JP2013175154A - Wireless communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wireless communication system capable of preventing a situation that a radio station cannot receive a radio signal due to a variation of the strength of received signal.SOLUTION: The wireless communication system includes plural fire alarms TR0 (radio station). Each of the fire alarms TR0 includes: an antenna 1; a radio transmission/reception part 2 that transmits and receives radio signals; and a control section 6 that controls the transmission and reception of radio signals. A control section 6 of a master station TR1 as one of the radio stations causes each of slave stations TR2,... as the other radio stations to periodically transmit a synchronizing signal including a regular monitor message. The control section 6 of the master station TR1 sets at least either one of a transmission timing of the synchronizing signal and transmission frequency per cycle of the synchronizing signal based on the strength of the received signal of the radio signal at each slave stations TR2, ....

Description

  The present invention relates to a wireless communication system including a plurality of wireless stations.

  In recent years, the obligation to install fire alarms in houses has been legislated to reduce the number of victims of house fires, so multiple fire alarms can be linked using wireless signals from the viewpoint of workability in existing houses. A fire alarm system is desired. Such a fire alarm system has a function in which a plurality of fire alarms (wireless stations) installed in many places sense a fire and sound a warning sound. When any of the fire alarms senses a fire, the fire alarm sounds an alarm sound and transmits information (fire detection information) for notifying the fire detection to another fire alarm with a wireless signal. Thereby, not only the fire source fire alarm device but also a plurality of fire alarm devices are interlocked to sound an alarm sound all at once, so that the occurrence of a fire can be notified quickly and reliably. Such a fire alarm is driven using a battery as a power source in order to take advantage of the characteristic of transmitting fire detection information by radio signals. Moreover, since it is usually installed in a place where maintenance (battery replacement) is difficult, such as an indoor ceiling, it is desirable that it can be used without maintenance for a long period of time, such as several years.

  Here, in the fire alarm system as described above, when a fire is detected, a wireless signal is transmitted between a plurality of fire alarms. B) If radio signals are transmitted, the radio signals will collide. In order to avoid such a collision, for example, Patent Document 1 describes a fire alarm system in which a plurality of fire alarm devices transmit radio signals by a TDMA (Time Division Multiple Access) method.

JP 2009-251903 A

  By the way, in a wireless communication system such as the fire alarm system described in Patent Document 1, each wireless station is operating normally by periodically transmitting a monitoring message from the wireless station to other wireless stations. The operation of confirming whether or not is performed. Here, in the space where the wireless communication system is constructed, fading may occur due to human movement or the like, and the received signal strength of the wireless signal at each wireless station may vary. Conventionally, a specific wireless station periodically transmits a monitoring message regardless of fluctuations in received signal strength. For this reason, when the received signal strength of another radio station fluctuates at the time of transmitting the monitoring message, there is a possibility that the other radio station cannot receive the radio signal and the operation check cannot be performed normally. The fluctuation of the received signal strength due to fading is a problem that can occur not only when the operation is confirmed as described above, but also when wireless signals are transmitted and received between wireless stations.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a wireless communication system that can avoid a situation in which a wireless station cannot receive a wireless signal due to fluctuations in received signal strength.

  The wireless communication system of the present invention is a wireless communication system that includes a plurality of wireless stations, and transmits and receives wireless signals using a radio wave as a medium between the plurality of wireless stations, and each wireless station includes a plurality of antennas. A radio transmission / reception unit including a transmission unit that transmits a radio signal using any one of the antennas, and a reception unit that receives a radio signal using any one of the antennas; The transmission unit is activated when a predetermined event occurs, and an operation of transmitting a radio signal including a message corresponding to the event in a predetermined transmission period and pausing transmission of the radio signal in a predetermined pause period are alternately performed. Repetitive transmission control means for stopping the transmission means when the event has not occurred, timer means for repeatedly counting a constant intermittent reception interval, and A control unit having reception control means for stopping the reception means during counting of the intermittent reception interval by the timer means and starting the reception means each time counting of the intermittent reception interval by the timer means is completed; and a battery Power supply means for supplying operating power to the respective means using the power supply as a power source, and the control unit of one of the radio stations activates the transmission means and periodically transmits to other radio stations. And the control unit of the one wireless station transmits the periodic wireless signal transmission timing or the periodic wireless signal based on the reception level of the wireless signal in the other wireless station. It is characterized in that at least one of the number of transmissions per cycle is set.

  In this radio communication system, it is preferable that the control unit of the one radio station sets the transmission timing of the periodic radio signal in a time zone in which the fluctuation of the reception level is relatively small.

  In this wireless communication system, the control unit of the one wireless station obtains a time distribution of the reception level by transmitting and receiving a wireless signal to and from the other wireless station, and the reception based on the time distribution It is preferable to set the transmission timing of the periodic radio signal in a time zone in which the level fluctuation is relatively small.

  In this wireless communication system, the control unit of the one wireless station obtains a probability distribution of the reception level by transmitting and receiving a wireless signal to and from the other wireless station, and the periodic transmission is performed based on the probability distribution. It is preferable to set the number of transmissions of a typical wireless signal per cycle.

  In this radio communication system, the control unit of the one radio station sets an arbitrary fixed period as a test period, and transmits the radio signal at an interval shorter than the periodic radio signal transmission interval in the test period. It is preferable to obtain the data of the reception level by transmitting / receiving to / from another radio station.

  In this wireless communication system, each wireless station includes a fire alarm that detects the occurrence of a fire, a wireless station that has an air quality sensor that measures air quality, and a wireless station that has a human sensor that detects the presence of a person. At least one of them is preferable.

  The present invention has an effect of avoiding a situation in which a radio station cannot receive a radio signal due to a decrease in received signal strength.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows embodiment of the radio | wireless communications system which concerns on this invention, (a) is a block diagram of a fire alarm device, (b) is a figure which shows the time distribution of the received signal strength in either slave station. It is a frame format of a radio signal in the above radio communication system. 4 is a time chart for explaining a communication operation when a fire is detected in the above wireless communication system. It is a figure which shows the probability distribution of the received signal strength in either slave station of a radio | wireless communications system same as the above.

  Hereinafter, embodiments of a wireless communication system according to the present invention will be described with reference to the drawings. As shown in FIG. 1A, the present embodiment includes a plurality (two in the figure) of fire alarms (wireless stations). In the following description, fire alarms are indicated as fire alarms TR1, TR2,..., TRn when indicated individually, and are indicated as fire alarms TR0 when indicated collectively. In the following description, one fire alarm device TR1 is referred to as “master station TR1,” and the other fire alarm devices TR2,.

  The fire alarm device TR0 includes an antenna 1, a wireless transmission / reception unit 2 (transmission unit, reception unit), an alarm unit 3, and an operation input reception unit 4. The fire alarm TR0 includes a fire detection unit 5, a control unit 6 (transmission control unit, reception control unit, timer unit), and a power source unit 7 (power supply) that supplies operating power to each unit using a battery such as a dry battery as a power source. Means).

  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. The wireless transmission / reception unit 2 transmits a radio signal using radio waves as a medium from the antenna 1 and receives a radio signal transmitted from another fire alarm device TR0 by the antenna 1. The antenna 1 may have a design that protrudes from the main body of the fire alarm device TR0, but an antenna having a design that is built in the main body so that the antenna 1 is not conspicuous can be produced.

  The alarm unit 3 includes a buzzer that sounds a buzzer sound and a speaker that sounds a voice message, and a fire alarm (hereinafter referred to as “alarm sound”) by a buzzer sound or a voice message (for example, “is a fire”). Is notified.

  The operation input receiving unit 4 includes one or more switches (for example, push button switches), and receives an operation input corresponding to each switch when the switch is operated and outputs an operation signal corresponding to the operation input. Output to the control unit 6. For example, the operation input accepting unit 4 accepts an operation input for stopping the sounding of the alarm sound by the alarm unit 3.

  The fire sensing unit 5 senses a fire by detecting smoke, heat, flame, and the like generated with the fire, for example. In addition, since the structure of the fire detection part 5 is conventionally well-known, detailed description is abbreviate | omitted here.

  The control unit 6 includes a memory unit 6A including a microcomputer or a rewritable nonvolatile semiconductor memory as a main component. The control part 6 implement | achieves the various functions mentioned later by running the program stored in memory (ROM or EEPROM etc.) which is not illustrated with a microcomputer. For example, when the fire detection unit 5 detects the occurrence of a fire, the control unit 6 drives the alarm unit 3 to sound an alarm sound, or for alarms stored in the memory (or the memory unit 6A) in advance. It has a function to notify a fire alarm by sounding a voice message. The control unit 6 also has a function of causing the wireless transmission / reception unit 2 to transmit a radio signal including a fire alarm message in order to notify the fire alarm also in other fire alarm devices TR0. In addition, the control unit 6 controls the alarm unit 3 to generate an alarm even when the control unit 6 receives a fire alarm message by receiving a radio signal transmitted from another fire alarm device TR0. It also has a function to sound.

  Each of the fire alarm devices TR1, TR2,... Is assigned a unique identification code and stored in the memory unit 6A, and the destination of the radio signal and the source fire alarm devices TR1, TR2,. Can be specified.

  Here, Article 49-17 “Radio Equipment for Radio Stations of Low Power Security System” of Radio Equipment Regulations of the Radio Law Enforcement Regulation stipulates that the transmission period is 3 seconds or less and the suspension period is 2 seconds or more. (See item 5 of the same article). The “transmission period” indicates a period during which the radio signal may be transmitted continuously, and the “pause period” is a period provided between the transmission period and the transmission period during which the radio signal should not be transmitted. Indicates. For this reason, the control unit 6 in the present embodiment transmits a radio signal during a transmission period that complies with the radio equipment rules, and stops transmission during a pause period and enables reception.

  The controller 6 repeatedly counts a predetermined intermittent reception interval (however, the intermittent reception interval is longer than the transmission period) by a timer (timer means) built in the microcomputer. Then, every time the counting is completed, the control unit 6 activates the wireless transmission / reception unit 2 to check whether or not a desired radio wave (a radio signal transmitted by another fire alarm device TR0) can be received. If the signal is not detected, the wireless transmission / reception unit 2 is immediately stopped to shift to a standby state. Thereby, the average power consumption is greatly reduced, and the battery life of the power supply unit 7 is made as long as possible. Here, the radio wave reception check is performed by the control unit 6 based on the RSSI signal, which is a DC voltage signal proportional to the magnitude of the received signal strength (reception level) output from the wireless transmission / reception unit 2. Is omitted because it is well known. The “RSSI signal” refers to a receiving signal strength (Receiving Signal Strength Indication) signal.

  Further, the control unit 6 of the master station TR1 causes the wireless transmission / reception unit 2 to be activated periodically (for example, every 24 hours) to transmit a wireless signal including a periodic monitoring message in order to perform periodic monitoring. Here, “periodic monitoring” means checking whether or not the slave stations TR2,... Are operating normally. After transmitting the radio signal including the regular monitoring message, the control unit 6 of the master station TR1 switches the radio transmission / reception unit 2 to the reception state and receives the radio signal transmitted from each of the slave stations TR2,.

  In the slave stations TR2,..., The control unit 6 monitors whether or not the fire detection unit 5 has failed and whether or not the power supply unit 7 has run out of battery at regular intervals (for example, every hour), and the monitoring result (failure) The presence / absence of the battery and the presence / absence of the battery dead) are stored in the memory unit 6A. Then, the control unit 6 of the slave stations TR2,... Receives a radio signal including a notification message for notifying the monitoring result stored in the memory unit 6A when receiving the regular monitoring message from the master station TR1. Reply to TR1.

  Here, if there is a slave station TR2,... That does not reply within a predetermined time after transmitting a radio signal including a periodic monitoring message, the control unit 6 of the master station TR1 drives the buzzer of the alarm unit 3. An alarm is sounded to notify the slave stations TR2,... That an abnormality has occurred. Here, “abnormal” indicates failure or battery exhaustion. Further, when the notification message returned from any of the slave stations TR2,... Notifies the monitoring result that there is an abnormality, the control unit 6 of the master station TR1 has an abnormality in the slave stations TR2,. Notify that it has occurred. When the control unit 6 of the fire alarm devices TR1, TR2,... Determines that an abnormality has occurred, a warning sound for notifying the occurrence of the abnormality immediately from the alarm unit 3 sounds from the buzzer or speaker of the alarm unit 3. It is supposed to let you.

  Also, the control unit 6 of the master station TR1 receives a fire alarm message from any of the slave stations TR2,. Thereafter, the wireless transmission unit 2 is caused to transmit a synchronization beacon at a constant cycle. The synchronous beacon is a signal that defines a time slot necessary for performing TDMA (time division multiple access) wireless communication (hereinafter referred to as “synchronous communication”) between a plurality of fire alarms TR0. One period (cycle) of the synchronization beacon is divided into a plurality of time slots, and one different time slot is assigned 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 TR0 (master station TR1 and slave stations TR2,...). The time slot assignment for each fire alarm TR0 may be fixed, but 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 TR0. In this frame format, one frame is composed of a synchronization bit (preamble: PA), a frame synchronization pattern (unique word: UW), a destination address (DA), a source address (SA), a message (M), and a CRC code. Yes. Here, if the identification code of each fire alarm device TR0 is set as the destination address (DA), only the fire alarm device TR0 with the identification code receives the radio signal and acquires the message. Also, if a special bit string that is not assigned to any fire alarm device TR0 is set as the destination address (DA) (for example, a bit string in which all bits are set to 1), all fire alarms are transmitted by multicasting radio signals. The message can be acquired by the device TR0. For example, a radio signal including a fire alarm message is multicast from the master station TR1 to all the slave stations TR2,.

  Next, the communication operation of this embodiment before and after the fire detection will be described with reference to FIG. For example, when the fire detection unit 5 detects a fire in the slave station TR2, the control unit 6 of the slave station TR2 sounds an alarm sound from the alarm unit 3, and before the count of the intermittent reception interval T1 by the timer is completed, the radio transmission / reception unit 2 is started. Then, the control unit 6 of the slave station TR2 sends a radio signal including a fire alarm message to all other fire alarm devices TR (the master station TR1 and other slave stations TR3,...) Within a transmission period including the count completion time. Send to. At this time, the control unit 6 of the transmission source child 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.

  As will be described later, when the fire alarm devices TR1, TR2,... Are ready to complete counting of the intermittent reception interval T1, a radio signal including a fire alarm message is received in one transmission period. be able to.

  Here, if the low-power radio is used, the wireless communication distance can be sufficiently covered as long as it is in an area of a normal house. Therefore, the fire station 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, the communication path between the slave stations TR2 to TR4 has not been confirmed. For this reason, 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 6 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 source slave station TR2, and an intermittent reception interval T1 by the timer. It is transmitted in the transmission period including the time point of completion of counting. When the control unit 6 of the other slave stations TR3 and TR4 receives the fire alarm message transmitted from the slave station TR2 or the master station TR1, the alarm unit 3 immediately sounds an alarm sound. Further, the control units 6 of the other slave stations TR3 and TR4 send back a response message (ACK) for confirming reception of the fire alarm message from the radio transmission / reception unit 2 by a radio signal. In addition, when all the fire alarm devices TR0 notify a fire alarm (sound an alarm sound) when a fire is detected by at least one fire alarm device TR0 in this way, it is hereinafter referred to as “linked sounding”. .

  When the control unit 6 of the master station TR1 receives the response message (ACK) from all the other slave stations TR3 and TR4, the control unit 6 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 is assigned to the child station TR2, the second time slot is assigned to the child station TR3, and the third time slot is assigned to the child station TR4.

  Here, 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, the communication path between the slave 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,. Exhaustion becomes intense. Therefore, in the present embodiment, as described above, one fire alarm device TR1 is a master station, and other fire alarm devices TR2,... Are slave stations, and the master station TR1 sends a fire alarm message to each slave station TR2,. Other messages (described later) are notified. As a result, even when there are slave stations that cannot establish a communication path with each other, the interlocking ringing can be reliably performed.

  Also, when all the fire alarms TR0 sound an alarm sound and the linked sounding is started, the control unit 6 of the master station TR1 includes the fire alarm message M1 (see FIG. 4) by including it in the synchronous beacon. It is repeatedly transmitted to all the slave stations TR2,. Then, the control unit 6 of each slave station TR2,... Checks the state of the alarm unit 3 every time the fire alarm message M1 transmitted from the master station TR1 is received, and if the alarm unit 3 is stopped, the alarm unit 3 causes the alarm to sound again.

  As described above, in the present embodiment, after fire alarms are started to be notified by all the fire alarm devices TR0, collision can be avoided by performing wireless communication by time division multiple access (TDMA). Furthermore, in this embodiment, the fire alarm message M1 is included in the synchronous beacon and periodically transmitted from one fire alarm (master station) TR1 to all other fire alarms (slave stations) TR2,. Thus, it is possible to reliably notify the fire alarm. As a result, a plurality of fire alarm devices TR0 can be effectively linked while avoiding radio signal collision. Moreover, in this embodiment, since fire alarms are notified by all fire alarm devices TR0 in the event of a fire, the user has more opportunities to perceive the fire alarm (listen to the alarm sound) to improve safety. Can do.

  Incidentally, in the above communication operation, the timings at which the fire alarm devices TR1, TR2,... Start operation (the timer starts counting the intermittent reception interval T1) do not normally coincide. For this reason, the timing (refer to the downward arrow in FIG. 3) at which the control unit 6 of each fire alarm device TR1, TR2,... On the other hand, in this embodiment, as shown in FIG. 3, when the synchronization signal is received by the wireless transmission / reception unit 2 of each fire alarm device TR1, TR2,..., The control unit 6 sets the intermittent reception interval T1 by the timer. Stop counting. And the control part 6 restarts the count of the intermittent reception interval T1 by a timer when the fixed standby | waiting time T2 passes from the end time (t = t0) of a synchronizing signal.

  Therefore, after receiving the synchronization signal, the fire alarm devices TR1, TR2,... Have the same timing to complete the counting of the intermittent reception interval T1, so that the radio signal transmitted from one radio station is transmitted. 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 power consumption and extending battery life. .

  In the present embodiment, a radio signal including a periodic monitoring message transmitted from the master station TR1 to the slave stations TR2,... At a constant cycle is also used as a synchronization signal. For this reason, since periodic monitoring and synchronization of each fire alarm device TR1, TR2,... Can be performed collectively, power consumption is reduced compared to the case where a radio signal including a periodic monitoring message and a synchronization signal are individually transmitted. can do. In addition, this configuration has an advantage that the system configuration can be simplified because a dedicated transmitter (transmitting station) for transmitting the synchronization signal is not required.

  By the way, when the master station TR1 transmits a synchronization signal to each slave station TR2,..., Fading occurs due to the movement of a person existing in the space, and the received signal strength of the radio signal at each slave station TR2,. May fluctuate. For this reason, at the time of transmission of the synchronization signal, for example, when the received signal strength of the slave station TR2 varies, there is a possibility that the slave station TR2 cannot receive the synchronization signal and the operation check cannot be performed normally. When the slave station TR2 cannot receive the synchronization signal in this way, the master station TR1 determines that an error has occurred in the slave station TR2 because there is no reply even if the slave station TR2 is normal. Alarm sound.

  Therefore, in the present embodiment, the control unit 6 of the master station TR1 (one radio station) is based on the received signal strength (reception level) of the radio signal received by each slave station TR2,... (Other radio station). The transmission timing of the synchronization signal (periodic wireless signal) is determined. As an example, a configuration in which the control unit 6 of the master station TR1 sets a time zone in which the fluctuation of the received signal strength of each of the slave stations TR2,. Note that “a time period in which the variation in received signal strength is relatively small” means that the width of the variation in the received signal strength is small compared to other time zones. Examples of the time zone in which the fluctuation of the received signal intensity is relatively small include midnight when a person is asleep.

  As described above, the control unit 6 of the master station TR1 sets the transmission timing of the synchronization signal in a time zone in which the fluctuation of the received signal strength is relatively small, so that each slave station TR2,. A situation in which the synchronization signal cannot be received can be avoided. As a method of setting the transmission timing as described above, for example, a fixed time (for example, 16 hours) is counted with a timer based on the time when the power of the master station TR1 is switched on or the time when the synchronization signal is transmitted, A method of transmitting a synchronization signal at the end of counting can be considered.

  In addition, the master station TR1 includes a clock unit for measuring the current time, and when the clock unit indicates a preset time (for example, 2:00 am), a synchronization signal is transmitted to each of the slave stations TR2,. A method is also conceivable. Also in this case, as described above, since the synchronization signal can be transmitted in a time zone in which the variation in the received signal strength is relatively small, each slave station TR2,... Receives the synchronization signal due to the variation in the received signal strength. It is possible to avoid a situation where it becomes impossible.

  As another embodiment, a time distribution of the received signal strength in each of the slave stations TR2,... Is obtained, and a time zone in which the fluctuation of the received signal strength is relatively small is set as the synchronization signal transmission timing based on the time distribution. Configuration is conceivable. That is, when each of the slave stations TR2,... Receives the synchronization signal transmitted from the master station TR1, it measures the received signal strength when received. Each slave station TR2,... Includes the measured received signal strength data in the reply signal and returns it to the master station TR1.

  The control unit 6 of the master station TR1 associates the received signal strength data included in the return signal from each slave station TR2,... With the return time of the return signal (or the transmission time of the corresponding synchronization signal). It is stored in (memory unit 6A). Then, the control unit 6 of the master station TR1 obtains a time distribution of the received signal strength from the data of the received signal strength, and based on the time distribution, a time zone in which the fluctuation of the received signal strength is relatively small (FIG. 1 (b ) Is set to “A1”). Here, the time distribution of the received signal strength is obtained using the average value of the received signal strength of each of the slave stations TR2,.

  As a method for obtaining a time zone in which fluctuations in received signal strength are relatively small, for example, there are the following methods. That is, the above time distribution is divided into fixed intervals, the fluctuation width of the received signal strength in each section (that is, the difference between the maximum value and the minimum value of the received signal strength) is obtained, and the fluctuation is relative to the section where the fluctuation width is the smallest. There is a method of setting as a small time zone. In addition, there is a method in which a section having a fluctuation width of 50% or less of the fluctuation width of the section having the largest fluctuation width is defined as a time zone in which the fluctuation of the received signal strength is relatively small. Of course, the method for determining such a time zone need not be limited to the above.

  As described above, the control unit 6 of the master station TR1 sets the transmission timing of the synchronization signal in a time zone in which the fluctuation of the received signal strength is relatively small, so that each slave station TR2,. A situation in which the synchronization signal cannot be received can be avoided.

  Is obtained individually for each slave station TR2,..., And the transmission timing of the synchronization signal to each slave station TR2,... Is based on each time distribution of the received signal strength of each slave station TR2,. May be set individually. In this case, it is possible to set an optimal transmission timing according to the installation environment of each of the slave stations TR2,.

  By the way, a probability distribution of the received signal strength is obtained based on the received signal strength of the radio signal received by each of the slave stations TR2,..., And based on this probability distribution, the number of times of transmission of the synchronization signal per cycle (hereinafter, simply “ May be set (refer to FIG. 4). That is, when each of the slave stations TR2,... Receives the synchronization signal transmitted from the master station TR1, it measures the received signal strength when received. Each slave station TR2,... Includes the measured received signal strength data in the reply signal and returns it to the master station TR1.

The control unit 6 of the master station TR1 obtains an average value and variance from the received signal strength data included in the return signal from each of the slave stations TR2,..., And uses the average value and variance to determine the received signal strength as a random variable. A probability distribution having a probability density function is obtained. Here, the probability distribution of the received signal strength is obtained using the average value of the received signal strength of each of the slave stations TR2,. Further, the control unit 6 of the master station TR1 assumes that it is difficult to receive a radio signal when the received signal strength is less than a predetermined value, and the received signal strength is less than the predetermined value based on the average value and variance of the probability distribution. The probability x is calculated. Then, assuming that the probability of successful radio signal reception is p and the number of transmissions is n, the control unit 6 of the master station TR1 sets the number of transmissions n so as to satisfy p ≧ 1- ^xn .

For example, it is assumed that it is difficult to receive a radio signal when the received signal strength is −100 dBm or less. Then, based on the average value and variance of the probability distribution of received signal strength, it is assumed that the probability that the received signal strength is −100 dBm or less is 0.1. Here, if the target value of the probability p of successful radio signal reception is 0.9999, 0.9999 = 1− (0.1) ⁿ from the above equation. For this reason, the control unit 6 of the master station TR1 sets the number n of transmissions of the synchronization signal to four.

  Then, the control unit 6 of the master station TR1 transmits the synchronization signal four times to each of the slave stations TR2,... In each cycle of transmitting the synchronization signal. In this example, each slave station TR2,... Has a probability of receiving at least any one of the synchronization signals transmitted four times, which is 0.9999. The synchronization signal can be received almost certainly.

  As described above, the control unit 6 of the master station TR1 sets the number of transmissions of the synchronization signal based on the probability distribution of the received signal strength, so that the synchronization signal is sent to each slave station TR2,... Without setting the transmission timing. Can be received. Therefore, it is possible to avoid a situation in which each slave station TR2,... Cannot receive the synchronization signal due to fluctuations in the received signal strength.

  It is to be noted that a probability distribution of received signal strength is obtained individually for each slave station TR2,..., And one period of a synchronization signal for each slave station TR2,... Based on each probability distribution of received signal strength of each slave station TR2,. The number of hit transmissions may be set individually. In this case, it is possible to set the optimum number of transmissions according to the installation environment of each of the slave stations TR2,.

  Of course, both the transmission timing of the synchronization signal and the number of retransmissions may be determined based on the received signal strength. In this case, it is possible to further increase the probability of avoiding a situation in which the wireless station cannot receive a wireless signal due to fluctuations in received signal strength.

  By the way, when the time distribution or probability distribution of the received signal strength is obtained, it is desirable that the number of received signal strength data is larger. However, since the transmission interval of a normal synchronization signal is as long as 24 hours, for example, it takes a very long time to secure a sufficient number of data to obtain each distribution.

  Therefore, an arbitrary fixed period is set as a test period, and wireless communication is performed between the master station TR1 and each of the slave stations TR2,... A desired number of data may be obtained. For example, a fixed period (for example, 24 hours) from the time when the power of the master station TR1 is switched on is set as the test period, and the control unit 6 of the master station TR1 performs a test for each slave station TR2,. It is conceivable to configure to transmit a synchronization signal. In this case, only one received signal strength data can be obtained from each of the slave stations TR2,... At a normal synchronization signal transmission interval, whereas 100 or more received signal strength data can be obtained. Thus, by setting the test period, it is possible to secure a sufficient number of data to obtain each distribution of received signal strength in a short period.

  Of course, when the master station TR1 has already secured a sufficient number of data to obtain each distribution of received signal strength, it is not necessary to set the above test period. During the test period, the radio signal transmitted from the master station TR1 to each of the slave stations TR2,. That is, the radio signal transmitted by the master station TR1 may be any radio signal that instructs each slave station TR2,... To send back the data including the received signal strength data.

  In addition, the radio station of this embodiment is not limited to the above-mentioned fire alarm device TR0. For example, the wireless communication system of the present embodiment may be constructed using a wireless station other than the fire alarm TR0.

  For example, the wireless communication system of the present embodiment may be constructed using a wireless station having an air quality sensor that measures a so-called air quality such as humidity in the air. An example of an air quality sensor is a gas sensor. Gas sensors measure fuel gas such as city gas and LP gas, COx gas components that measure the environment, such as carbon dioxide and carbon monoxide, or other gas components and dirt such as dust floating in the air. To do. As a radio station having this gas sensor, there is a gas alarm device that notifies the occurrence of gas leakage or incomplete combustion with an alarm sound.

  Moreover, you may construct | assemble the radio | wireless communications system of this embodiment using the radio station which has a human sensor which detects presence of a person. The human sensor is a method of detecting the presence of a person by detecting infrared rays emitted from the human body, or a method of detecting the presence of a person by performing image processing analysis on an image obtained by imaging a target area. It is possible to adopt. Or you may employ | adopt as a human sensor combining the said both systems.

  Further, a wireless communication system may be constructed by mixing a wireless station having the air quality sensor or a wireless station having a human sensor with the wireless fire alarm TR0 described above. In this case, it is possible to construct a wireless communication system that serves not only for fire detection but also for the purpose of human body detection and ventilation warning.

DESCRIPTION OF SYMBOLS 1 Antenna 2 Wireless transmission / reception part (Transmission means, reception means)
6 Control unit (transmission control means, reception control means, timer means)
7 Power supply (power supply means)
TR1, TR2 Fire alarm (radio station)

Claims (6)

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 of the radio stations receives a radio signal using a plurality of antennas, a transmission unit that transmits a radio signal using any one of the antennas, and any one of the antennas. A wireless transmission / reception unit having a reception unit configured to activate the transmission unit when a predetermined event occurs, transmit a radio signal including a message corresponding to the event during a predetermined transmission period, and perform radio transmission during a predetermined pause period The operation of pausing the transmission of the signal is alternately repeated, and the transmission means for stopping the transmission means when the event has not occurred, the timer means for repeatedly counting a constant intermittent reception interval, and the intermittent by the timer means While the reception interval is being counted, the reception unit is stopped, and every time the intermittent reception interval is counted by the timer unit, And a control unit having a receiving control means for activating the reception means, a feeding means for feeding the operating power to each unit of the battery as the power source,
The control unit of one radio station among the radio stations activates the transmission means to periodically transmit radio signals to other radio stations,
The control unit of the one radio station may determine the transmission timing of the periodic radio signal or the number of transmissions per period of the periodic radio signal based on the reception level of the radio signal in the other radio station. A wireless communication system, wherein at least one of them is set.   2. The wireless communication system according to claim 1, wherein the control unit of the one wireless station sets the transmission timing of the periodic wireless signal in a time zone in which the variation of the reception level is relatively small. .   The control unit of the one radio station obtains a time distribution of the reception level by transmitting and receiving a radio signal to and from the other radio station, and the fluctuation of the reception level is relatively based on the time distribution. The wireless communication system according to claim 1, wherein the transmission timing of the periodic wireless signal is set in a small time zone.   The control unit of the one radio station obtains a probability distribution of the reception level by transmitting / receiving a radio signal to / from the other radio station, and 1 of the periodic radio signal is obtained based on the probability distribution. The radio communication system according to claim 1, wherein the number of transmissions per period is set.   The control unit of the one radio station sets an arbitrary fixed period as a test period, and transmits a radio signal to the other radio station at an interval shorter than the periodic radio signal transmission interval in the test period. 5. The wireless communication system according to claim 3, wherein the data of the reception level is obtained by transmitting / receiving data between the wireless communication systems. Each wireless station is at least one of a fire alarm that detects the occurrence of a fire, a wireless station that has an air quality sensor that measures air quality, and a wireless station that has a human sensor that detects the presence of a person. The wireless communication system according to claim 1, wherein there is a wireless communication system.

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