JPH06237212A - Mobile communication method - Google Patents

Abstract

PURPOSE:To obtain a base station selecting means by which an optimal commu nication state can be obtained in a base station and a mobile object, in the case of executing a communication of a host control part and plural mobile objects through the base station. CONSTITUTION:To a host control part, plural distributed and arranged base stations are connected, and a communication by radio is executed between each base station and plural mobile objects. In the mobile object, a sense frequency receiver 32 is provided in a mobile station 24. In such a way, at the time point when data transmission from the mobile station 24 to the base station is completed, a frequency of a receiving station of the base station in which receiving signal intensity is the largest is decided, and at the time point when the data transmission from the base station to the mobile station 24 is completed, a communication radio equipment 46 sets a transmitting/receiving frequency to its decided frequency of the base station and executes a communication to the base station. The base station side executes a parity check and a check of a packet format with respect to a signal of a prescribed value or above.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mobile communication method in which a host controller communicates with a plurality of mobiles.

[0002]

2. Description of the Related Art In response to a request for factory automation, an unmanned vehicle system has been developed which automatically carries luggage and the like by an unmanned vehicle. In such a system, a host controller and an unmanned vehicle are combined. Mobile communication systems have been introduced for data communication.

Further, in general, there is a demand for a mobile communication system which is more convenient and can perform reliable communication, against the backdrop of the utilization of mobile communication in recent years.

Japanese Patent Application Laid-Open No. 64-95008 describes a system to which a conventional mobile communication method is applied. In this conventional mobile communication system, data communication is performed between a host control unit and a plurality of unmanned traveling vehicles, and specifically, a plurality of base stations connected to the host control unit, Wireless communication is performed with a mobile station mounted on an unmanned vehicle. Each base station is arranged in a distributed manner in order to expand the communication area, and in order to prevent fading due to interference of radio waves from each base station, each base station is assigned different transmission and reception frequencies, Communication is performed by a so-called polling / selecting method.

Here, the entire traveling road area on which the unmanned vehicle travels is divided into a plurality of zones, one for each zone.
One base station is provided. Then, at the boundary points of the respective zones, zone marks are arranged near the traveling road.

On the other hand, a mark detector is arranged in the unmanned vehicle, and when a zone mark is detected while the unmanned vehicle is moving, the transmission / reception frequency of the mobile station is switched to the frequency of the base station in charge of the zone. Has been. As a result, communication with any one of the base stations is performed while the unmanned vehicle is traveling.

[0007]

However, in the above-mentioned conventional mobile communication method, the zone mark plate has to be arranged on the traveling path, which is complicated and promptly when the traveling path is changed. There is a problem that we cannot handle it. Further, there is a problem that zone setting becomes extremely difficult when the traveling path is complicated or when there are radio wave obstacles.

According to the invention by the present applicant to solve this conventional problem (Japanese Patent Application No. 3-332281, "Mobile communication method"), each mobile station has the highest received signal strength. Since the base station is determined and communication is performed with the base station, communication can always be performed under the best communication condition, and stable and reliable communication can be achieved.

By the way, in the above invention, each mobile station receives the carrier at the used frequency, and after confirming whether or not the carrier is from the base station, the frequency of the base station having the largest received signal strength is determined. The detection process is being performed. It is desirable that this processing be completed within the period in which polling / selecting is performed. However, in order to ensure that the above processing is performed in the remaining time after confirming the transmission source address from the data in the carrier in each mobile station, the load on the communication means, the unmanned vehicle computer, etc., performance, etc. Will be subject to some restrictions. On the other hand, the frequency-modulation (FM) radio receiver in the base station adopted for reception in the above invention has a so-called capture effect of receiving the stronger one of the two radio waves and sensitivity to the target frequency. It is known that due to the good characteristics of a good tuning circuit, it is unlikely to be affected by radio waves of adjacent frequencies or noise radio waves.

However, even in a base station which should not receive radio waves from a mobile station, radio waves of adjacent frequencies or noise radio waves are received, so that the set values of the respective frequencies of the base station of the own system are brought close to each other. After that, the normally received signal and the received signal of the adjacent frequency collide with each other on the line in the base station and cannot be transmitted to the host control unit connected to the base station as normal data. was there.

Further, when another system using a frequency adjacent to the frequency used in its own system is installed in the same place, a signal from this another system, a noise radio wave, or the like and a normally received signal are received. There is a problem in that a collision occurs on the line in the base station and normal data cannot be transmitted to the host control unit.

Furthermore, if another system using the same frequency exists at a distant place, there is a fear that the base station may receive the data as normal data although the data is erroneous. There was a problem.

The present invention has been made to solve the above problems, and an object thereof is to eliminate the need for complicated processing such as zone design and to establish an optimum communication state in a mobile station. At the same time you can select the base station without error,
It is an object of the present invention to provide a mobile communication method capable of surely performing the processing with less restrictions.

Another object of the present invention is to provide a mobile communication method in which a base station can more accurately receive data sent from the mobile station to be processed by the mobile station.

[0015]

In order to achieve the above object, the present invention provides a host control unit, a host control unit and a data line which are respectively connected and distributed in a distributed manner, and are assigned different frequencies. A plurality of mobile stations that perform radio communication with the base station, and a plurality of mobile bodies that perform data communication with the host control unit.

Further, in the above configuration, each of the base stations is
According to a predetermined mobile station rotation, transmission of the same content and reception of a response are sequentially performed for each mobile station, and each mobile station transmits data from the mobile station to the base station while the mobile body is moving. At the time of completion, a process of determining the base station having the highest received signal strength among the base stations is performed, and when the data transmission from the base station to the mobile station is completed, the determined base station is It is characterized by performing processing for setting a transmission / reception frequency to a frequency and communicating with the base station.

With the above arrangement, according to the present invention, in polling / selecting communication in which data is repeatedly transmitted and received between a base station and a mobile station, the mobile station does not receive the carrier but the carrier. Since the process of detecting the frequency of the base station having the highest received signal strength is started when the mobile station before that completes the data transmission to the base station, it is possible to take a long time to execute the process.

Still another aspect of the present invention is to provide a host control unit, a plurality of base stations connected to the host control unit by a data line and arranged in a distributed manner, to which different frequencies are assigned, and the base station. And a plurality of mobile units that perform data communication with the host control unit, the base station checks the radio level at the time of data reception, and has a predetermined value or more. The received data is judged to be a legitimate signal only when the wireless level becomes, and the data is transmitted to the host controller after the data consistency check.

With the above configuration, it is possible to prevent erroneous data reception and data interference.

[0020]

According to the above construction, each base station transmits to each mobile station at a frequency different from each other in accordance with a predetermined rotation, and receives a response from each mobile station.

Each mobile station determines the base station having the highest received signal strength among the base stations when the data transmission from the mobile station to the base station is completed. Then, when the data transmission from the base station to the mobile station is completed, a process of setting the transmission / reception frequency to the determined frequency of the base station is performed, and communication with the base station is performed.

As described above, the base station having the highest received signal strength is determined by each mobile station, and the communication with the base station is surely performed. Therefore, the communication can always be performed under the best communication condition. Stable and reliable communication can be achieved.

Further, for example, when the present invention is applied to an unmanned vehicle system, there is an advantage that complicated processing such as zone setting described above is completely unnecessary, and the system can be easily designed and changed. . According to the invention,
Even if there is a radio wave obstruction at a specific position, the radio wave of the base station affected by the obstacle is not selected because the signal strength will be weak. Is selected.

On the other hand, according to another aspect of the invention, each base station checks the radio level of the data to be received, and only when the radio level exceeds a predetermined specified value, the data is sent to itself. Judge as a legitimate signal. After checking the data consistency with respect to the data determined to be the data of its own station, the data is transmitted to the host control unit.
Thereby, more accurate data can be normally transmitted to the host controller.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the overall configuration of a system to which the mobile communication method according to the present invention is applied. In the present embodiment, this mobile communication system is applied to an unmanned traveling vehicle system that automatically carries luggage and the like by an unmanned traveling vehicle, but can of course be applied to other systems.

In FIG. 1, a plurality of base stations 14, 16 and 18 are connected to the host controller 10 by a data line 12. These base stations 14, 16, 18
For example, it is distributed in a factory, and different frequencies f1, f2, and f3 are set as transmission and reception frequencies. These frequencies are basically fixed, but can be changed by instructions of the host controller 10 as long as the frequencies do not overlap with each other.

In FIG. 1, reference numerals 20 and 22 denote unmanned vehicles for automatically carrying luggage and the like. Each unmanned vehicle has a mobile station 24, 26 as a transceiver and an unmanned vehicle computer 28, 30. Is installed. Although two unmanned traveling vehicles are shown in FIG. 1, it is assumed that nine unmanned traveling vehicles exist in some cases in the following description.

In order to control the unmanned vehicle described above, the host control unit 10 and the unmanned vehicle computers 28, 30.
Data communication is performed between the base stations 14, 16 and 18 and the mobile stations 24 and 26, but the data communication is performed wirelessly.

In this mobile communication system, communication by the so-called polling / selecting system is performed, and the transmission / reception timing is shown in FIG.

In FIG. 2, each base station 14, 16, 18
Synchronize with each other, first transmit to the first mobile station and then receive a response from the first mobile station. This is sequentially performed from the first mobile station to the ninth mobile station, and such rotation is repeated.

Here, in principle, each mobile station responds to one of the base stations, and in FIG. 2, the first mobile station, the second mobile station, and the third mobile station are the base stations 14. The fourth mobile station and the fifth mobile station respond to the base station 16, and the sixth mobile station to the ninth mobile station respond to the base station 18. There is. Of course, the response destination from each mobile station is not fixed to a specific base station, but the optimum base station is sequentially selected by the base station selection method described in detail later.

The contents of communication from the base station to the mobile station include an unmanned vehicle number and a polling command. In the communication from the mobile station to the base station, the unmanned vehicle number, course name, current position, etc. Information is included.

Therefore, according to the polling / selecting method as described above, each base station simultaneously transmits to each mobile station. Then, in principle, each mobile station responds to one of the base stations.

FIG. 3 shows the main configuration of the unmanned traveling vehicle shown in FIG. 1. As shown in FIG.
0 includes a mobile station 24 and an unmanned vehicle computer 28. The mobile station 24 includes a communication radio 46 and a sense frequency receiver 32.

Here, the communication radio device 46 is provided with a modulation circuit 34 for modulating communication data and a demodulation circuit 36 for demodulating a received signal received, and these circuits are controlled by the transmission / reception control unit 38. Controlled. Further, a PLL circuit 40 for setting the transmission / reception frequency is provided.

The sense frequency receiver 32 is provided with a reception level detection circuit 42 and a base station selection control unit 44.

The reception level detection circuit 42 detects the reception level of the reception signal of the sense frequency variably set for each base station frequency by the base station selection control section 44, and the detected result is the reception level signal. Is sent to the base station selection control unit 44.

The base station selection control unit 44 determines whether the received signal is from the base station or the mobile station according to a base station selection control signal described later. It has a signal discrimination function and a frequency switching function for switching the above-mentioned sense frequency. Then, as will be described later, signals from each base station are sequentially received, the base station having the highest reception level among them is determined, and the transmission / reception control unit 38 is instructed to use the determined frequency as a selected frequency. There is.

On the other hand, the transmission / reception control unit 38 has a PLL circuit 40.
And has a function of setting a use frequency which is a transmission / reception frequency. When the use frequency at which transmission / reception is actually performed is different from the selected frequency, the use frequency is changed to the selected frequency.

The mobile station 24 is, for example, RS-232.
The reception data is sent to the unmanned vehicle computer 28 by being connected to the unmanned vehicle computer 28 by a C cable or the like, and the transmission data is sent from the unmanned vehicle computer 28 to the mobile station 24.

The unmanned vehicle computer 28 has a function of outputting a base station selection control signal. The base station selection control signal is lowered when the data transmission from the mobile station to the base station is completed, and is raised when the data transmission from the base station to the mobile station is completed. In addition, the DTR inversion timer set / reset at the time of abnormality processing, which will be described later, is also activated and deactivated, and thus the base station selection control signal is repeatedly activated and deactivated according to the above conditions. In the present embodiment, the DTR signal of the RS-232C cable, which is not particularly required at the time of communication in the polling / selecting method, is used as the base station selection control signal, and D
The TR signal line is connected to the base station selection control unit 44.

Regarding the operation of the moving body 20 described above,
This will be described in detail with reference to FIGS. 4, 5 and 6. It should be noted that processing not particularly necessary for explaining the features of this embodiment is not shown in the flowchart.

The feature of this embodiment is that during normal operation, the reception level detection process is started at the time when the data transmission from the mobile station to the base station is completed, and the data transmission from the base station to the mobile station is started. When the process is completed, the transmission / reception frequency setting process is performed. As a result, a sufficient amount of time is taken to perform each process, and each of the above processes can be reliably performed. In the present embodiment, the mobile station 24 is controlled by the unmanned vehicle computer 26 by raising or lowering the DTR signal in order to control the above processes.
Control against.

First, in the mobile station 24, the frequency used,
The selection frequency and the sense frequency are initialized. here,
As described above, the used frequency is the frequency actually set for communication in the communication radio 46, and the selected frequency is the frequency of the base station with the highest received signal strength,
The sense frequency is a frequency for detecting the intensity of the received signal which is variably set by the base station selection control unit 44.
Here, as the sense frequency, the frequency of each base station is selected by a predetermined rotation.

The carrier received at the used frequency is sent to the unmanned computer 28 via the demodulation circuit 36. The carrier received at the sense frequency is sent to the reception level detection circuit 42. The frame of data to be transmitted / received is composed of data transmission / reception direction, mobile station address, command, data, etc. in addition to protocol data.

The unmanned computer 28 will be described below with reference to FIG.
The operation of will be described. Other than the repeated processing, for example, the initial setting of each processing is omitted from the drawing.

In step 101, when the data frame of the carrier is fetched from the mobile station 24, the reception timer for the abnormality processing described later is reset in step 102. If the received data frame is not from the base station in step 103, the DTR signal described later is deactivated (step 108) and the process returns to step 101. In step 104, if the received data frame is from the base station and the data frame is for broadcasting, the data transmission from the base station to the mobile station is continued, so the DTR signal is lowered. The process returns to step 101 without performing (step 108).
Then, in step 105, the DTR signal is raised, and at this time, the mobile station 24 performs a transmission / reception frequency setting process described later. In step 106, it is determined whether or not the received data frame is addressed to its own station. If it is not addressed to its own station, the DTR signal is not lowered (step 108) and the process returns to step 101.
In step 107, the command, data, etc. of the data frame determined to be addressed to the own station are analyzed, and the transmission data of the own station is transmitted to the base station via the mobile station 24 at the set use frequency. Then, in step 108, the DTR signal is dropped, and at this point the mobile station 2
4, the detection processing of the reception level of the sense frequency described later is performed.

After step 108 is completed, the procedure returns to step 101, and the above processing is repeated in this manner.

Now, in step 101, the mobile station 2
If no data frame is fetched from No. 4, the following abnormality processing is performed.

This abnormality processing detects the reception level of the sense frequency by forcibly inverting the DTR signal even when some abnormality occurs such as when no data frame is captured or when the data frame is not a normal data frame. Processing and transmission / reception frequency setting processing are performed in the same manner as in normal operation. In this embodiment, a timer is used to control the abnormality processing.

In this embodiment, the reception timer is turned on when a normal data frame cannot be captured for 10 seconds, for example.
In step 111, the process returns to step 101 until the reception timer is turned on.
The reception timer is reset at step 102 described above. When 10 seconds elapse after the reception timer is reset, in step 112, the DTR inversion timer is turned on.
Check / OFF. The DTR inversion timer is a timer used to forcibly invert the DTR signal after, for example, 100 ms has elapsed after the DTR inversion timer reset (step 114) described later. When the DTR inversion timer is ON, that is, when 100 ms has elapsed after resetting the DTR inversion timer, DT is entered in step 113.
Invert the R signal. This allows the mobile station 24 to perform the detection process of the reception level of the sense frequency and the setting process of the transmission / reception frequency even if normal communication between the base stations and mobile stations cannot be performed. After resetting the DTR inversion timer in step 114, the process returns to the data frame acquisition step 101. Also, when the DTR inversion timer is OFF in step 112, the process similarly returns to the data frame acquisition step 101.

As described above, the unmanned computer 28
Operates to cause the mobile station 24 to perform detection processing of the reception level of the sense frequency and setting processing of the transmission / reception frequency.

Next, the operation of the mobile station 24 when the DTR signal rises or falls will be described below.

When the base station selection control section 44 detects the fall of the DTR signal, the detection processing of the reception level of the sense frequency shown in FIG. 5 is started.

In step 201, it is determined whether or not the sense frequency at which the received signal strength is currently detected matches the used frequency. If they match, the determination signal level is updated to the current reception signal level in step 202. Here, the determination reception level is stored for comparison and is the reception signal level of the sense frequency.

Then, after step 202, step 2
At 03, the sense frequency is changed to the next frequency.

On the other hand, if the sense frequency does not match the used frequency in step 201, step 2
At 04, it is determined whether the reception level of the sense frequency is higher than the determination reception level stored in advance. Here, if the condition is not satisfied, the above step 203 is executed, while if the condition is satisfied, the step 20 is executed.
In step 5, the sense frequency reception level is substituted for the determination reception level, and in step 206, the sense frequency is substituted for the selected frequency. Then, the above step 203
Is executed.

In this way, the base station having the highest reception level is successively determined by the reception level detection processing.

In the base station selection control unit 44, D
When the rise of the TR signal is detected, the transmission / reception frequency setting process shown in FIG. 6 is performed.

In step 303, it is determined whether the selected frequency matches the used frequency. In this case, if they do not match, the used frequency is changed to the selected frequency in step 304.

If the selected frequency matches the used frequency in step 303, the used frequency is maintained as it is.

As described above, according to the mobile communication method of this embodiment, in the data communication between the host control unit and the plurality of unmanned vehicles, the base station having the highest received signal strength is automatically and automatically transmitted. Since it is possible to make a reliable judgment and communicate with the base station, there is an effect that it is not necessary to set zones and the like as in the conventional case, and stable communication can always be secured. In addition, even if there are large machine tools in the factory where the unmanned vehicle travels and it is difficult for radio waves from a base station close to the unmanned vehicle to reach the unmanned vehicle, radio waves from other base stations Can be received to reliably control the unmanned vehicle.

Although the DTR signal of the RS-232C cable is used as the base station selection control signal in the above embodiment, the ON / OFF of this signal may be reversed, or
A signal line other than the DTR signal or a new means may be used.

Further, in the above embodiment, the base station selection control signal is output from the unmanned computer 28 to control the base station selection control unit 44 of the mobile station 24.
4 may control the output of the base station selection control signal.

The above embodiment relates to a configuration for surely controlling the unmanned vehicles 20, 22 in the mobile communication method according to the present invention shown in FIG. 16 and 18, the unmanned vehicle 20,
A method for receiving data from 22 more accurately will be described.

FIG. 7 shows a main configuration of the base station shown in FIG. 1. As shown in FIG. 7, the base station 14 includes a communication radio transmitter / receiver 52 and a communication control unit 54. include. The radio transmitter / receiver 52 for communication receives the influence of radio waves of adjacent frequencies or noise radio waves due to the so-called capture effect of receiving the stronger one of the two radio waves and the original characteristics of the tuning circuit that is sensitive to the target frequency. Mobile station 2 that has a function that is difficult to receive and is installed in unmanned vehicles 20 and 22.
Data is wirelessly transmitted / received to / from Nos. 4 and 26. The communication control unit 54 uses the communication wireless transceiver 52 to transmit the data from the host control unit 10 to the mobile stations 24 and 26.
After checking the data received by the communication wireless transceiver 52, which will be described later, only the data is transmitted to the host controller 10.

Regarding the operation of the base station 14 described above,
This will be described in detail with reference to FIGS. 8 and 9. It should be noted that processing not particularly necessary for explaining the features of this embodiment is not shown in the flowchart.

A feature of this embodiment is that the data received by the base station is subjected to a predetermined check and then the data is transmitted to the host controller 10. That is, the communication control unit 54 checks whether the received data is at a level higher than a specified value, performs a data consistency check by checking a parity check and a packet format, and after confirming that the data is normal, the host Data is transmitted to the control unit 10. Thereby, more accurate data can be transmitted to the host controller 10.

First, in the wireless transceiver 52 for communication,
Receive some data (signal) (step 40)
1). In step 402, the communication controller 54 checks the level of the received signal. This check
If a preset value is set in advance, and only if the level is above the preset value, a regular signal, that is, reception at the local station,
Judge as data to be processed. Data that does not reach the specified value is regarded as noise radio waves and is not transmitted to the host control unit 10. In step 403, a parity check is performed on the received data (1 character). When a parity error is detected, the data is discarded.

Packets that the base station 14 normally receives will be described with reference to FIG. FIG. 9 shows a packet processed by the base station 14, and the packet 5
6 is a format of a normal packet sent from each mobile station 24, 26. In this embodiment, the packet 56 is processed as received data for each character, but the data sent from the communication wireless transceiver 52 to the communication control unit 54 forms the format shown in the packet 56. The synchronization character (55 in FIG. 9)
The H) portion is transmitted from tens of mobile stations 24 and 26, and the base station 14 only needs to be able to receive a few of them. The packet 58 has the synchronization character of the packet 56 removed by the communication control unit 54, and this packet 58 is sent to the host control unit 10.

In step 404, it is checked whether the received data is the packet start which is the control character shown in FIG. If it is a packet start, the data transfer flag indicating the data transmission state to the host control unit 10 is turned on.
(Step 405). In this case, in step 406, since the data transfer flag is ON in this case, the process proceeds to the next process.
The data is transmitted to the host controller 10 (step 40)
7). It is checked whether the data is the packet end which is the control character shown in FIG. 9 (step 40).
8) The above process is repeated until the packet end is detected. When the packet end is detected, the data transfer flag is turned off (step 409), and the processing in the base station 14 ends.

As described above, when the base station 14 receives data, the above-mentioned check is performed, so that the received data can be detected more accurately. Further, it is possible to prevent the collision between the normal data on the data line 12 and the abnormal data created by processing the adjacent frequency, the noise radio wave and the like.

Therefore, it is possible to realize a system that is strong against adjacent frequencies, noise radio waves, etc., and to effectively use the frequencies.

[0075]

As described above, according to the present invention,
Each mobile station reliably determines the base station with the strongest received signal strength and communicates with that base station, so communication can always be performed under the best communication conditions, and stable and reliable communication is achieved. The effect is that you can do it.

Further, in the base station, it is possible to prevent erroneous data reception and data interference by checking the received data. Therefore,
It is possible to realize a mobile communication system that is strong against noise radio waves and the like. Further, it becomes possible to effectively use the frequency.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of a mobile communication system to which the present invention is applied.

FIG. 2 is an explanatory diagram showing transmission / reception timing when a polling / selecting method is applied.

FIG. 3 is a block diagram showing a specific configuration of a mobile station mounted on a mobile body.

FIG. 4 is a flowchart showing the operation of the unmanned computer.

FIG. 5 is a flowchart showing an operation of detecting a reception level in a mobile station.

FIG. 6 is a flowchart showing an operation of a transmission / reception frequency setting process in a mobile station.

FIG. 7 is a block diagram showing a specific configuration of a base station.

FIG. 8 is a flowchart showing an operation of the base station.

FIG. 9 is a diagram showing a packet processed in a base station.

[Explanation of symbols]

 10 host control unit 14, 16, 18 base station 20, 22 unmanned vehicle 24, 26 mobile station 28, 30 unmanned vehicle computer 32 sense frequency receiver 38 transmission / reception control unit 42 reception level detection circuit 44 base station selection control unit 46 communication Wireless device 52 Communication wireless transceiver 54 Communication control unit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yuji Katayama 4-21 Minami Naruse, Machida, Tokyo Sanritsu Automation Co., Ltd. Naruse Plant (72) Inventor Hiroyoshi Takakura 4-21 Minami Naruse, Machida, Tokyo Sanritsu Automation Naruse Office Co., Ltd.

Claims (2)

[Claims] 1. A host controller, a plurality of base stations which are respectively connected to the host controller by a data line, are arranged in a distributed manner, and are assigned different frequencies, and perform wireless communication with the base station. A plurality of mobile units each having a mobile station and performing data communication with the host control unit, wherein each base station transmits the same content and receives a response in accordance with a predetermined mobile station rotation. For each mobile station, while the mobile unit is moving, the base station with the highest received signal strength among the base stations at the time when data transmission from the mobile station to the base station is completed. Is performed, and when the data transmission from the base station to the mobile station is completed, the transmission / reception frequency is set to the frequency of the determined base station, Mobile communication method, characterized in that communicate with Chikyoku. 2. The mobile communication method according to claim 1, wherein the base station checks the radio level at the time of receiving the data, and the data received only when the radio level becomes equal to or higher than a predetermined specified value. Is determined to be a legitimate signal, the data consistency is checked, and then the data is transmitted to the host control unit.