JP5302877B2 - Wireless communication system - Google Patents

Description

  The present invention relates to a radio communication system including a plurality of radio stations, and more particularly to a radio communication system in which each radio station operates using a battery as a power source.

  For radio stations used in Japan, the characteristics of radio waves used (RF characteristics) such as occupied frequency bandwidth and adjacent channel leakage power must satisfy the provisions of the Radio Law. In the Radio Law, different standards (communication standards) are defined for each purpose of use. For example, “low-power radio stations” defined as one of the radio stations that do not require a license in the proviso to Article 4 of the Radio Law include “wireless stations for cordless telephones”, “specified low-power radio stations”, “low-power radio stations” There are “security system”, “low-power data communication system radio station”, etc., and the standards for the radio equipment of each radio station are stipulated by the equipment regulations of the law.

  Conventionally, there is one described in Patent Document 1 as a wireless communication system including a plurality of wireless stations that operate using a battery as a power source. In the conventional system described in Patent Document 1, each radio station intermittently activates a reception circuit to check whether or not a desired radio wave (a radio signal transmitted by another radio station) can be received. If radio waves are not captured, the average power consumption is greatly reduced by immediately stopping the receiving circuit and shifting to a standby state.

  However, when the intermittent reception operation is performed as described above, the timing of receiving the radio signal that should be received is delayed by the intermittent reception interval of the reception circuit. Therefore, the intermittent reception interval cannot be simply extended for the purpose of reducing power consumption.

  Accordingly, the present inventor has determined that each wireless station that has received a synchronization signal transmitted in a period of several hours to several tens of hours counts the intermittent reception interval in synchronization with the synchronization signal, so that any wireless station transmits A wireless communication system has been devised that shortens the delay time until another wireless station can receive the wireless signal.

JP 2008-176515 A

  By the way, if the frequency stability (frequency deviation) of the signal generator (clock generator) used by each wireless station for counting the intermittent reception interval is about ± 50 ppm and the signal width of the synchronization signal is 2.8 seconds, There was a risk of loss of synchronization in about 7.8 hours.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a wireless communication system capable of preventing loss of synchronization due to a time lag of timer means for counting intermittent reception intervals.

In order to achieve the above object, the invention of claim 1 is a radio communication system comprising a plurality of radio stations, and transmitting and receiving radio signals using radio waves as a medium between the plurality of radio stations. Transmitting means for transmitting a radio signal; receiving means for receiving a radio signal; and starting a transmitting means when a predetermined event occurs, and transmitting a radio signal including a message corresponding to the event during a predetermined transmission period And an operation for alternately stopping the transmission of radio signals during a predetermined pause period, and a transmission control means for stopping the transmission means when the event has not occurred, and a timer means for repeatedly counting a fixed intermittent reception interval; When the intermittent reception interval is counted by the timer means, the reception means is stopped and the reception means is counted each time the intermittent reception interval is counted by the timer means. A reception control means for starting and a power supply means for supplying operation power of each means using a battery as a power source. When the reception means receives a synchronization signal, the reception control means stops counting the intermittent reception interval by the timer means. In addition, when a certain waiting time has elapsed from the end of the synchronization signal, the timer means restarts the counting of the intermittent reception interval, and when the event occurs, the transmission control means In the wireless communication system in which the wireless signal is transmitted from the transmission means during the transmission period overlapping with the time point when the counting is completed, the transmission control means of the specific wireless station among the plurality of wireless stations is configured to count the intermittent reception interval by the timer means. The transmission means transmits the synchronization signal every time a certain number of times are completed, and other wireless stations except the specific wireless station A time lag detecting means for detecting a time lag between the reception timing of the sync signal and the intermittent reception interval counted by the timer means when the sync signal is received at the other radio station. A radio signal including information on the time shift detected by the detection means is transmitted to the specific radio station, and the transmission control means of the specific radio station is based on the time shift information received from another radio station. The time width of the synchronization signal or the predetermined number of times is adjusted.

  According to the first aspect of the invention, the time lag between the reception timing of the synchronization signal and the intermittent reception interval counted by the timer means is detected by the time lag detection means provided in other radio stations excluding the specific radio station that transmits the synchronization signal. Detecting and transmitting time lag information from the other radio station to the specific radio station, and the transmission control means of the specific radio station is based on the time lag information received from the other radio station. Since the time width of the synchronization signal or the predetermined number of times is adjusted, loss of synchronization due to the time lag of the timer means for counting the intermittent reception interval can be prevented.

  According to a second aspect of the present invention, in the first aspect of the invention, the transmission control means of the specific radio station decreases the predetermined number of times when a time lag in another radio station exceeds a predetermined threshold value. It is characterized by.

  According to a third aspect of the invention, in the first aspect of the invention, the transmission control means of the specific radio station extends the time width of the synchronization signal when a time lag in another radio station exceeds a predetermined threshold value. It is characterized by doing.

  The invention according to claim 4 is the invention according to any one of claims 1 to 3, wherein the transmission control means of the specific radio station sets a transmission period for transmitting a radio signal addressed to another radio station. It shifts according to the time lag in the radio station.

  According to the present invention, it is possible to prevent loss of synchronization due to a time lag of the timer means for counting the intermittent reception interval.

It is a block diagram of a fire alarm device (master station and slave station) in an embodiment of the present invention. It is a frame format of the radio signal in the same as above. It is a flowchart for demonstrating the operation | movement which changes to a fire interlocking state from a standby state same as the above. It is a time chart for demonstrating the operation | movement which changes to the interlocking stop state from the interlocking ringing state same as the above. It is a time chart for demonstrating the operation | movement which changes to the interlocking stop state from the interlocking ringing state same as the above. It is a time chart for demonstrating the operation | movement which changes to a standby state from a fire interlocking state same as the above. It is a time chart for demonstrating the operation | movement in a fire interlocking state same as the above. It is operation | movement explanatory drawing of the time shift detection means in the same as the above. It is operation | movement explanatory drawing of the time shift detection means in the same as the above. It is operation | movement explanatory drawing of the time shift detection means in the same as the above. It is operation | movement explanatory drawing of the correction means in the same as the above. It is operation | movement explanatory drawing of the correction means in the same as the above. It is operation | movement explanatory drawing of the correction means in the same as the above.

  The technical idea of the present invention will be described below in a radio communication system (fire alarm system) in which a fire alarm device that emits a radio signal including a fire detection message using a radio wave as a medium while detecting a fire is used as a radio station. An embodiment to which is applied will be described.

  FIG. 1 is a system configuration diagram of this embodiment, and a fire alarm system is configured by a plurality of (only two in the drawing) fire alarm devices TR. In the following description, when the fire alarm devices TR are individually shown, they are expressed as fire alarm devices TR1, TR2,..., TRn, and when collectively shown, they are expressed as fire alarm devices TR.

  The fire alarm TR transmits a radio signal using radio waves as a medium from the antenna 3 and receives a radio signal transmitted from another fire alarm TR by the antenna 3, and a sound (buzzer sound or voice message). The main component is an alarm unit 5 for informing (sound from a speaker) a fire alarm (hereinafter referred to as “alarm sound”) and a memory unit 1a including a microcomputer and a rewritable nonvolatile semiconductor memory. When a fire is detected by the fire detection unit 4, a radio signal including a fire alarm message is transmitted from the radio transmission / reception unit 2 to cause the alarm unit 5 to sound an alarm sound and to notify other fire alarms TR of the fire alarm. The control unit 1 to be transmitted, the operation input receiving unit 6 that receives an operation input for stopping the alarm sound, as will be described later, and a battery such as a dry battery as a power source. And comprising a battery power supply unit 7 supplies power. The operation input receiving unit 6 has one or more switches (for example, push button switches). When the switch is operated, an operation input corresponding to each switch is received and an operation signal corresponding to the operation input is controlled. Output to part 1. Each of the fire alarm devices TR1, TR2,... Is assigned a unique identification code and stored in the memory unit 1a. The destination of the radio signal and the fire alarm devices TR1, TR2,. Can be identified.

  The radio transmission / reception unit 2 transmits / receives a radio signal using radio waves as a medium in accordance with “radio station of low power security system” defined in Article 6, Paragraph 4, Item 3 of the Radio Law Enforcement Regulations. In addition, the fire detection unit 4 detects fire by detecting smoke, heat, flames, and the like generated with the fire, for example. However, detailed configurations of the wireless transmission / reception unit 2 and the fire detection unit 4 are well known in the art and will not be described in detail.

The control unit 1 realizes various functions to be described later by executing a program stored in a memory (ROM or EEPROM) (not shown) by a microcomputer. When the fire detection unit 4 detects the occurrence of a fire, the control unit 1 drives a buzzer included in the alarm unit 5 to sound an alarm sound, or an alarm stored in the memory (or the memory unit 1a) in advance. In order to notify a fire alarm by sounding a voice message (for example, “This is a fire”) on the speaker, and to notify the fire alarm also in other fire alarm devices TR, a radio signal including a fire alarm message is transmitted. The wireless transmission / reception unit 2 transmits the data. Also, when the wireless transmission / reception unit 2 receives a wireless signal transmitted from another fire alarm device TR, the control unit 1 controls the alarm unit 5 to sound an alarm sound. That is, in the control unit 1, when the fire detection unit 4 detects a fire, the alarm unit 5 sounds an alarm sound to notify the fire alarm, and the wireless transmission / reception unit 2 transmits a radio signal including the fire alarm message. Have.

  Here, in the radio equipment regulation Article 49-17 “Radio equipment of radio stations of the low power security system” of the Radio Law Enforcement Regulation, the period during which radio signals may be continuously transmitted (transmission period) is 3 seconds or less. It is stipulated that the period (pause period) provided between the transmission period and the transmission period in which the radio signal should not be transmitted is 2 seconds or more (see No. 5 of the same article). For this reason, in the control unit 1 in the present embodiment, the wireless signal is transmitted during the transmission period that complies with the wireless facility rules, and the transmission is stopped and received during the suspension period.

  In order to extend the battery life of the battery power supply unit 7 as much as possible, the control unit 1 repeatedly counts a predetermined intermittent reception interval (however, the intermittent reception interval is longer than the transmission period) by a timer (timer means). In addition, every time the intermittent reception interval is counted, the wireless transmission / reception unit 2 is activated to check whether a desired radio wave (radio signal transmitted by another fire alarm device TR) can be received, and the radio wave is captured. If not, the average power consumption is greatly reduced by immediately stopping the wireless transmission / reception unit 2 and shifting to the standby state. The radio wave reception check is performed based on the received signal strength indication signal (Receiving Signal Strength Indication: RSSI signal) output from the wireless transmission / reception unit 2 and is a DC voltage signal proportional to the magnitude of the received signal strength. The details are well known in the art and will be omitted.

  Further, the control unit 1 of a specific fire alarm device TR1 (hereinafter referred to as a master station) activates the wireless transmission / reception unit 2 periodically (for example, every 24 hours) to establish other fire alarm devices TR2, TR3,. A radio signal including a periodic monitoring message is transmitted in order to confirm (periodic monitoring) whether or not (hereinafter referred to as a slave station) is operating normally. In the slave stations TR2,..., The control unit 1 monitors whether or not the fire detection unit 4 has failed and whether or not the battery power supply unit 7 has run out of battery at regular intervals (for example, every hour), and the monitoring result ( The presence or absence of a failure and the presence or absence of a battery are stored in the memory unit 1a, and when a periodic monitoring message is received from the master station TR1, a notification message for notifying the monitoring result stored in the memory unit 1a The included radio signal is returned to the master station TR1. After transmitting the radio signal including the notification message, the control unit 1 of the master station TR1 switches the radio transmission / reception unit 2 to the reception state, receives the radio signal transmitted from each of the slave stations TR2,. There is a slave station TR2,... That does not transmit a radio signal including a notification message within a predetermined time after transmission of the included radio signal, or a notification message transmitted from any of the slave stations TR2,. When notifying the result of monitoring that the battery has run out, the slave station TR2,. ) Has also been reported. When the control unit 1 of the master station TR1 and the slave stations TR2,... Determines that a failure or a battery has run out, a warning sound for immediately informing the occurrence of an abnormality (failure or battery runout) from the alarm unit 5. (Buzzer sound, voice message, etc.) are sounded from the speaker of the alarm unit 5.

Further, the control unit 1 of the master station TR1 detects the fire and causes the alarm unit 5 to sound an alarm sound and transmits a fire alarm message to each of the slave stations TR2,..., Or any of the slave stations TR2. After receiving the fire alarm message from,..., The wireless transmission unit 2 is caused to transmit a synchronous beacon at a constant cycle. This synchronous beacon is a signal that defines a time slot required for performing TDMA (time division multiple access) wireless communication (hereinafter referred to as “synchronous communication”) between a plurality of fire alarms TR. The one cycle is divided into a plurality of time slots, and one different time slot is allocated to each of the slave stations TR2,. Then, a message from the master station TR1 to the slave station TR2,... Is transmitted in a synchronous beacon, and a radio signal including a message from the slave station TR2,... To the master station TR1 is assigned to each slave station TR2,. Stored in the current time slot and transmitted. Therefore, it is possible to reliably avoid collision of radio signals transmitted from a plurality of fire alarm devices TR (the master station TR1 and the slave stations TR2,...). Although the time slot assignment to each fire alarm device TR may be fixed, the time slot assignment information may be notified to each slave station TR2,... By a synchronous beacon transmitted from the master station TR1.

  FIG. 2 shows a frame format of a radio signal transmitted and received by the fire alarm device TR. A synchronization bit (preamble: PA), a frame synchronization pattern (unique word: UW), a destination address DA, a source address SA, a message M, One frame is composed of a CRC code. Here, if the identification code of each fire alarm device TR is set as the destination address DA, only the fire alarm device TR of the identification code receives a radio signal and acquires a message. By setting a special bit string that is not assigned to the fire alarm TR (for example, a bit string with all bits set to 1), a wireless signal is broadcast (multicast) to obtain a message for all the fire alarm TRs. Can be made. For example, a radio signal including a fire alarm message is broadcast from the master station TR1 to all the slave stations TR2,.

  Next, the transmission / reception operation of this embodiment before and after the fire detection will be described with reference to the time chart of FIG.

  Here, since the timing at which each fire alarm device TR (the master station TR1 and the slave stations TR2,...) Starts operating (the timer starts counting the intermittent reception interval) usually does not match, the control unit 1 is the wireless transmission / reception unit. The timing of activating 2 and receiving radio waves (see the downward arrow in FIG. 3) is also uneven. On the other hand, in the present embodiment, when the synchronization signal transmitted from the master station TR1 is received by the radio transmission / reception unit 2 of the slave stations TR2,..., The control unit 1 of each slave station TR2,. The counting of the interval Tx is stopped and the counting of the intermittent reception interval Tx by the timer is resumed when a certain waiting time Tw has elapsed from the end point of the synchronization signal (t = t0). Therefore, after receiving the synchronization signal, the timing at which the timer completes the counting of the intermittent reception interval Tx is set in each fire alarm device TR (the master station TR1 and the slave stations TR2,...).

  For example, when the fire detection unit 4 detects a fire in the slave station TR2, the control unit 1 of the slave station TR2 sounds an alarm sound from the alarm unit 5, and before the count of the intermittent reception interval Tx by the timer is completed, the radio transmission / reception unit 2 And a radio signal including a fire alarm message is transmitted to all other fire alarm devices TR (master station TR1 and other slave stations TR3,...) Within a transmission period including the count completion time. At this time, the control unit 1 of the transmission source slave station TR2 continuously transmits the radio signal by the number of frames that can be transmitted within the transmission period, and the radio transmission / reception unit 2 during the pause period (reception period) after the transmission period. To the receiving state. In addition, since the timing for completing the intermittent reception interval Tx is complete in each fire alarm device TR, a radio signal including a fire alarm message can be received in one transmission period.

Here, if the low-power radio is used, the wireless communication distance can be sufficiently covered as long as it is within an area of a normal house. Therefore, the fire source child station TR2 can connect other fire alarm devices TR (master station TR1 and master station TR1). It is usually possible to send a message to other slave stations TR3,. However, as described above, the master station TR1 periodically monitors the slave stations TR2 to TR4, and the normality of the communication path is confirmed between the master station TR1 and each of the slave stations TR2 to TR4. However, since the communication path between the slave stations TR2 to TR4 is not confirmed, there is a possibility that a message does not reach a certain slave station due to the influence of an obstacle, for example.

  Therefore, the control unit 1 of the master station TR1 that has received the fire alarm message transmits a radio signal including the fire alarm message to the other slave stations TR3 and TR4 other than the slave station TR2 that is the transmission source, and an intermittent reception interval Tx by a timer. It is transmitted in the transmission period including the time point of completion of counting. When the control unit 1 of the other slave stations TR3 and TR4 receives the fire alarm message transmitted from the slave station TR2 or the master station TR1, it immediately sounds an alarm sound from the alarm unit 5 and sends a fire alarm message from the radio transceiver unit 2. A response message (ACK) for confirming reception is returned by a radio signal. In addition, when all of the fire alarms TR notify the fire alarm (sounds an alarm sound) when a fire is detected by at least one fire alarm TR in this manner, hereinafter, it is referred to as “fire interlocking”. .

  When receiving the ACK from all the other slave stations TR3 and TR4, the control unit 1 of the master station TR1 causes the radio transmission / reception unit 2 to transmit a synchronization beacon for defining a time slot at a constant period. In the present embodiment, the first time slot TS1 is assigned to the child station TR2, the second time slot TS2 is assigned to the child station TR3, and the third time slot TS3 is assigned to the child station TR4.

  Here, the master station TR1 periodically monitors each slave station TR2 to TR4, and the normality of the communication path is confirmed between the master station TR1 and each slave station TR2 to TR4. The communication path between the stations TR2 to TR4 has not been confirmed. Therefore, when a large number of slave stations TR2,... Are arranged, the number of communication paths between the slave stations TR2,. Since the exhaustion becomes intense, as described above, the specific fire alarm device TR1 is set as the master station, and the other fire alarm devices TR2,. By notifying a message (to be described later), even if there are slave stations that cannot establish a communication path with each other, it is possible to reliably link the fire.

  Moreover, when all the fire alarms TR start the alarm by sounding an alarm sound, as described above, a synchronous beacon is transmitted from the master station TR1 at a constant cycle, and the operation shifts to TDMA synchronous communication. However, the control unit 1 of the master station TR1 repeatedly transmits a fire alarm message to all the slave stations TR2,. Then, the control unit 1 of each slave station TR2,... Checks the state of the alarm unit 5 every time it receives a fire alarm message transmitted from the master station TR1, and if the alarm unit 5 is stopped, the alarm unit 5 Sound the alarm again. Therefore, after the fire alarm is started to be notified by all the fire alarms TR, all the other fire alarms (children) are set in a plurality of time slots defined by the synchronous beacon transmitted by the specific fire alarm (master station) TR1. Stations) TR2,... Can be assigned to perform wireless communication by time division multiple access (TDMA) to avoid collisions. Furthermore, all other fire alarms from a specific fire alarm (master station) TR1 The fire alarm can be reliably notified to the slave stations TR2,. As a result, a plurality of fire alarms TR can be effectively interlocked while avoiding collision of radio signals.

  As described above, according to the present embodiment, since a fire alarm is notified by all the fire alarm devices TR in the event of a fire, the user has more opportunities to perceive the fire alarm (listen to the alarm sound), thereby increasing safety. Can be improved.

By the way, the fire alarm system of this embodiment is in a state where no fire is detected in any of the fire alarms TR (standby state), and in a state where all the fire alarms TR are sounding an alarm sound (linked sounding) State), as described later, only the fire alarm TR that detects the fire (fire source) sounds the alarm sound, and the fire alarm TR other than the fire source stops the alarm sound (interlocked) The operation state is transited between (stop state). That is, when a fire is detected by at least one of the fire alarm devices TR (for example, the slave station TR2) in the standby state, as described above, all the other slaves from the fire source slave station TR2 and the master station TR1. When the fire alarm message is transmitted to the stations TR3,..., An alarm sound is generated in all the fire alarm devices TR including the master station TR1 and the slave stations TR2,.

  When an operation input for stopping the alarm sound is received by the operation input receiving unit 6 of any fire alarm device TR in the interlocking sounding state, if the fire alarm device TR is the master station TR1, The station TR1 transmits a message (alarm stop message) requesting the stop of the alarm sound to all the slave stations TR2,... Or if the fire alarm device TR is the slave station TR2,. When the master station TR1 receives the alarm stop message from the stations TR2,... And transmits the alarm stop message to the other slave stations TR2,. Transition to the stop state. However, when an operation input for stopping the alarm sound is received by the operation input receiving unit 6 of the fire source fire alarm device TR, the alarm sound is also stopped in the fire alarm device TR of the fire source. Here, the control unit 1 of the master station TR1 holds the fire detection status for each master station TR1 and each slave station TR2,... When a fire is no longer detected in, transition from the fire-linked state to the standby state.

  When the interlocking ringing state is changed to the interlocking stop state, the control unit 1 of the master station TR1 starts a time limit for a predetermined alarm sound stop time (for example, 5 minutes). Then, after the alarm sound stop time has elapsed, the control unit 1 of the master station TR1 refers to the fire detection status held in the memory unit 1a, and if all the fire alarms TR do not detect a fire, the control unit 1 By sending a recovery notification message using a beacon, it is possible to transition from a fire-linked state to a standby state. If a fire is detected by at least one fire alarm TR, a fire alarm message can be sent using a synchronous beacon. Transition from the linked stop state to the linked ringing state. Even when any fire alarm TR newly detects a fire in the interlock stop state, the control unit 1 of the master station TR1 transmits a fire alarm message by a synchronous beacon to change from the interlock stop state to the interlock ringing state. Transition.

  For example, as shown in the time chart of FIG. 4, in a fire-linked state (linked ringing state) in which the master station TR1 is a fire source, an operation input for stopping an alarm sound is received by the operation input reception unit 6 of the slave station TR4 that is not a fire source. When the alarm stop message is transmitted from the slave station TR4 by being accepted, the control unit 1 of the master station TR1 that has received the alarm stop message transmits the alarm stop message M2 by the synchronous beacon and sets the time limit of the alarm sound stop time. Do. However, in the master station TR1 that is the source of fire, the alarm unit 5 continues to sound an alarm sound. After the alarm sound stop time has elapsed, the control unit 1 of the master station TR1 confirms the fire detection status of its own fire detection unit 4 and the fire detection status of the slave stations TR2,..., And at least one of the fires is detected. When the alarm device TR detects a fire, a fire alarm message is transmitted again to each of the slave stations TR2,.

  On the other hand, as shown in the time chart of FIG. 5, if the fire is extinguished within the warning sound stop time and the fire detection unit 4 stops detecting the fire, the control unit 1 of the master station TR1 After the elapse of time, a recovery notification message is transmitted to each slave station TR2,... By a synchronous beacon, and when an ACK returned from all the slave stations TR2,. By stopping the transmission, the wireless communication by the TDMA method returns to the wireless communication by intermittent transmission / intermittent reception.

Further, as shown in the time chart of FIG. 6, if the fire at the fire station extinguishes and the fire detection unit 4 of the slave station TR 4 does not detect the fire in the interlocking ringing state with the slave station TR 4 as the fire source, A recovery notification message is transmitted from the station TR4 to the parent station TR1. The control unit 1 of the master station TR1 that has received the recovery notification message refers to the fire detection status held in the memory unit 1a. If no fire is detected by all the fire alarms TR, the recovery notification message is transmitted by a synchronous beacon. M3 is transmitted to each of the slave stations TR2,. When the control unit 1 of the master station TR1 receives ACKs returned from all the slave stations TR2,. Return to wireless communication by intermittent transmission and reception.

  On the other hand, as shown in the time chart of FIG. 7, when a fire is newly detected by another fire alarm device (for example, the slave station TR3), a recovery notification message is received from the slave station TR4 that is the first fire source. The control unit 1 of the master station TR1 refers to the fire detection status held in the memory unit 1a, and does not transmit a recovery notification message because the slave station TR3 is detecting a fire, and continues to transmit a fire alarm message. To maintain a fire-linked state.

  Thus, according to this embodiment, the reception control unit (control unit 1) of each radio station (fire alarm device TR) receives the synchronization signal, and the timing for starting the reception unit (radio transmission / reception unit 2) is aligned. In addition, since the transmission control means (control unit 1) of the wireless station where the event (fire detection) has occurred transmits a wireless signal in accordance with the timing when the receiving means is activated, the wireless signal transmitted from one wireless station is All other radio stations can receive almost simultaneously. As a result, by performing intermittent reception, it is possible to shorten the delay time until another wireless station can receive a wireless signal transmitted from any wireless station while reducing the power consumption and extending the battery life.

  In the present embodiment, the transmission control means (control unit 1) of a specific radio station (master station TR1) among the plurality of radio stations (fire alarm device TR) has a constant count of intermittent reception intervals by the timer means. A synchronization signal is transmitted from the transmission means (radio transmission / reception unit 2) every time the number of times is completed, and there is an advantage that a dedicated transmitter (transmission station) for transmitting the synchronization signal is not required and the system configuration can be simplified. is there. Note that the interval for transmitting the synchronization signal (the predetermined number of times) may be several hours (several hundred times), for example.

  Incidentally, an oscillator using a tuning fork type crystal resonator is used as a timer clock for a timer that counts intermittent reception intervals. Such an oscillator generally oscillates at an oscillation frequency of 32.768 kHz. For example, when the intermittent reception interval is 5 seconds, intermittent reception is performed every 163840 (32.768 kHz × 5 s) counts. However, the frequency stability (frequency deviation) is about ± 50 to 100 ppm, and the time shift of the intermittent reception interval gradually increases due to long-term use, and there is a possibility that synchronization with the synchronization signal may eventually be lost. Therefore, in this embodiment, each slave station TR2 is provided with a time lag detecting means for detecting a time lag between the reception timing of the synchronization signal and the intermittent reception interval counted by the timer when the radio transmission / reception unit 2 receives the synchronization signal. The control unit 1 of the child station TR2 transmits a radio signal including information on the time lag detected by the time lag detection means to the parent station TR1, and the control unit 1 of the parent station TR1 receives from the child station TR2. The count operation of the timer is corrected based on the time lag information. However, the time shift detection means is realized by causing the microcomputer of the control unit 1 to execute a dedicated program.

  As shown in FIG. 8, when the synchronization signal has a frame configuration consisting of a preamble and a unique word (UW), the control unit 1 serving as a time lag detection means completes the reception of the unique word from the time t0 when the preamble of the synchronization signal is received. The time (detection time) until time t1 is measured. For example, assuming that the time width of the synchronization signal is T (seconds) and the intermediate value (= T / 2) of the synchronization signal is a reference point for time shift detection, the time shift ΔT is calculated as ΔT = detection time−T / 2. (See FIG. 8).

Alternatively, as shown in FIG. 9, the frame structure of the synchronization signal includes a header HD consisting of a bit synchronization preamble and a frame synchronization unique word, and a data field to which numbers (continuous transmission numbers) are assigned in order from the top. In the case of a frame configuration in which a plurality of pairs of synchronous frames are continuously transmitted, the control unit 1 serving as a time lag detection means continuously transmits the serial number i (i = 1, 2,...) Of the data field received first in intermittent reception. , N) to detect a time lag. For example, assuming that the serial number i of the synchronization frame received first is i = 2 when the serial number i assigned to the data field is based on the synchronization frame of n / 2, the time shift ΔT is ΔT. = T * (n / 2-2).

  Alternatively, instead of the serial number i described above, a time lag value (0 ppm, ± 1 ppm,..., ± 10 ppm) with the intermediate value of the synchronization signal as a reference point is stored in the data field as shown in FIG. The control unit 1 serving as a time shift detection means can detect the time shift ΔT from the data (0 ppm, ± 1 ppm,..., ± 10 ppm) received first in the intermittent reception.

  Further, the control unit 1 of the slave stations TR2,... Sets the identification code of the master station TR1 as the destination address DA and sets its own identification code as the transmission source address SA, and stores the detected time lag ΔT information in the data field. The wireless transmission / reception unit 2 transmits the wireless signal set to “1”.

  On the other hand, the control unit 1 of the master station TR1 recognizes the time lag ΔT in each of the slave stations TR2,... By receiving the radio signal, and the time lag ΔT in any of the slave stations TR2,. When it exceeds, correction is performed by finely adjusting the count operation of the timer according to the magnitude of the time difference ΔT. That is, since the intermittent reception interval Tx can be changed by increasing / decreasing the count value of the timer that counts the intermittent reception interval Tx from the normal value, the control unit 1 can increase the time by increasing / decreasing the timer count value. The shift ΔT can be corrected. That is, as shown in FIG. 11, it is only necessary to shorten the interval for transmitting the synchronization signal (decrease the predetermined number of times for counting the intermittent reception interval). Here, as described above, the tuning fork type crystal oscillator normally oscillates at 32.768 kHz. For example, when the intermittent reception interval Tx is 5 seconds, intermittent reception is performed every count of 163840 (= 32.768 kHz × 5). Therefore, the amount of change when increasing or decreasing by one count is approximately ± 6 ppm (≈1 ÷ 163840), which is the minimum unit that can be corrected. Therefore, the correction cannot be made if the time difference ΔT detected in the slave stations TR2,... Is smaller than the minimum value. In this case, the control unit 1 of the master station TR1 is, for example, once every 10 minutes. The time deviation ΔT is corrected by increasing or decreasing the count value at a rate. If the time width T of the synchronization signal is increased as shown in FIG. 12, the time shift ΔT in the slave stations TR2,... Is adjusted (corrected) before the time shift ΔT increases and synchronization with the synchronization signal cannot be achieved. can do. In this way, loss of synchronization due to the time difference ΔT of the timer means for counting the intermittent reception interval can be prevented.

  If a message (for example, a fire alarm message) must be transmitted from the master station TR1 to any one of the slave stations TR2,... Between the transmission of the synchronization signal and the transmission of the next synchronization signal, the master station TR1. As shown in FIG. 13, the control unit 1 shifts the transmission period for transmitting the radio signal including the message in accordance with the time difference ΔT between the slave stations TR2,. Thus, even in the slave stations TR2,... Where the time difference ΔT is large, the radio signal transmitted from the master station TR1 can be reliably received.

TR1 Fire alarm (specific radio station)
TR2 Fire alarm (other radio stations)
1 Control unit (transmission control means, reception control means, timer means, time lag detection means, correction means)
2 Wireless transceiver (transmitting means, receiving means)
7 Battery power supply (power supply means)

Claims (4)

A wireless communication system comprising a plurality of wireless stations and transmitting and receiving wireless signals using radio waves as a medium between the plurality of wireless stations,
Each radio station includes a transmission unit that transmits a radio signal, a reception unit that receives a radio signal, and activates the transmission unit when a predetermined event occurs, and includes a message corresponding to the event during a predetermined transmission period Transmitting a wireless signal and repeatedly stopping the transmission of the wireless signal during a predetermined pause period, and repeatedly counting a certain intermittent reception interval, and a transmission control means for stopping the transmitting means when the event does not occur Timer means for receiving, a reception control means for stopping the reception means during counting of the intermittent reception interval by the timer means, and starting the reception means every time counting of the intermittent reception interval by the timer means is completed, and each means using a battery as a power source Power supply means for supplying the operating power of
The reception control means stops counting the intermittent reception interval by the timer means when the synchronization signal is received by the reception means, and the intermittent reception interval by the timer means when a certain waiting time has elapsed from the end of the synchronization signal. Resume counting,
In the wireless communication system in which when the event occurs, the transmission control unit causes the transmission unit to transmit a radio signal during the transmission period that overlaps with a time point at which the intermittent reception interval is counted by the timer unit.
The transmission control means of a specific wireless station among the plurality of wireless stations causes the transmission means to transmit the synchronization signal every time counting of the intermittent reception interval by the timer means is completed a certain number of times,
Other radio stations excluding the specific radio station have a time lag detecting means for detecting a time lag between the reception timing of the synchronization signal and the intermittent reception interval counted by the timer means when the receiving means receives the synchronization signal. Prepared,
The transmission control unit of the other radio station transmits a radio signal including information on the time shift detected by the time shift detection unit to the specific radio station,
The radio communication system, wherein the transmission control means of the specific radio station adjusts the time width of the synchronization signal or the predetermined number of times based on the information on the time difference received from another radio station.   The radio communication system according to claim 1, wherein the transmission control means of the specific radio station decreases the predetermined number of times when a time lag in another radio station exceeds a predetermined threshold.   2. The radio communication system according to claim 1, wherein the transmission control means of the specific radio station extends the time width of the synchronization signal when a time lag in another radio station exceeds a predetermined threshold. .   The transmission control means of the specific radio station shifts a transmission period for transmitting a radio signal addressed to another radio station according to a time lag in the other radio station. The wireless communication system according to any one of the above.

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