JP2009033464A - Wireless communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable long-term use of a transmitter even when driven by a battery, by reducing power necessary for the transmitter to receive a reception confirmation message. <P>SOLUTION: The battery-driven transmitter 1 which transmits a message by radio, forms a wireless communication system together with a monitoring device 2 which sends a reception confirmation message to the transmitter 1 in return when the device receives the message, a first repeater 3, and a second repeater 4. In the transmitter 1, a communication protocol controller makes a wireless transmission/reception portion start its reception standby state from a reception/transmission timing after the transmission of the message, and monitors the reception confirmation message from the monitoring device 2. When the communication protocol controller can not detect any reception confirmation message, even if it monitors the reception confirmation message for a predetermined period of time from the reception/transmission timing, it causes the wireless transmission/reception portion to stop the reception standby state, and stops its operation up to the next reception/transmission timing by controlling a power supply controller. The transmitter 1 receives the reception confirmation message while intermittently performing the reception standby state. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a wireless communication system.

  As a conventional wireless communication system, a battery-powered transmitter that creates a message based on a signal from an input device such as a sensor and transmits it wirelessly, and reception that the message has been received normally when the message from the transmitter is received A monitoring device (for example, a center or the like) that sends back a confirmation message is provided, and transmission / reception is performed between the transmitter and the monitoring device by specific low-power radio.

As an example of a conventional wireless communication system using the specific low-power radio, there is a fire alarm system as disclosed in Patent Document 1. Such a fire alarm system has a function in which a plurality of fire detectors (transmitters) installed at multiple locations respectively notify a fire and a function to sound an alarm sound. When a fire is detected, the relevant fire detector sounds an alarm sound and transmits information (fire detection information) to notify the fire detection to other fire detectors by wireless signals. A plurality of fire detectors interlock and sound an alarm sound all at once, so that the occurrence of a fire can be notified quickly and reliably.
JP 2006-343983 A

  However, when the transmitter of the conventional wireless communication system detects an input signal from the input device and transmits a message based on the input signal to the monitoring device, the wireless reception function until the reception confirmation message from the monitoring device is received. It was necessary to continue operating. In other words, until the reception confirmation message including the processing time in the monitoring device is received, or until it is detected that the message from the transmitter does not reach the monitoring device due to a message collision with other devices. During the timeout period, it was necessary to keep the radio reception function continuously operating.

  As described above, the conventional wireless communication system has a problem that the power consumption (current consumption) required for receiving the reception confirmation message in the battery-powered transmitter increases, and the time until the next battery replacement is shortened. It was.

  The present invention has been made in view of the above points, and an object of the present invention is to reduce the power required for receiving the reception confirmation message in the transmitter and to enable long-term use even when the battery is driven. An object of the present invention is to provide a wireless communication system.

  The invention of claim 1 is a wireless communication system comprising: a battery-powered transmitter that wirelessly transmits a message; and a monitoring device that returns a reception confirmation message to the transmitter when the message is received. A wireless transmission means for transmitting the message, a wireless reception means for receiving the reception confirmation message, and a reception waiting state after the message is transmitted to the wireless reception means intermittently repeatedly. And a transmitter-side control means for controlling to receive the reception confirmation message when a reception confirmation message for the transmitted message is detected.

  According to a second aspect of the present invention, in the first aspect of the invention, the monitoring device transmits the confirmation message at a timing that is an integral multiple of a fixed transmission / reception timing after the message is received, and the transmitter-side control means includes: The wireless reception unit is controlled to intermittently repeat the reception waiting state in accordance with the transmission / reception timing.

  The invention according to claim 3 is the invention according to claim 2, wherein the message and the reception confirmation message are transmitted and received in accordance with the transmission / reception timing included in a communication path between the transmitter and the monitoring device. A monitoring device storing means for storing the timing of transmitting the reception confirmation message for each transmission source of the received message; and the monitoring device storing means when receiving the message. And a monitoring device-side control unit that extracts the timing corresponding to the transmission source of the received message stored in the message and transmits the reception confirmation message at the extracted timing, and the transmitter includes the repeater Transmitter-side storage means for storing the number of transmitters, the transmitter-side control means after the transmission of the message, The radio reception unit is stopped until a time (times the number of the repeaters stored in the transmitter-side storage unit + 1) times has elapsed, and after the elapse of the time, the radio reception unit On the other hand, the reception waiting state is controlled to be intermittently repeated according to the transmission / reception timing.

  According to a fourth aspect of the present invention, in the first or second aspect of the invention, the transmitter-side control means measures a response time until the reception confirmation message starts to be received after the message transmission, and at the next message transmission time. The wireless reception means is stopped until the response time has elapsed after the next message transmission, and the reception waiting state is intermittently repeated for the wireless reception means after the response time has elapsed. It is characterized by doing.

  According to the invention of claim 1, in the transmitter, the wireless reception means repeats the reception waiting state intermittently in order to receive the reception confirmation message, so that the wireless reception means is always in the reception waiting state. The power required for receiving the reception confirmation message can be reduced, and the battery can be used for a long time even if it is battery driven.

  According to the invention of claim 2, since the reception waiting state of the wireless receiving means is synchronized with the transmission / reception timing in the transmitter, the success probability of receiving the reception confirmation message can be increased.

  According to the invention of claim 3, the transmitter predicts the timing at which the monitoring device transmits the reception confirmation message, and the radio reception means can be stopped until this timing is reached. Necessary electric power can be further reduced, and it can be used for a long time.

  According to the invention of claim 4, in the transmitter, by obtaining the response time from the message transmission to the reception confirmation message reception, at the next message transmission, the wireless transmission / reception means is provided until the response time elapses after the message transmission. Since the driving can be stopped, the power required for receiving the reception confirmation message can be further reduced, and the device can be used for a long time.

(Embodiment 1)
First, the structure of the radio | wireless communications system of Embodiment 1 is demonstrated using FIGS. As shown in FIG. 1, this wireless communication system transmits a message, for example, a battery-powered transmitter 1 or 1 that transmits a message by a specific low-power radio, and when the message is received, a reception confirmation message for the message is transmitted. The monitoring device 2 that sends a reply to the transmitter 1, and the first relay 3 and the second relay that relay messages and reception confirmation messages that are included in the communication path between the transmitters 1, 1 and the monitoring device 2, respectively. And a repeater 4.

  As shown in FIG. 4, the message and reception confirmation message used in the present embodiment are composed of a header portion, a data portion, and a CRC (error detection code) portion. In the header part, a preamble (synchronization signal) PR, a unique word (frame synchronization signal) UW, a message directly transmitted from the transmitter 1, or a message relayed through any one of the relays 3 and 4 are displayed. A frame identifier FI for identification, a message size SZ, a destination identification code (transmission destination address) DA, and a call identification code (transmission source address) SA are included. Further, data based on an input signal from the input device 5 is included in a data section described later.

  Next, the configuration of the transmitter 1 will be described. As shown in FIG. 2, the transmitter 1 includes a wireless transmission / reception unit (wireless transmission unit and wireless reception unit) 10 having a wireless transmission function for transmitting a message and a wireless reception function for receiving a reception confirmation message, and the wireless transmission / reception unit. A wireless transmission / reception control unit 11 that controls 10, a power supply control unit 12 that supplies power to each unit of the transmitter 1 when a battery (not shown) is attached, a system configuration storage unit 13 that stores system configuration information, For example, the signal detection unit 14 that detects an input signal (detection result) from the input device 5 such as a sensor and the wireless transmission / reception control unit 11 are controlled so that the wireless transmission / reception unit 10 transmits a message and receives a reception confirmation message. And a communication protocol control unit 15 to be configured.

  In accordance with an instruction from the wireless transmission / reception control unit 11, the wireless transmission / reception unit 10 performs switching of transmission / reception antennas, frequency control of a wireless signal used for transmission / reception of a message or reception confirmation message, and stop and activation of the wireless transmission function and the wireless reception function. Do.

  The wireless transmission / reception control unit 11 controls the state of the wireless transmission / reception unit 10, the communication channel, the frequency, and the bit synchronization processing in accordance with an instruction from the communication protocol control unit 15.

  When the signal detection unit 14 detects an input signal from the input device 5, the communication protocol control unit 15 creates a message based on the input signal and outputs the message to the wireless transmission / reception unit 10 via the wireless transmission / reception control unit 11. The communication protocol control unit 15 controls the power supply control unit 12 to supply power to the wireless transmission / reception unit 10, and controls the wireless transmission / reception control unit 11 to send a message from the wireless transmission / reception unit 10 to the monitoring device 2. Send according to the process. After transmitting the message, the communication protocol control unit 15 controls the power supply control unit 12 to stop the power supply to the wireless transmission / reception unit 10.

  Next, the configuration of the monitoring device 2 will be described. The monitoring device 2 manages the transmitters 1 and 1, the first repeater 3 and the second repeater 4 in a unified manner, and as shown in FIG. 3, a wireless transmission / reception unit having a wireless reception function and a wireless transmission function 20, a wireless transmission / reception control unit 21 that controls the wireless transmission / reception unit 20, a system configuration storage unit 22 that stores the transmission timing of the reception confirmation message for each transmission source of the message received by the wireless transmission / reception unit 20, and wireless transmission / reception A communication protocol control unit 23 for extracting the timing corresponding to the transmission source of the received message from the system configuration storage unit 22 and transmitting the reception confirmation message at the extracted transmission timing when the unit 20 receives the message; I have.

  In the system configuration storage unit 22, the identification numbers of the transmitters 1, 1 and the first and second repeaters 3, 4 in the system, and the number of the repeaters 3, 4, etc. The system configuration of the repeaters 3 and 4 is registered in advance at the time of installation, and the timing for transmitting the reception confirmation message is stored for each transmission source of the message received by the wireless transmission / reception unit 20. Specifically, when the message is directly transmitted from the transmitter 1 to the monitoring device 2, since there is reception from the first and second repeaters 3 and 4 after reception, as a timing to transmit the reception confirmation message, A value that is three times the transmission / reception timing is registered. When the message is transmitted from the first repeater 3 to the monitoring device 2, there is reception from the second repeater 4 having a lower priority than the first repeater 3 after the reception as described later. A value that is twice the transmission / reception timing described later is registered as the message transmission timing. When the message is transmitted from the second repeater 4 to the monitoring device 2, since there is no reception from the transmitter 1 and the first repeater 3 after reception, the transmission / reception timing is registered as the timing for transmitting the reception confirmation message. Has been. In other words, the timing for transmitting the reception confirmation message is set so that the reception confirmation message can be transmitted at the same time regardless of which device (the transmitter 1 and the first and second repeaters 3 and 4) receives the message. Has been. The transmission / reception timing is set to a time interval that does not hinder the transmission / reception of the message and the reception confirmation message based on the message length and the reception confirmation message length (see FIG. 4).

  Depending on the system configuration, the message transmitted from the transmitter 1 may reach the monitoring device 2 directly, or may reach the monitoring device 2 via the first and second repeaters 3 and 4. The communication protocol control unit 23 determines whether the message has been received directly from the transmitter 1 or relayed through the first and second repeaters 3 and 4 based on the transmission source identification number of the message received by the wireless transmission / reception unit 20. At the same time, the timing for transmitting the reception confirmation message is determined using the information in the system configuration storage unit 22.

  Then, the structure of the 1st repeater 3 and the 2nd repeater 4 is demonstrated. Each of the first repeater 3 and the second repeater 4 is installed to expand the communication area between the transmitters 1, 1 and the monitoring device 2, and as shown in FIG. A system configuration storage unit 32 (42) in which priorities are registered in advance among the transmission / reception unit 30 (40), the wireless transmission / reception control unit 31 (41), and the other repeaters 3 and 4, and the wireless transmission / reception unit Similarly to the monitoring device 2, the communication protocol control unit 33 (43) is provided that relays and transmits a message and a reception confirmation message according to a transmission waiting time (wait time) described later with respect to 30 (40). Between the first repeater 3 and the second repeater 4, the first repeater 3 is set to have a higher priority than the second repeater 4.

  The communication protocol control unit 33 (43) calculates the timing (transmission waiting time) until the relay transmission is started according to the priority registered in the system configuration storage unit 32 (42) after receiving the message or the reception confirmation message. . This timing is calculated to be an integral multiple of a constant transmission / reception timing. The communication protocol control unit 33 (43) relays and transmits the message received by the wireless transmission / reception unit 30 (40) or the reception confirmation message at the calculated timing. Since the highest priority is given, relay transmission is performed in accordance with the next transmission / reception timing after reception. On the other hand, since the second repeater 4 has a lower priority than the first repeater 3, the second repeater 4 performs relay transmission in accordance with the transmission / reception timing next to the transmission / reception timing relayed by the first repeater 3.

  In the wireless communication system having such a configuration, the communication protocol control unit 15 of the transmitter 1 shown in FIG. 2 has a time measuring function, and measures the time from the message transmission to the transmission / reception timing, and the transmission / reception timing is reached. The power supply control unit 12 is controlled to supply power to the wireless transmission / reception unit 10, and the wireless transmission / reception unit 10 is placed in a reception waiting state for a certain period of time. When a certain time has elapsed, the power control unit 12 is controlled to stop supplying power to the wireless transmission / reception unit 10, and the wireless transmission / reception unit 10 is controlled to stop the reception waiting state. Further, the communication protocol control unit 15 measures the time until the next transmission / reception timing, and performs the same control on the power supply control unit 12 and the wireless transmission / reception unit 10 when the next transmission / reception timing comes. That is, the communication protocol control unit 15 performs control so that the wireless transmission / reception unit 10 intermittently repeats the reception waiting state in accordance with the transmission / reception timing. The predetermined time is, for example, a time required for receiving a preamble and a unique word in the reception confirmation message.

  When the wireless transmission / reception unit 10 detects a reception confirmation message for the message in any reception waiting state, the communication protocol control unit 15 continuously transmits / receives the power to / from the power control unit 12 after the predetermined time has elapsed. Control is performed to supply power to the unit 10, and control is performed so that the wireless transmission / reception unit 10 receives the reception confirmation message. On the other hand, the communication protocol control unit 15 performs wireless transmission / reception so that the communication protocol control unit 15 retransmits the message when the wireless transmission / reception unit 10 cannot receive the reception confirmation message even if the wireless transmission / reception unit 10 repeats the reception standby state intermittently a predetermined number of times The unit 10 is controlled.

  Next, an example of the operation of the present embodiment will be described with reference to FIG. First, in the transmitter 1, after the signal detection unit 14 detects an input signal from the input device 5 (t1 in FIG. 5), a message including data based on the input signal detected by the communication protocol control unit 15 is created. Thereafter, the communication protocol control unit 15 controls the wireless transmission / reception control unit 11 to transmit the message from the wireless transmission / reception unit 10 (t2). The message transmitted from the transmitter 1 is first received by the first repeater 3.

  The first repeater 3 that has received the message from the transmitter 1 has the highest priority among the repeaters 3 and 4, and therefore relays the message to the monitoring device 2 in accordance with the next transmission / reception timing (t3). Send.

  The message transmitted from the first repeater 3 reaches the monitoring device 2 and also reaches the second repeater 4. Here, the second repeater 4 has a lower priority than the first repeater 3, but since the first repeater 3 has already performed relay transmission, the message from the first repeater 3 is transmitted. Relay transmission is performed at the next transmission / reception timing (t4).

  On the other hand, in the monitoring device 2, the wireless transmission / reception unit 20 first receives a message from the first repeater 3 (t3). After receiving the message, the communication protocol control unit 23 receives the message directly from the transmitter 1 based on the frame identifier in the message received by the wireless transmission / reception unit 20 or which relay device 3 or 4 relays the message. Identify Thereafter, the communication protocol control unit 23 determines the transmission timing of the reception confirmation message by using the system configuration data of the transmitter 1 and the first and second repeaters 3 and 4 registered in the system configuration storage unit 22. . Thereafter, the wireless transceiver 20 receives a message from the second repeater 4 (t4).

  Thereafter, in accordance with the transmission timing, the communication protocol control unit 23 controls the wireless transmission / reception unit 20 to transmit a reception confirmation message (t5).

  The first repeater 3 receives the reception confirmation message from the monitoring device 2 (t5), and transmits the reception confirmation message to the transmitter 1 in accordance with the next transmission / reception timing (t6).

  On the other hand, the communication protocol control unit 15 of the transmitter 1 starts the reception waiting state of the wireless transmission / reception unit 10 immediately before the transmission / reception timing after transmitting the message, and monitors the reception confirmation message (t3 to t5). When the communication protocol control unit 15 does not detect the reception confirmation message after monitoring the reception confirmation message for a certain time ta from the transmission / reception timing, the communication protocol control unit 15 stops the reception waiting state of the wireless transmission / reception unit 10, and the power supply control unit 12. To stop driving until the next transmission / reception timing.

  As described above, the transmitter 1 can receive the reception confirmation message from the monitoring device 2 while intermittently performing the reception waiting state (t6).

  When the first repeater 3 receives the reception confirmation message from the monitoring device 2, the second repeater 4 also receives the reception confirmation message (t5). The second repeater 4 having a lower priority than the first repeater 3 receives the confirmation from the first repeater 3 after the first repeater 3 transmits a reception confirmation message to the transmitter 1 (t6). The message is relayed, but since the first relay 3 has already relayed the reception confirmation message, the reception confirmation message from the second relay 4 is discarded by the first relay 3. , Is not transmitted to the transmitter 1 (t7).

  As described above, according to the present embodiment, in the transmitter 1, when the wireless transmission / reception unit is always in the reception waiting state by the wireless transmission / reception unit 10 intermittently repeating the reception waiting state in order to receive the reception confirmation message. In comparison, the power required for receiving the reception confirmation message can be reduced, and the battery can be used for a long time even if it is battery driven.

  Further, in the transmitter 1, the reception waiting state of the wireless transmission / reception unit 10 is synchronized with the transmission / reception timing, so that the probability of successful reception of the reception confirmation message can be increased.

(Embodiment 2)
The wireless communication system according to the second embodiment is different from the transmitter 1 in FIG. 2 in that the communication protocol control unit 15 stops driving the wireless transmission / reception unit 10 after a message has been transmitted until a predetermined time described later elapses. 1 and different. In addition, about the component similar to Embodiment 1, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  In the system configuration storage unit 13 of the transmitter 1 of the present embodiment, the number of repeaters 3 and 4 in the system is stored in advance. That is, the number of repeaters 3 and 4 is shared between the transmitter 1 and the monitoring device 2.

  The communication protocol control unit 15 drives the wireless transmission / reception unit 10 as a predetermined time until a time that is (times the number of repeaters 3 and 4 stored in the system configuration storage unit +1) times the transmission / reception timing interval elapses. After the elapse of time for stopping and stopping driving of the wireless transmission / reception unit 10, the wireless transmission / reception unit 10 is controlled to intermittently repeat the reception waiting state in accordance with the transmission / reception timing.

  Next, an example of the operation of this embodiment will be described with reference to FIG. The operations of the repeaters 3 and 4 and the monitoring device 2 after the message is transmitted from the transmitter 1 are the same as those in the first embodiment. That is, the monitoring device 2 does not transmit the reception confirmation message until the relay with the lowest priority (second relay 4) in the middle ends the relay transmission.

  On the other hand, in the transmitter 1 after message transmission, the number of repeaters 3 and 4 registered in the system configuration storage unit 13 is shared with the monitoring device 2, so The wireless transmission / reception unit 10 is stopped driving under the control of the communication protocol control unit 15 until the time +1) times the number of repeaters 3 and 4 stored in the storage unit 13 has elapsed (t2 to t6 in FIG. 6).

  Thereafter, the communication protocol control unit 15 puts the wireless transmission / reception unit 10 in a reception waiting state immediately before the transmission / reception timing, and monitors the reception confirmation message for a predetermined time ta (t6, t7).

  As described above, according to the present embodiment, the transmitter 1 predicts the timing at which the monitoring device 2 transmits the reception confirmation message (t5 in FIG. 6), and stops driving the radio transceiver 10 until this timing is reached. Since it is possible (t2 to t5), the power required for receiving the reception confirmation message can be further reduced, and it can be used for a long time.

(Embodiment 3)
In the wireless communication system according to the third embodiment, in the transmitter 1 of FIG. 2, the communication protocol control unit 15 measures the response time until the reception confirmation message is started after the message transmission. This embodiment is different from the first embodiment in that driving of the wireless transmission / reception unit 10 is stopped until a response time elapses after the next message transmission. In addition, about the component similar to Embodiment 1, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  The communication protocol control unit 15 stops driving the wireless transmission / reception unit 10 until the response time elapses, and controls the reception waiting state to be intermittently repeated after the response time elapses.

  Further, the communication protocol control unit 15 analyzes from the received message whether the reception confirmation message for the previous message transmission has arrived directly from the monitoring device 2 or via the first and second repeaters 3 and 4 in the middle of the received message. The data is stored in the configuration storage unit 13.

  Next, an example of the operation of the present embodiment will be described with reference to FIG. The operations of the first and second repeaters 3 and 4 and the monitoring device 2 after the message is transmitted from the transmitter 1 are the same as those in the first embodiment.

  On the other hand, when the transmitter 1 receives the reception confirmation message for the previous message, the communication protocol control unit 15 determines whether the reception confirmation message for the previous message has arrived directly from the monitoring device 2. Whether the message has arrived via 3 or 4 is analyzed from the reception confirmation message, and the response time from reception of the message until reception of the reception confirmation message is stored in the system configuration storage unit 13.

  In the transmitter 1 after this message transmission, the communication protocol control unit 15 stops driving the wireless transmission / reception unit 10 until the response time stored in the system configuration storage unit 13 elapses (t2 to t6 in FIG. 7). When the response time elapses (t6), the power control unit 12 is controlled to supply power to the wireless transmission / reception unit 10, and the reception waiting state of the wireless transmission / reception unit 10 is intermittently repeated to monitor the reception confirmation message. To control.

  As described above, according to the present embodiment, the transmitter 1 obtains a response time from message transmission to reception confirmation message reception, so that at the next message transmission, the wireless transmission / reception unit until the response time elapses after the message transmission. 10 can be stopped, so that the power required to receive the reception confirmation message can be further reduced, and it can be used for a long time.

  As a modification of the first to third embodiments, the transmitter 1 includes a first mode (see FIG. 5) in which the reception wait state is intermittently repeated according to the transmission / reception timing as in the first embodiment, and the second embodiment. As described above, after the wireless transmission / reception unit 10 is stopped until a time ((number of repeaters 3 and 4 + 1)) has elapsed with respect to the transmission / reception timing interval, 6), and the response time until the reception of the reception confirmation message is started after the message transmission as in the third embodiment, and the wireless communication is continued until the response time elapses after the next message transmission in the next message transmission. After the transmission / reception unit 10 stops driving, it has a third mode (see FIG. 7) in which the reception waiting state is intermittently repeated, and these first to third modes can be switched by the mode switch 16. It may be. As a result, the user can appropriately change the reception waiting state in accordance with the application and usage scene.

It is a block diagram which shows the structure of the radio | wireless communications system of Embodiment 1-3. It is a block diagram which shows the structure of a transmitter same as the above. It is a block diagram which shows the structure of a repeater and a monitoring apparatus same as the above. It is a format figure of a message same as the above. FIG. 3 is a communication sequence diagram of the first embodiment. FIG. 6 is a communication sequence diagram of the second embodiment. FIG. 10 is a communication sequence diagram of the third embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transmitter 2 Monitoring apparatus 3 1st repeater 4 2nd repeater

Claims (4)

A wireless communication system comprising: a battery-powered transmitter that wirelessly transmits a message; and a monitoring device that returns a reception confirmation message to the transmitter when the message is received,
The transmitter includes: a wireless transmission unit that transmits the message; a wireless reception unit that receives the reception confirmation message; and a reception waiting state that is intermittently repeated after the message is transmitted to the wireless reception unit. A wireless communication system, comprising: a transmitter-side control unit that controls to receive a reception confirmation message when a reception confirmation message for the transmitted message is detected in a reception waiting state. The monitoring device, after receiving the message, transmits the confirmation message at a timing that is an integral multiple of a fixed transmission / reception timing,
The wireless communication system according to claim 1, wherein the transmitter-side control means controls the wireless reception means to repeat the reception waiting state intermittently in accordance with the transmission / reception timing. Including one or more repeaters that are included in a communication path between the transmitter and the monitoring device and perform transmission and reception of the message and the reception confirmation message in accordance with the transmission and reception timing;
The monitoring device is stored in the monitoring device side storage unit that stores the timing of transmitting the reception confirmation message for each transmission source of the received message, and stored in the monitoring device side storage unit when the message is received. Monitoring device side control means for extracting the timing corresponding to the transmission source of the received message and transmitting the reception confirmation message at the extracted timing;
The transmitter has transmitter-side storage means for storing the number of the repeaters,
After the transmission of the message, the transmitter-side control means performs the wireless reception until a time that is (times the number of the repeaters stored in the transmitter-side storage means + 1) times has elapsed with respect to the transmission / reception timing interval. 3. The wireless communication according to claim 2, wherein the driving is stopped and the wireless reception unit is controlled to intermittently repeat the reception waiting state in accordance with the transmission / reception timing after the time has elapsed. system. The transmitter-side control means measures a response time until the reception confirmation message starts to be received after the message transmission, and at the next message transmission, the response time elapses after the next message transmission. 3. The wireless communication system according to claim 1, wherein driving of the wireless reception unit is stopped, and the wireless reception unit is controlled to intermittently repeat the reception waiting state after the response time has elapsed. .

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