JP5896584B1 - Wireless communication system and communication terminal - Google Patents

Abstract

The wireless communication system 100 forms a network with the data station 10, the repeater 20, and the sensor 30. The plurality of communication terminals are configured to synchronize by transmitting and receiving a synchronization signal. As for a communication terminal in an asynchronous state among a plurality of communication terminals, a period from a predetermined start time of a day until a predetermined time elapses is set as a standby period, and a standby operation for receiving a synchronization signal is included in the standby period. The standby operation is performed in all periods of the standby period over a plurality of days.

Description

  The technology disclosed herein relates to a wireless communication system and a communication terminal.

  Conventionally, a wireless communication system including a plurality of communication terminals is known. The plurality of communication terminals perform wireless communication with each other to construct a network. In such a wireless communication system, it is necessary to synchronize between communication terminals in order to transmit and receive various types of information between communication terminals (see Patent Document 1). Synchronization between communication terminals is performed when a synchronization signal is transmitted from one communication terminal and the other communication terminal receives the synchronization signal.

JP 2011-176888 A

  By the way, there may occur a situation in which communication cannot be appropriately performed between the communication terminals for various reasons. In such a case, since communication signals cannot be properly transmitted and received between the communication terminals, the communication terminals are in an asynchronous state.

  The asynchronous communication terminal enters a standby state and waits for reception of a synchronization signal from another communication terminal. However, since the communication terminal in the asynchronous state does not maintain an accurate time, the timing of entering the standby state cannot be synchronized with the transmission timing of the synchronization signal of another communication terminal. Therefore, the communication terminal needs to continue the standby state for a long time, and the power consumption of the communication terminal increases.

  The technology disclosed herein has been made in view of such a point, and an object thereof is to reduce power consumption when an asynchronous communication terminal waits for a synchronization signal.

  The technology disclosed herein is intended for a wireless communication system in which a network is formed by a plurality of communication terminals. The plurality of communication terminals are configured to synchronize by transmitting and receiving a synchronization signal, and among the plurality of communication terminals, an asynchronous communication terminal has a predetermined time elapsed from a predetermined start time of the day. The standby period is set as a standby period, the standby operation for receiving the synchronization signal is performed for a part of the standby period, the partial period of the standby operation is changed for each day, and a plurality of days are spent. The standby operation is performed during the entire standby period.

  The technology disclosed herein is directed to a communication terminal that receives a synchronization signal from another communication terminal and synchronizes with the other communication terminal. When the communication terminal is in an asynchronous state with the other communication terminal, the standby period is a predetermined period from a predetermined start time of a day, and a standby operation for receiving the synchronization signal is performed in the standby mode. It is assumed that a part of the period is performed, a part of the period for performing the standby operation is changed for each day, and the standby operation is performed over the entire period of the standby period over a plurality of days.

  According to the wireless communication system disclosed herein, it is possible to reduce power consumption when an asynchronous communication terminal waits for a synchronization signal.

  According to the communication terminal disclosed here, it is possible to reduce power consumption when waiting for a synchronization signal in an asynchronous state.

FIG. 1 is a schematic diagram of a wireless communication system. FIG. 2 is a block diagram of the data station. FIG. 3 is a block diagram of the repeater. FIG. 4 is a block diagram of the sensor. FIG. 5 is a diagram showing a communication schedule. FIG. 6 is a functional block diagram of the repeater. FIG. 7 is a functional block diagram of the sensor. FIG. 8 is a flowchart showing the processing of the repeater. FIG. 9 is a diagram illustrating the transmission timing of the synchronization signal. FIG. 10 is an explanatory diagram showing a standby operation in the synchronization process of the repeater. FIG. 11 is a diagram showing a synchronization schedule. FIG. 12 is a flowchart showing the synchronization process. FIG. 13 is a flowchart showing sensor processing.

  Hereinafter, exemplary embodiments will be described in detail with reference to the drawings.

  FIG. 1 is a schematic diagram of a wireless communication system 100. The wireless communication system 100 includes a data station 10, a plurality of relay devices 20, and a plurality of sensors 30. The data station 10, the repeater 20, and the sensor 30 are communication terminals that perform wireless communication with each other and autonomously construct a network. In the wireless communication system 100, a multi-hop wireless network is formed. The data station 10 communicates only with the relay device 20, and the sensor 30 communicates only with the relay device 20. The data station 10 and the repeater 20 have a tree-type network topology with the data station 10 as a vertex. In the present specification, in the network, the data station 10 side is the upstream side or the upper side, and the end side of the tree is the downstream side or the lower side. Further, when the data station 10, the repeater 20, and the sensor 30 are not distinguished, they may be simply referred to as communication terminals. In addition, when distinguishing each relay machine 20, an alphabet is added after the reference numeral “20”.

  In the wireless communication system 100, the sensor 30 detects a predetermined physical quantity, and the detected value, that is, the detected data is collected in the data station 10 via the relay device 20. In the example in the present disclosure, the wireless communication system 100 is installed in a factory having a steam system. The steam system has a plurality of steam traps T (only one is shown in FIG. 1). The sensor 30 detects the vibration and temperature of the steam trap T.

<Data station configuration>
FIG. 2 is a block diagram of the data station 10. The data station 10 establishes a communication path of the wireless communication system 100 and collects and manages detection data of the sensor 30. Although not shown, the data station 10 is connected to an upper server or the like via an external network or the like. The data station 10 transfers the detection data of the sensor 30 to a server or the like as necessary.

  The data station 10 includes a CPU 11, a memory 12, a storage unit 13, a wireless communication circuit 14, a timing circuit 15, a higher level interface unit 16, and a power supply circuit 17.

  The storage unit 13 stores various programs and various information. The CPU 11 performs various processes by reading and executing various programs from the storage unit 13. For example, the storage unit 13 defines a program for forming a network communication path, a program for collecting detection data of the sensor 30, tree information on the network communication path, and a schedule for communicating with the repeater 20. Schedule information, collected detection data, and the like are stored.

  The wireless communication circuit 14 performs wireless communication with other communication terminals such as the repeater 20. The wireless communication circuit 14 operates under the control of the CPU 11, converts various signals into wireless signals by processing such as encoding and modulation, and transmits the signals via an antenna. In addition, the wireless communication circuit 14 converts a signal received via the antenna into an appropriate signal by processing such as demodulation / combination.

  The clock circuit 15 generates a predetermined clock and clocks the time serving as the reference for the data station 10.

  The upper interface unit 16 performs interface processing with a server or the like.

  The power supply circuit 17 is connected to an external power supply (not shown) and supplies power to each element of the data station 10.

<Configuration of repeater>
FIG. 3 is a block diagram of the repeater 20. The relay machine 20 relays the detection data of the sensor 30 according to the command of the data station 10 and transmits it to the data station 10.

  The repeater 20 includes a CPU 21, a memory 22, a storage unit 23, a wireless communication circuit 24, a timer circuit 25, a power supply circuit 26, and a battery 27.

  The storage unit 23 stores various programs and various information. The CPU 21 performs various processes by reading and executing various programs from the storage unit 23. For example, in the storage unit 23, a program for forming a network communication path, a program for relaying detection data of the sensor 30, information on upper and lower communication terminals, detection data acquired from the sensor 30, and the like Is remembered.

  The wireless communication circuit 24 performs wireless communication with other communication terminals. The wireless communication circuit 24 operates under the control of the CPU 21, converts various signals into wireless signals through processing such as encoding and modulation, and transmits the signals via an antenna. The wireless communication circuit 24 converts the signal received via the antenna into an appropriate signal by processing such as demodulation and decoding.

  The clock circuit 25 generates a predetermined clock and clocks a time that is a reference for the repeater 20. In addition, the time measuring circuit 25 corrects the time serving as a reference for the repeater 20 based on the synchronization signal from the upper communication terminal.

  A battery 27 is connected to the power circuit 26. The power supply circuit 26 supplies power to each element of the repeater 20.

<Sensor configuration>
FIG. 4 is a block diagram of the sensor 30. The sensor 30 detects the vibration and temperature of the steam trap T and transmits the detected data to the corresponding relay device 20. The sensor 30 includes a sensor unit 40 and a processing unit 50.

  The sensor unit 40 includes a vibration sensor and a temperature sensor, and detects the vibration and temperature of the steam trap T. The sensor unit 40 is installed so as to be in contact with the casing of the steam trap T (for example, an inflow portion into which steam and drain flow), and detects vibration and temperature of the contacted portion. The sensor unit 40 outputs an electrical signal corresponding to the detected vibration and temperature to the processing unit 50.

  The processing unit 50 includes a CPU 51, a memory 52, a storage unit 53, a wireless communication circuit 54, a timing circuit 55, a sensor interface unit 56, a power supply circuit 57, and a battery 58.

  The storage unit 53 stores various programs and various information. The CPU 51 performs various processes by reading and executing various programs from the storage unit 53. For example, in the storage unit 53, a program for forming a network communication path, a program for acquiring vibration and temperature from the sensor unit 40, and transmitting the vibration and temperature to the relay device 20 as detection data, information on a higher-level communication terminal, In addition, detection data and the like are stored.

  The wireless communication circuit 54 performs wireless communication with other communication terminals. The wireless communication circuit 54 operates under the control of the CPU 51, converts various signals into wireless signals by processing such as encoding and modulation, and transmits the signals via an antenna. The wireless communication circuit 54 converts the signal received via the antenna into an appropriate signal by processing such as demodulation / compositing.

  The timer circuit 55 generates a predetermined clock and measures the time that is the reference of the sensor 30. In addition, the timer circuit 55 corrects the time serving as the reference of the sensor 30 based on the synchronization signal from the upper communication terminal.

  The sensor interface unit 56 performs interface processing with the sensor unit 40.

  A battery 58 is connected to the power supply circuit 57. The power supply circuit 57 supplies power to each element of the sensor 30.

<System operation>
The operation of the wireless communication system 100 configured as described above will be described in detail below.

<Data collection>
The wireless communication system 100 collects data detected by the sensor 30 in the data station 10 as a normal driving operation. The data station 10 communicates with each repeater 20 according to the communication schedule shown in FIG. The operation mode of the data station 10, the repeater 20, and the sensor 30 that perform operations related to this data collection is set to a normal mode.

  The communication schedule of FIG. 5 shows one cycle of data collection, and the communication schedule of FIG. 5 is repeatedly executed. The communication schedule is divided into a plurality of time slots. Each repeater 20 is assigned a specific time slot. Each repeater 20 communicates with the data station 10 in the corresponding time slot, and transmits detection data from the sensor 30 connected to the repeater 20 to the data station 10 (hereinafter, this process is also referred to as “reply process”). Say). Basically, each repeater 20 is in an active state in a corresponding time slot, and is in a sleep state in a time other than the corresponding time slot. However, since the relay device 20 existing on the communication path between the other relay device 20 and the data station 10 needs to perform relay processing when the lower-order relay device 20 communicates with the data station 10, In the time slot of the machine 20, the relay process is executed in the active state. Further, since the sensor 30 transmits detection data to the relay device 20 in the time slot of the connected relay device 20, the sensor 30 is active in the time slot of the relay device 20. The sensor 30 is basically in a sleep state when it is not necessary to transmit detection data to the relay device 20.

  In the communication schedule of FIG. 5, time slots are defined in a matrix. Time slots are assigned according to the hierarchy of communication paths in a tree structure. Specifically, a tree structure hierarchy is assigned to each column. For example, the data station 10 is assigned to the column L0, the first layer (ie, the number of hops is 1) is assigned to the column L1, and the second layer (ie, the number of hops is 2) is assigned to the column L2. Is assigned. The same applies to the third and subsequent layers.

  Normally, any one time slot is assigned to each repeater 20. The time slot of the column L1 is allocated to the first layer relay devices 20a and 20j. The second slot relay units 20b, 20c, 20d, and 20k are assigned the time slot of the column L2. The time slot of the column L3 is assigned to the third-layer repeaters 20e, 20f, and 20g. The time slots in the column L4 are allocated to the fourth-layer repeaters 20h and 20i. On the other hand, since the data station 10 has more processing content than the repeater 20, a plurality of time slots (all time slots in the row L0 in FIG. 5) are assigned to the data station 10 instead of one time slot. . In addition, since the number of time slots included in the column is different from the number of repeaters 20 included in each layer (usually, the number of time slots included in the column is larger), the time slots included in the column include There are some relays that are not assigned.

  In the communication schedule, time slot processing proceeds in the column direction. For example, in a certain column, the processing of the time slot proceeds in ascending order (that is, the order of rows N1 to Nm) with respect to the row number, and the processing of the time slot of the last row number (row Nm) of the row ends. The processing proceeds in the same order from the time slot of the first row number (row N1) in the next column.

  Time slots are assigned by the data station when a communication path is established. For example, a path is formed between communication terminals prior to establishment of the entire communication path of the wireless communication system 100. Thereafter, the data station 10 acquires route information indicating which communication terminals are connected to each other, and establishes the entire communication route of the wireless communication system 100. When the communication path is established, the data station 10 assigns a time slot to each relay device 20 and notifies the number of the time slot corresponding to each relay device 20. At this time, in addition to its own time slot, the time slot of the lower relay machine 20 is also notified to the relay machine 20 that needs to perform the relay process of the lower relay machine 20. Further, the relay machine 20 notifies the connected sensor 30 of the time slot of the relay machine 20. The data station 10 stores the communication schedule (that is, allocation of the time slot to the repeater 20) in the storage unit 13. The repeater 20 stores the time slot of its own time slot and the time slot of the subordinate repeater 20 that needs to perform the relay process in the storage unit 23. The sensor 30 stores the time slot of the connected repeater 20 in the storage unit 53.

  In data collection, the data station 10 transmits a request signal for requesting detection data of the sensor 30 to the corresponding relay 20 according to the communication schedule. On the other hand, the relay device 20 becomes active at the timing of the assigned time slot according to the communication schedule, and waits for a request signal from the data station 10. In addition, the relay machine 20 acquires detection data from the sensor 30 connected to the relay machine 20 according to the assigned time slot. When receiving the request signal, the relay machine 20 returns detection data from the sensor 30 to the data station 10. In addition, the relay device 20 becomes active at the timing of the time slot assigned to the lower relay device 20 on the communication path, and performs relay processing between the data station 10 and the lower relay device 20. The sensor 30 becomes active according to the time slot of the connected repeater 20, and transmits detection data to the repeater 20.

<Synchronous processing>
Thus, in order for the data station 10, the relay device 20, and the sensor 30 to execute processing based on a common communication schedule, the data station 10, the relay device 20, and the sensor 30 need to be synchronized. Therefore, the data station 10 transmits a synchronization signal including a synchronization time (reference time) when transmitting various signals to the repeater 20. The repeater 20 that has received the synchronization signal synchronizes the time of the timer circuit 25 with the synchronization time. The relay device 20 also transmits a synchronization signal including the synchronization time when transmitting various signals to the other relay device 20 or the sensor 30. Similarly, the repeater 20 or the sensor 30 that has received the synchronization signal synchronizes the time of the timer circuit 25 or the timer circuit 55 with the synchronization time. In this way, the synchronization time (reference time) of the data station 10 is transmitted to the repeater 20 and the sensor 30. Eventually, all the times of the data station 10, the repeater 20, and the sensor 30 are synchronized.

  However, communication terminals are arranged over a wide range, and there may be an obstacle that hinders communication between the communication terminals, and communication failure may occur between some communication terminals. In such a case, a communication terminal lower than the point where the communication failure occurs cannot receive the synchronization signal, and cannot synchronize with the upper communication terminal, and hence the data station 10. In the wireless communication system 100, the data station 10, the repeater 20, and the sensor 30 maintain a common communication schedule, and the repeater 20 and the sensor 30 autonomously switch between the sleep state and the active state based on the communication schedule. Allows communication in the corresponding time slot. Therefore, the relay machine 20 and the sensor 30 that are not synchronized become inappropriate for switching between the sleep state and the active state based on the communication schedule, and it becomes difficult to appropriately communicate with other communication terminals. In particular, when the repeater 20 and the sensor 30 are installed in a relatively high temperature environment, such as when the wireless communication system 100 is applied to a steam system, the temperature characteristics of the timer circuit 25 and the timer circuit 55 are affected. The resulting clock shift is likely to occur.

  Therefore, the asynchronous repeater 20 and the sensor 30 are in the synchronous mode. In the synchronous mode, the relay machine 20 and the sensor 30 are in a state of waiting for a synchronization signal from another communication terminal without performing processing related to collection of detection data of the sensor 30. The repeater 20 and the sensor 30 in the synchronization mode receive the synchronization signal and shift to the normal mode when the synchronization is completed.

  FIG. 6 is a functional block diagram of the repeater 20. The relay machine 20 includes a communication unit 201, a determination unit 202, and a synchronization unit 203 as functional blocks.

  The communication unit 201 performs communication with other wireless communication. The communication unit 201 includes the CPU 21 and the wireless communication circuit 24. The communication unit 201 appropriately performs communication with other wireless communication according to the processing of the relay device 20.

  The determination unit 202 determines whether or not the relay device 20 is synchronized with other communication terminals. The determination unit 202 includes the CPU 21 and the storage unit 23. The storage unit 23 stores a time when a synchronization signal from another communication terminal is received. The CPU 21 as the determination unit 202 determines whether or not the repeater 20 is in an asynchronous state with another communication terminal based on the elapsed time from the reception of the previous synchronization signal stored in the storage unit 23.

  The synchronization unit 203 corrects the reference time of the repeater 20 when receiving the synchronization signal (normal synchronization process), while performing a synchronization operation (details will be described later) when the repeater 20 is in an asynchronous state. Synchronize with other communication terminals (synchronization processing in an asynchronous state). The synchronization unit 203 includes a CPU 21 and a timer circuit 25. The CPU 21 as the synchronization unit 203 corrects the time of the clock circuit 25 based on the received synchronization signal in normal synchronization processing. On the other hand, in the synchronization processing in the asynchronous state, the CPU 21 performs a synchronization operation described later by switching between the sleep state and the active state of the repeater 20 in cooperation with the timing circuit 25.

  FIG. 7 is a functional block diagram of the sensor 30. The sensor 30 includes a communication unit 301, a determination unit 302, and a synchronization unit 303 as functional blocks.

  The communication unit 301 executes communication with other wireless communication. The communication unit 301 includes a CPU 51 and a wireless communication circuit 54. The communication unit 301 appropriately performs communication with other wireless communication according to the processing of the sensor 30.

  The determination unit 302 determines whether or not the sensor 30 is synchronized with other communication terminals. The determination unit 302 includes a CPU 51 and a storage unit 53. The storage unit 53 stores a time when a synchronization signal from another communication terminal is received. The CPU 51 as the determination unit 302 determines whether or not the sensor 30 is in an asynchronous state with another communication terminal based on the elapsed time from the reception of the previous synchronization signal stored in the storage unit 53.

  The synchronization unit 303 corrects the reference time of the sensor 30 when a synchronization signal is received (normal synchronization processing), while another operation is performed by performing a synchronization operation (described later in detail) when the sensor 30 is in an asynchronous state. Synchronize with the communication terminal (synchronization processing in the asynchronous state). The synchronization unit 303 includes a CPU 51 and a timing circuit 55. The CPU 51 as the synchronization unit 303 corrects the time of the time measuring circuit 55 based on the received synchronization signal in normal synchronization processing. On the other hand, in the synchronization process in the asynchronous state, the CPU 51 performs a synchronization operation, which will be described later, by switching between the sleep state and the active state of the sensor 30 in cooperation with the timing circuit 55.

<Processing flow>
Hereinafter, the processing flow of the wireless communication system 100 will be described in more detail.

  When collecting data, the data station 10 proceeds with processing according to the communication schedule. Specifically, the data station 10 performs processing necessary for the data station 10 in the time slot allocated to itself. Subsequently, the data station 10 sequentially communicates with the repeaters 20 assigned to the time slots in the order of the time slots. At this time, the signal sent from the data station 10 to each repeater 20 includes at least a request signal for requesting a return of detection data of the sensor 30 and a synchronization signal for synchronizing with the reference signal of the data station 10. ing.

-Repeater-
The processing of the repeater 20 at this time will be described with reference to the flowchart of FIG.

  As described above, the repeater 20 includes a time slot to which the repeater 20 is assigned and a time to which the lower repeater 20 is assigned when the repeater 20 is on the communication path of the lower repeater 20. The slot is in an active state, and the other time slots are in a sleep state. The CPU 21 sets the start time of the next time slot that should be in the active state in the timekeeping circuit 25 when going into the sleep state. The timer circuit 25 continues to count the time and notifies the CPU 21 of the arrival of the time when the set time is reached. The CPU 21 changes from the sleep state to the active state in response to the notification from the time measuring circuit 25 (step Sa1). Thus, the repeater 20 becomes active in the corresponding time slot.

  Next, in step Sa2, the relay machine 20 determines whether the process to be performed is a reply process or a relay process. That is, if the current time slot is a time slot assigned to the repeater 20, the process to be performed is a reply process, and if the current time slot is a time slot assigned to the lower repeater 20, the process is performed. The process is a relay process.

  If the process to be performed is a relay process, the relay machine 20 performs the relay process in step Sa3. Although detailed description is omitted, when the relay device 20 (communication unit 201) receives the request signal from the data station 10, the relay device 20 transmits the request signal to the lower communication terminal, and the detection data from the lower relay device 20 is transmitted. When received, the detection data is transmitted to the upper communication terminal.

  The relay device 20 changes from the active state to the sleep state when the relay processing is completed or the time slot is ended (step Sa6). Specifically, as described above, the CPU 21 sets the start time of the next time slot that should be in the active state in the timer circuit 25 and enters the sleep state.

  On the other hand, if the process to be performed is a reply process, the repeater 20 waits for a request signal from the data station 10 (step Sa4).

  And the relay machine 20 (communication part 201) will transmit the detection data from the sensor 30 toward the data station 10, if a request signal is received (step Sa5). At this time, the repeater 20 (synchronization unit 203) corrects the time of the time measuring circuit 25 based on the synchronization signal sent together with the request signal from the data station 10. Thereby, the repeater 20 synchronizes with the data station 10. When the transmission of the detection data is completed, the relay device 20 changes from the active state to the sleep state (step Sa6).

  On the other hand, if the repeater 20 cannot receive the request signal during the time slot, there is a possibility that a communication failure has occurred between the data station 10 and the repeater 20. Therefore, the repeater 20 (determination unit 202) determines whether or not the non-communication time, which is the time from when the request signal was received last time to the present, is equal to or greater than a predetermined determination time α (step Sa7).

  Communication failure may occur when communication is accidentally unsuccessful, or communication failure may occur when there is a structure that becomes an obstacle to communication due to regular repairs in the factory.

  Therefore, when the non-communication time is shorter than the determination time α, it is assumed that the communication failure is temporary, and the repeater 20 gives up communication with the data station 10 in the current time slot and performs special processing. Not performed. That is, the repeater 20 goes from the active state to the sleep state at the end of the time slot (step Sa6).

  On the other hand, if the disconnection time is longer than the determination time α, the communication failure continues for a long time. If the communication failure continues for a long period of time, the repeater 20 cannot receive a synchronization signal from a higher-level communication terminal, and thus is not synchronized. Therefore, when the non-communication time is equal to or longer than the determination time α, the repeater 20 enters the synchronous mode, and the synchronization unit 203 executes the synchronization process in the asynchronous state (step Sa8).

  Hereinafter, the synchronization process will be described in detail. FIG. 9 is a diagram illustrating the transmission timing of the synchronization signal. FIG. 10 is an explanatory diagram showing a standby operation in the synchronization process of the repeater 20.

  Prior to the description of the synchronization processing, transmission of the synchronization signal will be described. The synchronization signal is transmitted when the data station 10 and the repeater 20 transmit various signals in each time slot. That is, each of the data station 10 and the repeater 20 transmits a synchronization signal at least once within a predetermined time interval (that is, one cycle of the communication schedule). The synchronization signal is intermittently transmitted during a predetermined period of the time slot (for example, at the end of the time slot). For example, in the example illustrated in FIG. 9, the synchronization signal is repeatedly transmitted at a cycle of 1 second.

  On the other hand, the relay 20 in the synchronous mode performs a standby operation as shown in FIG. Specifically, the repeater 20 does not always enter an active state, but alternately repeats an active state and a sleep state. The active state is a state in which a synchronization signal can be received. By repeating the active state and the sleep state, power consumption can be saved even in the standby operation. In the example of FIG. 10, both the active period and the sleep period are the same length in 2 seconds. The active period is a period longer than the transmission period of the synchronization signal (1 second in the example of FIG. 9). For this reason, when the synchronization signal properly reaches the repeater 20, at least one synchronization signal can be received in the active period.

  The repeater 20 in the synchronous mode does not always perform such a standby operation until the synchronization signal is received, and repeats the standby operation and the sleep state. This repetition of the standby operation and the sleep state is referred to as a synchronization operation.

  The time for which the standby operation is continued is the same time as one cycle of the communication schedule or longer. For example, when one cycle of the communication schedule takes 1 hour, the standby operation is continued for at least 1 hour. Since one cycle of the communication schedule always includes the time slot of the upper communication terminal (that is, the communication terminal that transmits the synchronization signal) of the repeater 20, the synchronization signal to the repeater 20 is always transmitted during the standby operation. It will be reported once. The repeater 20 can perform synchronization not only when receiving a synchronization signal from a higher-level communication terminal, but also when receiving a synchronization signal from another communication terminal existing in a range where radio waves reach. Also in this point, the possibility of receiving a synchronization signal from another communication terminal can be increased by continuing the standby operation for at least the same time as one cycle of the communication schedule.

  The repeater 20 changes the number and timing of performing the standby operation for each day in the synchronous operation. The repeater 20 performs a synchronization operation based on a synchronization schedule as shown in FIG. Specifically, the number of standby operations included in 24 hours decreases with the passage of days. The starting time of 24 hours can be arbitrarily set. For example, the starting time may be the time when it is determined that the state is asynchronous. Alternatively, the starting time may be midnight or the time when the relay 20 is turned on. In this case, when the time determined to be in the asynchronous state has passed the counting time, the standby operation may be executed from the middle of the first day synchronization schedule.

  In the example of FIG. 11, the time for which one standby operation is continued is 1 hour. In this case, the time of one cycle of the communication schedule is 1 hour or less. On the first day, the standby operation is performed seven times (however, the first and second standby operations are continuous), on the second day, the standby operation is performed five times, and on the third day, the standby operation is performed. Is performed twice. If the communication failure is resolved at an early stage, the repeater 20 can receive the synchronization signal by performing the standby operation several times. In other words, the longer time during which the synchronization signal cannot be received means that there is a long-term cause of communication failure. For example, there is a case where a scaffold for regular repair is installed for one month, and this scaffold causes a communication failure. In such a case, performing standby operation many times a day is a waste of power consumption. By confirming whether or not the synchronization signal can be received once or twice a day, it is possible to confirm whether or not the long-term communication failure has been resolved. Therefore, the repeater 20 decreases the number of standby operations every time a day has elapsed since a communication failure occurred. Thereby, the relay machine 20 can save power consumption.

  Eventually, the repeater 20 performs the standby operation only once a day, and makes the duration shorter than one cycle of the communication schedule. Specifically, a part of a period (hereinafter referred to as “standby period”) from a predetermined start time of a day until a time corresponding to one cycle of the communication schedule elapses (hereinafter referred to as a “small period”). The standby operation is performed. And the relay machine 20 changes the timing of a small period for every day, and finally performs standby operation in the whole period of a standby period over several days.

  In the example of FIG. 11, the time corresponding to the 0th hour of the elapsed time is the start time, and the period until 1 hour elapses from the time corresponding to the 0th hour is the standby period. After the fourth day, the standby operation is performed only during the standby period. Specifically, on the fourth day, the standby operation is performed for 10 minutes from the start time of the standby period. This 10 minutes corresponds to a small period. On the fifth day, the small period is shifted in the direction of delay, and the standby operation is performed for 10 minutes from 8 minutes after the start time of the standby period. After the 6th day, the small period gradually shifts in the direction of slowing down. On the sixth day, the standby operation is performed for 10 minutes from 17 minutes after the start time of the standby period. On the seventh day, the standby operation is performed for 10 minutes from 25 minutes after the start time of the standby period. On the eighth day, the standby operation is performed for 10 minutes from 34 minutes after the start time of the standby period. On the ninth day, the standby operation is performed for 10 minutes from 42 minutes after the start time of the standby period. On the 10th day, the standby operation is performed for 10 minutes from 51 minutes after the start time of the standby period. On the 10th day, the standby operation is performed for one minute longer than the end time of the standby period. On and after the 11th day, the operations on and after the 4th day are repeated.

  Thus, the power consumption per day can be reduced by performing the standby operation performed once in several days. In other words, when the standby operation is not divided into a plurality of days, at least the power necessary for the standby operation for a time corresponding to one cycle of the communication schedule is consumed every day. On the other hand, when the standby operation is divided into a plurality of days, the standby operation for several days can be performed with the power required for the standby operation for a time corresponding to one cycle of the communication schedule. Since the standby operation time for each day is shorter than one cycle of the communication schedule, there is a possibility that the communication failure will be resolved for a long time. However, the standby operation is performed over the entire standby period over several days. The cancellation of the communication failure is eventually detected.

  In addition, since the repeater 20 in the synchronous mode is not synchronized, there is a possibility that the timing when performing the standby operation is not accurate. Therefore, even if the repeater 20 performs the standby operation based on the synchronization schedule and the time measured by the time measuring circuit 25, the timing of the standby operation may be shifted from an accurate time. On the other hand, the repeater 20 changes the small period so that the small period in which the standby operation is performed continues every day. Thereby, the bad influence by the inaccuracy of timekeeping can be reduced. For example, if the end time of one small period and the start time of another small period coincide with each other on the synchronization schedule, if the timing is inaccurate, a gap is actually generated between the two small periods. There is a possibility that a period during which the standby operation is not executed during the standby period (hereinafter referred to as “blank period”) may occur. Since the time difference can increase every day, if the standby operation for one small period and the standby operation for another small period are performed several days apart, the blank period can also be long. On the other hand, when the small period for performing the standby operation continues every day, the standby period for the other small period is performed on the next day after performing the standby operation for the one small period described above, thereby reducing the blank period. be able to.

  Furthermore, the repeater 20 partially overlaps two consecutive small periods. In the example of FIG. 11, each two consecutive small periods overlap by 1 minute or 2 minutes. For this reason, even if a time shift of the repeater 20 occurs, it is possible to suppress the occurrence of a blank period between the two small periods. Further, the overlapping portion of the small periods is set longer than the daily maximum deviation amount of the timing circuit 25. Thereby, generation | occurrence | production of a blank period can further be suppressed.

  The flow of the synchronization process will be described with reference to the flowchart of FIG.

  When the relay device 20 shifts to the synchronous mode, the relay device 20 performs the above-described synchronization operation in step Sb1.

  And the relay machine 20 determines whether the synchronous signal was received in step Sb2. If the synchronization signal has not been received, the repeater 20 returns to step Sb1 and continues the synchronization operation.

  On the other hand, when receiving the synchronization signal, the repeater 20 synchronizes the time of the timer circuit 25 with the synchronization time included in the synchronization signal. When the synchronization processing is completed, the relay device 20 shifts from the synchronization mode to the normal mode, and returns to the normal processing flow of FIG. That is, the relay device 20 is changed from the active state to the sleep state (step Sa6). At this time, as described above, the CPU 21 sets the start time of the next time slot to be in the active state in the timer circuit 25, and enters the sleep state.

  In this way, the relay 20 in the synchronous mode reduces the number of standby operations every day, and eventually performs a standby operation only for a small period within a predetermined standby period of the day, and the small period is changed every day. Instead, the standby operation can be continued for a long period of time by reducing the power consumption by performing the standby operation over the entire standby period over a plurality of days. In particular, since the repeater 20 is battery-driven, it is very effective to reduce power consumption.

-Sensor-
In the above description, the processing of the repeater 20 has been described, but the sensor 30 also has a normal mode and a synchronization mode, and performs the same processing as the repeater 20. FIG. 13 is a flowchart of the normal mode process of the sensor 30.

  As described above, the sensor 30 is in the active state in the time slot assigned to the connected repeater 20, and is in the sleep state in the other time slots. The CPU 51 sets the start time of the next time slot that should be in the active state when entering the sleep state in the time counting circuit 55. The timer circuit 55 continues to count the time and notifies the CPU 51 of the arrival of the time when the set time is reached. The CPU 51 changes from the sleep state to the active state in response to the notification from the timing circuit 55 (step Sc1). Thus, the sensor 30 becomes active in the time slot of the corresponding repeater 20.

  Next, the sensor 30 waits for a detection signal from the repeater 20 (step Sc2). The detection signal is a signal transmitted from the relay device 20 to the sensor 30 when the relay device 20 requests detection data from the sensor 30. And if the sensor 30 receives a detection signal, the sensor part 40 will detect the vibration and temperature of the steam trap T, and the process part 50 (communication part 301) will transmit detection data to the relay machine 20 (step Sc3). At this time, the sensor 30 (synchronization unit 303) corrects the time of the time counting circuit 55 based on the synchronization signal sent together with the detection signal from the relay machine 20. Thereby, the sensor 30 synchronizes with the repeater 20, and as a result, synchronizes with the data station 10. When the transmission of the detection data is completed, the sensor 30 changes from the active state to the sleep state (step Sc4).

  On the other hand, if the sensor 30 cannot receive a detection signal within a predetermined period, there may be a communication failure between the repeater 20 and the sensor 30. Therefore, the sensor 30 (determination unit 302) determines whether or not the disconnection time, which is the time from when the detection signal was received last time to the present, is equal to or longer than the predetermined determination time α (step Sc5). This determination time α may be the same as or different from the determination time α when the relay 20 determines a communication failure.

  If the non-communication time is shorter than the determination time α, it is assumed that the communication failure is temporary, and the sensor 30 gives up communication with the repeater 20 in the current time slot and does not perform any special processing. The sensor 30 changes from the active state to the sleep state at a predetermined timing in the time slot or at the end of the time slot (step Sc4).

  On the other hand, when the disconnection time is equal to or longer than the determination time α, the sensor 30 enters the synchronous mode, and the synchronization unit 303 executes the synchronization process in the asynchronous state (step Sc6).

  When the synchronization process is completed, the sensor 30 changes from the active state to the sleep state (step Sc4).

  The content of the synchronization process of the sensor 30 is the same as the synchronization process of the repeater 20. That is, the sensor 30 performs a synchronization operation that repeats the standby operation and the sleep state until a synchronization signal is received. At this time, the sensor 30 reduces the number of times of performing the standby operation for each day. In any case, the sensor 30 performs a standby operation only for a small period within a predetermined standby period of the day, and changes the small period for each day, and performs a standby operation over the entire period of the standby period over a plurality of days. I do. Thereby, the sensor 30 can reduce power consumption and can continue standby operation for a long period of time. In particular, since the sensor 30 is battery-driven, it is very effective to reduce power consumption.

  As described above, the wireless communication system 100 forms a network by the data station 10, the repeater 20, and the sensor 30 (a plurality of communication terminals), and the plurality of communication terminals are synchronized by transmitting and receiving a synchronization signal. The asynchronous communication terminal of the plurality of communication terminals has a predetermined period from a predetermined start time of the day as a standby period, and a standby operation for receiving a synchronization signal is a small period of the standby period. Only a period (a part of the period) is performed, a small period for performing the standby operation is changed for each day, and the standby operation is performed over the entire period of the standby period over a plurality of days.

  In addition, when the relay machine 20 and the sensor 30 are in an asynchronous state with other communication terminals, a standby operation for receiving a synchronization signal with a predetermined period from a predetermined start time of a day as a standby period Is performed for only a small period (partial period) of the standby period, the small period for performing the standby operation is changed for each day, and the standby operation is performed over the entire standby period over a plurality of days.

  According to this configuration, the communication terminal in the asynchronous state performs the standby operation for all the standby periods in a plurality of days instead of performing the standby operation in one day. Thereby, since the power consumption of the communication terminal per day can be reduced, the communication terminal can perform a standby operation for a long period of time.

  Further, the communication terminal in the asynchronous state performs the standby operation over the entire period of the standby period over a plurality of days by continuing the sub-period for performing the standby operation for each day.

  According to this configuration, since the standby operation in two adjacent small periods in the standby period is performed on consecutive days, even if the timing of the communication terminal is inaccurate, it occurs between the two small periods. It is possible to reduce the blank period in which the standby operation is not performed.

  Furthermore, the small period for performing the standby operation partially overlaps with the small period for performing the standby operation for the next day. In other words, the end portion of a sub-period of a certain day partially overlaps the head portion of the sub-period of the next day. Moreover, it can be said that the beginning part of the small period of a certain day partially overlaps with the end part of the small period of the previous day.

  According to this configuration, it is possible to further reduce the blank period that can occur between two adjacent small periods in the standby period.

  In addition, a communication terminal that transmits a synchronization signal among a plurality of communication terminals transmits the synchronization signal at least once within the time interval every predetermined time interval, and the standby period is equal to or greater than the time interval.

  That is, each of the data station 10 and the repeater 20 transmits a synchronization signal at least once in one cycle for each cycle of the communication schedule. The standby period is set to a length of one cycle or more of the communication schedule. Thereby, if the communication failure is eliminated, the communication terminal can receive the synchronization signal while performing the standby operation over the entire standby period over a plurality of days.

<< Other Embodiments >>
As described above, the embodiment has been described as an example of the technique disclosed in the present application. However, the technology in the present disclosure is not limited to this, and can also be applied to an embodiment in which changes, replacements, additions, omissions, and the like are appropriately performed. Moreover, it is also possible to combine each component demonstrated by the said embodiment and it can also be set as a new embodiment. In addition, among the components described in the attached drawings and detailed description, not only the components essential for solving the problem, but also the components not essential for solving the problem in order to illustrate the technology. May also be included. Therefore, it should not be immediately recognized that these non-essential components are essential as those non-essential components are described in the accompanying drawings and detailed description.

  About the said embodiment, it is good also as following structures.

  For example, the wireless communication system 100 may be applied to other than the steam system. Moreover, although the sensor 30 detects the vibration and temperature of the steam trap T, you may detect physical quantities (for example, electric power etc.) other than this.

  Further, the wireless communication system 100 collects the detection data of the sensor 30 as a normal operation, but the above-described synchronization processing is not limited to the content of the normal operation.

  Furthermore, in the above description, when it is determined that the communication terminal has changed from the synchronous state to the asynchronous state, the synchronous mode is set. However, the present invention is not limited to this. For example, when a wireless terminal is not yet established, such as when a communication terminal is newly installed and participates in the network of the wireless communication system 100, the synchronization mode may be performed and the above-described synchronization processing may be executed.

  In the synchronous operation, the number of standby operations per day is reduced after entering the asynchronous state, and the standby operation in a small period within the standby period is executed after the fourth day after entering the asynchronous state. As soon as the asynchronous state is reached, a standby operation in a small period within the standby period may be executed. That is, you may start from the synchronous process after the 4th day of the example of FIG.

  The standby period may not be the same as one cycle of the communication schedule, and may be longer than the one cycle. Further, the length of the small period is not limited to 10 minutes and can be arbitrarily set. Moreover, the length of the small period does not need to be uniform, and may be a different length. Moreover, in the said embodiment, although standby operation is performed in the whole period of a standby period over 7 days, it is not restricted to this.

  Furthermore, although the small period is delayed for each day in the standby period, the small period may be scheduled to be advanced for each day. In addition, the small period during which the standby operation is performed within the standby period is continued every day, but may not be continued every day. In the example of FIG. 11, on the fourth day, the standby operation is performed for 10 minutes from 8 minutes after the start time of the standby period, and on the fifth day, only for 10 minutes from 34 minutes after the start time of the standby period. A standby operation is performed. On the sixth day, the standby operation is performed for 10 minutes from 51 minutes after the start time of the standby period. On the seventh day, the standby operation is performed for 10 minutes from 17 minutes after the start time of the standby period. On the 8th day, the standby operation is performed for 10 minutes from 42 minutes after the start time of the standby period. On the 9th day, the standby operation is performed for 10 minutes from 25 minutes after the start time of the standby period. On the 10th day, the standby operation may be performed for 10 minutes from the start time of the standby period.

  Moreover, although each two continuous small periods partially overlap, it does not need to overlap.

  In the embodiment, the sensor 30 is configured to synchronize with the relay machine 20, but may be synchronized with the data station 10.

  As described above, the technology disclosed herein is useful for wireless communication systems and communication terminals.

100 wireless communication system 10 data station (communication terminal)
20 Repeater (communication terminal)
30 sensor (communication terminal)

Claims (5)

A wireless communication system that forms a network with a plurality of communication terminals,
The plurality of communication terminals are configured to synchronize by transmitting and receiving a synchronization signal,
The asynchronous communication terminal among the plurality of communication terminals has a predetermined period from a predetermined start time of a day as a standby period, and a standby operation for receiving the synchronization signal is a part of the standby period. The wireless communication system is characterized in that a part of the period during which the standby operation is performed is changed for each day, and the standby operation is performed over the entire period of the standby period over a plurality of days. The wireless communication system according to claim 1, wherein
The non-synchronized communication terminal performs the standby operation over the entire period of the standby period over a plurality of days by continuing a part of the period for performing the standby operation for each day. Communications system. The wireless communication system according to claim 2,
A part of a period during which the standby operation is performed partially overlaps a part of a period during which the standby operation is performed on the next day. The wireless communication system according to any one of claims 1 to 3,
A communication terminal that transmits a synchronization signal among the plurality of communication terminals transmits the synchronization signal at least once within the time interval every predetermined time interval,
The length of the waiting period is equal to or greater than the time interval. A communication terminal that receives a synchronization signal from another communication terminal and synchronizes with the other communication terminal,
In the case of an asynchronous state with the other communication terminal, a predetermined period from a predetermined start time of the day is set as a standby period, and a standby operation for receiving the synchronization signal is performed as a part of the standby period. A communication terminal characterized by performing a period of time, changing a part of the period for performing the standby operation for each day, and performing the standby operation over the entire period of the standby period over a plurality of days.

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