Communication system and communication device

Abstract

To provide a communication system capable of suppressing failure in transmission of meter reading information due to congestion.SOLUTION: A communication system 100 includes a first communication device 2 and a second communication device 1 capable of communicating with the first communication device 2. The first communication device 2 includes an acquisition unit 251, a first communication unit 25, and a first switching unit 252. The acquisition unit 251 obtains meter reading results from a meter reading device. The first communication unit 25 communicates with the second communication device 1. The first switching unit 252 switches between a first communication channel ch1 and a second communication channel ch2. The second communication device 1 includes a second communication unit 12 and a second switching unit 152. The second communication unit 12 communicates with the first communication device 2. The second switching unit 152 switches between the first communication channel ch1 and the second communication channel ch2.SELECTED DRAWING: Figure 4

Description

[Technical Field]

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

[0002] The wireless communication system described in Patent Document 1 includes a wireless meter reading means and a plurality of wireless terminals. The wireless meter reading means is used in a wireless automatic meter reading system. The plurality of wireless terminals communicate wirelessly using a plurality of frequencies that are assigned in advance. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-16663 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the wireless communication system described in Patent Document 1, multiple wireless terminals communicate wirelessly using assigned frequencies, but congestion occurs when wireless terminals communicate wirelessly at the same time using the same frequency.

[0005] The present invention has been made in view of the above-mentioned problems, and aims to provide a communication system and a communication device that can prevent failure of transmission of meter reading information due to congestion. [Means for solving the problem]

[0006] According to one aspect of the present invention, a communication system includes a first communication device and a second communication device capable of communicating with the first communication device. The first communication device includes an acquisition unit, a first communication unit, and a first switching unit. The acquisition unit acquires a meter reading result from a meter reading device. The first communication unit communicates with the second communication device. The first switching unit switches between a first communication channel and a second communication channel. The second communication device includes a second communication unit and a second switching unit. The second communication unit communicates with the first communication device. The second switching unit switches between the first communication channel and the second communication channel. The first communication channel indicates a communication channel used to establish a connection between the first communication device and the second communication device. The second communication channel indicates a communication channel used to transmit the meter reading result from the first communication device to the second communication device. The frequency of the first communication channel is different from the frequency of the second communication channel.

[0007] According to another aspect of the present invention, a communication device is capable of communicating with another communication device. The acquisition unit acquires a meter reading result. The communication unit communicates with the other communication device. The switching unit switches the communication channel of the communication unit to a first communication channel or a second communication channel. The first communication channel indicates a communication channel used to establish a connection between the communication device and the other communication device. The second communication channel indicates a communication channel used to transmit the meter reading result from the communication device to the other communication device. The frequency of the first communication channel is different from the frequency of the second communication channel. [Effects of the Invention]

[0008] According to the communication system and communication device of the present invention, it is possible to prevent failure of transmission of meter reading information due to congestion. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram showing a communication system including a communication master unit and a communication slave unit according to an embodiment of the present invention; [Figure 2] FIG. 2 is a block diagram showing the configuration of a communication master device according to the present embodiment. [Figure 3] FIG. 2 is a block diagram showing the configuration of a communication slave unit according to the present embodiment. [Figure 4] 1 shows a flowchart of a process executed by a communication system according to the present embodiment. [Figure 5] FIG. 10 is a block diagram showing a configuration of a communication slave unit according to a modified example of the present embodiment. [Figure 6] 10 shows a flowchart of a process executed by a communication system according to a modified example. [Figure 7] 10 is a flowchart of a change process executed by a slave unit according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the communication base unit of the present invention will be described with reference to the drawings (FIGS. 1 to 4). 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.

[0011] 1 is a diagram showing a communication system 100 according to this embodiment, which includes a communication master 1 and a communication slave 2. In this embodiment, the communication system 100 is a telemetry system, and meter reading information from a plurality of meters 3 is collected by a central device 4.

[0012] 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 a "base unit 1." The communication base unit 1 corresponds to an example of a "second communication device." Furthermore, the communication slave unit 2 may be referred to as a "slave unit 2." The meter 3 corresponds to an example of a "meter reading device."

[0013] 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 meter reading information. The meter reading information is the meter reading result of the meter 3. The meter reading result includes a measurement value.

[0014] 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 a message indicating the meter reading information output from the corresponding meter 3 to the master unit 1. Specifically, each slave unit 2 performs scheduled meter reading and transmits a message indicating the meter reading information to the master unit 1 at a predetermined time. Scheduled meter reading refers to the process of acquiring meter reading information from the meter 3 at a predetermined date and time. For example, each slave unit 2 acquires meter reading information from the corresponding meter 3 at Y hour, Y minute, Y second on Y day of every month.

[0015] The multiple slave units 2 include a slave unit 2 that communicates directly with the base unit 1. The slave unit 2 that communicates directly with the base unit 1 corresponds to an example of a "first communication device." Furthermore, another slave unit 2 that is different from the slave unit 2 that communicates directly with the base unit 1 corresponds to an example of a "third communication device."

[0016] For example, specified low-power radio communication is used for communication between the base unit 1 and the slave unit 2. The frequency band for specified low-power radio communication is, for example, the 920 MHz band. When each of the multiple slave units 2 communicates with the base unit 1, it forms a link L. The formation of a link L between the slave unit 2 and the base unit 1 indicates that a connection between the slave unit 2 and the base unit 1 has been established. Each of the multiple slave units 2 communicates with the base unit 1 via at least one link L established between them.

[0017] In this embodiment, the multiple slave units 2 include two slave units 2a and 2b, and the multiple meters 3 include two meters 3a and 3b. After acquiring the meter reading information of meter 3a, slave unit 2a creates a message indicating the meter reading information of meter 3a and transmits it to master unit 1. Similarly, slave unit 2b transmits a message indicating the meter reading information of meter 3b to master unit 1.

[0018] When the slave device 2a communicates with the master device 1, a first link L1 is formed between the slave device 2a and the master device 1. When the slave device 2b communicates with the master device 1, a second link L2 is formed between the slave device 2b and the master device 1.

[0019] 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, the slave unit 2a is assigned the identification code ID "N1." Similarly, the slave unit 2b is assigned the identification code ID "N2."

[0020] The master unit 1 sets the communication start time after the scheduled meter reading for each slave unit 2. For example, when installing the master unit 1 and two slave units 2a and 2b, the master unit 1 sets the communication start time after the scheduled meter reading for each slave unit 2. Alternatively, when installing additional slave units 2, the master unit 1 sets the communication start time after the scheduled meter reading for each slave unit 2.

[0021] When the current time reaches the communication start time, each slave 2 starts communication and transmits a message indicating meter reading information to the master 1. After receiving messages indicating meter reading information from slaves 2a and 2b, the master 1 transmits the messages indicating meter reading information to the center device 4. Note that the master 1 may transmit a message indicating meter reading information to the center device 4 every time it receives a message indicating meter reading information from each slave 2.

[0022] 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.

[0023] 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.

[0024] 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 meter reading information of the meter 3 from a message received from the base unit 1 via the wide area wireless network Ne and the center-side network control device 5, and stores the meter reading information for each meter 3. In other words, the center device 4 stores the meter reading information of the meter 3 for each consumer. The center device 4 includes, for example, a server.

[0025] 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.

[0026] 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 communication unit 11, a communication unit 12, a storage unit 13, a clock circuit 14, and a control unit 15.

[0027] The communication unit 11 is communicatively connected to the center device 4. Specifically, the 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 communication unit 11 is communicatively connected to the wide area wireless network Ne by wireless communication. Then, the 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 communication unit 11 and the center device 4. The communication unit 11 is a communication module capable of wide area communication such as a PHS network, a FOMA network, an LTE network, a 4G network, and a 5G network.

[0028] The communication unit 12 communicates with the handset 2. Specifically, the communication unit 12 performs wireless communication with the handset 2. For example, the communication unit 12 forms a link L with the handset 2a and transmits and receives messages to and from the handset 2a. In this embodiment, the communication unit 12 performs wireless communication with the handset 2a and the handset 2b. The communication unit 12 includes, for example, a communication module having an RF-LSI for 920 MHz band communication. The communication unit 12 corresponds to an example of a "second communication unit."

[0029] The storage unit 13 stores various computer programs and various data. The various computer programs include, for example, a computer program for setting the communication start time of each slave unit 2. The various data include, for example, data indicating the identification code ID of the own device (base unit 1) and each slave unit 2, and destination information of the own device (base unit 1) and each slave unit 2. The storage unit 13 has, for example, semiconductor memory such as a ROM (Read Only Memory), a RAM (Random Access Memory), and a flash memory.

[0030] The clock circuit 14 keeps time. The control unit 15 obtains the current time based on the time kept by the clock circuit 14.

[0031] The control unit 15 controls each element of the device. For example, the control unit 15 controls the communication unit 11, the 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.

[0032] The control unit 15 executes various processes. Specifically, the processor executes the computer programs stored in the storage unit 13 to execute various processes. For example, the control unit 15 executes a process to set the communication start time of each slave unit 2.

[0033] Furthermore, when the communication unit 12 receives a telegram indicating meter reading information, the control unit 15 acquires the reception time, which is the time when the telegram indicating meter reading information was received, and stores it in the memory unit 13. In detail, when the communication unit 12 receives a telegram indicating meter reading information, the control unit 15 acquires the current time from the clock circuit 14 and stores the time acquired from the clock circuit 14 as the reception time in the memory unit 13. The control unit 15 receives telegrams indicating meter reading information from the slaves 2a and 2b, stores the reception times of all telegrams indicating meter reading information in the memory unit 13, and then updates the communication start time of each slave 2 based on the reception times stored in the memory unit 13.

[0034] The control unit 15 includes a switching unit 152. The control unit 15 executes a computer program stored in the storage unit 13 to function as the switching unit 152.

[0035] The switching unit 152 switches between the first communication channel ch1 and the second communication channel ch2. The switching unit 152 corresponds to an example of a "second switching unit." The first communication channel ch1 indicates a communication channel used to establish a connection between the master unit 1 and the slave unit 2. The second communication channel ch2 indicates a communication channel used to transmit meter reading information from the slave unit 2 to the master unit 1.

[0036] 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.

[0037] 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 meter reading information from the meter 3 via the connection unit 21.

[0038] The communication unit 22 communicates with the base unit 1. The communication unit 22 performs wireless communication with the base unit 1. Specifically, the communication unit 22 of the slave unit 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 slave unit 2b 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 includes, for example, a communication module having an RF-LSI for 920 MHz band communication. The communication unit 22 corresponds to an example of a "first communication unit."

[0039] The storage unit 23 stores various computer programs and various data. The various computer programs include, for example, a computer program for acquiring meter reading information from the meter 3 at the scheduled meter reading date and time, and a computer program for performing wireless communication with a communication partner. The various data include, for example, data indicating the scheduled meter reading date and time, the communication start time of the device itself, the identification code ID of the device itself, destination information of the device itself, 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.

[0040] 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 includes the date and time. The calendar information is stored in the storage unit 23.

[0041] 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.

[0042] The control unit 25 executes various processes. Specifically, the processor executes various processes by executing a computer program stored in the storage unit 23. For example, when the scheduled meter reading date and time arrives, the control unit 25 acquires meter reading information from the meter 3 and stores it in the storage unit 23.

[0043] Next, the communication system 100 will be described in detail with reference to Figures 2 and 3. The control unit 25 includes an acquisition unit 251 and a switching unit 252. The control unit 25 executes a computer program stored in the storage unit 23 to function as the acquisition unit 251 and the switching unit 252.

[0044] The acquisition unit 251 acquires meter reading information from the meter reading device. The control unit 25 starts a process of transmitting a message indicating the meter reading information to the master unit 1 when the communication start time arrives.

[0045] The switching unit 252 switches between the first communication channel ch1 and the second communication channel ch2. The switching unit 252 corresponds to an example of a "first switching unit." The frequency of the first communication channel ch1 is set to, for example, any frequency in the 920 MHz band. The frequency of the second communication channel ch2 is set to, for example, any frequency in the 920 MHz band. The frequency of the first communication channel ch1 is different from the frequency of the second communication channel ch2. Therefore, the frequency when the master unit 1 and the slave unit 2 form the link L is different from the frequency when the slave unit 2 transmits meter reading information to the master unit 1. This prevents multiple slave units 2 from connecting to the master unit 1 on one channel. In other words, it is possible to avoid congestion, such as connections concentrating on one channel. As a result, it is possible to prevent failures in transmitting meter reading information due to congestion.

[0046] Furthermore, the timing at which the switching unit 252 switches the communication channel is after the connection between the master unit 1 and the slave unit 2 is established. Specifically, after the link L is formed between the master unit 1 and the slave unit 2, the switching unit 252 switches the communication channel of the communication unit 22 from the first communication channel ch1 to the second communication channel ch2. Furthermore, after the link L is formed between the master unit 1 and the slave unit 2, the switching unit 252 switches the communication channel of the communication unit 22 from the first communication channel ch1 to the second communication channel ch2. This allows the master unit 1 to recognize that meter reading information will be transmitted from the slave unit 2 with which the link L is formed. In other words, the communication channel can be switched after each of the master unit 1 and the slave unit 2 recognizes that the communication channel will be switched. As a result, the timing at which the master unit 1 receives the meter reading information and the timing at which the slave unit 2 transmits the meter reading information can be matched, thereby enabling accurate transmission and reception of meter reading information.

[0047] Furthermore, in communication system 100 of this embodiment, handset 2 transmits a first electronic message after link L is formed between base unit 1 and handset 2, or when link L is formed between base unit 1 and handset 2. The first electronic message is a message requesting that communication unit 12 switch the communication channel of communication unit 12 from first communication channel ch1 to second communication channel ch2. Specifically, communication unit 22 transmits to base unit 1 the first electronic message requesting that communication unit 12 switch the communication channel of communication unit 12 from first communication channel ch1 to second communication channel ch2.

[0048] When base unit 1 receives the first electronic message, communication unit 12 transmits a second electronic message to handset 2. The second electronic message indicates a response to the request of the first electronic message. After transmitting the second electronic message, switching unit 152 switches the communication channel of communication unit 12 from first communication channel ch1 to second communication channel ch2.

[0049] Furthermore, after the communication unit 22 receives the second electronic message, the switching unit 252 switches the communication channel of the communication unit 22 from the first communication channel ch1 to the second communication channel ch2. Therefore, the meter reading information is transmitted from the slave 2 to the master 1 using the second communication channel ch2. For example, even if the slave 2b transmits the first electronic message to the master 1 using the first communication channel ch1, the slave 2a can avoid congestion with the slave 2b. As a result, the slave 2a can transmit the meter reading information to the master 1 while avoiding congestion with the other slaves 2. The other slaves 2 correspond to an example of a "third communication device."

[0050] Furthermore, in the communication system 100 of this embodiment, when the transmission and reception of meter reading information is completed, a third electronic message is transmitted from the center device 4 to the master unit 1. Then, the master unit 1 transmits the third electronic message to the slave unit 2. The third electronic message is a message indicating the end of communication between the master unit 1 and the slave unit 2. Specifically, the communication unit 12 transmits the third electronic message to the communication unit 22. After the master unit 1 transmits the third electronic message, the switching unit 152 switches the communication channel of the communication unit 22 from the second communication channel ch2 to the first communication channel ch1. When the communication unit 22 receives the third electronic message from the communication unit 12, the switching unit 252 switches the communication channel of the communication unit 22 from the second communication channel ch2 to the first communication channel ch1. Therefore, after the transmission and reception of meter reading information is completed, the master unit 1 becomes able to receive meter reading information transmitted from other slave units 2. As a result, it becomes possible to receive meter reading information from each of the multiple slave units 2 with high accuracy.

[0051] 2, control unit 15 of base unit 1 includes prohibition unit 153. Control unit 15 functions as prohibition unit 153 by executing a computer program stored in storage unit 13.

[0052] The prohibition unit 153 prohibits the reception of a fourth electronic message from another slave 2. The fourth electronic message indicates a request to establish a connection from another slave 2 different from the slave 2. Specifically, the prohibition unit 153 prohibits the reception of a fourth electronic message from another slave 2 only during the period from when the communication unit 12 transmits the second electronic message to the communication unit 22 until when the communication unit 12 transmits the third electronic message to the communication unit 22. Therefore, when the slave 2 transmits the second electronic message to the master 1 over the second communication channel ch2, it is possible to prevent congestion from occurring when the other slave 2 transmits the first electronic message over the first communication channel ch1. As a result, it is possible to transmit meter reading information from the slave 2 to the master 1 while avoiding congestion during the period from when the second electronic message is transmitted to the master 1 until when the third electronic message is transmitted.

[0053] For example, prohibition unit 153 prohibits acceptance of a fourth electronic message from slave 2b for the period from when communication unit 12 of master 1 transmits the second electronic message to communication unit 22 of slave 2a until communication unit 12 of master 1 transmits the third electronic message to communication unit 22 of slave 2a. Therefore, when slave 2a transmits the second electronic message to master 1 over second communication channel ch2, it is possible to prevent congestion from occurring when slave 2b transmits the first electronic message over first communication channel ch1. As a result, it is possible to transmit meter reading information from slave 2a to master 1 while avoiding congestion during the period from the transmission of the second electronic message to the transmission of the third electronic message.

[0054] Next, the communication system 100 according to this embodiment will be described with reference to Fig. 4. Fig. 4 shows a flowchart of the processing executed by the communication system 100. The flowchart shown in Fig. 4 includes processing by the center device 4, processing by the master device 1, processing by the slave device 2a, and processing by the slave device 2b. The processing executed by the communication system 100 includes steps S101 to S120.

[0055] In this embodiment, the communication order of each slave device 2 is the order of the identification code ID of each slave device 2. In other words, the smaller the identification code ID, the earlier the communication order. In this embodiment, the communication order of slave device 2a and slave device 2b is slave device 2a, slave device 2b.

[0056] In step S101, when the communication start time after the regular meter reading arrives, the control unit 25 of the slave 2a controls the communication unit 22 to form a first link L1 between the master 1 and the slave 2a on the first communication channel ch1 and to transmit a first electronic message to the communication unit 12 of the master 1. As shown in FIG. 4, the frequency of the first communication channel ch1 of the slave 2a is "923.4 MHz." After transmitting the first electronic message to the master 1, the control unit 25 of the slave 2a releases (disconnects) the first link L1. The process proceeds to step S102.

[0057] In step S102, control unit 15 of base unit 1 controls communication unit 12 to transmit a second electronic message to communication unit 22 of handset 2 over first communication channel ch1 based on the first electronic message. As shown in FIG. 4, the frequency of first communication channel ch1 of base unit 1 is "923.4 MHz." After transmitting the first electronic message to handset 2a, control unit 15 of base unit 1 releases (disconnects) first link L1. The process proceeds to step S103.

[0058] In step S103, after receiving the second telegram, the switching unit 252 of the handset 2a controls the communication unit 22 to switch the communication channel of the communication unit 22 from the first communication channel ch1 to the second communication channel ch2. As shown in Fig. 4, the frequency of the second communication channel ch2 of the handset 2a is "924.0 MHz." The process proceeds to step S104.

[0059] In step S104, after transmitting the second telegram, switching unit 152 of base unit 1 controls communication unit 12 to switch the communication channel of communication unit 12 from first communication channel ch1 to second communication channel ch2. As shown in Fig. 4, the frequency of second communication channel ch2 of base unit 1 is "924.0 MHz." The process proceeds to step S105.

[0060] In step S105, prohibition unit 153 of base unit 1 prohibits the acceptance of the fourth electronic message. The process proceeds to step S106.

[0061] In step S106, the control unit 25 of the slave 2a controls the communication unit 22 so that the communication unit 22 transmits the meter reading information to the communication unit 12 of the master 1 through the second communication channel ch2. Specifically, the control unit 25 of the slave 2a controls the communication unit 22 so that the first link L1 is formed between the master 1 and the slave 2a through the second communication channel ch2 and the communication unit 22 transmits the meter reading information to the communication unit 12 of the master 1. The process proceeds to step S107.

[0062] In step S107, the control unit 15 of the master unit 1 that has received the meter reading information 1 The communication unit 1 transmits meter reading information to the center device 4. 1 The process proceeds to step S108.

[0063] In step S108, the center device 4 transmits a third electronic message to the base device 1. The process proceeds to step S109.

[0064] In step S109, control unit 15 of base unit 1 controls communication unit 12 so that communication unit 12 transmits the third telegram to handset 2a through second communication channel ch2. The process proceeds to step S110.

[0065] In step S110, after receiving the third electronic message, control unit 25 of slave unit 2a controls communication unit 22 to switch the communication channel of communication unit 22 from second communication channel ch2 to first communication channel ch1. After receiving the third electronic message from master unit 1, control unit 25 of slave unit 2a releases (disconnects) first link L1. The process proceeds to step S110.

[0066] In step S110, after transmitting the third electronic message, control unit 15 of base unit 1 controls communication unit 12 to switch the communication channel of communication unit 12 from second communication channel ch2 to first communication channel ch1. The process proceeds to step S112.

[0067] In step S112, prohibition unit 153 of base unit 1 cancels the prohibited acceptance of the fourth electronic message. After transmitting the third electronic message to slave unit 2a, control unit 15 of base unit 1 releases (disconnects) first link L1. The process then ends.

[0068] In step S120, when the communication start time after the scheduled meter reading arrives, the control unit 25 of the slave 2b controls the communication unit 22 to transmit the fourth electronic message to the communication unit 12 of the master 1 through the first communication channel ch1. Note that, since the prohibition unit 153 of the master 1 prohibits the reception of the fourth electronic message in step S105, the master 1 does not accept the fourth electronic message. This prevents multiple slaves 2 from connecting to the master 1 through a single channel. In other words, it is possible to avoid the occurrence of congestion, such as connections concentrating on a single channel. As a result, it is possible to prevent the transmission of meter reading information from failing due to congestion.

[0069] Note that the first communication channel ch1 shown in FIG. 4 is merely an example and may be in the 920 MHz band. In addition, in the present embodiment, step S104 is described after step S103, but the order of steps S103 and S104 is not limited to this. Steps S103 and S104 may be performed simultaneously. Also, step S104 may be performed before step S103. In addition, in the present embodiment, step S105 is described after step S104, but the order of step S105 is not limited to this. For example, step S102 and step S105 may be performed simultaneously. Also, step S105 may be performed before step S104. In addition, in the present embodiment, step S111 is described after step S1010, but the order of steps S110 and S111 is not limited to this. Steps S110 and S111 may be performed simultaneously. Also, step S111 may be performed before step S110.

[0070] [Variations] A communication system 100 according to a modified example of the first embodiment will be described with reference to Figures 2, 3, 5, 6, and 7. The modified example differs from the first embodiment described with reference to Figures 1 to 4 in the processing executed by the control unit 25 of the handset 2. The following mainly describes the differences between the modified example and the first embodiment.

[0071] 5 is a block diagram showing the configuration of a modified communication cordless handset 2. The control unit 25 of the modified communication cordless handset 2 further includes a change unit 254. The control unit 25 executes a computer program stored in the storage unit 23 to function as the change unit 254.

[0072] The change unit 254 changes the frequency of the second communication channel ch2. Specifically, the change unit 254 changes the frequency of the second communication channel ch2 to a frequency that is not being used by other handset units 2. Specifically, the change unit 254 searches for a frequency that is not being used by other handset units 2. For example, the change unit 254 changes the frequency of the second communication channel ch2 to the 920 MHz band. Then, the change unit 254 controls the communication unit 22 so that the communication unit 22 transmits a determination message at the changed frequency. The determination message is used to check whether there is a response from other handset units 2 at the changed frequency. If there is no response from other handset units 2 at the changed frequency, the change unit 254 determines that the frequency is not being used by other handset units 2 and sets it to the frequency of the second communication channel ch2. Furthermore, if there is a response from other handset units 2 at the changed frequency, the change unit 254 further changes the frequency. Then, the change unit 254 transmits the determination message. The changing unit 254 changes the frequency until it finds a frequency that is not being used by another slave unit 2.

[0073] The communication unit 22 of the slave unit 2 in the communication system 100 of the modified example transmits a fifth electronic message to the master unit 1. The fifth electronic message includes a request for the switching unit 152 to switch the communication channel of the communication unit 12 of the master unit 1 to the second communication channel ch2, the frequency to which the change unit 254 has changed the communication channel of the communication unit 12. When the communication unit 12 of the master unit 1 receives the fifth electronic message, it transmits a sixth electronic message to the slave unit 2 indicating a response to the request of the fifth electronic message. Therefore, an unused frequency can be set as the frequency of the second communication channel ch2. This makes it possible to avoid the occurrence of congestion, such as connections concentrating on one channel. As a result, it is possible to prevent failures in transmitting meter reading information due to congestion.

[0074] Next, a communication system 100 according to a modified example will be described with reference to Fig. 6. Fig. 6 shows a flowchart of processing executed by the communication system 100 according to the modified example. The flowchart shown in Fig. 6 includes processing by the center device 4, processing by the master device 1, processing by the slave device 2a, and processing by the slave device 2b. The processing executed by the communication system 100 according to the modified example includes steps S200 to S220. Steps S204 to S220 shown in Fig. 6 correspond to steps S104 to S120 shown in Fig. 4. Therefore, a description of steps S204 to S220 will be omitted.

[0075] In step S200, the change unit 254 of the slave unit 2a executes a change process. The change process refers to a process of changing the frequency of the second communication channel ch2. The change process will be described later with reference to Fig. 8. The process proceeds to step S201.

[0076] In step S201, when the communication start time after the regular meter reading arrives, the control unit 25 of the slave 2a controls the communication unit 22 to form a first link L1 between the master 1 and the slave 2a over the first communication channel ch1 and to transmit a fifth telegram to the communication unit 12 of the master 1. As shown in FIG. 6, the frequency of the first communication channel ch1 of the slave 2a is "923.4 MHz." After transmitting the fifth telegram to the master 1, the control unit 25 of the slave 2a releases (disconnects) the first link L1. The process proceeds to step S202.

[0077] In step S202, control unit 15 of base unit 1 controls communication unit 12 to transmit a sixth electronic message to communication unit 22 of handset 2 over first communication channel ch1 based on the fifth electronic message. As shown in FIG. 6, the frequency of first communication channel ch1 of base unit 1 is "923.4 MHz." After transmitting the sixth electronic message to handset 2a, control unit 15 of base unit 1 releases (disconnects) first link L1. The process proceeds to step S203.

[0078] Next, the change processing executed by the slave unit 2 will be described in detail with reference to Fig. 7. Fig. 7 is a flowchart of the change processing executed by the slave unit 2 in a modified example. As shown in Fig. 7, the change processing includes steps S301 to S305.

[0079] In step S301, the change unit 254 determines whether "920.0 Mhz" is already in use. If "920.0 Mhz" is not in use (No in step S301), the process proceeds to step S304. If "920.0 Mhz" is in use (Yes in step S301), the process proceeds to step S302.

[0080] In step S302, the change unit 254 changes the frequency by substituting "0.1" for the constant N. The process proceeds to step S303.

[0081] In step S303, the change unit 254 determines whether the changed frequency (920+NMhz) is already in use. If the changed frequency is in use (Yes in step S303), the process proceeds to step S305. If the changed frequency is not in use (No in step S303), the process proceeds to step S304.

[0082] If the answer is No in step S301 and if the answer is No in step S303, then in step S304, the change unit 254 determines the frequency of the second communication channel ch2, and the process ends.

[0083] If the answer is Yes in step S303, in step S305, the change unit 254 increments the constant N by "0.1." The process returns to step S303.

[0084] The embodiments of the present invention have been described above with reference to the drawings. However, the present invention is not limited to the above embodiments and can be embodied in various forms without departing from the spirit and scope of the present invention. Furthermore, the drawings mainly show each component in a schematic manner for ease of understanding, and the thickness, length, number, spacing, etc. of each illustrated component may differ from the actual components due to the convenience of creating the drawings. Furthermore, the speed, material, shape, dimensions, etc. of each component shown in the above embodiments are merely examples and are not particularly limited, and various modifications are possible without substantially departing from the configuration of the present invention.

[0085] (1) In the embodiment, the control unit 15 of the parent device 1 has a switching unit 152 and a prohibition unit 153, but for example, if the control unit of the parent device does not have a switching unit and a prohibition unit, the switching unit 252 of the child device 2 may be configured not to switch the communication channel.

[0086] (2) In the embodiment, the slave unit 2 transmits the first electronic message to the master unit 1, but this is not limited to this. For example, the master unit 1 may transmit the first electronic message. In this case, the slave unit 2 transmits the second electronic message to the master unit 1. Also, in the modified example, the slave unit 2 transmits the fifth electronic message to the master unit 1, but this is not limited to this. For example, the master unit 1 may transmit the fifth electronic message. In this case, the slave unit 2 transmits the electronic message to the master unit 1. [Industrial Applicability]

[0087] The present invention provides a communication system and a communication device, and has industrial applicability. [Explanation of symbols]

[0088] 1: Parent device (second communication device) 2: Child device (first communication device) 12: Communication Department (Second Communication Department) 22: Communication Department (First Communication Department) 100: Communication Systems 152: Switching unit (second switching unit) 153: Prohibited part 251: Acquisition Department 252: Switching unit (first switching unit) 254: Change section ch1: First communication channel ch2: Second communication channel

Claims

1. A communication system including a first communication device, a center device, and a second communication device capable of communicating with the first communication device and the center device, The first communication device an acquisition unit that acquires a meter reading result from the meter reading device; a first communication unit that communicates with the second communication device; a first switching unit that switches between the first communication channel and the second communication channel; Equipped with the second communication device, a second communication unit that communicates with the first communication device; a second switching unit that switches between the first communication channel and the second communication channel; a third communication unit that communicates with the center device; Equipped with the first communication channel indicates a communication channel used by the first communication device and the second communication device to establish a connection; the second communication channel indicates a communication channel used to transmit the meter reading result from the first communication device to the second communication device; the frequency of the first communication channel is different from the frequency of the second communication channel; after the connection between the second communication device and the first communication device is established, the first switching unit switches the communication channel of the first communication unit from the first communication channel to the second communication channel; after the connection between the second communication device and the first communication device is established, the second switching unit switches the communication channel of the second communication unit from the first communication channel to the second communication channel; the first communication unit transmits to the second communication device a first telegram requesting that the second switching unit switch the communication channel of the second communication unit from the first communication channel to the second communication channel; when the second communication unit receives the first electronic message, it transmits a second electronic message indicating a response to the request of the first electronic message to the first communication device; the second switching unit switches the communication channel of the second communication unit from the first communication channel to the second communication channel; after the first communication unit receives the second telegram, the first switching unit switches the communication channel of the first communication unit from the first communication channel to the second communication channel; the third communication unit transmits the meter reading result to the center device, and after transmitting the meter reading result, receives a third message from the center device indicating an end of communication between the second communication device and the first communication device; the second communication unit, after receiving the third electronic message from the center device, transmits the third electronic message to the first communication unit; after receiving the third telegram, the second switching unit switches the communication channel of the second communication unit from the second communication channel to the first communication channel; A communication system in which, when the first communication unit receives the third telegram from the second communication unit, the first switching unit switches the communication channel of the first communication unit from the second communication channel to the first communication channel.

2. the second communication device further includes a prohibition unit that prohibits acceptance of a fourth electronic message during a period from when the second electronic message is transmitted to the first communication unit until when the third electronic message is transmitted to the second communication unit; The communication system according to claim 1 , wherein the fourth telegram indicates a request to establish a connection from a third communication device different from the first communication device.

3. the first communication device further includes a change unit that changes the frequency of the second communication channel; the first communication unit transmits a fifth electronic message to the second communication device; the fifth telegram includes a request for the second switching unit to switch the communication channel of the second communication unit to the second communication channel of the frequency changed by the changing unit, 3. The communication system according to claim 1, wherein when the second communication unit receives the fifth telegram, the second communication unit transmits a sixth telegram indicating a response to the request of the fifth telegram to the first communication device.

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