JP2006245666A - Wireless communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a noise from being misrecognized as a wireless carrier in a wireless communication system comprising a wireless master unit and a wireless slave unit for making communication with each other by employing the specified low power wireless communication. <P>SOLUTION: When demodulation data of the received wireless carrier are dissident with demodulation data of a call signal stored in advance from the wireless master unit, the wireless slave unit discriminates the received wireless carrier to be a noise B, requests the wireless master unit to transmit a test wireless signal, and receives the test wireless signal A<SB>2</SB>from the wireless master unit. Correcting a threshold value Th for detecting the wireless carrier to be greater than the amplitude of the noise B and to be equal to or less than the amplitude of the test wireless signal A<SB>2</SB>prevents the noise B from being misrecognized as the wireless carrier from the wireless master unit. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  In the present invention, in response to a call signal from the wireless master device, the wireless slave device transmits meter reading data such as gas and water to the wireless master device, and the wireless master device transmits the received meter reading data to the center device via the network. The present invention relates to a radio communication system suitable for use in a meter reading data collection system that transmits data.

  In recent years, a meter reading data collection system that automatically collects meter reading data such as a gas meter by a remote center device using a telephone line has been put into practical use. This system is installed in close proximity to each home gas meter, etc., and receives the measurement value transmitted from the wireless slave unit that transmits the measurement value (meter reading data) of the meter by specific low-power radio. And a wireless master device that transmits the measured value to the center device via a public line (see Patent Document 1).

In this system, the wireless master unit that has received a periodic meter reading request from the center device requests transmission of meter reading data to the wireless slave unit. If the wireless slave unit is battery-powered, the power consumption of the wireless slave unit is In order to save energy, the wireless slave unit is driven intermittently. That is, power is supplied to the wireless communication unit of the wireless slave unit for a certain period of time (for example, 1 to 500 msec) every predetermined time (for example, 1 to 60 seconds), and the presence or absence of a calling signal (transmission request for meter reading data) from the wireless master unit The intermittent drive is canceled only when the call signal is confirmed, and the meter value is measured and transmitted. Here, the presence / absence of a paging signal is checked by first determining the presence / absence of a radio carrier in the target frequency band, and if there is, the radio carrier is demodulated to determine whether an ID addressed to itself is included. The process which determines is performed. If the calling signal from the wireless master unit is not confirmed within a certain time, the power supply to the wireless communication means is stopped until the next predetermined time comes. This makes it possible to extend the battery life in the wireless slave unit.
Japanese Patent Laid-Open No. 7-184278

  However, in the above system, since the reception operation of the wireless slave unit is performed for a certain period of time, even if noise is mixed in the target frequency band within the certain period of time, it is misidentified as a wireless carrier and the presence or absence of a call signal By performing this check operation, useless power may be consumed. In the specific low-power radio used for communication between the radio base unit and the radio slave unit in the system, whether or not a radio carrier exists in a frequency band to be transmitted before transmission. In the environment where noise is always generated within the target frequency band, the noise is transmitted between the wireless master unit and the wireless slave unit. If it is mistaken for a wireless carrier used for communication, the wireless master unit may not be able to transmit a call signal, and the wireless slave unit may not be able to transmit meter reading data.

  The present invention has been made in view of such problems. The purpose of the present invention is to detect a radio carrier when starting transmission and to transmit to a counterpart communication terminal when the radio carrier is not detected. In a wireless communication system including a pair of wireless communication terminals to be started, by preventing a situation in which the wireless communication terminal misidentifies noise in the wireless carrier band as a wireless carrier, wasteful power consumption is reduced and transmission is disabled. It is to realize the prevention of falling.

The invention according to claim 1 is a wireless communication system comprising a pair of wireless communication terminals that detect a radio carrier when starting transmission and start transmission to a communication counterpart terminal when the wireless carrier is not detected. The radio communication terminal includes a carrier amplitude detection unit that detects an amplitude of a radio carrier from the communication partner terminal, a noise amplitude detection unit that detects an amplitude of noise within a band of the radio carrier, and a carrier amplitude detection unit. Carrier detection threshold setting means for setting a carrier detection threshold larger than the amplitude of the noise detected by the noise amplitude detection means and less than or equal to the amplitude of the radio carrier detected by the carrier amplitude detection means A wireless communication system is characterized.
The invention according to claim 2 is the wireless communication system according to claim 1, further comprising means for periodically operating the carrier amplitude detection means, the noise amplitude detection means, and the carrier detection threshold setting means. A wireless communication system.
The invention according to claim 3 is the radio communication system according to claim 2, further comprising carrier amplitude storage means for storing the carrier amplitude detected by the carrier amplitude detection means, and the carrier amplitude detection means during the regular operation. When the amplitude of the wireless carrier from the communication partner terminal cannot be detected, the carrier detection threshold setting means sets the threshold using the carrier amplitude previously stored in the carrier amplitude storage means, A wireless communication system.

(Function)
According to the first aspect of the present invention, in the wireless communication terminal, the wireless carrier amplitude detection is performed based on the detection result of the wireless carrier amplitude from each other communication partner terminal and the detection result of the noise amplitude in the wireless carrier band. By setting the threshold value higher than the noise amplitude and lower than the radio carrier amplitude, even if the wireless communication terminal receives noise within the radio carrier band, it will not be mistaken for a radio carrier, so unnecessary reception processing starts. And no transmission failure occurs.
According to the second aspect of the invention, it is possible to cope with fluctuations in the radio carrier amplitude and noise amplitude of the radio communication terminal by periodically updating the radio carrier detection threshold.
According to the third aspect of the present invention, when the radio carrier detection threshold is regularly updated, even if the latest radio carrier amplitude cannot be detected, the detected value of the previous radio carrier amplitude is used instead. By doing so, the threshold value is updated to cope with fluctuations in noise amplitude.

  According to the present invention, in a wireless communication system comprising a pair of wireless communication terminals that detect a radio carrier when starting transmission and start transmission to a communication counterpart terminal when the wireless carrier is not detected, It is possible to prevent a situation in which noise in the band is mistaken as a wireless carrier, to reduce wasteful power consumption and to prevent occurrence of a transmission disabled state.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram for explaining a configuration of a meter reading data collection system according to an embodiment of the present invention. This data communication system is connected to a mobile phone base station 8 via a radio handset 1 to which a meter 2 is connected, a radio base unit 3 to which a mobile phone radio modem 4 is connected, a center modem 6 and an exchange 7. Center device 5.

  The meter 2 is a measuring instrument that measures a gas usage fee. The wireless slave device 1 and the wireless master device 3 communicate FSK (Frequency Shift Keying) modulation data using a specific low power radio wave. The wireless master device 3 and the center device 5 perform data communication via the mobile phone wireless modem 4, the mobile phone base station 8, the exchange 7, and the center modem 6. The wireless slave device 1 operates using a battery as a driving power source. The wireless master device 3 operates using a battery or a commercial AC power source as a driving power source.

  An outline of the operation of this wireless communication system will be described. The center device 5 sends a meter reading data request signal for requesting meter reading data of the meter 2 via the center modem 6, the exchange 7, and the cell phone base station 8 at a predetermined time, for example, one day per month. Send to. The meter reading data request signal is received by the mobile phone wireless modem 4 and sent to the wireless master unit 3. When the wireless master device 3 receives the meter reading data request signal, the wireless master device 3 transmits a calling signal for requesting meter reading data of the meter 2 to the wireless slave device 1 using a specific low power radio wave. The wireless handset 1 performs a reception operation intermittently (for example, 30 msec every 25 seconds), checks the presence or absence of a call signal from the wireless base unit during the reception operation, and releases the intermittent drive only when the call signal is confirmed. The meter reading data of the meter 2 is transmitted to the wireless master device 3. The wireless master device 3 transmits the received meter reading data of the meter 2 to the center device 5 using the mobile phone wireless modem 4. Although the number of the wireless slave units 2 is one here, two or more wireless slave units may be combined with the wireless master unit 3. In this case, it sets so that the mutual reception operation | movement timing of a some radio | wireless handset may not overlap. Further, here, the wireless master device 3 and the mobile phone wireless modem 4 are configured separately, but they may be configured integrally.

  Next, the internal configuration of the wireless slave device 1 will be described with reference to the block diagram shown in FIG. The wireless slave unit 1 includes a control unit 11 that controls the entire wireless slave unit, an antenna switching unit 12 connected to an antenna, a reception unit 13 and a transmission unit 14 connected to the control unit 11, respectively, wired communication The interface unit 15, the storage unit 16, the operation unit 17, the visual display unit 18 including LEDs and the like, the sound output unit 19 including a buzzer and the like, and the power source unit 20 for supplying driving power to the above-described units. The receiving unit 13 has an input side connected to the receiving side of the antenna switching unit 12, and an output side connected to the control unit 11. The transmission unit 14 has an input side connected to the control unit 11, and an output side connected to the transmission side of the antenna switching unit 12. The wired communication interface unit 15 is an interface between the control unit 11 and the external meter 2.

  The antenna switching unit 12 is switched under the control of the control unit 11, and outputs a reception signal from the antenna to the reception unit 13 during a reception operation, and outputs an output signal of the transmission unit 14 to the antenna during a transmission operation.

  The receiving unit 13 is supplied with driving power from the power source unit 20 only when the intermittent driving timer 11a built in the control unit 11 is operating, and performs an intermittent receiving operation. During the reception operation, the wireless carrier detection signal (carrier sense), the amplitude data of the wireless carrier, and the demodulated data are output to the control unit 11. Here, one of the 20 receivable channels of the receiving unit 13 is set in advance when the wireless master device 3 and the wireless slave device 1 are installed, and is registered in the receiving channel register of the storage unit 16, During the reception operation, the data is read by the control unit 11 and set in the reception unit 13. The carrier sense threshold value is set as a default value at the time of shipment of the wireless master device 3 and the wireless slave device 1, and is registered in advance in the threshold register of the storage unit 16, and is read out by the control unit 11 during the reception operation. Is set in the receiver 13. Further, the carrier sense threshold is measured by measuring the radio field intensity of the other party when the wireless master unit 3 and the wireless slave unit 1 are installed, and the set value is corrected according to the measured value. (When the handset 1 detects noise), the radio base station 3 and the wireless handset 1 can cope with fluctuations in the radio wave transmission / reception environment. Details of the carrier sense threshold setting procedure will be described later. The reception channel number, the carrier sense threshold, and the installation location of the wireless slave device 1 are notified to the center device 5 via the wireless master device 3 and stored.

  When the control unit 11 confirms that the demodulated data from the receiving unit 13 is a calling signal having an ID addressed to itself transmitted from the wireless master device 3, the meter reading data of the meter 2 is transmitted via the wired communication interface unit 15. Read and output to the transmitter 14 as data for transmission. The transmission unit 14 modulates the FSK carrier with the transmission data to generate an FSK modulated wave, amplifies it, and outputs it to the antenna switching unit 12. The FSK modulated wave passes through the antenna switching unit 12 and is transmitted from the antenna to the wireless master device 3. Here, as for the transmission channel of the transmission unit 14, one of the 20 channels that can be transmitted is set in advance when the wireless master device 3 and the wireless slave device 1 are installed, and is registered in the transmission channel register of the storage unit 16. During the transmission operation, the data is read by the control unit 11 and set in the transmission unit 14. Further, this transmission channel number is notified to the center device 5 via the wireless master device 3 at the time of installation and stored.

  The operation unit 17 is a switch, a button, or the like, and is used when the user sets the wireless slave device 1 or the like. The visual display unit 18 and the audio output unit 19 operate when the control unit 11 detects that the reception unit 13 has received the jamming radio wave. The procedure for detecting the reception of jamming radio waves will be described later. The power supply unit 20 is composed of a battery and a regulator that stabilizes the output voltage. The power supply unit 20 always supplies power for driving to the control unit 11, and is driven only for a predetermined time according to the control of the control unit 11 to the other parts. Supply power.

  Next, the internal configuration of the wireless master device 3 will be described with reference to the block diagram shown in FIG. The wireless master device 3 includes a control unit 21 that controls the entire wireless master device 1, an antenna switching unit 22 connected to the antenna, a receiving unit 23, a transmitting unit 24, a modem connected to the control unit 21, respectively. An interface unit 25, a storage unit 26, an operation unit 27, a visual display unit 28 including LEDs and the like, an audio output unit 29 including a buzzer and the like, and a power source unit 30 for supplying driving power to the above-described units. The receiving unit 23 has an input side connected to the receiving side of the antenna switching unit 22 and an output side connected to the control unit 21. The transmission unit 24 has an input side connected to the control unit 21, and an output side connected to the transmission side of the antenna switching unit 22. The modem interface unit 25 is an interface between the control unit 21 and the external mobile phone wireless modem 4.

  When the control unit 21 receives the meter-reading data request signal transmitted from the center device 5 via the mobile phone wireless modem 4 and the modem interface unit 25, the control unit 21 transmits transmission data for a call signal to be transmitted to the wireless slave unit 1. Send to 24. The transmission unit 24 modulates the FSK carrier with the transmission data to generate an FSK modulated wave, amplifies it, and outputs it to the antenna switching unit 22. The FSK modulated wave passes through the antenna switching unit 22 and is transmitted from the antenna to the wireless slave unit 1. Here, as for the transmission channel of the transmission unit 24, one of the 20 channels that can be transmitted is set in advance when the wireless master device 3 and the wireless slave device 1 are installed, and is registered in the transmission channel register of the storage unit 26, During the transmission operation, the data is read by the control unit 21 and set in the transmission unit 24. The transmission channel number is notified to the center device 5 at the time of installation and stored.

  The receiving unit 23 outputs a radio carrier detection signal (carrier sense), amplitude data and demodulated data of the radio carrier to the control unit 21 during the operation. Here, one of the 20 receivable channels of the receiving unit 23 is set in advance when the wireless master device 3 and the wireless slave device 1 are installed, and is registered in the receiving channel register of the storage unit 26. During reception operation, the data is read by the control unit 21 and set in the reception unit 23. The carrier sense threshold is set to a default value at the time of shipment of the wireless master device 3 and the wireless slave device 1 and is registered in the threshold register of the storage unit 26, and is read out by the control unit 21 during the reception operation. It is set in the receiving unit 23. Furthermore, the carrier sense threshold value is measured when the radio master unit 3 and the radio slave unit 1 are installed, and the other party's radio wave intensity is measured, and the set value is corrected according to the measured value. When the base unit 3 detects noise), it is updated to cope with fluctuations in the radio wave transmission / reception environment between the base unit 3 and the base unit 1. The reception channel number, carrier sense threshold, and installation location of the wireless master device 3 are notified to the center device 5 at the time of installation and stored.

  When the control unit 21 confirms that the demodulated data from the receiving unit 23 is meter reading data of the meter 2, the control unit 21 transmits the meter reading data to the center device 5 via the modem interface unit 25 and the cellular phone modem 4. The center device 5 stores the received meter reading data.

  The operation unit 27 is a switch, a button, or the like, and is used when a user sets a transmission / reception channel number and a reception threshold when the user installs the wireless master device 3 as will be described later. The visual display unit 28 and the audio output unit 29 are used for displaying or confirming the setting contents. Further, it operates also when the control unit 21 detects that the receiving unit 23 has received the jamming radio wave. The power supply unit 30 includes a commercial AC power supply and a regulator that stabilizes the output voltage thereof, and constantly supplies driving power to each unit.

  The configuration and normal operation of the wireless slave device 1 and the wireless master device 2 have been described above. Next, a procedure for setting a carrier sense threshold when the wireless master device 3 and the wireless slave device 1 are installed will be described with reference to FIGS. Here, FIG. 4 is a flowchart showing a procedure for setting the carrier sense threshold value of the wireless slave device 1 when the wireless master device 3 and the wireless slave device 1 are installed, and FIG. 5 is a diagram showing the received electric field strength waveform and the threshold value. is there.

First, the wireless master device 3 and the wireless slave device 1 are installed at predetermined locations (step S1), and a test switch provided on the operation unit 17 of the wireless slave device 3 is pressed (step S2). When detecting the pressing of the test switch, the control unit 11 of the wireless slave device 1 generates a test wireless signal, sends it as transmission data to the transmission unit 14, and transmits it to the wireless master device 3 (step S3). When the wireless master device 3 receives the test wireless signal transmitted from the wireless slave device 1, the wireless master device 3 transmits to the wireless slave device 1 a test wireless signal (same waveform as the calling signal) A ₁ as shown in FIG. .

The wireless slave device 1 receives the test wireless signal A ₁ transmitted from the wireless master device 3 (step S4), detects the amplitude at the reception unit 13, and outputs the detected amplitude to the control unit 11 as a carrier amplitude. The control unit 11 stores the input carrier amplitude, that is, the value corresponding to the electric field strength of the test radio signal, and the demodulated data of the test radio signal in the storage unit 16 (step S5). Then, the control unit 11, a threshold Th1 which is set by default in the threshold register of the storage unit 16, as shown in FIG. 5 (b), according to the electric field strength of the test radio signal A ₁ stored in step S5, For example, correction is performed so that the electric field intensity is about 50% (step S6).

  FIG. 4 shows a threshold setting procedure in the wireless slave unit 1. In the wireless master unit 3, a receiving unit is transmitted according to the electric field strength of the test wireless signal transmitted from the wireless slave unit 1 in step S 3 of FIG. 4. A threshold at 23 can also be set.

  Next, referring to FIGS. 6 and 7, a procedure for correcting the carrier sense threshold when noise is received during the intermittent reception operation after the wireless master device 3 and the wireless slave device 1 are installed will be described. FIG. 6 is a flowchart showing a procedure for correcting the carrier sense threshold, and FIG. 7 is a diagram showing a received electric field intensity waveform, a noise waveform, and a threshold when the carrier sense threshold is corrected.

  First, intermittent reception is started by starting the intermittent drive timer 11a (step S11), and the presence or absence (carrier sense) of a wireless carrier from the receiving unit 13 is determined (step S12). If there is no wireless carrier, this determination process is repeated until the intermittent drive timer 11a expires. If there is a radio carrier, it is determined whether or not the demodulated data matches the demodulated data of the paging signal stored in advance in the storage unit 16 (step S13). When it is determined that they match, a normal communication process, that is, a process of receiving meter reading data of the meter 2 and transmitting it to the wireless master device 3 is executed (step S14).

When it is determined in step S13 that the demodulated data of the call signal A ₂ stored in the storage unit 16 in advance and the demodulated data of the received radio carrier B do not match, as shown in FIG. The received radio carrier B is determined to be noise, and a test radio signal is transmitted to the radio cell station 3 as in step S3 (step S15). At this time, the amplitude of the wireless carrier B is stored in the storage unit 16.

When the wireless master device 3 receives the wireless test signal transmitted from the wireless slave device 1, the wireless master device 3 transmits a test wireless signal A ₂ as shown in FIG. 7B to the wireless slave device 1. Radio personal station 1 receives a radio base unit 3 has been tested radio signal A ₂ transmitted from (step S16), and detects the amplitude at the receiving unit 13, and outputs to the control unit 11 as a carrier amplitude. The control unit 11 stores the input carrier amplitude, that is, a value corresponding to the electric field strength of the test radio signal A _{2 in} the storage unit 16 (step S17). Next, the control unit 11 corrects the threshold value set in the threshold value register of the storage unit 16 based on the electric field strength stored in Step S17 and the noise level stored in Step S15 (Step S18). For example, as shown in FIG. 7B, when the amplitude of the noise B is larger than the threshold value Th2, a value larger than the amplitude of the noise B and smaller than the amplitude of the test radio signal A ₂ as shown in FIG. Figure in corrects the threshold Th3 is a noise amplitude and substantially intermediate value of the amplitude of the test radio signal a ₂ of B). Here, the test radio signal transmitted in step S15, or can not receive the test radio signal in step S16, if it could not be measured electric field strength of the test radio signal A ₂ from the radio base unit 3, the previously stored test The threshold is set using the amplitude of the radio signal.

  6 shows a threshold value correction procedure in the wireless slave unit 1. In the wireless master unit 3, a receiving unit is transmitted according to the electric field strength of the test wireless signal transmitted from the wireless slave unit 1 in step S15 in FIG. A threshold at 23 can also be set. In addition, by transmitting the set and corrected threshold values, the date and time when they were executed, the noise level, and the reception date and time to the center device 5, the center device 5 can know the tendency of the noise detection frequency, etc. Time correspondence becomes easy. Further, by periodically correcting the threshold value, it is possible to cope with the noise level and the seasonal variation of the transmission signal level from the wireless master device 3.

It is a figure for demonstrating the structure of the data communication system which concerns on embodiment of this invention. It is a block diagram which shows the internal structure of the radio | wireless subunit | mobile_unit in FIG. It is a block diagram which shows the internal structure of the wireless main | base station in FIG. It is a flowchart which shows the procedure which sets the threshold value of the carrier sense of a radio | wireless subunit | mobile_unit when installing the radio | wireless parent | base station and radio | wireless slave | mobile_unit which concern on embodiment of this invention. It is a figure which shows the received electric field strength waveform and threshold value in a wireless cordless handset. It is a flowchart which shows the procedure which correct | amends the threshold value of the carrier sense in embodiment of this invention. It is a figure which shows the received electric field strength waveform, noise waveform, and threshold value when correcting the threshold value of the carrier sense in the embodiment of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Wireless cordless handset, 2 ... Meter, 3 ... Wireless master phone, 5 ... Center apparatus, 11, 21 ... Control part, 13, 23 ... Reception part, 14, 24 ... Transmission unit.

Claims (3)

In a wireless communication system comprising a pair of wireless communication terminals that perform detection of a wireless carrier when starting transmission and start transmission to a communication counterpart terminal when the wireless carrier is not detected,
The radio communication terminal includes a carrier amplitude detection unit that detects an amplitude of a radio carrier from the communication partner terminal, a noise amplitude detection unit that detects an amplitude of noise within a band of the radio carrier, and a carrier amplitude detection unit. Carrier detection threshold setting means for setting a carrier detection threshold larger than the amplitude of the noise detected by the noise amplitude detection means and less than or equal to the amplitude of the radio carrier detected by the carrier amplitude detection means A wireless communication system. The wireless communication system according to claim 1, wherein
A radio communication system comprising means for periodically operating the carrier amplitude detection means, the noise amplitude detection means, and the carrier detection threshold setting means. The wireless communication system according to claim 2, wherein
When carrier amplitude storage means for storing the carrier amplitude detected by the carrier amplitude detection means is provided, and when the carrier amplitude detection means cannot detect the amplitude of the radio carrier from the communication counterpart terminal during the regular operation The wireless communication system is characterized in that the carrier detection threshold value setting means sets a threshold value using the carrier amplitude previously stored in the carrier amplitude storage means.

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