JPH1022896A - Bidirectional radio unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce power consumption by decreasing the number of times of periodical synchronous correction, without using any high-accuracy clock by performing synchronous correction at the time of data communication start, in addition to the periodical synchronous correction. SOLUTION: At specified synchronous correction time, a slave radio equipment 6 performs receiving operation, receives a synchronous correction request signal from a master radio equipment 1 and makes its own clock coincident with the clock of the master radio equipment 1. Thus, the periodical synchronous correction between the master radio equipment 1 and the slave radio equipment 6 is performed. Then, when the transmission/reception part of the slave radio equipment 6 receives a calling signal from the master radio equipment 1 at the time of wait reception, the slave radio equipment 6 is synchronized at the timing of the master radio equipment 1 by a repetition block number contained in the calling signal received by the transmission/reception part during the receiving operation. Thus, in addition to the periodical synchronous correction for matching the clocks of the master radio equipment 1 and the slave radio equipment 6, at the time of data communication start, the synchronous correction is also performed for matching the timing between the master radio equipment 1 and the slave radio equipment 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio system for automatic meter reading that transmits data indicating the usage of gas, water, electricity, etc. between a terminal device and a center device using a telephone line. It relates to a two-way wireless unit to be used.

[0002]

2. Description of the Related Art For example, in a wireless system for automatic meter reading that transmits data indicating the usage amount of gas, water, electricity or the like using a telephone line, a network control device for terminals is provided from a center device via a telephone line by a no-ringing communication method. And the terminal network control device calls the terminal device via a wireless circuit, thereby collecting data from the terminal device in the center device. Also, in response to a call request from the terminal device, the terminal device calls the terminal network control device via the wireless line, and the terminal network control device calls the center device via the telephone line, so that the terminal device can call the center device. Is collected in the center device.

In this type of automatic meter reading radio system, a so-called synchronous system is adopted in which data transmission / reception is performed in a state where the times of the master radio and the slave radio are synchronized. For this reason, each of the master wireless device and the slave wireless device has a built-in clock, and the wireless device is activated only when a predetermined wireless communication time is reached, so that the master wireless device and the slave wireless device can communicate with each other. Data transmission is in progress.

[0004]

In the above-mentioned synchronous system, data transmission between the two radios is performed mutually on the premise that the clocks of the two radios are synchronized. Clocks are provided independently of each other,
As the device is used for a long time, the clocks of the two wireless devices gradually become time-shifted, and eventually become out of synchronization.
For this reason, it is necessary to periodically synchronize the clocks incorporated in both wireless devices.

[0005] However, if the period for periodically synchronizing is lengthened, high-precision clocks for both radios must be used, causing a problem that the cost increases. On the other hand, if the period for periodic synchronization is shortened, the number of processing operations for synchronizing increases, thereby increasing the power consumption of both radios and reducing the battery power that is the operating power supply of both radios. The problem of hastening wear occurs.

In the above-described wireless system for automatic meter reading, a so-called asynchronous system in which data is transmitted without synchronizing the clocks between the two wireless devices may be adopted. Each time data transmission is performed during the wireless period, it is necessary to transmit a communication request signal for synchronizing with the partner wireless device for a relatively long time before data transmission, and if the frequency of data transmission is high, power consumption is low. Increase,
There is a problem that the frequency channel is occupied for a long time.

Therefore, the present invention has been made in view of the above-mentioned problems, and does not use a high-precision clock, but reduces the number of periodic synchronization corrections to reduce power consumption. It is intended to provide.

[0008]

In order to achieve the above object, according to the first aspect of the present invention, a master wireless device and a slave wireless device synchronize with each other at a preset standby time of a fixed period from a partner wireless device. In the two-way wireless unit that confirms the presence / absence of a call signal and continuously transmits and receives data when the call signal is confirmed, the master wireless device and the slave wireless device usually have a clock included therein. At the standby time, a reception operation is performed for a certain period of time to detect the presence or absence of a call signal from the other wireless device at the standby time, and the master wireless device has a cycle longer than the standby time and matches the standby time in advance. At the set synchronization correction time, a synchronization correction signal is transmitted to perform periodic synchronization correction with the slave radio, and the master radio starts data communication by calling the master radio. In the standby time, the master wireless device and the slave wireless device are predicted from the accuracy of the clock of the master wireless device and the slave wireless device and the elapsed time from the periodic synchronization correction. For a time corresponding to the maximum deviation of the standby time, the call signal including the synchronization correction information is continuously transmitted, the synchronization is corrected with the slave wireless device, and thereafter, the slave wireless device and the data of the slave wireless device are continuously transmitted at a prescribed timing. Performs transmission and reception, the slave radio, at the synchronization correction time, receives the synchronization correction signal transmitted by the parent wireless device, performs periodic synchronization correction with the parent wireless device, and the child wireless device When data communication is started by calling a slave wireless device, the standby time is predicted from the accuracy of the clocks of the master wireless device and the slave wireless device and the elapsed time from the periodic synchronization correction. Be said parent radio and front The call signal including the synchronization correction information is continuously transmitted for a time corresponding to the maximum deviation of the standby time with the slave wireless device, the synchronization is corrected with the master wireless device, and thereafter, the master is continued at a prescribed timing. It is characterized by transmitting and receiving data to and from a wireless device.

[0009] In the two-way wireless unit of claim 1,
The parent wireless device is the synchronization correction time, and the parent wireless device and the child wireless device are predicted from the accuracy of the clock and the cycle of the synchronization correction time that the parent wireless device and the child wireless device have. The transmission of the synchronization correction signal may be continuously performed for a time corresponding to the maximum deviation of the standby time.

[0010] In the two-way wireless unit of claim 1,
The slave wireless device, at the synchronization correction time, the master wireless device and the slave wireless device predicted from the accuracy of the clock and the cycle of the synchronization correction time that the master wireless device and the slave wireless device have, The reception operation of the synchronization correction signal may be continuously performed for a time corresponding to the maximum deviation of the standby time.

In the above radio unit, the master radio 1
Transmits a synchronization correction request signal when a specified synchronization correction time comes. The slave wireless device 6 performs a receiving operation when a specified synchronization correction time comes, receives the synchronization correction request signal of the parent wireless device 1, and matches its own clock with the clock of the parent wireless device 1. As a result, periodic synchronization correction between the master wireless device 1 and the slave wireless device 6 is performed.

When data communication is started by a call from the master radio 1, a call signal is continuously transmitted for a time set in accordance with a synchronization shift with the slave radio 6 during standby reception. The child radio 6 is the parent radio 1 at the time of standby reception.
When the call signal is received, the clock of the master wireless device 1 is synchronized with the call signal. Thereafter, data transmission and reception are performed alternately at prescribed timings.

When data communication is started by a call from the child wireless device 6, a call signal is continuously transmitted for a time set according to a synchronization deviation with the parent wireless device 1 at the time of standby reception. The master radio 1 is set to the child radio 6 at the time of standby reception.
When the call signal is received, the clock of the slave radio 6 is synchronized with the call signal. Thereafter, data transmission and reception are performed alternately at prescribed timings.

As described above, by performing the synchronization correction at the start of data communication in addition to the periodic synchronization correction, the number of the periodic synchronization corrections can be reduced.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing the overall configuration of a wireless system for automatic meter reading using a bidirectional wireless unit according to the present invention.

As shown in FIG. 1, the wireless system for automatic meter reading includes a master radio 1, a terminal network controller 2, a telephone line 3,
It has a schematic configuration including an automatic meter reading center device 4, a terminal device 5, and a slave radio device 6. The master radio 1 is a terminal network controller 2
, And the terminal network control device 2 is connected to the automatic meter reading center device 4 via the telephone line 3. Terminal device 5
Is installed in a consumer such as a general household, and is configured by a meter that measures the usage of gas, water, electricity, and the like. The terminal device 5 is connected to a slave radio 6. Master radio 1
And the slave wireless device 6 are connected via a wireless line.

In this automatic meter reading wireless system, the wireless communication is performed between the master wireless device 1 and the slave wireless device 6 via a wireless line, so that the automatic meter reading center device 4 and the terminal device 5 are connected.
Data transmission is performed between the automatic meter reading center device 4 and the data indicating the usage amount of, for example, gas, water, and electricity.

FIG. 2 is a block diagram showing the internal configuration of the master radio and the slave radio used in the radio system. The master wireless device 1 and the slave wireless device 6 have the same configuration except that some of the functions of the CPU are different.

The master wireless device 1 and the slave wireless device 6 have an antenna 7 for transmitting and receiving wireless signals. Antenna 7
Is connected to a modulation / demodulation circuit 9 via a radio section (RF section) 8 which performs FM modulation / demodulation in a radio frequency band of a predetermined frequency. The modulation / demodulation circuit 9 constituting the transmission / reception unit 10 together with the radio unit 8 is supplied with transmission data from the CPU (control unit) 11 and supplies the reception data processed by the radio unit 8 to the CPU 11 via the antenna 7. ing.

Specifically, the digital signal from the CPU 11 is modulated by, for example, an MSK signal or a binary FSK signal. Conversely, the received MSK signal or binary FSK signal is demodulated into a predetermined digital signal.

CPU 11 of parent wireless device 1 and child wireless device 6
(11a, 11b) sequentially switches and selects the radio frequency of the radio unit 8, performs the carrier sense by the selected radio frequency at every predetermined constant period T, and sets the radio signal of the radio unit 8 to receive. The presence or absence of a radio frequency free channel is determined based on the level. Then, when it is determined that there is an empty channel, the transmission / reception unit 10 is controlled to transmit / receive a wireless signal.

An interface circuit 12 and a clock circuit 13 including an oscillator for managing a time when wireless communication is performed with a partner wireless device are connected to the CPUs 11 of the master wireless device 1 and the slave wireless device 6. I have. In addition, a battery 14 serving as an operation power supply is directly connected to the CPU 11.
The interface circuit 12 is connected to the terminal network controller 2 in the case of the parent wireless device 1, and the terminal network controller 2
In the case of the slave wireless device 6, a terminal device 5 composed of a meter is connected, and the level conversion of the data signal from the terminal device 5 is performed.

The battery 14 is connected to the radio section 8 and the modulation / demodulation circuit 9 constituting the transmission / reception section 10 via a power switch 15. The supply / stop of the operating power from the battery 14 to the radio unit 8 and the modulation / demodulation circuit 9 is determined by C
The control is performed based on ON / OFF of the power switch 15 by the PU 11.

The CPU 11a of the master radio 1 has a clock circuit 1
When the specified synchronization correction time is reached for the number 3, the transmission / reception unit 10 is controlled to transmit the synchronization correction request signal shown in FIG. Here, when performing the periodic synchronization correction shown in FIG. 5B, the transmission time of the synchronization correction request signal is set to be longer than the standby reception time of the slave wireless device 1. The transmission time t0 is set to a value fixed in advance from the time corresponding to the synchronization deviation between the master wireless device 1 and the slave wireless device 6 determined by the period of the synchronization correction time periodically performed and the accuracy of the clock circuit. Have been.

FIG. 3 shows the structure of the synchronization correction request signal transmitted by the master radio. The synchronization correction request signal includes a bit synchronization signal, a frame synchronization signal, a device address, synchronization correction request data, master wireless device clock information, and a cyclic code (for example, a CRC code) for error detection. Although not shown, the synchronization correction request signal transmitted from the master wireless device 1 is repeatedly added with a block number in addition to the above configuration. The repetition block number is given by encoding the block number in the total number of blocks by the binary signal “0, 1”.

The bit synchronization signal is a signal for recognizing a reading position of each bit of the received signal output in the transmission / reception unit 10, and is a pulse signal obtained by periodically repeating a binary signal "0, 1". The frame synchronization signal is a signal for recognizing a start point of information, and is a binary signal “0,
It is composed of a plurality of bits of the signal "1". The device address is a code for designating the called wireless device to be connected to the line, and the designated called wireless device is given as an encoded number (personal identification number).

As the synchronization correction request data, data indicating a request to reset the clock of the slave wireless device 6 to a predetermined time (for example, 0 seconds or time) is encoded and given by the binary signal “0, 1”. The cyclic code is generated from information data after the device address at the time of transmission and reception, and when the contents match in both transmission and reception, the content of the data is determined to be normal.

The CPU 11a of the master wireless device 1 performs a data communication by calling from the master wireless device 1 in response to a communication request from the automatic metering center device 4, and when the standby reception time comes, the master wireless device 1 and the slave wireless device The transmission / reception unit 10 is controlled so that the call signal shown in FIG. 4 is continuously transmitted for a time corresponding to the synchronization deviation between the transmission / reception unit 6 and the data transmission / reception at a prescribed timing.

The CPU 11b of the slave radio 6 has a clock circuit 1
3 controls the transmitting and receiving unit 10 so as to receive the radio signal when the specified synchronization correction time has come. Here, when performing the periodic synchronization correction shown in FIG. 5A, the reception time t0 for receiving the synchronization correction request signal from the parent wireless device 1 is set longer than the transmission time of the parent wireless device 1. Have been. The reception time t0 is set to a value fixed in advance from a time corresponding to the synchronization deviation between the master wireless device 1 and the slave wireless device 6 determined by the period of the synchronization correction time periodically performed and the accuracy of the clock circuit. Have been.

The CPU 11b of the slave transceiver 6 controls the clock of the slave transceiver 6 to match the clock of the master transceiver 1 by the synchronization correction request signal of the master transceiver 1 received by the transmission / reception unit 10 during the receiving operation. doing. Specifically, the clock of the slave wireless device 6 is reset to, for example, 0 second by the clock information included in the received synchronization correction request signal. Further, as the clock information, a time and a cycle time T of standby reception may be used.
In addition, the clocks can be synchronized based on the pattern of the frame synchronization signal included in the synchronization correction request signal.
In the synchronous operation shown in FIG. 5B, the repetition block number included in the synchronous correction request signal may be used.

The CPU 11b of the slave radio 6
When performing the data communication by calling from the telephone, when the standby reception time comes, the call signal shown in FIG. 4 is continuously transmitted for a time corresponding to the synchronization deviation between the parent wireless device 1 and the child wireless device 6, The transmission / reception unit 10 is controlled so that data transmission / reception is continuously performed at a specified timing.

FIG. 4 shows the structure of a call signal transmitted by the master radio or the slave radio. This call signal
Bit synchronization signal, frame synchronization signal, device address, communication data, repetition block number data, cyclic code
The block data is composed of data corresponding to the number of preset n repetition block numbers. The time t of the call signal is a time centered on the standby reception time, and is a time between the master wireless device 1 and the slave wireless device 6 determined by the elapsed time from the synchronization correction performed periodically and the accuracy of the clock circuit. It is set in advance to a variable value corresponding to the synchronization deviation.

Note that a bit synchronization signal, a frame synchronization signal,
The device address and the cyclic code are as described above, and the communication data is given as data of a predetermined number of bits encoded by the binary signal “0, 1”. The repetition block number is given by encoding the block number in the total number of blocks by the binary signal “0, 1”.

Next, the operation when synchronization is established by the automatic meter reading wireless system configured as described above is shown in FIG.
And the timing chart of FIG.

First, with reference to the timing chart of FIG. 5A, a description will be given of a periodic synchronization operation when the reception time of the slave radio is set to be long.

In this synchronization operation, the period of the synchronization correction time for periodically synchronizing the parent wireless device 1 and the child wireless device 6 is fixedly set to several hours to several tens of hours.

When the synchronization correction time comes, the CPU 11a of the parent wireless device 1 controls the transmission / reception unit 10 to cause the transmission / reception unit 10 to transmit the synchronization request signal shown in FIG. A reception operation for detecting the presence or absence of a response signal is performed. On the other hand, when the synchronization correction time comes, the slave radio 6 enters the standby reception state for the reception time t0 set according to the synchronization deviation between the master radio 1 and the slave radio 6.

When the transmission / reception unit 10 of the child radio 6 receives the synchronization correction request signal from the parent radio 1 within the reception time t0, the CPU 11b of the child radio 6 receives the synchronization correction signal during the reception operation. The clock of the slave wireless device 6 is made to match the clock of the master wireless device 1 based on the clock information included in the synchronization correction request signal.

Next, the CPU 11b of the slave radio device 6 controls the transmission / reception unit 10 and acknowledges that synchronization has been established (AC
K). Since the clock of the slave wireless device 6 and the clock of the master wireless device 1 match, the CPU 11b of the slave wireless device 6 can be set to transmit ACK in accordance with the reception time of the master wireless device 1. When the parent wireless device 1 receives the ACK from the child wireless device 6, a series of operations for periodically synchronizing is completed. As a result, the clocks of the master wireless device 1 and the slave wireless device 6 coincide with each other, resulting in a completely synchronized state. Thereafter, the master wireless device 1 and the slave wireless device 6 perform a standby reception operation including carrier sense at regular intervals T.

Next, with reference to the timing chart of FIG. 5B, a description will be given of a periodic synchronization operation when the transmission time of the master radio is set long.

In this synchronous operation, FIG.
Similarly, the period of the synchronization correction time for periodically synchronizing the parent wireless device 1 and the child wireless device 6 is fixedly set to several hours to several tens of hours.

When the synchronization correction time comes, the CPU 11a of the parent wireless device 1 controls the transmission / reception unit 10 to cause the transmission / reception unit 10 to transmit the synchronization request signal shown in FIG. A reception operation for detecting the presence or absence of a response signal is performed. On the other hand, the slave wireless device 6 enters a standby reception state when the synchronization correction time comes.

When the transmission / reception unit 10 of the child radio 6 receives the synchronization correction request signal from the parent radio 1 transmitted within the transmission time t0, the CPU 11b of the child radio 6 sets the transmission / reception unit during the reception operation. The clock of the slave wireless device 6 is made to match the clock of the master wireless device 1 based on the clock information included in the synchronization correction request signal received by 10.

Next, the CPU 11b of the slave radio device 6 controls the transmission / reception unit 10 and acknowledges that synchronization has been established (AC
K). Since the clock of the slave wireless device 6 and the clock of the master wireless device 1 match, the CPU 11b of the slave wireless device 6 can be set to transmit ACK in accordance with the reception time of the master wireless device 1. When the parent wireless device 1 receives the ACK from the child wireless device 6, a series of operations for periodically synchronizing is completed. As a result, the clocks of the master wireless device 1 and the slave wireless device 6 coincide with each other, resulting in a completely synchronized state. Thereafter, the master wireless device 1 and the slave wireless device 6 perform a standby reception operation including carrier sense at regular intervals T.

According to this synchronous operation, the transmission time t0 is set to be long so that the synchronization correction request signal transmitted from the master wireless device 1 is received by the slave wireless device 6 at the time of standby reception at regular intervals T. 5A, it is less susceptible to external signals due to noise, interference, and the like, as compared with the synchronous operation of FIG.

Next, referring to the timing chart of FIG. 6 (a), a description will be given of the synchronous operation at the time of data communication by calling the master radio.

In this synchronous operation, when there is a communication request from the automatic meter reading center device 4, the CPU 11a of the parent wireless device 1 performs data communication by calling from the parent wireless device 1.
At the next standby reception time, the transmission / reception unit 10 is controlled to continuously transmit the call signal shown in FIG. 4 for a time t set according to the synchronization deviation between the master wireless device 1 and the slave wireless device 6, Further, after t1 of the standby time, a reception operation for detecting the presence / absence of a response signal of the slave radio 6 is performed.

Then, at the standby reception time, the child radio 6
When the transmitting / receiving unit 10 receives the calling signal from the master wireless device 1, the CPU 11b of the slave wireless device 6 sends the calling signal to the terminal device 5 and includes the calling signal in the calling signal received by the transmitting / receiving unit 10 during the receiving operation. The slave wireless device 6 is synchronized with the timing of the master wireless device 1 by the repeated block number.

Then, the CPU 11b of the slave radio device 6 measures the timing of transmitting an acknowledgment (ACK) indicating that synchronization has been established from the repetition block number of the call signal, controls the transmission / reception unit 10 and transmits ACK after t2. Send. When the master wireless device 1 receives the ACK from the slave wireless device 6 and recognizes that synchronization has been established, a series of operations for establishing synchronization between the master wireless device 1 and the slave wireless device 6 are completed.

When synchronization is established in this manner, data transmitted from the terminal device 5 via the child wireless device 6 is received by the parent wireless device 1 and is transmitted via the terminal network control device 2 and the telephone line 3. It is transmitted to the automatic meter reading center device 4. Thereafter, when a termination request signal for data communication is transmitted from the parent wireless device 1 based on a command from the automatic meter reading center device 4, the child wireless device 6 receives the termination request signal from the parent wireless device 1, and performs data communication. Is transmitted to the terminal device 5 indicating that the data communication has been terminated, and then AC is received as an acknowledgment that the data communication has been terminated.
Send K. When the master wireless device 1 receives this ACK, the data communication between the master wireless device 1 and the slave wireless device 6 ends.

Next, referring to the timing chart of FIG. 6B, a description will be given of a synchronous operation at the time of data communication by calling a slave radio.

In this synchronous operation, when there is a communication request from the terminal device 5, the CPU 11 b of the slave radio 6 sets the transmission / reception unit 10 at the next standby reception time in order to perform data communication by calling from the slave radio 6. 4 to continuously transmit the call signal of FIG. 4 for a time t set according to the synchronization deviation between the parent wireless device 1 and the child wireless device 6, and further, after t1 of the standby time, the parent wireless device 1 to perform a receiving operation for detecting the presence or absence of the response signal.

Then, at the standby reception time, the parent wireless device 1
When the transmission / reception unit 10 receives the calling signal from the slave wireless device 6, the CPU 11a of the master wireless device 1 sends the calling signal to the automatic metering center device 4 via the terminal network control device 2 and the telephone line 3, and The master wireless device 1 is synchronized with the timing of the slave wireless device 6 by the repetition block number included in the call signal received by the transmitting / receiving section 10 during the receiving operation.

Then, the CPU 11a of the parent wireless device 1 measures the timing of transmitting an acknowledgment (ACK) indicating that synchronization has been established from the repetition block number of the call signal, controls the transmission / reception unit 10, and performs ACK after t2 '. Is sent. When the child wireless device 6 receives the ACK from the master wireless device 1 and recognizes that synchronization has been established, the master wireless device 1 and the slave wireless device 6
A series of operations for synchronizing with is completed.

When synchronization is established in this way, data transmitted from the automatic meter reading center device 4, the telephone line 3, and the terminal network control device 2 via the parent wireless device 1 is received by the child wireless device 6, and the terminal It is transmitted to the device 5. Thereafter, when the master wireless device 1 transmits a data communication end request signal based on a command from the automatic meter reading center device 4, the child wireless device 6
Receives the termination request signal from the master wireless device 1, transmits a signal indicating the end of the data communication to the terminal device 5, and then transmits ACK as an acknowledgment that the termination of the data communication has been received. Then, when the parent wireless device 1 receives this ACK,
The data communication between the master wireless device 1 and the slave wireless device 6 ends.

Therefore, according to the above-mentioned radio system, in addition to the periodic synchronization correction for synchronizing the clocks of the master wireless device 1 and the slave wireless device 6, the master wireless device 1 and the slave wireless device 6 Since the synchronization correction that adjusts the timing between the two is performed, the master wireless device 1 does not use a high-precision clock, reduces the number of periodic synchronization corrections, and reduces power consumption.
And the child wireless device 6 can be synchronized.

In the example of FIG. 5 (a), most of the power consumption required for the periodic synchronization correction is borne by the slave radio 6, so that one master radio 1 and a plurality of slave radios are used. When the system is extended to a 1: N wireless system having the wireless device 6, the burden on the master wireless device 1 can be greatly reduced, and efficient synchronization correction can be performed.

[0058]

As described above, according to the present invention,
Since the synchronization correction is performed at the start of data communication in addition to the periodic synchronization correction, it is possible to reduce the power consumption by reducing the number of periodic synchronization corrections without using a highly accurate clock. In addition, since most of the power consumption required for periodic synchronization correction is borne by the child wireless device, when expanded to a wireless system having one parent wireless device and a plurality of child wireless devices, The burden on the master wireless device can be greatly reduced, and the synchronization correction can be performed efficiently.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of a wireless system for automatic meter reading using a bidirectional wireless unit according to the present invention.

FIG. 2 is a block diagram showing an internal configuration of a master wireless device and a slave wireless device in the wireless system.

FIG. 3 is a diagram showing a configuration of a synchronization correction request signal transmitted by a parent wireless device of the wireless system.

FIG. 4 is a diagram showing a configuration of a call signal transmitted by a parent wireless device or a child wireless device of the wireless system.

FIGS. 5A and 5B are timing charts in a case where periodic synchronization is performed in the wireless system.

FIGS. 6A and 6B are timing charts when synchronizing data communication in the wireless system.

[Explanation of symbols]

1 ... parent wireless device, 2 ... terminal network control device, 3 ... telephone line,
4 ... Automatic metering center device, 5 ... Terminal device (meter),
6 slave radio, 7 antenna, 8 radio section, 9 modulation / demodulation circuit, 10 transmission / reception section, 11 CPU (control section), 12
... Interface circuit, 13 ... Clock circuit, 14 ... Battery, 15 ... Power switch.

Claims (3)

[Claims] When a parent wireless device and a child wireless device synchronize with each other at a standby time set at a predetermined period set in advance to confirm the presence / absence of a call signal from a partner wireless device, and when the call signal is confirmed, In the two-way wireless unit that continuously transmits and receives data, the master wireless device and the slave wireless device usually detect the presence / absence of a call signal from a partner wireless device at the standby time of a clock included therein, respectively. The parent wireless device transmits a synchronization correction signal at a synchronization correction time set in advance so that the period is longer than the standby time and coincides with the standby time. When the master wireless device starts data communication by calling the master wireless device, the master wireless device and the slave wireless device are enabled at the standby time. Only the time corresponding to the maximum deviation of the standby time between the master wireless device and the slave wireless device predicted from the accuracy of the clock and the elapsed time from the periodic synchronization correction includes synchronization correction information. Continuously transmit a call signal, perform synchronization correction with the slave radio, and then continuously transmit and receive data with the slave radio at a prescribed timing.The slave radio, at the synchronization correction time, Receiving the synchronization correction signal transmitted by the parent wireless device, performing periodic synchronization correction with the parent wireless device, and when the child wireless device starts data communication by calling a child wireless device, the standby time The maximum of the standby time between the master wireless device and the slave wireless device, which is predicted from the accuracy of the clock of the master wireless device and the slave wireless device and the elapsed time from the periodic synchronization correction. For the time corresponding to the deviation, Bi-directional wireless communication, characterized by continuously transmitting a call signal including initial correction information, performing synchronous correction with the parent wireless device, and subsequently transmitting and receiving data to and from the parent wireless device at a prescribed timing. unit. 2. The master wireless device according to claim 1, wherein the synchronization correction time is
Only the time corresponding to the maximum deviation of the standby time between the parent wireless device and the child wireless device, which is predicted from the accuracy of the clock and the period of the synchronization correction time that the parent wireless device and the child wireless device have, The two-way wireless unit according to claim 1, wherein the transmission of the synchronization correction signal is continuously performed. 3. The slave radio device according to claim 1, wherein the synchronization correction time is:
Only the time corresponding to the maximum deviation of the standby time between the parent wireless device and the child wireless device, which is predicted from the accuracy of the clock and the period of the synchronization correction time that the parent wireless device and the child wireless device have, 2. The bidirectional wireless unit according to claim 1, wherein the operation of receiving the synchronization correction signal is continuously performed.