Receiving device, receiving method, alarm system, alarm device, transfer method, and program

Abstract

To provide a technique for reducing power consumption of a receiving device.SOLUTION: A first-class relay device 200 can receive communication signals from each of a plurality of fire alarms 100. A plurality of communication time slots in which each of the plurality of fire alarms 100 can transmit a communication signal and a monitoring time slot in which the fire alarm 100 scheduled to transmit the communication signal should transmit the monitoring signal in the communication time slots are arranged in a time axis. A monitoring unit 226 monitors to receive the monitoring signal in the monitoring time slot. When the monitoring unit 226 does not detect receiving the monitoring signal, a control unit 224 stops the communication signal reception processing in the plurality of communication time slots. When the monitoring unit 226 detects receiving the monitoring signal, the control unit 224 executes the communication signal reception processing in one or more of the plurality of communication time slots.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a receiving technology, and in particular to a receiving device for receiving a signal, a receiving method, an alarm system, an alarm device, a transfer method, and a program. [Background technology]

[0002] Residential fire alarms (hereinafter referred to as "fire alarms") detect fires in homes and issue an alarm. In addition, multiple fire alarms communicate with each other, so that abnormal information from one fire alarm is also reported by the other fire alarms. As the number of fire alarms increases, the occurrence of collisions between wireless signals transmitted from the fire alarms also increases. To avoid collisions, TDMA (Time Division Multiple Access) is used (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-169552 Summary of the Invention [Problem to be solved by the invention]

[0004] When multiple fire alarms are connected to a single relay device, each of the multiple fire alarms transmits a signal to the relay device in an assigned time slot. Therefore, the relay device must wait for a signal in each of the multiple time slots, regardless of whether or not a signal from the fire alarm is received. It is desirable to reduce the power consumption of such relay devices (receiving devices).

[0005] The present disclosure has been made in view of these circumstances, and its purpose is to provide a technique for reducing the power consumption of a receiving device. [Means for solving the problem]

[0006] In order to solve the above problem, a receiving device according to one aspect of the present disclosure is a receiving device capable of receiving communication signals from each of a plurality of transmitting devices, in which a plurality of communication time slots in which each of the plurality of transmitting devices can transmit a communication signal and a monitoring time slot in which a transmitting device that is scheduled to transmit a communication signal in the communication time slot should transmit a monitoring signal are arranged on a time axis. In this frame, a monitoring unit that monitors reception of a supervisory signal in a supervisory time slot; and when the monitoring unit does not detect reception of a supervisory signal, stopping reception processing of the communication signal in the plurality of communication time slots; and when the monitoring unit detects reception of a supervisory signal, In one frame, Multiple communication time slots In each and a control unit that executes a process for receiving a communication signal.

[0007] Another aspect of the present disclosure is a receiving method for a receiving device capable of receiving communication signals from a plurality of transmitting devices, in which a plurality of communication time slots in which each of the plurality of transmitting devices can transmit a communication signal and a monitoring time slot in which a transmitting device that is scheduled to transmit a communication signal in the communication time slot should transmit a monitoring signal are arranged on a time axis. In this frame, a step of monitoring reception of a supervisory signal in a supervisory time slot, and if reception of the supervisory signal is not detected, stopping reception processing of communication signals in a plurality of communication time slots; and if reception of the supervisory signal is detected, In one frame, Multiple communication time slots In each and a step of causing the device to execute a reception process for a communication signal.

[0008] Yet another aspect of the present disclosure is an alarm system. This alarm system comprises a plurality of alarm devices that form a multi-hop network extending from a relay device. The plurality of alarm devices include a first alarm device, a second alarm device, and a third alarm device, and the first alarm device is capable of communicating with the relay device over i (i is an integer of 1 or greater) hops, and the second alarm device and the third alarm device are connected to the first alarm device and are capable of communicating with the relay device over i+1 hops, In the frame,a first communication time slot in which a first alarm device can transmit a communication signal, a second communication time slot in which a second alarm device can transmit a communication signal, and a third communication time slot in which a third alarm device can transmit a communication signal are arranged on the time axis, In the frame, Monitoring time slots in which the first, second or third alarm device, which is scheduled to transmit a communication signal, should transmit a monitoring signal, are arranged before the first, second and third communication time slots, and the first alarm device monitors for reception of a monitoring signal in the monitoring time slots, and if it does not detect the reception of a monitoring signal, it stops reception processing of communication signals in the second and third communication time slots, and if the first alarm device detects the reception of a monitoring signal: In one frame, Second communication time slot and In the third communication time slot, a communication signal Execute the reception process of Then, a supervisory signal is transmitted in the supervisory time slot, and a communication signal is transferred in the first communication time slot.

[0009] Yet another aspect of the present disclosure is an alarm device. This alarm device is one of multiple alarm devices that make up a multi-hop network spreading out from a relay device, and has a communication unit that is capable of communicating with the relay device over i (i is an integer of 1 or greater) hops, and is also capable of communicating with other alarm devices that can communicate with the relay device over i+1 hops, and with further alarm devices; In the frame, A first communication time slot in which an alarm device can transmit a communication signal, a second communication time slot in which other alarm devices can transmit communication signals, and a third communication time slot in which further other alarm devices can transmit communication signals are arranged on the time axis, and monitoring time slots in which the alarm device scheduled to transmit a communication signal or another alarm device or a further other alarm device should transmit a monitoring signal are arranged before the first communication time slot, second communication time slot and third communication time slot, and a monitoring unit monitors reception of a monitoring signal in the monitoring time slot, and if the monitoring unit does not detect reception of a monitoring signal, reception processing of communication signals in the second communication time slot and third communication time slot is stopped, and if the monitoring unit detects reception of a monitoring signal, In one frame, Second communication time slot and In the third communication time slot, a communication signal Execute the reception process of a control unit that causes the first communication time slot to transmit a monitoring signal in the monitoring time slot and transfer a communication signal in the first communication time slot.

[0010] Yet another aspect of the present disclosure is a forwarding method for an alarm device among multiple alarm devices that make up a multi-hop network extending from a relay device, wherein the alarm device is capable of communicating with the relay device over i hops (i is an integer greater than or equal to 1), and is also capable of communicating with other alarm devices that can communicate with the relay device over i+1 hops, and with further alarm devices; In the frame, A first communication time slot in which an alarm device can transmit a communication signal, a second communication time slot in which another alarm device can transmit a communication signal, and a third communication time slot in which a further other alarm device can transmit a communication signal are arranged on the time axis, and monitoring time slots in which the alarm device scheduled to transmit a communication signal or another alarm device or a further other alarm device should transmit a monitoring signal are arranged before the first communication time slot, second communication time slot and third communication time slot, and there is a step of monitoring reception of a monitoring signal in the monitoring time slot, and if reception of a monitoring signal is not detected, stopping reception processing of communication signals in the second communication time slot and third communication time slot, and if reception of a monitoring signal is detected, In one frame, Second communication time slot and In the third communication time slot, a communication signal Execute the reception process of the step of transmitting a supervisory signal in the supervisory time slot and transferring a communication signal in the first communication time slot.

[0011] Any combination of the above components, and conversion of the present disclosure into a method, device, system, recording medium, computer program, etc., are also valid aspects of the present disclosure. [Effects of the Invention]

[0012] According to the present disclosure, it is possible to reduce the power consumption of a receiving device. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a diagram illustrating a configuration of an alarm system according to a first embodiment. [Figure 2] FIG. 10 is a diagram showing an outline of communication between a fire alarm and a first type relay device to be compared. [Figure 3] FIG. 2 is a diagram illustrating the configuration of the fire alarm and the first type relay device of FIG. [Figure 4] FIG. 4 is a diagram showing an outline of communication between the fire alarm device and the first type relay device in FIG. 3. [Figure 5] 4 is a diagram showing another outline of communication between the fire alarm device and the first type relay device in FIG. 3. FIG. [Figure 6] 10 is a diagram showing yet another outline of communication between the fire alarm device and the first type relay device of FIG. 3. FIG. [Figure 7] FIG. 10 is a diagram illustrating a configuration of an alarm system according to a second embodiment. [Figure 8] FIG. 8 is a diagram showing the configuration of the fire alarm device of FIG. [Figure 9] 9(a)-(d) are diagrams showing the structure of a superframe used in the alarm system of FIG. [Figure 10] FIG. 8 is a diagram showing an example of time slot allocation in the alarm system of FIG. 7. [Figure 11] FIG. 8 is a diagram showing an outline of downstream communication in the alarm system of FIG. [Figure 12] FIG. 8 is a diagram showing an outline of upstream communication in the alarm system of FIG. [Figure 13] FIG. 8 is a diagram showing an overview of routing in the alarm system of FIG. 7. [Figure 14] FIG. 8 is a sequence diagram showing a routing procedure in the alarm system of FIG. 7. [Figure 15] 15(a)-(b) are diagrams showing an outline of the installation of the alarm system of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0014] Example 1 Before describing the present disclosure in detail, an overview will be provided. Example 1 relates to an alarm system installed in facilities such as apartment buildings, detached houses, offices, and hospitals. In the alarm system, a relay device (hereinafter referred to as a "first-class relay device") is connected to a management device, another relay device (hereinafter referred to as a "second-class relay device") is connected to the first-class relay device, and one or more fire alarms are connected to each of the first-class relay device and the second-class relay device (hereinafter sometimes collectively referred to as a "relay device"). In this tree structure, the management device corresponds to the upper side, and the fire alarms correspond to the lower side. When the fire alarm detects a fire, it sounds an alarm and transmits the detection result to the relay device. The relay device relays the detection result between the first-class relay device and the second-class relay device and transmits the detection result to the fire alarm. When the fire alarm receives an alarm signal, it emits an alarm. Furthermore, the first-class relay device transmits the detection result to the management device. The management device manages the detection results.

[0015] When signals are transmitted from multiple fire alarm devices to a relay device, the more fire alarm devices there are, the more likely the signals are to collide. To prevent signal collisions, TDMA is used for communication between the relay device and multiple fire alarm devices. In TDMA, each fire alarm device is assigned a time slot, and multiple time slots are arranged on a time axis. The fire alarm device transmits a signal in its assigned time slot. Meanwhile, the relay device waits to receive a signal in each of the multiple time slots. However, even when the fire alarm device does not transmit a signal, the relay device must wait to receive a signal in each time slot. As a result, the power consumption of the relay device increases. Here, the line for signals from the relay device to the fire alarm is called the "downlink," while the line for signals from the fire alarm to the relay device is called the "uplink."

[0016] In order to suppress an increase in the power consumption of the relay device, the embodiment performs the following process. The relay device defines a frame including one communication time slot for the downlink (hereinafter referred to as a "downlink communication time slot") and multiple communication time slots for the uplink (hereinafter referred to as "uplink communication time slots"). Here, one uplink communication time slot is assigned to one fire alarm. The frame also includes a monitoring time slot (hereinafter referred to as a "monitoring time slot") in which a fire alarm that is scheduled to transmit a signal (hereinafter referred to as a "communication signal") in the assigned uplink communication time slot transmits a signal (hereinafter referred to as a "monitoring signal"). The relay device waits to receive a monitoring signal in the monitoring time slot. If the relay device receives a monitoring signal in the monitoring time slot, the relay device waits to receive a communication signal in the uplink communication time slot. On the other hand, if the relay device does not receive a monitoring signal in the monitoring time slot, the relay device does not wait to receive a communication signal in the uplink communication time slot.

[0017] 1 shows the configuration of an alarm system 1000. The alarm system 1000 includes a first fire alarm device 100a to a sixth fire alarm device 100f, collectively referred to as fire alarm devices 100, a first type relay device 200, a second type relay device 202, and a management device 300. The number of fire alarm devices 100 is not limited to "6". As mentioned above, the first type relay device 200 and the second type relay device 202 are collectively referred to as "relay devices".

[0018] The alarm system 1000 is applied to facilities such as homes, and is a system that detects fires and notifies users that a fire has occurred. The alarm system 1000 may also be applied to facilities such as offices and commercial facilities. The multiple fire alarms 100 are, for example, residential fire alarms and are equipped with fire detection sensors. The multiple fire alarms 100 are installed, for example, on the ceiling of the facility, but may also be installed on the walls, etc.

[0019] Here, the first fire alarm device 100a to the third fire alarm device 100c perform wireless communication with the first type relay device 200, and the fourth fire alarm device 100d to the sixth fire alarm device 100f perform wireless communication with the second type relay device 202. In other words, a star-shaped network topology is formed with the first type relay device 200 and the second type relay device 202 at the center of the network. In addition, the first type relay device 200 and the second type relay device 202 perform wired communication. As a result, when the first fire alarm 100a detects the occurrence of a fire, the detection result indicating the occurrence of a fire is transmitted to the second fire alarm device 100b etc. via the first type relay device 200, or to the fourth fire alarm 100d via the first type relay device 200 and the second type relay device 202. As a result, the detection result is shared among the multiple fire alarm devices 100, and the multiple fire alarm devices 100 issue fire alarms in cooperation with each other.

[0020] The fire alarm 100 is equipped with a fire detection sensor for detecting the occurrence of a fire. Known technology may be used for the fire detection sensor. For example, the fire detection sensor may be an optical smoke detection sensor, which may detect a fire by using diffuse reflection of light to detect smoke during a fire. For example, the fire detection sensor may be a heat detection sensor, which may detect a fire by detecting heat during a fire. For example, the fire detection sensor may be a carbon monoxide detection sensor, which may detect a fire by detecting the concentration of carbon monoxide generated by combustion during a fire. For example, the fire detection sensor may be an infrared detection sensor, which may detect a fire by detecting infrared rays emitted by combustion during a fire.

[0021] When the fire detection sensor of a fire alarm 100 detects a fire, the fire alarm 100 wirelessly transmits the detection result to the first type relay device 200 or the second type relay device 202. The fire alarm 100 wirelessly receives the detection result of another fire alarm 100 from the first type relay device 200 or the second type relay device 202. For example, a specified low-power radio in the 426 MHz band is used for wireless communication with the first type relay device 200 or the second type relay device 202. When the fire detection sensor detects a fire or when the fire alarm 100 receives a detection result from another fire alarm 100, the fire alarm 100 alerts the occurrence of a fire. The alert is made, for example, by outputting audio from a speaker or sounding a buzzer. The alert may also be made by flashing the light-emitting device.

[0022] The first type relay device 200 performs wireless communication with the first fire alarm device 100a to the third fire alarm device 100c. Specifically, the first fire alarm device 100a to the third fire alarm device 100c operate as slave devices, and the first type relay device 200 operates as a master device. Operating as a master device corresponds to the master device acting as a central controller to control at least the slave devices. For example, the master device broadcasts a beacon signal, and the slave devices operate in response to the received beacon signal. Alternatively, the master device may transmit a control signal to each slave device by unicast. The second type relay device 202 also performs the same processing as the first type relay device 200 with the fourth fire alarm device 100d to the sixth fire alarm device 100f. The second type relay device 202 is connected to the first type relay device 200 by a cable, and performs wired communication with the first type relay device 200.

[0023] When the type 1 relay device 200 receives a detection result wirelessly from the first fire alarm device 100a, it transmits the detection result wirelessly to the second fire alarm device 100b and the third fire alarm device 100c. The type 1 relay device 200 also transmits the detection result wired to the type 2 relay device 202. When the type 2 relay device 202 receives a detection result from the type 1 relay device 200, it transmits the detection result wirelessly to the fourth fire alarm device 100d to the sixth fire alarm device 100f. The same process is performed when the type 1 relay device 200 or the type 2 relay device 202 receives a detection result wirelessly from a fire alarm device 100 other than the first fire alarm 100a.

[0024] Unlike the second type relay device 202, the first type relay device 200 is capable of communicating with the management device 300. That is, among the relay devices, the relay device that can directly communicate with the management device 300 is the first type relay device 200, and the relay device that can communicate with the management device 300 via the first type relay device 200 is the second type relay device 202. For example, 920 MHz wireless communication conforming to the Wi-SUN (registered trademark) standard (international standard IEEE 802.15.4g) is used for communication between the first type relay device 200 and the management device 300. However, the communication is not limited to this, and wired communication may also be performed.

[0025] The management device 300 is, for example, a controller for a Home Energy Management System (HEMS) installed in a facility. The management device 300 can communicate with multiple devices installed in the facility. The multiple devices include, for example, air conditioners, lighting devices, water heaters, and the like, each having a communication function. The management device 300 can also communicate with a first-class relay device 200 installed in the facility. The management device 300 can also communicate with a second-class relay device 202 and multiple fire alarm devices 100 via the first-class relay device 200. When the management device 300 receives a detection result from the fire alarm device 100 from the first-class relay device 200, the management device 300 manages the detection result and may display a message on a display indicating that a fire has occurred based on the detection result. The management device 300 may also control devices based on the detection result. The management device 300 may also control the operation of the fire alarm device 100 via the first-class relay device 200.

[0026] FIG. 2 shows an overview of communication between a fire alarm 400 and a first-class relay device 500, which are used for comparison. The fire alarm 400 corresponds to the fire alarm 100 in FIG. 1, and the first-class relay device 500 corresponds to the first-class relay device 200 in FIG. 1. The horizontal axis in FIG. 2 represents time, with "Down" representing the downstream communication time slot, "Up 1" representing the first upstream communication time slot, "Up 2" representing the second upstream communication time slot, and "Up 3" representing the third upstream communication time slot. One frame is formed by arranging the downstream communication time slot, the first upstream communication time slot, the second upstream communication time slot, and the third upstream communication time slot on the time axis. The number of upstream communication time slots included in one frame is not limited to "3." Here, the frames are represented in chronological order as "frame 1" to "frame 6."

[0027] In the downstream communication time slot, the type 1 repeater device 500 may or may not transmit a communication signal. Also, the type 1 repeater device 500 periodically transmits a beacon signal in the downstream communication time slot. The first fire alarm device 400a to the third fire alarm device 400c receive the beacon signal and generate a frame synchronized with the type 1 repeater device 500. In the downstream communication time slot, the first fire alarm device 400a to the third fire alarm device 400c operate to receive a communication signal from the type 1 repeater device 500.

[0028] The first upstream communication time slot is assigned to the first fire alarm device 400a, the second upstream communication time slot is assigned to the second fire alarm device 400b, and the third upstream communication time slot is assigned to the third fire alarm device 400c. In the first upstream communication time slot to the third upstream communication time slot, the type 1 repeater 500 operates to receive communication signals from the first fire alarm device 400a to the third fire alarm device 400c. In the first upstream communication time slot of the third frame, the first fire alarm 400a transmits a communication signal to the type 1 repeater 500, and in the second upstream communication time slot, the second fire alarm 400b transmits a communication signal to the type 1 repeater 500.

[0029] According to this process, the type 1 repeater device 500 must operate in the first to third upstream communication time slots regardless of whether or not it receives a communication signal from the fire alarm device 400. In order to reduce the power consumption of the type 1 repeater device 500, the fire alarm device 100 and the type 1 repeater device 200 according to this embodiment execute the following process.

[0030] 3 shows the configuration of the fire alarm 100 and the first type relay device 200. The fire alarm 100 includes a communication unit 120, a processing unit 122, and a control unit 124, while the first type relay device 200 includes a communication unit 220, a processing unit 222, and a control unit 224. The control unit 224 includes a monitoring unit 226. Here, the configuration for performing wireless communication between the fire alarm 100 and the first type relay device 200 is shown, so for example, the fire detection sensor, speaker, buzzer, etc. of the fire alarm 100 are omitted. The second type relay device 202 has a configuration similar to that of the first type relay device 200.

[0031] The communication unit 120 in the fire alarm device 100 performs wireless communication with the first type relay device 200. The processing unit 122 processes signals received by the communication unit 120 and generates signals to be transmitted from the communication unit 120. The control unit 124 controls the operation of the communication unit 120 and the processing unit 122. The communication unit 220 in the first type relay device 200 performs wireless communication with the fire alarm 100. The processing unit 222 processes signals received by the communication unit 220 and generates signals to be transmitted from the communication unit 220. The control unit 224 controls the operation of the communication unit 220 and the processing unit 222.

[0032] Here, Figure 4 will also be used to explain the processing of the fire alarm device 100 and the first type relay device 200. Figure 4 shows an overview of communication between the fire alarm device 100 and the first type relay device 200. The horizontal axis in Figure 4 indicates time, and "Down," "Up 1," "Up 2," and "Up 3" are the same as in Figure 2. The following will focus on the differences from Figure 2. "Monitoring" indicates a monitoring time slot. One frame is formed by arranging the monitoring time slot, downstream communication time slot, first upstream communication time slot, second upstream communication time slot, and third upstream communication time slot on the time axis. The number of upstream communication time slots included in one frame is not limited to "3." Here, the frames are shown in chronological order as "first frame" to "fifth frame."

[0033] The monitoring time slot is a time slot in which the fire alarm device 100 that is scheduled to transmit a communication signal in the upstream communication time slot transmits the monitoring signal. The monitoring signal is an upstream communication time slot that follows the monitoring time slot, and is a signal that notifies the fire alarm device 100 that it will transmit a communication signal in the upstream communication time slot assigned to the fire alarm device 100. On the other hand, the upstream communication time slot is a time slot in which the fire alarm device 100 can transmit a communication signal.

[0034] When the processing unit 122 of the fire alarm device 100 generates a communication signal to be transmitted from the communication unit 120, the control unit 124 instructs the communication unit 120 to transmit the monitoring signal in the monitoring time slot. The communication unit 120 transmits the monitoring signal in the monitoring time slot in response to the instruction from the control unit 124. Subsequently, the communication unit 120 transmits the communication signal in the allocated upstream communication time slot.

[0035] For example, in the second frame, the first fire alarm device 100a transmits a monitoring signal in the monitoring time slot and a communication signal in the first upstream communication time slot. The same is true for the second fire alarm device 100b in the third frame. In the fourth frame, the second fire alarm device 100b and the third fire alarm device 100c transmit monitoring signals in the monitoring time slot. Following this, the second fire alarm device 100b transmits a communication signal in the second upstream communication time slot, and the third fire alarm device 100c transmits a communication signal in the third upstream communication time slot. On the other hand, in the first frame, none of the fire alarm devices 100 transmits a monitoring signal in the monitoring time slot.

[0036] The control unit 224 of the first type relay device 200 causes the communication unit 220 to wait for reception of a supervisory signal in the supervisory time slot. The communication unit 220 outputs the reception result in the supervisory time slot to the monitoring unit 226. The monitoring unit 226 monitors the reception of the supervisory signal in the supervisory time slot based on the reception result received from the communication unit 220. For example, the monitoring unit 226 detects the reception of a supervisory signal when the received power in the supervisory time slot is greater than a threshold value. For example, the monitoring unit 226 detects the reception of a supervisory signal because the received power in the supervisory time slots of the second to fourth frames is greater than a threshold value.

[0037] On the other hand, if the received power in the monitoring time slot is equal to or less than the threshold, the monitoring unit 226 determines that a monitoring signal is not being received. For example, the monitoring unit 226 does not detect the reception of a monitoring signal because the received power in the management time slot of the first frame is equal to or less than the threshold.

[0038] When the monitoring unit 226 detects the reception of a monitoring signal, the control unit 224 causes the communication unit 220 to perform reception processing of the communication signal in one or more of the multiple upstream communication time slots. At this time, reception processing of the communication signal is performed in the multiple upstream communication time slots of the frame including the monitoring time slot in which reception of the monitoring signal was detected. For example, reception processing of the communication signal is performed in the first to third upstream communication time slots of the second to fourth frames.

[0039] On the other hand, when the monitoring unit 226 does not detect the reception of a monitoring signal, the control unit 224 causes the communication unit 220 to stop the reception process of the communication signal in the multiple upstream communication time slots. For example, the reception process of the communication signal is stopped in the first to third upstream communication time slots of the first frame.

[0040] As a result, from the first upstream communication time slot to the second upstream communication time slot of the first frame, the communication unit 220 does not execute reception processing and does not receive a communication signal. In the first upstream communication time slot of the second frame, the communication unit 220 receives a communication signal from the first fire alarm device 100a, and in the second upstream communication time slot of the third frame, the communication unit 220 receives a communication signal from the second fire alarm device 100b. Furthermore, the communication unit 220 receives a communication signal from the second fire alarm device 100b in the second upstream communication time slot of the fourth frame, and receives a communication signal from the third fire alarm device 100c in the third upstream communication time slot. When focusing on the upstream line, the fire alarm device 100 corresponds to a transmitting device, and the type 1 relay device 200 or the management device 300 corresponds to a receiving device.

[0041] Here, another process in the first type relay device 200 will be explained with reference to Fig. 5. Fig. 5 shows another overview of communication between the fire alarm device 100 and the first type relay device 200. The frame structure and the timing of the monitoring signals transmitted from each fire alarm device 100 are the same as those in Fig. 4.

[0042] The monitoring signal transmitted by the communication unit 120 of the fire alarm 100 in the monitoring time slot includes identification information for identifying the upstream communication time slot in which the fire alarm 100 is scheduled to transmit a communication signal. For example, the monitoring signal transmitted from the first fire alarm 100a in the second frame includes identification information for identifying the first upstream communication time slot in which the first fire alarm 100a is scheduled to transmit a communication signal. In the first type relay device 200, the upstream communication time slots and the fire alarms 100 are associated one-to-one, so the monitoring signal may include identification information for identifying the fire alarm 100 that is the transmission source. The same applies to the monitoring signals transmitted in the third and fourth frames.

[0043] As described above, the monitoring unit 226 of the first type relay device 200 monitors the reception of a monitoring signal in the monitoring time slot based on the reception result received from the communication unit 220. When the monitoring unit 226 detects the reception of a monitoring signal, it acquires identification information included in the monitoring signal. When the monitoring unit 226 acquires the identification information, it notifies the control unit 224 of the identification information. For example, in the monitoring time slot of the second frame, the monitoring unit 226 detects the reception of a monitoring signal and acquires identification information for identifying the first upstream communication time slot. The monitoring unit 226 notifies the control unit 224 of the identification information for identifying the first upstream communication time slot. The same is true for the third frame.

[0044] On the other hand, if the monitoring unit 226 detects the reception of a monitoring signal but is unable to acquire the identification information, it notifies the control unit 224 of the detection of the reception of a monitoring signal. For example, in the monitoring time slot of the fourth frame, the monitoring unit 226 detects the reception of a monitoring signal, but is unable to acquire the identification information because a collision has occurred between the monitoring signal from the second fire alarm device 100b and the monitoring signal from the third fire alarm device 100c. The monitoring unit 226 notifies the control unit 224 of the detection of the reception of a monitoring signal. In other words, the monitoring unit 226 detects the reception of a monitoring signal based on the content of the message included in the monitoring signal in the monitoring time slot.

[0045] When the control unit 224 is notified of the identification information by the monitoring unit 226, the control unit 224 causes the communication unit 220 to execute reception processing of the communication signal in the upstream communication time slot corresponding to the identification information. At that time, the control unit 224 causes the communication unit 220 to stop reception processing of the communication signal in the upstream communication time slot different from the upstream communication time slot corresponding to the identification information. For example, reception processing of the communication signal is executed in the first upstream communication time slot of the second frame, and reception processing of the communication signal is stopped in the second upstream communication time slot and the third upstream communication time slot. The same applies to the third frame.

[0046] When the control unit 224 is notified by the monitoring unit 226 that reception of a monitoring signal has been detected, the control unit 224 causes the communication unit 220 to perform reception processing of the communication signal in the multiple upstream communication time slots of the frame including the monitoring time slot in which reception of the monitoring signal has been detected. For example, reception processing of the communication signal is performed in the first to third upstream communication time slots of the fourth frame.

[0047] Here, further processing in the first type relay device 200 will be explained with reference to Fig. 6. Fig. 6 shows yet another overview of communication between the fire alarm device 100 and the first type relay device 200. The frame structure and the timing of the monitoring signals transmitted from each fire alarm device 100 are the same as those in Fig. 4.

[0048] The monitoring signal transmitted by the communication unit 120 of the fire alarm 100 in the monitoring time slot contains information with the same content as the communication signal that the fire alarm 100 is scheduled to transmit. In other words, the fire alarm 100 transmits information with the same content in the monitoring signal and the communication signal. For example, the monitoring signal transmitted from the first fire alarm 100a in the second frame contains information with the same content as the communication signal that the first fire alarm 100a is scheduled to transmit. The same is true for the monitoring signals transmitted in the third and fourth frames.

[0049] As described above, the monitoring unit 226 of the first type relay device 200 monitors the reception of a supervisory signal in the monitoring time slot based on the reception result received from the communication unit 220. When the monitoring unit 226 detects the reception of a supervisory signal, it acquires information included in the supervisory signal. The acquisition of the information may be performed by the processing unit 222. When the monitoring unit 226 acquires the information, it notifies the control unit 224 that the information has been acquired. For example, in the monitoring time slot of the second frame, when the monitoring unit 226 detects the reception of a supervisory signal and acquires the information included in the supervisory signal, it notifies the control unit 224 that the information has been acquired. The same applies to the third frame.

[0050] On the other hand, if the monitoring unit 226 detects the reception of a monitoring signal but is unable to acquire information, it notifies the control unit 224 that it has detected the reception of a monitoring signal. For example, in the monitoring time slot of the fourth frame, the monitoring unit 226 detects the reception of a monitoring signal, but is unable to acquire information because a collision has occurred between the monitoring signal from the second fire alarm device 100b and the monitoring signal from the third fire alarm device 100c. The monitoring unit 226 notifies the control unit 224 that it has detected the reception of a monitoring signal.

[0051] When the control unit 224 is notified by the monitoring unit 226 that information has been acquired, it causes the communication unit 220 to stop receiving the communication signals in the multiple upstream communication time slots. For example, the control unit 224 stops receiving the communication signals in the first to third upstream communication time slots of the second frame. The same applies to the third frame.

[0052] When the control unit 224 is notified by the monitoring unit 226 that reception of a monitoring signal has been detected, the control unit 224 causes the communication unit 220 to perform reception processing of the communication signal in the multiple upstream communication time slots of the frame including the monitoring time slot in which reception of the monitoring signal has been detected. For example, reception processing of the communication signal is performed in the first to third upstream communication time slots of the fourth frame.

[0053] The subject of the device, system, or method of the present disclosure includes a computer. The computer executes a program to realize the functions of the subject of the device, system, or method of the present disclosure. The computer includes, as its main hardware component, a processor that operates according to the program. The processor may be of any type, as long as it can realize the functions by executing the program. The processor may be composed of one or more electronic circuits, including a semiconductor integrated circuit (IC) or a large-scale integration (LSI). The electronic circuits may be integrated into a single chip or may be provided on multiple chips. The multiple chips may be integrated into a single device or may be provided on multiple devices. The program is recorded on a non-transitory recording medium, such as a computer-readable ROM, optical disk, or hard disk drive. The program may be pre-stored on the recording medium or may be supplied to the recording medium via a wide-area communication network, including the Internet.

[0054] According to this embodiment, when reception of a supervisory signal is detected in a supervisory time slot, reception processing of the communication signal in one or more of the multiple upstream communication time slots is executed, thereby enabling reception of the communication signal. Furthermore, when reception of a supervisory signal is not detected in a supervisory time slot, reception processing of the communication signal in the multiple upstream communication time slots is stopped, thereby reducing power consumption of the repeater device. Furthermore, reception processing of the communication signal is executed or stopped depending on whether reception of a supervisory signal is detected in a supervisory time slot, thereby reducing power consumption of the repeater device while receiving the communication signal. Furthermore, reception of the supervisory signal is detected based on the received power in the supervisory time slot, thereby simplifying the detection process. Furthermore, reception of the supervisory signal is detected based on the content of the message included in the supervisory signal in the supervisory time slot, thereby improving detection accuracy.

[0055] Furthermore, when reception of a supervisory signal is detected, reception processing of communication signals in multiple upstream communication time slots is executed, thereby simplifying processing. Furthermore, when reception of a supervisory signal is detected and identification information included in the supervisory signal is acquired, reception processing of communication signals in upstream communication time slots different from the upstream communication time slot corresponding to the identification information is stopped, thereby reducing power consumption. Furthermore, when reception of a supervisory signal is detected and information included in the supervisory signal is acquired, reception processing of communication signals in multiple upstream communication time slots is stopped, thereby reducing power consumption.

[0056] An overview of one aspect of the present disclosure is as follows: A receiving device (200, 202) of an aspect of the present disclosure is a receiving device (200, 202) capable of receiving a communication signal from each of a plurality of transmitting devices (100), in which a plurality of communication time slots in which each of the plurality of transmitting devices (100) can transmit a communication signal and a monitoring time slot in which a transmitting device (100) scheduled to transmit a communication signal in a communication time slot should transmit a monitoring signal are arranged on a time axis, and the receiving device (200, 202) includes a monitoring unit (226) that monitors reception of the monitoring signal in the monitoring time slot, and a control unit (224) that stops reception processing of the communication signal in the plurality of communication time slots when the monitoring unit (226) does not detect reception of the monitoring signal, and that executes reception processing of the communication signal in one or more of the plurality of communication time slots when the monitoring unit (226) detects reception of the monitoring signal.

[0057] The monitoring unit (226) may detect reception of a monitoring signal based on the received power in a monitoring time slot.

[0058] The monitoring unit (226) may detect the reception of a supervisory signal based on the contents of a message included in the supervisory signal in a supervisory time slot.

[0059] When the monitoring unit 226 detects reception of a monitoring signal, the control unit 224 may execute reception processing of the communication signal in a plurality of communication time slots.

[0060] The monitoring signal transmitted by the transmitting device (100) in the monitoring time slot includes identification information for identifying the communication time slot in which the transmitting device (100) plans to transmit the communication signal, and when the monitoring unit (226) detects reception of the monitoring signal and acquires the identification information included in the monitoring signal, the control unit (224) may execute reception processing of the communication signal in the communication time slot corresponding to the identification information and may stop reception processing of the communication signal in a communication time slot different from the communication time slot corresponding to the identification information.

[0061] The monitoring signal transmitted by the transmitting device (100) in the monitoring time slot contains the same information as the communication signal, and the control unit (224) may stop the reception process of the communication signal in the multiple communication time slots when the monitoring unit (226) detects the reception of the monitoring signal and acquires the information contained in the monitoring signal.

[0062] Another aspect of the present disclosure is a receiving method in a receiving device (200, 202) capable of receiving a communication signal from each of a plurality of transmitting devices (100), wherein a plurality of communication time slots in which each of the plurality of transmitting devices (100) can transmit a communication signal and a monitoring time slot in which a transmitting device (100) that is scheduled to transmit a communication signal in a communication time slot should transmit a monitoring signal are arranged on a time axis, and the method includes the steps of: monitoring reception of a monitoring signal in the monitoring time slot; stopping reception processing of the communication signal in the plurality of communication time slots if reception of the monitoring signal is not detected; and executing reception processing of the communication signal in one or more of the plurality of communication time slots if reception of the monitoring signal is detected.

[0063] Example 2 Next, a second embodiment will be described. Like the first embodiment, the second embodiment relates to an alarm system installed in a facility. In the alarm system according to the first embodiment, a plurality of fire alarm devices are connected in a star configuration with a relay device at the center. In the alarm system according to the second embodiment, a plurality of fire alarm devices are connected via a wireless multi-hop network in order to expand the installation range of the fire alarm devices. In the alarm system, a relay device is connected to a management device, another relay device is connected to the relay device, and one or more fire alarm devices are connected to each relay device via the multi-hop network. In such a network, the management device corresponds to the upper side, and the fire alarm device that is the furthest hop from the relay device corresponds to the lower side.

[0064] When a fire alarm detects a fire, it transfers the detection result to a relay device, and the relay device transfers the detection result to a management device. When the management device receives the detection result, it selects one or more fire alarms to sound, and sends a sounding instruction to the selected one or more fire alarms as the final destination. The relay device and the fire alarm transfer the sounding instruction to the final destination fire alarm, and the final destination fire alarm sounds upon receiving the sounding instruction.

[0065] Here, the line for a signal from the relay device to the fire alarm device with the greatest number of hops from the relay device is called the "downlink," while the line for a signal from the fire alarm device with the greatest number of hops from the relay device to the relay device is called the "uplink." In this embodiment, one frame is formed by arranging multiple time slots, and one superframe is formed by arranging multiple frames. Furthermore, one fire alarm device is assigned to one time slot for the downlink (hereinafter referred to as the "downlink communication time slot") and one time slot for the uplink (hereinafter referred to as the "uplink communication time slot"). The downlink communication time slot is used for transfer on the downlink, and the uplink communication time slot is used for transfer on the uplink.

[0066] In addition to alarm instructions, signals for establishing synchronization in the multi-hop network (hereinafter referred to as "synchronization signals") are periodically transferred on the downlink. On the other hand, since the uplink mainly transfers detection results, the traffic on the uplink is extremely low. However, fire alarms in a multi-hop network must monitor whether detection results are being transmitted in the uplink communication time slots assigned to other fire alarms on the lower side. In particular, as the number of fire alarms on the lower side increases, the number of uplink communication time slots that must be monitored increases, resulting in an increase in the power consumption of the fire alarms. In the following description, the synchronization signals, detection results, and alarm instructions are sometimes collectively referred to as "communication signals."

[0067] In order to suppress an increase in the power consumption of a fire alarm, the embodiment performs the following process. As described above, a frame includes multiple downstream communication time slots and multiple upstream communication time slots. The frame also includes a monitoring time slot (hereinafter referred to as a "monitoring time slot") in which a fire alarm that is scheduled to transmit a communication signal in an assigned upstream communication time slot transmits a signal (hereinafter referred to as a "monitoring signal"). Each fire alarm waits to receive a monitoring signal in the monitoring time slot. If a monitoring signal is received in the monitoring time slot, the fire alarm waits to receive a communication signal in the upstream communication time slot. On the other hand, if a monitoring signal is not received in the monitoring time slot, the fire alarm does not wait to receive a communication signal in the upstream communication time slot.

[0068] The present embodiment will be described below in the order of (1) basic configuration, (2) routing, and (3) installation. (1) Basic configuration 7 shows the configuration of an alarm system 1000. The alarm system 1000 includes a first fire alarm 600a through a ninth fire alarm 600i collectively referred to as fire alarms 600, a first relay device 700a through a third relay device 700c collectively referred to as relay devices 700, and a management device 800. The number of fire alarms 600 is not limited to "9", and the number of relay devices 700 is not limited to "3".

[0069] The alarm system 1000 is applied to facilities such as homes, offices, and commercial facilities, and is a system that detects fires and notifies the occurrence of a fire. The multiple fire alarms 600 are, for example, residential fire alarms and are equipped with fire detection sensors. The multiple fire alarms 600 are installed, for example, on the ceiling of the facility, but may also be installed on the wall, etc.

[0070] Here, the first fire alarm device 600a to the sixth fire alarm device 600f form a wireless multi-hop network extending from the first relay device 700a. For example, a relay route is formed connecting the first relay device 700a, the first fire alarm device 600a, and the second fire alarm device 600b, and a relay route is formed connecting the first relay device 700a, the fourth fire alarm device 600d, the fifth fire alarm device 600e, and the third fire alarm device 600c. A relay route is also formed connecting the first relay device 700a, the fourth fire alarm device 600d, the fifth fire alarm device 600e, and the sixth fire alarm 600f, and a relay route is also formed connecting the first relay device 700a and the seventh fire alarm device 600g. These relay routes are determined by each fire alarm device 600 and are shared by the first relay device 700a and the management device 800.

[0071] In these relay routes, the first fire alarm 600a, the fourth fire alarm 600d, and the seventh fire alarm 600g can communicate with the first relay 700a via one hop. The second fire alarm 600b and the fifth fire alarm 600e can communicate with the first relay 700a via two hops. The third fire alarm 600c and the sixth fire alarm 600f can communicate with the first relay 700a via three hops.

[0072] The second relay 700b, the third relay 700c, the eighth fire alarm 600h, and the ninth fire alarm 600i are configured similarly to the first relay 700a and the first fire alarm 600a. For example, a multi-hop network originating from the first relay 700a is installed on the first floor of a facility, a multi-hop network originating from the second relay 700b is installed on the second floor of the facility, and a multi-hop network originating from the third relay 700c is installed on the third floor of the facility. Different frequencies are used for the multi-hop network originating from the first relay 700a, the multi-hop network originating from the second relay 700b, and the multi-hop network originating from the third relay 700c. Furthermore, the first relay 700a, the second relay 700b, and the third relay 700c communicate with each other wirelessly or via wires.

[0073] In this way, the relay device 700 performs wireless communication with the multiple fire alarm devices 600 that make up the multi-hop network, and also performs wireless or wired communication with other relay devices 700. It can also be said that the relay device 700 relays communication between the multiple fire alarm devices 600 included in the multi-hop network. Furthermore, the first relay device 700a is connected to the management device 800 by a cable, and performs wired communication with the management device 800.

[0074] The management device 800 is, for example, a controller for a Home Energy Management System (HEMS) installed in a facility. The management device 800 is capable of communicating with multiple devices installed in the facility. The multiple devices include, for example, air conditioners, lighting equipment, water heaters, and the like, all of which have communication functions. The management device 800 is also capable of communicating with a first relay 700a installed in the facility. Furthermore, the management device 800 is also capable of communicating with a second relay 700b, a third relay 700c, and each of the fire alarms 600 via the first relay 700a.

[0075] FIG. 8 shows the configuration of a fire alarm 600. The fire alarm 600 includes a communication unit 620, a processing unit 622, a control unit 624, a fire detection sensor 630, and a buzzer 632, and the control unit 624 includes a monitoring unit 626. The fire detection sensor 630 may use known technology. For example, the fire detection sensor 630 may be an optical smoke detection sensor that may detect a fire by using diffuse reflection of light to detect smoke during a fire. For example, the fire detection sensor 630 may be a heat detection sensor that may detect a fire by detecting heat during a fire. For example, the fire detection sensor 630 may be a carbon monoxide detection sensor that may detect a fire by detecting the concentration of carbon monoxide generated by combustion during a fire. For example, the fire detection sensor 630 may be an infrared detection sensor that may detect a fire by detecting infrared rays emitted by combustion during a fire.

[0076] The communication unit 620 performs wireless communication with other fire alarm devices 600 or relay devices 700. The processing unit 622 processes signals received by the communication unit 620 and generates signals to be transmitted from the communication unit 620. The control unit 624 controls the operation of the communication unit 620 and the processing unit 622. Details of the processing by the control unit 624 will be described later. The buzzer 632 is capable of sounding a buzzer sound. The fire alarm 600 may not include the buzzer 632 but may include the fire detection sensor 630, that is, may have both a detection function and a communication function. Such a fire alarm 600 can also be said to be a sensor that is capable of issuing an alarm when a fire is detected.

[0077] 9(a)-(d) show the structure of a superframe 1010 used in the alarm system 1000. As shown in FIG. 9(a), a certain period is defined as a superframe 1010. The superframe 1010 is arranged repeatedly. The superframe 1010 is divided into a plurality of frames 1020. As shown in FIG. 9(b), one frame 1020 is divided into a plurality of time slots 1030. FIG. 9(c) shows one time slot 1030. A communication signal or a monitoring signal is transmitted within the time slot 1030. The period of the communication signal or monitoring signal is shorter than the period of one time slot 1030.

[0078] FIG. 9(d) shows the uses of the multiple time slots 1030 included in the frame 1020 shown in FIG. 9(b). Of the multiple time slots 1030, one or more time slots 1030 at the beginning are used as "downstream communication time slots." One time slot 1030 following the downstream communication time slot is used as a "monitoring time slot." One or more time slots 1030 following the monitoring time slot are used as "upstream communication time slots." One or more time slots 1030 following the upstream communication time slot are used as "spare." The number of downstream communication time slots and the number of upstream communication time slots are the same and are equal to or greater than the number of fire alarm devices 600 included in the multi-hop network. Spare slots are not required.

[0079] Fig. 10 shows an example of allocation of time slots 1030 in the alarm system 1000, and is shown in the same manner as Fig. 9(d). This shows the allocation of multiple time slots 1030 to the first relay 700a and the first fire alarm 600a to the seventh fire alarm 600g in Fig. 7. "M" in Fig. 10 indicates the first relay 700a, and "S1" to "S7" indicate the first fire alarm 600a to the seventh fire alarm 600g, respectively. The downstream communication time slots are allocated to the first relay 700a, the first fire alarm 600a, the fourth fire alarm 600d, the seventh fire alarm 600g, the second fire alarm 600b, the fifth fire alarm 600e, the third fire alarm 600c, and the sixth fire alarm 600f, in order from the front. As described above, the number of hops from the first fire alarm 600a, the fourth fire alarm 600d, and the seventh fire alarm 600g to the first relay 700a is "1." The number of hops from the second fire alarm 600b and the fifth fire alarm 600e to the first relay 700a is "2," and the number of hops from the third fire alarm 600c and the sixth fire alarm 600f to the first relay 700a is "3." In other words, the fire alarm 600 with the fewer hops to the first relay 700a is assigned closer to the front of the downstream communication time slot.

[0080] The upstream communication time slots are allocated to the sixth fire alarm device 600f, the third fire alarm device 600c, the fifth fire alarm device 600e, the second fire alarm device 600b, the seventh fire alarm device 600g, the fourth fire alarm device 600d, the first fire alarm device 600a, and the first relay 700a in order from the front. In other words, the fire alarm 600 with the greater number of hops to the first relay 700a is allocated closer to the front of the upstream communication time slots.

[0081] When focusing on the fifth fire alarm device 600e, in the downstream communication time slot, the fifth fire alarm device 600e is allocated to the front side of the third fire alarm device 600c and the sixth fire alarm device 600f. In the upstream communication time slot, the fifth fire alarm device 600e is allocated to the back side of the third fire alarm device 600c and the sixth fire alarm device 600f.

[0082] The allocation of these time slots 1030 is decided by the first relay device 700a or the management device 800. For example, the first relay device 700a or the management device 800 decides the allocation of the time slots 1030 based on information about the relay route. The first relay device 700a or the management device 800 notifies each fire alarm device 600 of the decided allocation of the time slots 1030. Therefore, each fire alarm device 600 also knows the allocation of these time slots 1030. As a result, the fire alarm device 600 knows the time slot 1030 in which it should transmit a communication signal and which has been allocated to itself. The fire alarm device 600 also knows the time slot 1030 in which it can receive a communication signal from an adjacent fire alarm device 600 or relay device 700 on the relay route.

[0083] In such a situation, the communication unit 620 of the fire alarm 600 may perform an intermittent reception operation to reduce power consumption. In the intermittent reception operation in the communication unit 620, the reception operation is performed during a portion of the beginning of the time slot 1030, and if no signal (communication signal, monitoring signal) is received during that portion of the period, the reception operation is stopped for the remainder of the time slot 1030. On the other hand, if a signal is received during that portion of the beginning of the time slot 1030, the reception operation continues for the remainder of the time slot 1030.

[0084] FIG. 11 shows an overview of downstream communication in the alarm system 1000. This shows the downstream communication time slots in FIG. 10. The first relay 700a periodically transmits a synchronization signal to the multiple fire alarm devices 600 that make up the multi-hop network. The synchronization signal is, for example, a beacon signal. The synchronization signal is transmitted, for example, in the first frame 1020 of the superframe 1010 shown in FIG. 9(a), and is not transmitted in the remaining frames 1020. The first relay 700a transmits the synchronization signal in time slot 1030 “M” of the first frame 1020 of the superframe 1010. When the fourth fire alarm device 600d receives the synchronization signal in time slot 1030 “M”, it forwards the synchronization signal in time slot 1030 “S4”. In addition, the fourth fire alarm device 600d transmits a response signal to the first relay 700a in time slot 1030 “S4”. The response signal is, for example, an Ack (ACKnowledgement) and may be included as part of the synchronization signal.

[0085] The first relay 700a receives the response signal in the time slot 1030 "S4". When the fifth fire alarm device 600e receives the synchronization signal in the time slot 1030 "S4", it transfers the synchronization signal in the time slot 1030 "S5" and also transmits a response signal to the fourth fire alarm device 600d. The fourth fire alarm device 600d receives the response signal in the time slot 1030 "S5". Although omitted in FIG. 11 , the fourth fire alarm device 600d transfers the response signal from the fifth fire alarm device 600e to the first relay 700a in the time slot 1030 "S4" of the next frame.

[0086] When the third fire alarm device 600c receives a synchronization signal in time slot 1030 "S5", it transfers the synchronization signal in time slot 1030 "S3" and transmits a response signal to the fifth fire alarm device 600e. When the sixth fire alarm device 600f receives a synchronization signal in time slot 1030 "S5", it transfers the synchronization signal in time slot 1030 "S6" and transmits a response signal to the fifth fire alarm 600e.

[0087] The fifth fire alarm device 600e receives the response signals in time slots 1030 "S3" and "S6". Although omitted in Fig. 11, the fifth fire alarm device 600e transfers the response signals from the third fire alarm device 600c and the sixth fire alarm device 600f to the fourth fire alarm device 600d in time slot 1030 "S5" of the next frame. The fourth fire alarm 600d further transfers the response signal from the fifth fire alarm device 600e to the first relay 700a in time slot 1030 "S4" of the next frame.

[0088] In this way, the synchronization signal is transferred in frame 1020 in which the first relay 700a transmitted the synchronization signal. Furthermore, each fire alarm 600 that receives the synchronization signal from the first relay 700a establishes timing synchronization with the first relay 700a based on the synchronization signal. Known techniques can be used for timing synchronization, so a description thereof will be omitted here.

[0089] FIG. 12 shows an overview of upstream communications in the alarm system 1000. This shows the monitoring time slots and upstream communication time slots in FIG. 10. "Monitor" indicates a monitoring time slot. Here, it is assumed that the fire detection sensor 630 of the sixth fire alarm 600f detects the occurrence of a fire. The processing unit 622 of the sixth fire alarm 600f causes the communication unit 620 to transmit the detection result. The detection result includes identification information of the sixth fire alarm 600f that detected the fire. The communication unit 620 of the sixth fire alarm 600f transmits a monitoring signal in the monitoring time slot of frame 1020 "K" and transmits the detection result in time slot 1030 "S6".

[0090] The fifth fire alarm device 600e receives a monitoring signal in the monitoring time slot of frame 1020 "K" and receives a detection result in time slot 1030 "S6". In other words, the monitoring unit 626 of the fifth fire alarm device 600e monitors the reception of a monitoring signal in the monitoring time slot, and if no reception of a monitoring signal is detected, the fifth fire alarm device 600e stops receiving the communication signal in time slots 1030 "S3" and "S6". On the other hand, if the monitoring unit 626 of the fifth fire alarm device 600e of the first alarm device detects the reception of a monitoring signal, the fifth fire alarm device 600e receives a communication signal in time slot 1030 "S3" or "S6". Subsequently, the fifth fire alarm device 600e transmits a monitoring signal in the monitoring time slot of frame 1020 "K+1" and transfers the detection result in time slot 1030 "S5". Furthermore, the fifth fire alarm device 600e transmits a response signal to the sixth fire alarm device 600f in the time slot "S5" 1030. The response signal may be included as part of the synchronization signal.

[0091] The sixth fire alarm device 600f receives the response signal in time slot 1030 "S5" of frame 1020 "K+1". The fourth fire alarm device 600d receives the monitoring signal in the monitoring time slot of frame 1020 "K+1", and receives the detection result in time slot 1030 "S5". The fourth fire alarm device 600d transmits a monitoring signal in the monitoring time slot of frame 1020 "K+2", and transfers the detection result in time slot 1030 "S4", while also transmitting a response signal to the fifth fire alarm device 600e.

[0092] The fifth fire alarm device 600e receives the response signal in time slot 1030 "S4" of frame 1020 "K+2." Although omitted in Fig. 12, the fifth fire alarm device 600e transmits a monitoring signal in the monitoring time slot of frame 1020 "K+3," and transfers the response signal from the fourth fire alarm device 600d to the sixth relay 700f in time slot 1030 "S5."

[0093] The first relay 700a receives the monitoring signal in the monitoring time slot "K+2" of frame 1020, and receives the detection result in time slot 1030 "S4." As before, the first relay 700a transmits the monitoring signal in the monitoring time slot "K+3" of frame 1020, and transmits a response signal in time slot 1030 "M." The response signal is transferred by the fourth fire alarm device 600d and the fifth fire alarm device 600e, and is received by the sixth fire alarm device 600f.

[0094] When the first relay 700a receives the detection result from the fourth fire alarm 600d, it transmits the detection result to the management device 800. When the management device 800 receives the detection result, it identifies the fire alarm 600 to be activated based on the identification information included in the detection result. The correspondence between the identification information and the information of the fire alarm 600 to be activated is stored in advance in the management device 800. The management device 800 transmits an instruction to activate the fire alarm to the first relay 700a, with the identified fire alarm 600 as the final destination.

[0095] If the fire alarm devices 600 identified by the management device 800 are the third fire alarm device 600c and the sixth fire alarm device 600f, a similar transfer to that shown in Fig. 11 is performed, and the sounding instruction is received by the third fire alarm device 600c and the sixth fire alarm device 600f. Here, the sounding instruction is transmitted instead of the synchronization signal shown in Fig. 11. When the second relay device 700b and the third relay device 700c receive a sounding instruction from the management device 800 via the first relay device 700a, they transfer the sounding instruction to the fire alarms 600. When the communication units 620 of the third fire alarm device 600c and the sixth fire alarm device 600f receive the sounding instruction, the control unit 624 causes the buzzer 632 to sound. The control unit 624 may also cause the light-emitting device to flash.

[0096] (2) Routing Up to now, it has been assumed that a relay route as shown in Fig. 7 has been formed, but here, the formation of a relay route will be explained using Fig. 13 as well. Fig. 13 shows an overview of routing in the alarm system 1000. Fig. 13 shows the (n+1)th fire alarm 600n+1, the (n+2)th fire alarm 600n+2, the (n+3)th fire alarm 600n+3, and the relay device 700 of the alarm system 1000. The (n+1)th fire alarm 600n+1, the (n+2)th fire alarm 600n+2, and the (n+3)th fire alarm 600n+3 correspond to any of the fire alarms 600 in Fig. 7. There may be a fire alarm 600 other than the (n+1)th fire alarm 600n+1 and the (n+2)th fire alarm 600n+2, for example, the (n+4)th fire alarm 600n+4 (not shown), around the (n+3)th fire alarm 600n+3.

[0097] FIG. 14 is a sequence diagram showing the routing procedure in the alarm system 1000. Here, the routing process will be explained focusing on the (n+3)th fire alarm device 600n+3. Each fire alarm device 600 broadcasts a HELLO message at regular time intervals. The HELLO message includes route quality information to the relay device 700. The communication unit 620 of the (n+3)th fire alarm device 600n+3 receives HELLO messages from the (n+1)th fire alarm 600n+1, the (n+2)th fire alarm 600n+2, and the (n+4)th fire alarm 600n+4 (S10, S12, S14).

[0098] The communication unit 620 of the (n+3)th fire alarm device 600n+3 measures the received power of each received HELLO message, and the processing unit 622 derives the link quality for each fire alarm device 600 based on the measured received power. The link quality varies depending on the received power, and the value decreases as the received power increases. The control unit 624 derives a tentative route cost by adding the link quality of the (n+1)th fire alarm device 600n+1 and the route quality included in the HELLO message from the (n+1)th fire alarm device 600n+1. The control unit 624 also derives tentative route costs for the other fire alarm devices 600. The control unit 624 compares multiple tentative route costs and selects several fire alarms 600 with the lowest tentative route costs as priority link destinations. Here, for example, the (n+1)th fire alarm 600n+1 and the (n+2)th fire alarm 600n+2 are selected as priority link destinations.

[0099] The communication unit 620 of the (n+3)th fire alarm device 600n+3 transmits the address of the selected fire alarm device 600 and the link quality at the time of reception in a LINK_REQ sub-message of a HELLO message (S16, S18). The (n+1)th fire alarm device 600n+1 and the (n+2)th fire alarm device 600n+2 transmit the link quality in the opposite direction in a LINK_REP sub-message (S20, S22).

[0100] The communication unit 620 of the (n+3)th fire alarm device 600n+3 receives the LINK_REP sub-message. The control unit 624 of the (n+3)th fire alarm device 600n+3 compares the link quality included in the LINK_REP sub-message from the (n+1)th fire alarm device 600n+1 with the link quality derived based on the previously measured received power, and selects the larger link quality. The control unit 624 also derives an official route cost for the (n+2)th fire alarm device 600n+2 by adding the selected link quality and the route quality for the (n+1)th fire alarm device 600n+1. The control unit 624 also compares the official route cost for the (n+1)th fire alarm device 600n+1 with the official route cost for the (n+2)th fire alarm device 600n+2, and selects the smaller one as the relay route. The relay route not selected may be used as an alternative route.

[0101] That is, the (n+3)th fire alarm device 600n+3 exchanges link quality information with the (n+1)th fire alarm device 600n+1, thereby deriving an official route cost (hereinafter referred to as the "first cost") for a relay route (hereinafter referred to as the "first relay route") for communicating with the relay device 700 via the (n+1)th fire alarm device 600n+1. The (n+3)th fire alarm device 600n+3 also exchanges link quality information with the (n+2)th fire alarm device 600n+2, thereby deriving an official route cost (hereinafter referred to as the "second cost") for a relay route (hereinafter referred to as the "second relay route") for communicating with the relay device 700 via the (n+2)th fire alarm 600n+2. Furthermore, the (n+3)th fire alarm 600n+3 compares the first cost with the second cost and selects the relay route which has the smaller cost preferentially. A relay route is formed by performing such processing in each fire alarm device 600. Information about the relay route (alternative route) formed in each fire alarm device 600 is transmitted to the management device 800 via the relay device 700. The management device 800 determines the allocation of time slots 1030 according to the number of hops based on the information about the relay route (alternative route).

[0102] (3) Construction Here, a technique for facilitating the construction of a multi-hop network for an alarm system 1000 will be described. Figures 15(a) and 15(b) show an overview of the construction of an alarm system 1000. Figure 15(a) shows a first example. The alarm system 1000 includes an external device 900 in addition to the configuration of Figure 13. The external device 900 is, for example, a computer, and is capable of communicating with the management device 800.

[0103] Routing in the multi-hop network is not performed after all fire alarm devices 600 have been installed, but rather after several fire alarm devices 600 have been installed near the relay device 700. After routing for several fire alarm devices 600 has been completed, several more fire alarm devices 600 are installed and then the routing is updated. In this way, the routing is updated in accordance with the stepwise increase in the number of fire alarm devices 600.

[0104] Here, it is assumed that the n+1th fire alarm 600n+1 and the n+2nd fire alarm 600n+2 have been installed before the n+3rd fire alarm 600n+3 is installed. The n+1th fire alarm 600n+1 and the n+2nd fire alarm 600n+2 each derive an official route cost through the above-described process, and then select a relay route based on the official route cost. The communication unit 620 of each of the n+1th fire alarm 600n+1 and the n+2nd fire alarm 600n+2 transmits information regarding the relay route. The information regarding the relay route includes the official route cost. The information regarding the relay route may also include the official route cost for a relay route other than the selected relay route, for example, an alternative route.

[0105] Information regarding the relay route transmitted from the (n+1)th fire alarm device 600n+1 and the (n+2)th fire alarm device 600n+2 is transferred along the relay route and received by the relay device 700. The relay device 700 transmits the information regarding the relay route to the management device 800. The management device 800 receives the information regarding the relay route. The installer operates the external device 900 to access the management device 800, and the external device 900 receives the information regarding the relay route from the management device 800. The external device 900 displays the information regarding the relay route. The installer checks the displayed information regarding the relay route to confirm the status of the relay route.

[0106] The installer adds and installs an (n+3)th fire alarm 600n+3 as a new fire alarm 600 in the multi-hop network. The multiple fire alarms 600, including the (n+1)th fire alarm 600n+1, the (n+2)th fire alarm 600n+2, and the (n+3)th fire alarm 600n+3, update the official route costs with the addition of the new fire alarm 600, and update the relay route based on the updated official route costs. The communication unit 620 of each of the multiple fire alarms 600 transmits information related to the relay route. As before, the management device 800 receives the information related to the relay route, and the external device 900 displays the information related to the updated relay route.

[0107] Figure 15(b) shows a second example. The alarm system 1000 includes an external device 910 and an information processing device 912 in addition to the configuration of Figure 13. The external device 910 is a communication device that can receive signals transmitted from the fire alarm 600 and the relay device 700. The information processing device 912 is, for example, a computer, and is connected to the external device 910. In the multi-hop network, the same processing as before is performed. The external device 910 receives information related to the relay route, and the information processing device 912 displays the information related to the updated relay route.

[0108] According to this embodiment, since the frame 1020 of the multi-hop network includes a monitoring slot, the power consumption of the fire alarm 600 can be reduced. Furthermore, since the power consumption of the fire alarm 600 is reduced, the frequency of battery replacement can be reduced even if the fire alarm 600 is battery-powered. Furthermore, since the frequency of battery replacement is reduced, user convenience can be improved. Furthermore, since the frame 1020 of the multi-hop network includes multiple time slots 1030 and each time slot 1030 is assigned to a fire alarm 600, the occurrence of signal collisions can be suppressed. Furthermore, since the fire alarm 600 is assigned to the time slots 1030 in an order according to the number of hops from the relay device 700, transfer can be performed efficiently.

[0109] An overview of one aspect of the present disclosure is as follows. Yet another aspect of the present disclosure is an alarm system (1000). This alarm system (1000) comprises multiple alarm devices (600) that form a multi-hop network extending from a relay device (700). The multiple alarm devices (600) include a first alarm device (600), a second alarm device (600), and a third alarm device (600). The first alarm device (600) is capable of communicating with the relay device (700) over i (i is an integer of 1 or greater) hops, the second alarm device (600) and third alarm device (600) are connected to the first alarm device (600) and are capable of communicating with the relay device (700) over i+1 hops, a first communication time slot in which the first alarm device (600) can transmit a communication signal, a second communication time slot in which the second alarm device (600) can transmit a communication signal, and a third communication time slot in which the third alarm device (600) can transmit a communication signal are arranged on the time axis, and the first communication time slot, second communication time slot, and third communication time slot are arranged before the first communication time slot, second communication time slot, and third communication time slot. Monitoring time slots in which the first alarm device (600), second alarm device (600) or third alarm device (600) should transmit monitoring signals are arranged, the first alarm device (600) monitors the reception of monitoring signals in the monitoring time slots, and if it does not detect the reception of a monitoring signal it stops reception processing of communication signals in the second communication time slot and third communication time slot, and if the first alarm device (600) detects the reception of a monitoring signal it receives communication signals in the second communication time slot or third communication time slot, transmits monitoring signals in the monitoring time slot, and transfers communication signals in the first communication time slot.

[0110] The first communication time slot may be arranged after the second communication time slot and the third communication time slot.

[0111] Yet another aspect of the present disclosure is an alarm device (600). This alarm device (600) is one of multiple alarm devices (600) that make up a multi-hop network spreading out from a relay device (700), and has a communication section (620) that is capable of communicating with the relay device (700) over i (i is an integer greater than or equal to 1) hops, and is also capable of communicating with other alarm devices (600) that are capable of communicating with the relay device (700) over i+1 hops, and with further other alarm devices (600), a first communication time slot in which the alarm device (600) can transmit a communication signal, a second communication time slot in which the other alarm devices (600) can transmit a communication signal, and a third communication time slot in which the further other alarm devices (600) can transmit a communication signal, which are arranged on the time axis, and the first communication time slot, the second communication time slot, and the third communication time slot At the front of the slots are arranged monitoring time slots in which the alarm device (600) that is to transmit a communication signal, or another alarm device (600) or yet another alarm device (600) should transmit a monitoring signal, and there is provided a monitoring unit (626) that monitors the reception of a monitoring signal in the monitoring time slots, and a control unit (624) that, if the monitoring unit (626) does not detect the reception of a monitoring signal, stops reception processing of the communication signal in the second communication time slot and third communication time slot, and, if the monitoring unit (626) detects the reception of a monitoring signal, causes the communication signal to be received in the second communication time slot or the third communication time slot, causes the monitoring signal to be transmitted in the monitoring time slot, and causes the communication signal to be transferred in the first communication time slot.

[0112] Yet another aspect of the present disclosure is a forwarding method for an alarm device (600) out of multiple alarm devices (600) that make up a multi-hop network spreading out from a relay device (700), wherein the alarm device (600) is able to communicate with the relay device (700) over i (i is an integer greater than or equal to 1) hops, and is also able to communicate with other alarm devices (600) that are able to communicate with the relay device (700) over i+1 hops, and with further other alarm devices (600), a first communication time slot in which the alarm device (600) can transmit a communication signal, a second communication time slot in which the other alarm devices (600) can transmit a communication signal, and a third communication time slot in which the further other alarm devices (600) can transmit a communication signal are arranged on the time axis, and the first communication time slot and the second communication time slot The system comprises a step of monitoring reception of a monitoring signal in the monitoring time slots, in which the alarm device (600) that is scheduled to transmit a communication signal, or another alarm device (600) or yet another alarm device (600) should transmit a monitoring signal, arranged before the second communication time slot and the third communication time slot, and a step of stopping reception processing of the communication signal in the second communication time slot and the third communication time slot if reception of a monitoring signal is not detected, and receiving the communication signal in the second communication time slot or the third communication time slot, transmitting the monitoring signal in the monitoring time slot, and transferring the communication signal in the first communication time slot.

[0113] The present disclosure has been described above based on examples. These examples are merely illustrative, and it will be understood by those skilled in the art that various modifications are possible in the combination of each component or each treatment process, and that such modifications are also within the scope of the present disclosure.

[0114] In the first and second embodiments, the relay device connects to the fire alarm 100 and the fire alarm 600, which have both a fire detection function and an alarm sounding function. However, this is not a limitation, and for example, the fire alarm 100 and the fire alarm 600 may have only a fire detection function. Furthermore, instead of the fire alarm 100 and the fire alarm 600, sensors that are not limited to fires but also detect floods, earthquakes, gas leaks, and CO (carbon monoxide) generation due to incomplete combustion may be used. This modification improves the degree of freedom in the configuration.

[0115] In the first embodiment, a first type relay device 200 is connected to the management device 300, and a second type relay device 202 is connected to the first type relay device 200. However, the present invention is not limited to this, and for example, a plurality of first type relay devices 200 may be connected to the management device 300, a plurality of second type relay devices 202 may be connected to the first type relay device 200, or one or more second type relay devices 202 may be connected to the second type relay device 202. According to this modification, the degree of freedom of the configuration can be improved. [Explanation of symbols]

[0116] 100 Fire alarm (transmitting device), 120 Communication unit, 122 Processing unit, 124 Control unit, 200 Type 1 relay device (receiving device), 202 Type 2 relay device (receiving device), 220 Communication unit, 222 Processing unit, 224 Control unit, 226 Monitoring unit, 300 Management device, 400 Fire alarm, 500 Type 1 relay device, 1000 Alarm system.

Claims

1. A receiving device capable of receiving communication signals from each of a plurality of transmitting devices, a monitoring unit that monitors reception of the supervisory signal in the supervisory time slot within a frame in which a plurality of communication time slots in which each of a plurality of transmitting devices can transmit a communication signal and a supervisory time slot in which the transmitting device that is scheduled to transmit the communication signal in the communication time slot is to transmit a supervisory signal are arranged on a time axis; a control unit that stops reception processing of the communication signal in the plurality of communication time slots when the monitoring unit does not detect reception of the monitoring signal, and that executes reception processing of the communication signal in each of the plurality of communication time slots within one frame when the monitoring unit detects reception of the monitoring signal; A receiving device comprising:

2. 2. The receiving device according to claim 1, wherein the monitoring unit detects reception of the supervisory signal based on a received power in the supervisory time slot.

3. 3. The receiving device according to claim 1, wherein the monitoring unit detects reception of the supervisory signal based on the content of a message included in the supervisory signal in the supervisory time slot.

4. 4. The receiving device according to claim 1, wherein the control unit, when the monitoring unit detects reception of the monitoring signal, executes reception processing of the communication signal in the plurality of communication time slots.

5. the supervisory signal transmitted by the transmitting device in the supervisory time slot includes identification information for identifying the communication time slot in which the transmitting device is scheduled to transmit the communication signal; 4. The receiving device according to claim 1, wherein when the monitoring unit detects reception of the monitoring signal and acquires the identification information contained in the monitoring signal, the control unit executes reception processing of the communication signal in the communication time slot corresponding to the identification information, and stops reception processing of the communication signal in the communication time slot different from the communication time slot corresponding to the identification information.

6. the supervisory signal transmitted by the transmitting device in the supervisory time slot contains the same information as that of the communication signal, A receiving device described in any one of claims 1 to 3, wherein the control unit stops the reception processing of the communication signal in the multiple communication time slots when the monitoring unit detects the reception of the monitoring signal and acquires the information contained in the monitoring signal.

7. A receiving method in a receiving device capable of receiving communication signals from each of a plurality of transmitting devices, comprising: a step of monitoring reception of the supervisory signal in the supervisory time slot in a frame in which a plurality of communication time slots in which each of a plurality of transmitting devices can transmit a communication signal and a supervisory time slot in which the transmitting device that is scheduled to transmit the communication signal in the communication time slot is to transmit a supervisory signal are arranged on a time axis; If reception of the supervisory signal is not detected, stopping reception processing of the communication signal in the plurality of communication time slots; When reception of the supervisory signal is detected, a receiving process of the communication signal is executed in each of the plurality of communication time slots in one of the frames; A receiving method comprising:

8. It is equipped with multiple alarm devices that form a multi-hop network that spreads from the relay device, the plurality of alarm devices include a first alarm device, a second alarm device, and a third alarm device; the first alarm device is capable of communicating with the relay device over i hop counts (i is an integer greater than or equal to 1); the second alarm device and the third alarm device are connected to the first alarm device, and are capable of communicating with the relay device over i+1 hops, Within the frame, a first communication time slot in which the first alarm device can transmit a communication signal, a second communication time slot in which the second alarm device can transmit a communication signal, and a third communication time slot in which the third alarm device can transmit a communication signal are arranged on the time axis, Within the frame, monitoring time slots in which the first alarm device, the second alarm device or the third alarm device that is scheduled to transmit the communication signal should transmit a monitoring signal are arranged before the first communication time slot, the second communication time slot and the third communication time slot, the first alarm device monitors reception of the monitoring signal in the monitoring time slot, and if reception of the monitoring signal is not detected, stops reception processing of the communication signal in the second communication time slot and the third communication time slot; When the first alarm device detects the reception of the monitoring signal, it carries out reception processing of the communication signal in the second communication time slot and the third communication time slot within one frame, transmits the monitoring signal in the monitoring time slot, and transfers the communication signal in the first communication time slot. Alarm system.

9. 9. The alarm system according to claim 8, wherein the first communication time slot is arranged after the second communication time slot and the third communication time slot.

10. An alarm device among multiple alarm devices that make up a multi-hop network extending from a relay device, a communication unit that is capable of communicating with the relay device over i (i is an integer greater than or equal to 1) hops, and is also capable of communicating with other alarm devices that are capable of communicating with the relay device over i+1 hops, and with further alarm devices; Within the frame, a first communication time slot in which the alarm device can transmit a communication signal, a second communication time slot in which the other alarm device can transmit a communication signal, and a third communication time slot in which the further other alarm device can transmit a communication signal are arranged on the time axis, and monitoring time slots in which the alarm device or the other alarm device or the further other alarm device that is scheduled to transmit the communication signal are arranged before the first communication time slot, the second communication time slot and the third communication time slot, and in which monitoring signals should be transmitted by the alarm device or the other alarm device or the further other alarm device, and a monitoring unit that monitors the reception of the monitoring signal in the monitoring time slots; a control unit that, when the monitoring unit does not detect reception of the monitoring signal, stops reception processing of the communication signal in the second communication time slot and the third communication time slot, and, when the monitoring unit detects reception of the monitoring signal, executes reception processing of the communication signal in the second communication time slot and the third communication time slot within one frame, transmits the monitoring signal in the monitoring time slot, and transfers the communication signal in the first communication time slot; An alarm equipped with:

11. A forwarding method for an alarm device among multiple alarm devices that make up a multi-hop network spreading from a relay device, comprising: the alarm device is capable of communicating with the relay device over i (i is an integer greater than or equal to 1) hops, and is also capable of communicating with other alarm devices that are capable of communicating with the relay device over i+1 hops, and with further alarm devices; Within the frame, a first communication time slot in which the alarm device can transmit a communication signal, a second communication time slot in which the other alarm device can transmit a communication signal, and a third communication time slot in which the further other alarm device can transmit a communication signal are arranged on the time axis, and monitoring time slots in which the alarm device or the other alarm device or the further other alarm device that is scheduled to transmit the communication signal are arranged before the first communication time slot, the second communication time slot and the third communication time slot, and in which monitoring signals should be transmitted by the alarm device or the other alarm device or the further other alarm device, and a step of monitoring reception of the monitoring signal in the monitoring time slot; a step of stopping reception processing of the communication signal in the second communication time slot and the third communication time slot when reception of the supervisory signal is not detected, and executing reception processing of the communication signal in the second communication time slot and the third communication time slot within one frame when reception of the supervisory signal is detected, transmitting the supervisory signal in the supervisory time slot, and transferring the communication signal in the first communication time slot; A transfer method comprising:

12. A program to be executed by an alarm device among multiple alarm devices that make up a multi-hop network extending from a relay device, the alarm device is capable of communicating with the relay device over i (i is an integer greater than or equal to 1) hops, and is also capable of communicating with other alarm devices that are capable of communicating with the relay device over i+1 hops, and with further alarm devices; Within the frame, a first communication time slot in which the alarm device can transmit a communication signal, a second communication time slot in which the other alarm device can transmit a communication signal, and a third communication time slot in which the further other alarm device can transmit a communication signal are arranged on the time axis, and monitoring time slots in which the alarm device or the other alarm device or the further other alarm device that is scheduled to transmit the communication signal are arranged before the first communication time slot, the second communication time slot and the third communication time slot, and in which monitoring signals should be transmitted by the alarm device or the other alarm device or the further other alarm device, and a step of monitoring reception of the monitoring signal in the monitoring time slot; A program for causing a computer to execute the steps of: stopping reception processing of the communication signal in the second communication time slot and the third communication time slot when reception of the monitoring signal is not detected; and, when reception of the monitoring signal is detected, executing reception processing of the communication signal in the second communication time slot and the third communication time slot within one frame, transmitting the monitoring signal in the monitoring time slot, and transferring the communication signal in the first communication time slot.

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