JPH10191432A - Receiving frequency channel setting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To define a frequency channel which should be received originally by confirming the receiving level of all the frequency channel executing Multi Channel Access(MCA) operation to select a frequency channel more than a regulated value and searching transmitted radio data in order of lowering the frequency channel of a receiving level. SOLUTION: When a memory means 6 houses a receiving frequency channel No. more than a receiving level regulated value, the receiving frequency channel No. are rearranged in order of lowering the detected receiving level to set a receiving frequency channel No. based on this to search transmitted radio data for a fixed time longer than two-frame transmitting time. when radio data can not be received, the execution is repeated by switching to a next receiving frequency channel to house in the means 6 and when transmitted radio data being an object at all the receiving channel to store, reexecution is started from the initialization of the receiving frequency channel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reception frequency channel setting for a radio apparatus such as a specified low power radio station, which selects a reception frequency channel from a plurality of frequency channels using a Multi Channel Access (hereinafter referred to as MCA) system. It is about the method.

[0002]

2. Description of the Related Art In a radio device such as a specified low power radio station,
Many wireless users are performing wireless communication using the MCA method in which a plurality of wireless channels are jointly used to effectively use the frequency. In the wireless communication using the MCA method, the transmitter starts transmission. Before performing this, carrier sense is performed, a frequency channel that is not used around the transmitter is searched for from a plurality of frequency channels, and transmission is started on that frequency channel. The receiver receives the data while switching the plurality of frequency channels, and continues the receiving operation on the frequency channel on which the wireless data is received from the transmitter.

[0003] A conventional method of setting a reception frequency channel of a radio apparatus of this type will be described below.

FIG. 10 is a block diagram of a receiving frequency channel setting method disclosed in Japanese Patent Laid-Open No. 6-244777, and FIG. 11 is a flowchart of the method. Here, Figure 1
0, the reception level being received by the radio section 102 is detected by the electric field detection section 109 by the electric field detection section 109, and when the reception level is equal to or higher than the specified value as shown in the flowchart of FIG. A search is performed, and when the wireless data from the original target transmitter that matches the system information can be received, the reception frequency channel is determined.

[0005]

However, when another transmitter using another frequency channel exists around the transmitter, or when a frequency channel different from the frequency channel to be originally transmitted is used. If radio waves are leaking, intermodulation may occur between them. For example, assuming that a frequency channel to be originally transmitted is f ₁ and a frequency channel transmitted by another transmission source that becomes an interference wave is f ₂ ,
2f ₁ -f ₂ , 2f ₂ -f ₁ , 3f ₁ -2f ₂ , 3f ₂ -2f ₁
If a spectrum is generated in a frequency channel such as the above, and the other transmission source serving as the interfering signal is unmodulated data, the spectrum generated in these frequency channels will According to the above-mentioned conventional receiving frequency channel setting method, depending on the MCA operation timing, the wireless data from the target transmitter is transmitted on another frequency channel before the frequency channel to be transmitted. Is received, and the reception frequency channel is determined. Even in this case, reception is possible because the reception level is equal to or higher than the specified value, but the reception level is lower than the original frequency channel to be received, so that the reach distance decreases and the reception operation becomes unstable. Had the problem of getting lost.

[0006] Further, even when the signal is transmitted only through the frequency channel to be originally transmitted, the mutual transmission between the oscillation frequency of the oscillator in the receiver and the frequency of the noise entering the receiver and the frequency channel to be transmitted. Modulation may occur, and this case also has a similar problem.

The present invention solves such a conventional problem,
It is an object of the present invention to provide a highly reliable reception frequency channel setting method in which a reception operation can be started on an original frequency channel even in a situation where intermodulation occurs.

[0008]

In order to solve this problem, a method of setting a reception frequency channel according to the present invention comprises the steps of:
When the radio receiver of the system starts receiving operation on the original frequency channel, it checks the reception levels of all the frequency channels that perform the MCA operation, and selects a frequency channel whose reception level is equal to or higher than a specified value from among them. In this configuration, wireless data from the transmitter is searched in order from the frequency channel having the highest reception level.

According to the present invention, a highly reliable receiving frequency channel setting method capable of starting a receiving operation on an original frequency channel even in a situation where intermodulation occurs can be obtained.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the first aspect of the present invention, when a radio receiver of the MCA system starts a reception operation on an original frequency channel, the reception levels of all frequency channels performing the MCA operation are reduced. Confirmation, select a frequency channel whose reception level is equal to or higher than a specified value from them, and search for wireless data from the transmitter in order from the frequency channel with the highest reception level, so that intermodulation occurs. In such a situation, the receiving operation can be performed on the original frequency channel.

[0011] According to a second aspect of the present invention, in the first aspect of the present invention, the wireless data transmitted by the transmitter is transmitted in the frequency channel No. , And the frequency channel No. included in the wireless data. The receiving operation can be started on the frequency channel corresponding to the above, and the receiving operation can be performed on the original frequency channel even in a situation where intermodulation occurs, and the communication state during the MCA operation Even when the reception level of the original frequency channel to be transmitted is lowered, the original frequency channel can be determined and the receiving operation can be started.

According to a third aspect of the present invention, in the first or second aspect of the present invention, different data frames for transmitting wireless data in two-way wireless communication are different between a call connection request time and a normal communication time. And only when a call connection request is made, a frequency channel No. is added to the data frame of the wireless data. The function that the receiving operation can be performed on the original frequency channel even in a state where intermodulation occurs, and the reception of the original frequency channel to be transmitted due to the communication state during the MCA operation Even when the level is lowered, the operation that the receiving operation can be performed on the original frequency channel and the master unit can check the information of the frequency channel setting result of the slave unit,
Further, there is an effect that a highly reliable frequency channel can be set, and an operation that a communication response time can be shortened because the data frames are different when a call connection request is made and when a normal communication is made.

[0013] The invention according to claim 4 of the present invention is characterized in that MCA
In the two-way wireless communication using the method, the slave checks the reception levels of all the frequency channels performing the MCA operation,
A configuration in which frequency channels whose reception levels are equal to or higher than a specified value are selected from those, the frequency channels are grouped in descending order of the reception level, and wireless data from the master unit is searched in order from the frequency channel having the highest reception level. The master unit sets the wireless data continuous transmission time at the time of a call connection request in accordance with the reception time of each slave unit group, and does not require channel group management. Can be performed in a short time.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. (Embodiment 1) FIG. 1 is a block diagram for explaining a receiving frequency channel setting method according to a first embodiment of the present invention, and FIG. 2 is a flowchart thereof. In FIG. The receiving circuit 3 is a receiving level detecting means for detecting a receiving level being received by the receiving circuit 2, 4 is a receiving level setting means for setting a specified value of the receiving level in advance, and 5 is a receiving level detecting means 3. The comparison control means 6 for comparing the obtained reception level with the specified reception level value is a reception frequency channel No. 6 in which a reception level equal to or higher than the reception level specified value is detected. And memory means for storing reception levels corresponding thereto, 7 is a reception frequency channel setting means for setting a reception frequency channel for the reception circuit 2, 8 is data input means for inputting wireless data received by the reception circuit 2, 9 Is an arithmetic control means for confirming the received wireless data and controlling the memory means 6.

Hereinafter, a method of setting a reception frequency channel according to the present embodiment will be described with reference to FIGS.

First, the arithmetic control means 9 initializes the receiving frequency channel to the receiving circuit 2 through the receiving frequency channel setting means 7, and the receiving level detecting means 3 detects the receiving level of the currently set receiving frequency channel. . Then, the detected reception level is compared with the reception level prescribed value preset by the reception level prescribed value setting means 4 using the comparison control means 5, and if the detected reception level is equal to or more than the reception level prescribed value, the current setting is made. Received frequency channel No. Is stored in the memory means 6. The above operation is performed for all frequency channels that perform the MCA operation.

Next, the arithmetic control means 9 stores in the memory means 6 a reception frequency channel number equal to or higher than the specified reception level. Is stored, and if not stored, the process is re-executed from the initialization of the reception frequency channel. If they are stored, the reception frequency channel No. is set in descending order of the detected reception level. , And further rearranged reception frequency channel Nos. The receiving frequency channel is set to the receiving circuit 2 through the receiving frequency channel setting means 7 based on the data transmission means, and the target transmitted wireless data is searched through the data input means 8 for a certain period of time equal to or longer than two frame transmission times. When one frame of the target transmitted wireless data can be received within a predetermined time, the receiving frequency channel is determined and the receiving operation is started.

If the target transmitted radio data cannot be received within a certain period of time, it switches to the next reception frequency channel stored in the memory means 6 and repeats the same operation. When the target transmitted wireless data cannot be received in all the reception frequency channels stored in the memory means 6, the process is repeated from the initialization of the reception frequency channel.

As described above, the reception levels of all the frequency channels that perform the MCA operation are checked, and the frequency channels whose reception levels are equal to or higher than the specified value are selected from among them. By searching for wireless data that has been received, even when there are a plurality of frequency channels that can be received in a situation where intermodulation occurs, it is possible to determine a frequency channel to be originally received and start a receiving operation. .

In this embodiment, the reception level detection means 3, the reception level specified value setting means 4, the comparison control means 5, the memory means 6, the reception frequency channel setting means 7, the data input means 8, and the arithmetic control means Although 9 is an independent configuration, the same effect can be obtained by a configuration utilizing the function of a one-chip microcomputer.

(Embodiment 2) FIG. 3 is a configuration diagram of a radio data frame for explaining a reception frequency channel setting method according to a second embodiment of the present invention, and FIG. 4 is a flowchart of the same.

The configuration of this embodiment is the same as that of the first embodiment of the present invention shown in FIG.

The method of setting a reception frequency channel according to the present embodiment will be described below with reference to FIGS.

At first, as shown in FIG. The configuration of wireless data including Here, the frequency channel No. Is the frequency channel No. corresponding to the transmission frequency from the transmitter. And the transmitter continuously transmits the wireless data.

The receiver checks the reception levels of all the frequency channels that perform the MCA operation by the method described in the first embodiment of the present invention, and selects a frequency channel whose reception level is equal to or higher than a specified value from them. Then, wireless data from the transmitter is searched in order from the frequency channel having the highest reception level. As a result of the search, of the wireless data from the target transmitter, the frequency channel No. When one frame of the wireless data excluding the wireless data is received, the frequency channel No. of the wireless data is received. Is read, and if it matches the frequency channel currently set in the receiver, it is determined as a frequency channel to be received as it is.

Further, the frequency channel No.
If is different from the frequency channel currently set for the receiver,
Frequency channel No. of wireless data Is changed to the frequency channel indicated by, the frequency channel to be received is determined, and the receiving operation is started.

As described above, in a situation where intermodulation occurs, there are a plurality of frequency channels capable of receiving radio transmission data, and reception of a frequency channel to be originally received depends on the communication state during MCA operation. Even when the level temporarily drops and is not the maximum reception level, the frequency channel to be originally received can be determined and the reception operation can be started.

(Embodiment 3) FIG. 5 is a block diagram for explaining a reception frequency channel setting method according to a third embodiment of the present invention. However, detailed description is omitted.

In FIG. 5, reference numeral 11 denotes a transmission / reception circuit, 12 denotes transmission / reception frequency channel setting means for setting a frequency channel to be transmitted / received to / from the transmission / reception circuit 11, and 13 denotes transmission / reception circuit 11 Data input / output means for input / output.

FIG. 6 is a configuration diagram of a radio data frame at the time of a call connection request and at the time of normal communication for explaining the reception frequency channel setting method in the present embodiment, and FIG. 7 is a sequence diagram of the same.

The receiving frequency channel setting method according to the present embodiment will be described below with reference to FIGS.

First, as shown in FIG. 6, a call connection request signal used at the time of a call connection request and radio data used at the time of normal communication have different data frame configurations, and only the call connection request signal is transmitted to the radio data. Power channel number. And a data frame configuration including The base unit performs carrier sense and determines the frequency channel to be transmitted,
The corresponding frequency channel No. Is transmitted for N frames. Number of frames to be transmitted N
Is the MC at the time of detecting the reception level of the slave unit as shown below.
A operation cycle and MCA at the time of receiving a call connection request signal
Set from the operation cycle.

The MCA operation cycle at the time of detecting the reception level of the slave unit includes the switching time of the receiving frequency channel and the reception level detection time. For example, if the switching time of the receiving frequency channel is 50 ms and the receiving level detection time is 10 ms, the MCA operation cycle at the time of detecting the receiving level is 60 ms. Is 300 ms.

Also, when receiving the call connection request signal, the MC
The operation period A is set based on the switching time of the frequency channel to be received and the transmission time of one frame of the call connection request signal.
If the frequency channel of the master unit is the same as the frequency channel of the slave unit, one frame of the call connection request signal can be received if the reception state is continued for at least twice the transmission time of one frame of the call connection request signal. 50 ms reception duration per frequency channel while MCA is running
Then, since the switching time of the frequency channel is 50 ms, the MCA operation cycle at the time of receiving the call connection request signal is 100 ms.

Further, the reception of the call connection request signal is executed for a frequency channel in which a reception level equal to or higher than the specified value is detected. However, since the reception level equal to or higher than the specified value may be detected in all of the five channels for performing MCA. , It takes 500 ms to receive a call connection request signal on all frequency channels. Therefore, the master unit transmits a call connection request signal of 800 ms or more, that is, 40 frames or more.

The slave unit searches for wireless data transmitted from the master unit in the method described in the first embodiment of the present invention during 800 ms, and performs the search in the method described in the second embodiment of the present invention. The frequency channel to be received is determined, and a call connection response signal is transmitted to the base unit to notify that the call connection has been completed.

The master unit shifts to the normal communication by receiving the call connection response signal. In this way, the master unit can check the frequency channel setting result of the slave unit, and can set a more reliable frequency channel. In addition, the frequency frame No. is included in the data frame during normal communication. , The data frame can be shortened, so that the communication response time can be shortened.

Although the contents of the call connection response signal are not specifically described in the present embodiment, a more reliable frequency channel setting can be achieved by returning the received call connection request signal as it is as a call connection response signal. Can also be performed.

(Embodiment 4) Next, a method in which the above-described Embodiment 3 is further applied and developed will be described. That is, in the reception frequency channel setting method as in the third embodiment, the transmission time of the call connection request signal of the base station is set in consideration of the possibility of detecting the reception level equal to or higher than the specified value in all the channels for performing MCA. Therefore, it is necessary to increase the transmission time of the call connection request signal of the parent device as the number of channels for performing MCA increases.

The slave unit can determine the reception frequency when one frame of the target wireless data can be received. However, the slave unit remains connected to the master unit until the transmission of the call connection request signal is completed. The response signal could not be transmitted.

Accordingly, even when the reception level is sufficiently high and the target data can be received, there is a problem that the time required for call connection becomes longer if the number of channels for performing MCA increases. Was.

It is also conceivable to divide the channels to be used into a plurality of channel groups in advance and reduce the number of channels for performing MCA to reduce the time required for call connection. It is necessary to set a channel group by providing a dip switch, an EEPROM, and the like for each of them.

When all the channels in the channel group set when using the wireless device are occupied by another wireless device, the setting must be changed to another channel group. The work is complicated because it is incorporated in the remote control position.

Then, in order to prevent the operation of changing the setting of the channel group, there is a problem that the channel group must be managed according to the use situation in advance.

This embodiment solves such a problem.
The present invention realizes a receiving frequency channel setting method that does not require channel group management and that the higher the receiving level, the faster the call connection can be made.

FIG. 8 is a block diagram for realizing a receiving frequency channel setting method according to the fourth embodiment of the present invention. In FIG. 8, reference numeral 21 denotes an antenna, 22 denotes a transmitting / receiving circuit, and 23 denotes a signal being received by the transmitting / receiving circuit 22. Receiving level detecting means 24 for detecting a receiving level of the receiving level; receiving level specifying value setting means 24 for setting a predetermined value of the receiving level in advance;
5 is a comparison control means for comparing the reception level obtained by the reception level detection means 23 with the reception level specified value set by the reception level specification value setting means 24; Received frequency channel No. A data input / output means for inputting / outputting wireless data; a transmission / reception frequency channel setting means for setting a frequency channel to be transmitted / received to / from the transmission / reception circuit 22;
Numeral 9 is an arithmetic control unit for confirming the received wireless data and controlling the memory unit 26. FIG. 9 is a flowchart for realizing the reception frequency channel setting method in the embodiment.

The reception frequency channel setting method of the present embodiment will be described below with reference to FIGS.

The slave unit first initializes the reception frequency channel for the transmission / reception circuit 22 from the arithmetic control means 29 through the transmission / reception frequency channel setting means 28, and detects the reception level of the currently set reception frequency channel by the reception level detection means 23. I do. Then, the detected reception level is compared with the reception level prescribed value preset by the reception level prescribed value setting means 24 using the comparison control means 25. If the detected reception level is equal to or higher than the reception level prescribed value, the current setting is made. Received frequency channel No. Is stored in the memory means 26. The above operation is performed for all frequency channels that perform the MCA operation.

Next, the arithmetic control means 29 stores in the memory means 26 a reception frequency channel number having a reception level specified value or more. Is stored, and if not stored, the process is re-executed from the initialization of the reception frequency channel. If they are stored, the reception frequency channel No. is set in descending order of the detected reception level. Are rearranged and divided into M channel groups. The reception frequency channel is set to the transmission / reception circuit 22 through the transmission / reception frequency channel setting unit 28 in order from the channel group in which the reception frequency channel with the high reception level is stored, and the target transmitted wireless data is transmitted through the data input / output unit 27. Is searched for a fixed time longer than the transmission time of two frames.

When one frame of the target transmitted wireless data can be received within a predetermined time, the receiving frequency channel is determined, the transmission of the master unit is completed, and a call connection response signal is transmitted to the master unit. I do. If the target transmitted wireless data cannot be received within a certain period of time, it switches to the next receiving frequency channel stored in the memory means 26 and repeats the same operation. When the target transmitted wireless data cannot be received in all the stored channel groups, the processing is re-executed from the initialization of the reception frequency channel.

The master unit performs carrier sensing to determine a frequency channel to be transmitted, and transmits an N frame of a call connection request signal. The number N of frames to be transmitted is the MCA operation cycle at the time of detecting the reception level of all the frequency channels that perform MCA of the slave unit and the channel when all the frequency channels that perform MCA are divided into M channel groups as shown below. It is set from the MCA operation cycle at the time of receiving the call connection request signal per group. The MCA operation cycle at the time of detecting the reception level of the slave unit includes the switching time of the receiving frequency channel and the reception level detection time. For example, the switching time of the frequency channel to be received is 50 ms,
Assuming that the reception level detection time is 10 ms, the MCA operation cycle at the time of detection of the reception level is 60 ms. If the frequency channels for performing MCA are 40 channels, the time until the reception level detection is completed in all the frequency channels is 2400 ms.

Next, assuming that all 40 frequency channels for performing MCA are divided into eight channel groups, one channel group has five channels. The MCA operation cycle at the time of receiving the call connection request signal is set based on the switching time of the frequency channel to be received and the transmission time of one frame of the call connection request signal. For example, the transmission time of one frame of the call connection request signal is set to 20 ms. Then, when the frequency channel of the master unit and that of the slave unit are the same, one frame of the call connection request signal can be received by continuing the reception state for at least twice the transmission time of one frame of the call connection request signal. Assuming that the reception continuation time per one frequency channel during execution of MCA is 50 ms, the switching time of the frequency channel is 50 ms, so that the MCA operation cycle at the time of receiving the call connection request signal is 100 ms.

Further, the reception of the call connection request signal is executed for a frequency channel for which a reception level equal to or higher than a specified value has been detected. However, there is a possibility that a reception level equal to or higher than the specified value is detected in all five channels in the channel group. , 500 to receive a call connection request signal on all frequency channels
ms. Therefore, the master unit transmits a call connection request signal of 2900 ms or more, that is, 145 frames or more.

When a call connection response signal from the slave unit is received within a predetermined time, the operation shifts to normal communication. If the call connection response signal from the slave unit cannot be received within a predetermined time, transmission of the call connection request signal and reception of the call connection response signal are continued.

As described above, the master sets the wireless data continuous transmission time at the time of a call connection request in accordance with the reception time of each slave group, and the slave sets the call connection request signal from the master in descending order of the reception level. , The higher the reception level, the shorter the call connection time and the more the channel management becomes unnecessary.

In this embodiment, the reception level detection means 23, the reception level specified value setting means 24, the comparison control means 25, the memory means 26, the data input / output means 27, the transmission / reception frequency channel setting means 28, and the arithmetic control Means 2
Although 9 is an independent configuration, the same effect can be obtained by a configuration utilizing the function of a one-chip microcomputer.

[0057]

As described above, according to the receiving frequency channel setting method according to the present invention, the receiving levels of all the frequency channels that perform the MCA operation are confirmed, and the frequency channel whose receiving level is equal to or more than the specified value is selected from them. By searching for radio data transmitted in order from the frequency channel having the highest reception level, even if there are a plurality of frequency channels that can be received in a situation where intermodulation occurs, the frequency channel to be originally received is determined. It is possible to obtain the effect that the reception operation can be started after the determination is made.

The wireless data transmitted by the transmitter is transmitted to the frequency channel No. , And the frequency channel No. included in the wireless data. By starting the receiving operation on the frequency channel corresponding to
Even when the reception level of the frequency channel to be originally received is temporarily reduced due to the communication state during the CA operation and is not the maximum reception level, the frequency channel to be originally received is determined and the reception operation is started. The effect that can be obtained is obtained.

In the two-way wireless communication, the wireless data to be transmitted is separated into different data frames at the time of call connection request and at the time of normal communication. . With this configuration, the master unit can check the result of setting the frequency channel of the slave unit, and can set a highly reliable frequency channel. Since the data frame is not included, the data frame can be shortened, so that the effect that the communication response time can be shortened can be obtained.

Further, in the two-way wireless communication using the MCA method, the slave checks the reception levels of all the frequency channels performing the MCA operation, and selects a frequency channel whose reception level is equal to or higher than a specified value from them. Further, the frequency channels are grouped in descending order of the reception level, and the radio data from the master unit is searched in order from the frequency channel with the highest reception level, and the master unit matches the reception time of each slave unit group. The wireless data continuous transmission time at the time of a call connection request is set, and there is no need for channel group management, and the higher the reception level, the shorter the call connection can be made.

[Brief description of the drawings]

FIG. 1 is a block diagram for explaining a reception frequency channel setting method according to Embodiment 1 of the present invention.

FIG. 2 is the same flowchart.

FIG. 3 is a conceptual diagram showing a configuration of a transmission data frame used in a reception frequency channel setting method according to Embodiment 2 of the present invention.

FIG. 4 is the same flowchart.

FIG. 5 is a block diagram for describing a reception frequency channel setting method according to Embodiment 3 of the present invention.

FIG. 6 is a conceptual diagram showing a configuration of a normal data frame at the time of the same call connection request and at the time of normal communication.

FIG. 7 is a sequence diagram of the same.

FIG. 8 is a block diagram for explaining a reception frequency channel setting method according to Embodiment 4 of the present invention.

FIG. 9 is the same flowchart.

FIG. 10 is a block diagram for explaining a conventional reception frequency channel setting method.

FIG. 11 is the same flowchart.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 antenna 2 reception circuit 3 reception level detection means 4 reception level specified value setting means 5 comparison control means 6 memory means 7 reception frequency channel setting means 8 data input means 9 arithmetic control means 11 transmission / reception circuit 12 transmission / reception frequency channel setting means 13 data input Output means

 ──────────────────────────────────────────────────続 き Continued on front page (72) Inventor Tsutomu Sakuma 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] 1. Multi Channel Access
When the radio receiver of the ss (MCA) system starts the reception operation on the original frequency channel, the reception levels of all the frequency channels performing the MCA operation are checked, and the reception level of the reception level equal to or more than the specified value is checked from among them. , And searching for wireless data from the transmitter in order from the frequency channel with the highest reception level. 2. Transmitting wireless data transmitted by a transmitter to a frequency channel No. , And the frequency channel No. included in the wireless data. 2. A receiving operation is started on a frequency channel corresponding to the above.
The receiving frequency channel setting method described above. 3. In two-way wireless communication, wireless data to be transmitted is a separate data frame that is different between a call connection request and a normal communication, and a frequency channel number is included in the data frame of the wireless data only when a call connection request is made. . 3. The receiving frequency channel setting method according to claim 1, further comprising: 4. In the two-way wireless communication using the MCA method, the slave checks the reception levels of all frequency channels performing the MCA operation, and selects a frequency channel whose reception level is equal to or higher than a specified value from among them. Further, the frequency channels are grouped in descending order of the reception level, and the radio data from the master unit is searched in order from the frequency channel with the highest reception level, and the master unit matches the reception time of each slave unit group. A receiving frequency channel setting method in which a wireless data continuous transmission time at the time of a call connection request is set.