 of the parent unit 1 receives a response message Re24 from the child unit 2d indicating that the communication start time setting message D24 has been received, the control unit 15 creates a communication start time setting message D25 indicating the scheduled meter reading date and time and the communication start time t25, and transmits the communication start time setting message D25 to the child unit 2e via the second communication unit 12.

[0072] When the control unit 15 of the base unit 1 receives from the handset 2e a response message Re25 indicating that the communication start time setting message D25 has been received, the control unit 15 ends the communication start time setting process.

[0073] Next, the master unit 1 of this 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 master unit 1 of this embodiment. In particular, Fig. 9 shows the details of the operation of the master unit 1 when setting the regular meter reading date and time and the communication start time T for the slave units 2a and 2b.

[0074] As shown in Fig. 9, when communicating with the slave 2a, the control unit 15 of the master 1 executes initial communication with the slave 2a. The initial communication is a process for forming the link L described with reference to Fig. 1. When communicating with the slave 2a, the control unit 15 of the master 1 establishes a first link L1 (see Fig. 1) with the slave 2a through the initial communication. After the first link L1 is established, the control unit 15 of the master 1 transmits a communication start time setting message D21 to the slave 2a via the second communication unit 12.

[0075] In addition, the communication start time setting message D21 contains destination information for the slave 2a, and the control unit 25 of the slave 2a confirms that the destination information in the communication start time setting message D21 matches the destination of its own device, then extracts the regular meter reading date and time and communication start time T from the communication start time setting message D21 and stores them in the memory unit 23.

[0076] When the control unit 15 of the base unit 1 receives the response message Re21 from the slave unit 2a, it releases (disconnects) the first link L1. Thereafter, the control unit 15 of the base unit 1 executes initial communication with the slave unit 2a to establish the first link L1. After the first link L1 is established, the control unit 15 of the base unit 1 transmits a communication start time setting message D22 to the slave unit 2a via the second communication unit 12.

[0077] The communication start time setting telegram D22 includes destination information for the handset 2b, and the control unit 25 of the handset 2a executes initial communication with the handset 2b based on the destination information in the communication start time setting telegram D22. As a result, a second link L2 (see FIG. 1) is established between the handset 2a and the handset 2b. After the second link L2 is established, the control unit 25 of the handset 2a transmits the communication start time setting telegram D22 to the handset 2b via the communication unit 22.

[0078] When the control unit 25 of the slave device 2b receives the communication start time setting message D22, it transmits a response message Re22 to the slave device 2a. The response message Re22 includes destination information of the master device 1, and the control unit 25 of the slave device 2a transmits the response message Re22 to the master device 1 based on the destination information of the response message Re22. After transmitting the response message Re22 to the master device 1, the control unit 25 of the slave device 2a releases (disconnects) the second link L2. When the control unit 15 of the master device 1 receives the response message Re22 from the slave device 2a, it releases (disconnects) the first link L1.

[0079] In addition, the operation of the parent unit 1 when setting the regular meter reading date and time and the communication start time T for the other sub-units 2c to 2e is the same as the operation of the parent unit 1 when setting the regular meter reading date and time and the communication start time T for the sub-units 2a and 2b, so the explanation will be omitted.

[0080] Next, the slave unit 2 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 slave unit 2. In detail, Fig. 10 shows the operation when each slave unit 2 transmits a measurement value message to the master unit 1.

[0081] 10, when the current time reaches communication start time t21, control unit 25 of slave unit 2a transmits measurement value telegram D31 to master unit 1 via communication unit 22. When a first time interval X1 has elapsed since communication start time t21 and the current time reaches communication start time t22, control unit 25 of slave unit 2b transmits measurement value telegram D32 to master unit 1 via communication unit 22. When a second time interval X2 has elapsed since communication start time t22 and the current time reaches communication start time t23, control unit 25 of slave unit 2c transmits measurement value telegram D33 to master unit 1 via communication unit 22. When a third time interval X3 has elapsed since communication start time t23 and the current time reaches communication start time t24, control unit 25 of slave unit 2d transmits measurement value telegram D34 to master unit 1 via communication unit 22. When the first time interval X1 has elapsed since the communication start time t24 and the current time reaches the communication start time t25, the control unit 25 of the slave unit 2e transmits a measurement value telegram D35 to the master unit 1 via the communication unit 22.

[0082] After receiving the measurement value telegrams D31 to D35 from all of the slaves 2a to 2e, the control unit 15 of the master 1 creates a telegram D3 indicating the measurement values ​​of the meters 3a to 3e, and then transmits the telegram D3 to the center device 4 via the first communication unit 11.

[0083] Next, the master unit 1 and the slave unit 2 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 slave units 2a and 2b. In particular, Fig. 11 shows the details of the operation of the slave units 2a and 2b when transmitting a measurement value message.

[0084] 11, when communication is performed between the slave device 2a and the master device 1, the control unit 25 of the slave device 2a executes initial communication with the master device 1. As a result, a first link L1 (see FIG. 1) is established between the slave device 2a and the master device 1. After the first link L1 is established, the control unit 25 of the slave device 2a transmits a measurement value telegram D31 to the master device 1 via the communication unit 22.

[0085] When the control unit 15 of the parent device 1 receives the measurement value telegram D31, it creates a response telegram Re31 indicating that the measurement value telegram D31 has been received, and transmits the response telegram Re31 to the child device 2a via the second communication unit 12. The response telegram Re31 includes destination information for the child device 2a, and the control unit 25 of the child device 2a confirms that the destination information in the response telegram Re31 matches the destination of its own device, and then releases (disconnects) the first link L1.

[0086] The measurement value telegram D31 includes destination information of the parent device 1. After confirming that the destination information in the measurement value telegram D31 matches the destination of the parent device 1, the control unit 15 of the parent device 1 extracts the measurement value from the measurement value telegram D31 and stores it in the memory unit 13.

[0087] When the first time interval X1 has elapsed since communication start time t21 and the current time reaches communication start time t22, control unit 25 of slave device 2b executes initial communication with slave device 2a. As a result, a second link L2 (see FIG. 1) is established between slave device 2a and slave device 2b. After the second link L2 is established, control unit 25 of slave device 2b transmits a measurement value telegram D32 to slave device 2a via communication unit 22.

[0088] The measurement value telegram D32 includes destination information of the parent device 1, and the control unit 25 of the child device 2a executes initial communication with the parent device 1 based on the destination information in the measurement value telegram D32. As a result, a first link L1 is established. After the first link L1 is established, the control unit 25 of the child device 2a transmits the measurement value telegram D32 to the parent device 1 via the communication unit 22.

[0089] When the control unit 15 of the parent device 1 receives the measurement value telegram D32, it creates a response telegram Re32 indicating that the measurement value telegram D32 has been received, and transmits the response telegram Re32 to the child device 2a via the second communication unit 12. The response telegram Re32 includes destination information for the child device 2b.

[0090] When the control unit 25 of the slave device 2a receives the response message Re32, it transmits the response message Re32 to the slave device 2b and releases (disconnects) the first link L1. When the control unit 25 of the slave device 2b receives the response message Re32, it releases (disconnects) the second link L2.

[0091] In this embodiment, when the control unit 15 of the parent device 1 receives a measurement value telegram from the child device 2, it stores the time at which the measurement value telegram was received in the storage unit 13. Specifically, when the control unit 15 of the parent device 1 receives measurement value telegram D31, it stores reception time t31, which is the time at which measurement value telegram D31 was received, in the storage unit 13. Similarly, when the control unit 15 of the parent device 1 receives measurement value telegrams D32 to D35, it stores reception times t32 to t35, which are the times at which measurement value telegrams D32 to D35 were received, in the storage unit 13.

[0092] The operations of the slave units 2c to 2d when transmitting a measurement value message are the same as those of the slave units 2a and 2b, and therefore a description thereof will be omitted.

[0093] Next, the base unit 1 will be described with reference to Figs. 1 to 12. Fig. 12 is a flowchart showing the processing executed by the control unit 15 of the communication base unit 1 of this embodiment. In detail, Fig. 12 shows the processing for resetting the communication start time T. Hereinafter, the processing for resetting the communication start time T may be referred to as "communication start time resetting processing." As shown in Fig. 12, the communication start time resetting processing includes steps S11 to S15.

[0094] 11, the control unit 15 of the base unit 1 stores the reception times (reception times t31 to t35) of the respective measurement value telegrams (measurement value telegrams D31 to D35) in the storage unit 13 (step S11). More specifically, every time the control unit 15 of the base unit 1 receives a measurement value telegram, it acquires the current time from the clock circuit 14 as the reception time. Then, it stores the time acquired from the clock circuit 14 in the storage unit 13 as the reception time.

[0095] The control unit 15 of the base unit 1 receives the measurement value telegrams from all the slave units 2 (slave units 2a to 2e) and stores the reception times of the respective measurement value telegrams (measurement value telegrams D31 to D35) in the storage unit 13, and then calculates the communication time DL of each slave unit 2 (step S12). Here, the communication time DL indicates the difference between the communication start time T and the reception time.

[0096] The control unit 15 of the base unit 1 determines the communication start time T for each of the slave units 2 based on the communication time DL of each of the slave units 2 (step S13). Specifically, the control unit 15 determines the communication start time T for each of the slave units 2 so that the slave unit 2 with the longest communication time DL starts communication with the base unit 1 last. In this embodiment, the control unit 15 of the base unit 1 updates the communication start time T for each of the slave units 2 so that communication with the base unit 1 is performed in ascending order of communication time DL.

[0097] After determining the communication start time T for each slave 2, the control unit 15 of the base unit 1 notifies the center device 4 of the communication start time T for each slave 2, similar to step S3 in FIG. 4 (step S14).

[0098] After notifying the center device 4 of the communication start time T of each handset 2, the control unit 15 of the base unit 1 sets the communication start time T to each handset 2 (step S15), similar to step S4 in Figure 4, and terminates the communication start time resetting process.

[0099] Next, the communication time DL and the updated communication start time T will be described with reference to Figures 1 to 14. Figure 13 is a diagram showing an example of the communication time DL, and Figure 14 is a diagram showing an example of the updated communication start time T.

[0100] As shown in FIG. 13, the communication time DL1 of the slave device 2a indicates the difference between the communication start time t21 and the reception time t31. The communication time DL2 of the slave device 2b indicates the difference between the communication start time t22 and the reception time t32. The communication time DL3 of the slave device 2c indicates the difference between the communication start time t23 and the reception time t33. The communication time DL4 of the slave device 2d indicates the difference between the communication start time t24 and the reception time t34. The communication time DL5 of the slave device 2e indicates the difference between the communication start time t25 and the reception time t35. In this embodiment, the communication times DL1 and DL4 of the slave devices 2a and 2d are the shortest, the communication times DL2 and DL5 of the slave devices 2b and 2e are the next shortest, and the communication time DL3 of the slave device 2c is the longest.

[0101] 14, the control unit 15 of the base unit 1 determines the communication start time T for each of the slave units 2 so that communication with the base unit 1 is started in ascending order of communication time DL. In this embodiment, the control unit 15 determines the communication start time T for each of the slave units 2 so that communication with the base unit 1 is started in the following order: slave unit 2a, slave unit 2d, slave unit 2b, slave unit 2e, and slave unit 2c. Note that the method for determining the communication order for slave units 2 with the same communication time DL is arbitrary. For example, the control unit 15 may determine the communication start time T for slave units 2 with the same communication time DL so that communication is started in the order of identification code ID.

[0102] In this embodiment, the control unit 15 of the master unit 1 sets the communication start time T (t41) of the slave unit 2a to the meter reading time t1. The control unit 15 of the master unit 1 sets the communication start time T of the slave unit 2d to time t42, which is delayed by the first time interval X1 from time t41. The control unit 15 of the master unit 1 sets the communication start time T of the slave unit 2b to time t43, which is delayed by the first time interval X1 from time t42. The control unit 15 of the master unit 1 sets the communication start time T of the slave unit 2e to time t44, which is delayed by the second time interval X2 from time t43. The control unit 15 of the master unit 1 sets the communication start time T of the slave unit 2c to time t45, which is delayed by the second time interval X2 from time t44.

[0103] Therefore, according to this embodiment, it is possible to eliminate the waiting time of the third time interval X3, which is the maximum time interval X, from the time required for all the slave devices 2 to complete communication. This makes it possible to further shorten the time required for all the slave devices 2 to complete communication.

[0104] Next, the slave unit 2 will be described with reference to Fig. 1 to Fig. 15. Fig. 15 is a sequence diagram showing an example of the operation of the communication slave unit 2. In detail, Fig. 15 shows the operation when each slave unit 2 transmits a measurement value message to the master unit 1 after the communication start time T is reset (updated).

[0105] 15, when the current time reaches communication start time t41, control unit 25 of slave unit 2a transmits measurement value telegram D31 to master unit 1 via communication unit 22. When a first time interval X1 has elapsed since communication start time t41 and the current time reaches communication start time t42, control unit 25 of slave unit 2d transmits measurement value telegram D34 to master unit 1 via communication unit 22. When a first time interval X1 has elapsed since communication start time t42 and the current time reaches communication start time t43, control unit 25 of slave unit 2b transmits measurement value telegram D32 to master unit 1 via communication unit 22. When a second time interval X2 has elapsed since communication start time t43 and the current time reaches communication start time t44, control unit 25 of slave unit 2e transmits measurement value telegram D35 to master unit 1 via communication unit 22. When the second time interval X2 has elapsed since the communication start time t44 and the current time reaches the communication start time t45, the control unit 25 of the slave unit 2c transmits a measurement value telegram D33 to the master unit 1 via the communication unit 22.

[0106] The control unit 15 of the master device 1 receives the measurement value telegrams D31 to D35 from all of the slave devices 2a to 2e, and then transmits the telegram D3 to the center device 4.

[0107] As described above with reference to FIGS. 1 to 15, according to this embodiment, the time required for all communication handset devices 2 to complete communication can be shortened compared to a configuration in which the time interval for the communication start time T of each communication handset device 2 is set to the same time interval X. Furthermore, according to this embodiment, the communication order of each communication handset device 2 can be changed based on the communication time DL of each communication handset device 2. As a result, the time required for all communication handset devices 2 to complete communication can be further shortened.

[0108] The embodiments of the present invention have been described above with reference to the drawings (FIGS. 1 to 15). However, the present invention is not limited to the above embodiments and can be embodied in various forms without departing from the spirit of the present invention. Furthermore, the components disclosed in the above embodiments can be modified as appropriate. For example, some of the components shown in one embodiment may be added to the components of another embodiment, or some of the components shown in one embodiment may be deleted from the embodiment.

[0109] The drawings mainly show each component in a schematic manner 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 configuration of each component shown in the above embodiment is merely an example and is 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.

[0110] For example, in the embodiment described with reference to FIGS. 1 to 15, the slave 2 and the meter 3 are connected by wires PL, but the slave 2 and the meter 3 may be connected wirelessly.

[0111] Furthermore, in the embodiment described with reference to Figures 1 to 15, the communication start time T (t21) of the slave unit 2 (slave unit 2a) that starts communication first is set to the meter reading time t1, but the communication start time T (t21) of the slave unit 2 (slave unit 2a) that starts communication first may also be set to a time that is later than the meter reading time t1.

[0112] In the embodiment described with reference to FIGS. 1 to 15, the meter 3 is connected to the communication slave unit 2, but the present invention can also be applied to a communication system including a meter having the function of the communication slave unit 2. [Industrial Applicability]

[0113] The present invention is useful in the field of wireless communications. [Explanation of symbols]

[0114] 1: Communication base station 2, 2a~2e: Communication handset 3, 3a to 3e: Meter 4: Center device 12: Second Communication Department 13: Storage section 15: Control section HP: Number of hops L: Link L1: First link L2: Second link L3: Third link L4: Fourth link L5: 5th link T, t21~t25, t41~t45: Communication start time X: Time interval X1: First time interval X2: Second time interval X3: Third time interval t1: Meter reading time (set time) t31~t35: Receipt time

Claims

1. A communication base unit that communicates with a plurality of communication slave units, The plurality of communication slave units include: a first communication slave unit that directly communicates with the communication master unit; a second communication slave unit that communicates with the communication master unit via at least one other communication slave unit among the plurality of communication slave units; Including, each of the plurality of communication slave units communicates with the communication master unit via at least one link established between the communication slave units and the communication master unit; the hop number indicating the number of links of the first communication slave device indicates 1, the number of hops of the second communication terminal increases in accordance with the number of the other communication terminals between the second communication terminal and the communication base terminal, the communication base station includes a setting unit that sets a communication start time for each of the plurality of communication slave stations based on the number of hops for each of the plurality of communication slave stations; the setting unit determines, for each of the plurality of communication slave devices, a time interval for starting communication with the communication master device based on the number of hops of each of the plurality of communication slave devices, and sets the communication start time of each of the plurality of communication slave devices based on the time interval; The time interval is: a first time interval set after the communication slave device having the first hop number starts communication; a second time interval provided after a communication slave device having a second hop number greater than the first hop number starts communication; Including, the setting unit determines the time interval such that the second time interval is greater than the first time interval; the communication start time indicates a time when the communication slave device starts communication for transmitting the meter measurement value to the communication master device, an acquisition unit that acquires each reception time, which is a time when the measurement value is received from each of the plurality of communication slave devices; a storage unit that stores the reception times acquired by the acquisition unit; Further provided with The setting unit updates the communication start time of each of the plurality of communication slave devices based on the reception time.

2. a communication unit that communicates with a center device and receives the set time from the center device; The communication master device according to claim 1 , wherein the setting unit sets the communication start time for each of the plurality of communication slave devices based on the set time and the time interval.

3. The communication base unit according to claim 1 or claim 2, wherein the setting unit updates the communication start time of each of the plurality of communication terminals so that the communication terminal with the largest difference between the communication start time and the reception time starts communication with the communication base unit last.

4. The communication base unit according to any one of claims 1 to 3, wherein the setting unit updates the communication start time of each of the plurality of communication slave units so as to communicate with the communication base unit in order of the smallest difference between the communication start time and the reception time.

5. The communication master unit according to claim 1 , wherein the setting unit further sets a time at which each of the communication slave units acquires the measurement value of the meter.

Images