JP2018096799A - Communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication system in which communication interruption hardly occurs.SOLUTION: This communication system is a communication system between a mobile station and a base station using a prescribed frequency band, and includes a first mode in which the mobile station and the base station can communicate bidirectionally and a second mode in which the base station delivers positioning correction information. The base station stores a plurality of channel lists in which a plurality of channels included in the frequency band are divided into a plurality of groups. The base station transmits prescribed information to the mobile station in the first mode. The prescribed information includes information that indicates a channel list used in the second mode by the base station that is selected from the plurality of channel lists. The prescribed information also includes information that indicates a channel used in the second mode by the base station that is included in the selected channel list.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a communication system. Specifically, the present invention relates to a communication system between a mobile station and a base station using a predetermined frequency band.

  Conventionally, a communication system between a mobile station and a base station, where the mobile station receives positioning correction information from the base station every moment, and the mobile station accurately obtains its own positioning information based on the positioning correction information. Communication systems that can be acquired are known. Patent Document 1 discloses a travel control system including this type of communication system.

  Patent Document 1 only describes that communication between a mobile station (autonomous traveling work vehicle) and a base station (reference station) is performed by a wireless method or the like in the disclosed traveling control system. For communication between the mobile station and the base station, for example, a predetermined frequency band such as specific low power that can be used by anyone can be used.

International Publication No. 2015/119265

  However, when performing communication between the mobile station and the base station using the predetermined frequency band as described above, when other systems using the same frequency band are adjacent to each other, radio waves interfere, There was a possibility of communication interruption. For example, in a system in which it is important to continuously acquire an accurate current position of a mobile station without interruption, such as the travel control system of Patent Document 1, occurrence of communication interruption of positioning correction information distribution must be avoided. In other words, it has been desired to construct a communication system in which such a situation is less likely to occur.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a communication system in which communication interruption is unlikely to occur.

Means and effects for solving the problems

  The problems to be solved by the present invention are as described above. Next, means for solving the problems and the effects thereof will be described.

  According to an aspect of the present invention, a communication system having the following configuration is provided. That is, this system is a communication system between a mobile station and a base station using a predetermined frequency band. This communication system has a first mode in which the mobile station and the base station can perform two-way communication, and a second mode in which the base station distributes positioning correction information. The base station stores a plurality of channel lists obtained by dividing a plurality of channels included in the frequency band into a plurality of groups. In the first mode, the base station transmits predetermined information to the mobile station. The predetermined information includes a channel list used by the base station in the second mode and indicating any channel list selected from the plurality of channel lists. The predetermined information includes information indicating a channel used by the base station in the second mode and included in any of the selected channel lists.

  Thereby, the first mode can be a mode for registering a communication partner, for example, and the second mode can be a mode for distributing positioning correction information. In the first mode, the channel used by the base station Since the list and channel information are transmitted to the mobile station and the mobile station knows which channel the base station uses in the second mode, two-way communication is not required in the second mode. Thereby, it is possible to make it difficult to cause communication interruption due to radio wave interference and the like, and the mobile station can acquire accurate positioning correction information without stagnation.

  The above communication system preferably has the following configuration. That is, the base station includes a plurality of transmission modules including a first communication module and a second communication module that distribute the positioning correction information. In the second mode, the base station distributes the positioning correction information from the second communication module during a distribution suspension time after the first communication module distributes the positioning correction information.

  Accordingly, the positioning correction information can be distributed by the other communication module using the distribution suspension time of one communication module, and the frequency band can be effectively used.

  The above communication system preferably has the following configuration. That is, a bidirectional communication channel used for bidirectional communication between the base station and the mobile station in the first mode is a channel not included in the plurality of channel lists. The bidirectional communication channel and the channels included in the plurality of channel lists are channels that do not cause radio wave interference with each other.

  Thereby, by providing a channel for two-way communication, it is possible to easily perform work that requires the base station and the mobile station to cooperate. Further, since the channels used in the normal mode do not cause radio wave interference with each other, duplication of communication bands can be avoided and communication failure can be avoided.

  The above communication system preferably has the following configuration. That is, in the second mode, the base station changes the channel to be used to another channel included in any of the selected channel lists when the positioning correction information cannot be distributed for a predetermined time. . In the second mode, when acquisition of the positioning correction information is interrupted for a predetermined time, the mobile station changes the channel to be used to the other channel included in any of the selected channel lists.

  As a result, since the channel list is stored in the base station and the mobile station, even if the mobile station does not communicate for a predetermined time without transmitting information on the channel used from the base station each time, the channel list By changing to another channel according to, it is possible to match the channel with the base station. The channel change method / rule must be shared between the base station and the mobile station, as will be described later. On the other hand, as long as the rules are shared, any rule changes will not affect the implementation of this patent.

1 is a side view showing an overall configuration of a robot tractor that is a mobile station provided in a communication system according to an embodiment of the present invention. The top view of a robot tractor. The block diagram which shows the main structures of the robot tractor as a mobile station. The block diagram which shows the main structures of a base station. The table | surface which shows the several channel list memorize | stored in the memory | storage part of a robot tractor. The flowchart which shows the flow of a process mainly at the time of normal mode among the processes performed by the robot tractor side which is a mobile station. The flowchart which shows the flow of a process mainly at the time of registration mode among the processes performed by the robot tractor side which is a mobile station. The flowchart which shows the flow of a process mainly at the time of a normal mode among the processes performed in a base station. The flowchart which shows the flow of a process mainly at the time of a registration mode among the processes performed in a base station.

  Next, embodiments of the present invention will be described with reference to the drawings. In the following, the same members are denoted by the same reference symbols in the drawings, and redundant description may be omitted. In addition, names of members and the like corresponding to the same reference may be simply rephrased, or may be rephrased with a superordinate concept or a subordinate concept name.

  The present invention, for example, as shown in the following embodiment, when one or a plurality of work vehicles are run in a predetermined agricultural field, and all or part of the agricultural work in the agricultural field is executed. The present invention is applied to an autonomous traveling system that autonomously travels a vehicle. In this embodiment, a tractor will be described as an example of a work vehicle. However, as a work vehicle, in addition to a tractor, a padded work machine such as a rice transplanter, a combiner, a civil engineering / construction work device, a snowplow, a walking work A machine is also included. In this specification, autonomous traveling means that the configuration related to traveling provided by the tractor is controlled by a control unit (ECU) provided in the tractor, and the tractor travels along a predetermined route. This means that the control unit included in the tractor controls the configuration related to the work included in the tractor, and the tractor performs the work along a predetermined route. On the other hand, manual running / manual work means that each component provided in the tractor is operated by the user to run / work.

  In the following description, a tractor that autonomously travels and works autonomously may be referred to as an “unmanned tractor” or a “robot tractor”, and a tractor that travels manually and is manually operated is referred to as a “manned tractor”. Sometimes. When a part of the farm work is performed by the unmanned tractor in the field, the remaining farm work is performed by the manned tractor. Performing farm work in a single farm with unmanned tractors and manned tractors may be referred to as cooperative work of farm work, follow-up work, accompanying work, and the like. In this specification, the difference between an unmanned tractor and a manned tractor is the presence or absence of an operation by a user, and each configuration is basically common. That is, even if it is an unmanned tractor, the user can board (ride) and operate (that is, it can be used as a manned tractor), or even if it is a manned tractor, the user gets off and autonomously travels. It can be operated autonomously (that is, it can be used as an unmanned tractor). In addition, as cooperative work of farm work, in addition to “execution of farm work in a single farm field with unmanned vehicles and manned vehicles”, “farm work in different farm fields such as adjacent farm fields can be performed at the same time. "Execution" may be included.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a side view showing an overall configuration of a robot tractor 1 which is a mobile station provided in a communication system 100 according to an embodiment of the present invention. FIG. 2 is a plan view of the robot tractor 1. FIG. 3 is a block diagram showing a main configuration of the robot tractor 1 as a mobile station.

  In a communication system 100 according to an embodiment of the present invention, a robot tractor (work vehicle) 1 as a mobile station receives positioning correction information from the base station 80 every moment, and the robot tractor 1 as a mobile station It is a communication system that can accurately acquire its own positioning information based on positioning correction information.

  As shown in FIG. 1, the robot tractor 1 is operated by performing wireless communication with a wireless communication terminal 46 via a short-range wireless network. When the user operates the wireless communication terminal 46 and appropriately exchanges signals with the control unit 4 of the tractor 1, the tractor 1 can autonomously travel and work.

  The tractor 1 includes a traveling machine body 2 that can autonomously travel in the field. A work machine 3 shown in FIGS. 1 and 2 is detachably attached to the traveling machine body 2. Examples of the work machine 3 include various work machines such as a tillage machine, a plow, a fertilizer machine, a mowing machine, and a seeding machine, and a desired work machine 3 is selected from these as required. 2 can be attached. The traveling machine body 2 is configured to be able to change the height and posture of the attached work machine 3.

  The configuration of the tractor 1 will be described in more detail with reference to FIGS. 1 and 2. As shown in FIG. 1, the traveling body 2 of the tractor 1 is supported at its front by a pair of left and right front wheels (wheels) 7 and 7 and at its rear by a pair of left and right rear wheels 8 and 8. Yes.

  A bonnet 9 is disposed at the front of the traveling machine body 2. The bonnet 9 houses an engine 10 and a fuel tank (not shown) that are driving sources of the tractor 1. Although this engine 10 can be comprised, for example with a diesel engine, it is not restricted to this, For example, you may comprise with a gasoline engine. Further, as a drive source, an electric motor may be used in addition to or instead of the engine.

  A cabin 11 for a user to board is disposed behind the hood 9. Inside the cabin 11, there are mainly provided a steering handle 12 for a user to steer, a seat 13 on which a user can be seated, and various operation devices for performing various operations. However, the work vehicle as a mobile station is not limited to the one with the cabin 11 and may be one without the cabin 11.

  As the above operation device, the monitor device 14 shown in FIG. 2, the throttle lever 15, the main transmission lever 27, the plurality of hydraulic operation levers 16, the PTO switch 17, the PTO transmission lever 18, the auxiliary transmission lever 19, and the work equipment lift switch 28 etc. can be mentioned as an example. These operating devices are arranged in the vicinity of the seat 13 or in the vicinity of the steering handle 12.

  The monitor device 14 is configured to display various information of the tractor 1. The throttle lever 15 is an operating tool for setting the output rotational speed of the engine 10. The main transmission lever 27 is an operating tool for changing the traveling speed of the tractor 1 in a stepless manner. The hydraulic operation lever 16 is an operation tool for switching and operating a hydraulic external take-off valve (not shown). The PTO switch 17 is an operating tool for switching the transmission / cutoff of power to a PTO shaft (power take-off shaft) (not shown) protruding from the rear end of the transmission 22. That is, when the PTO switch 17 is in the ON state, the PTO shaft to which power is transmitted to the PTO shaft rotates and the work machine 3 is driven, while when the PTO switch 17 is in the OFF state, the power to the PTO shaft is cut off. Thus, the PTO shaft does not rotate and the work machine 3 is stopped. The PTO speed change lever 18 is used to change the power input to the work machine 3, and specifically, is an operating tool for changing speed of the rotational speed of the PTO shaft. The auxiliary transmission lever 19 is an operating tool for switching the gear ratio of the traveling auxiliary transmission gear mechanism in the transmission 22. The work implement raising / lowering switch 28 is an operating tool for raising and lowering the height of the work implement 3 attached to the traveling machine body 2 within a predetermined range.

  As shown in FIG. 1, a chassis 20 of the tractor 1 is provided at the lower part of the traveling machine body 2. The chassis 20 includes a body frame 21, a transmission 22, a front axle 23, a rear axle 24, and the like.

  The body frame 21 is a support member at the front portion of the tractor 1 and supports the engine 10 directly or via a vibration isolation member. The transmission 22 changes the power from the engine 10 and transmits it to the front axle 23 and the rear axle 24. The front axle 23 is configured to transmit the power input from the transmission 22 to the front wheels 7. The rear axle 24 is configured to transmit the power input from the transmission 22 to the rear wheel 8.

  As shown in FIG. 3, the tractor 1 includes a control unit 4 for controlling the operation of the traveling machine body 2 (forward, reverse, stop, turn, etc.) and the operation of the work machine 3 (elevation, drive, stop, etc.). . The control unit 4 includes a CPU, a ROM, a RAM, an I / O, and the like (not shown), and the CPU can read various programs from the ROM and execute them. The control unit 4 includes a controller for controlling each component (for example, the engine 10 and the like) included in the tractor 1 and a wireless communication device for wirelessly communicating with other wireless communication devices according to standards such as CAN. Electrically connected.

  As the controller, the tractor 1 includes at least an engine controller 41, a vehicle speed controller 42, a steering controller 43, and a lift controller 44. Each controller can control each component of the tractor 1 in accordance with an electrical signal from the control unit 4.

  The engine controller 41 controls the rotational speed of the engine 10 and the like. Specifically, the engine 10 is provided with a governor device (not shown) including an actuator that changes the rotational speed of the engine 10. The engine controller 41 can control the rotational speed of the engine 10 by controlling the governor device. Further, the engine 10 is provided with a fuel injection device (not shown) that adjusts the injection timing and the injection amount of fuel to be injected (supplied) into the combustion chamber of the engine 10. The engine controller 41 can stop the supply of fuel to the engine 10 and stop the driving of the engine 10 by controlling the fuel injection device, for example.

  The vehicle speed controller 42 controls the vehicle speed of the tractor 1. Specifically, the transmission 22 is provided with, for example, a movable swash plate type hydraulic continuously variable transmission (not shown). The vehicle speed controller 42 can change the speed ratio of the transmission 22 and realize a desired vehicle speed by changing the angle of the swash plate of the hydraulic continuously variable transmission with an actuator.

  The steering controller 43 controls the turning angle of the steering handle 12. Specifically, a steering actuator (not shown) is provided in the middle of the rotating shaft (steering shaft) of the steering handle 12. With this configuration, when the tractor 1 travels (as an unmanned tractor) on a predetermined route, the control unit 4 calculates an appropriate rotation angle of the steering handle 12 so that the tractor 1 travels along the route. Then, a control signal is output to the steering controller 43 so that the obtained rotation angle is obtained. The steering controller 43 drives the steering actuator based on the control signal input from the control unit 4 and controls the rotation angle of the steering handle 12. Note that the steering controller does not adjust the turning angle of the steering handle 12 but may adjust the steering angle of the front wheel 7 of the tractor 1. Does not rotate.

  The lifting controller 44 controls the lifting / lowering of the work machine 3. Specifically, the tractor 1 includes a lifting actuator (not shown) formed of a hydraulic cylinder or the like in the vicinity of a three-point link mechanism that connects the work machine 3 to the traveling machine body 2. With this configuration, the elevating controller 44 drives the elevating actuator based on the control signal input from the control unit 4 to appropriately elevate the work implement 3 so that the work implement 3 can perform farm work at a desired height. Can be done. By this control, the work machine 3 can be supported at a desired height such as a retreat height (a height at which farm work is not performed) and a work height (a height at which farm work is performed).

  The plurality of controllers 41, 42, 43, 44 described above control each unit such as the engine 10 based on a signal input from the control unit 4, so that the control unit 4 substantially controls each unit. You can grasp that you are doing.

  The tractor 1 including the control unit 4 as described above controls various parts of the tractor 1 (the traveling machine body 2, the work implement 3, etc.) by the control unit 4 when the user gets into the cabin 11 and performs various operations. Thus, the farm work can be performed while traveling in the field. In addition, the tractor 1 of the present embodiment can perform autonomous traveling and autonomous work based on a predetermined control signal output from the wireless communication terminal 46 without the user getting on the tractor 1. Yes.

  Specifically, as shown in FIG. 3 and the like, the tractor 1 includes various configurations for enabling autonomous traveling and autonomous work. For example, the tractor 1 includes a positioning antenna 6 and a first wireless communication antenna 5 that are necessary for accurately acquiring position information of itself (the traveling machine body 2) every moment based on the positioning system. With such a configuration, the tractor 1 can acquire its own position information based on the positioning system and can autonomously travel on the field.

  Next, the configuration of the tractor 1 for enabling autonomous traveling will be described in more detail. Specifically, as shown in FIG. 3 and the like, the tractor 1 of this embodiment includes a positioning antenna 6, a position information receiver 52, a first wireless communication antenna 5, a mobile station communication device 57, and a second wireless communication. Antenna 48, short-range wireless communication device 51, camera 56, inertial measurement unit (IMU) 54, storage unit 55, and the like.

  The positioning antenna 6 receives a signal from a positioning satellite 105 constituting a positioning system such as a satellite positioning system (GNSS). In the present embodiment, a global positioning system (GPS or the like) is used as the GNSS. As shown in FIG. 1, the positioning antenna 6 is attached to the upper surface of the roof 26 of the cabin 11 of the tractor 1. The positioning signal received by the positioning antenna 6 is input to the position information receiver 52.

  The position information receiver 52 processes the input positioning signal from the positioning satellite to obtain positioning information. In addition, the position information receiver 52 corrects the obtained positioning information based on the positioning correction information acquired by the mobile station communication device 57, so that the traveling machine body 2 of the tractor 1 (strictly, positioning is determined). The position information of the antenna 6) is calculated and acquired as latitude / longitude information, for example. By correcting the positioning information in this way, the position of the traveling machine body 2 can be acquired with higher accuracy than the normal GNSS positioning. The position information acquired by the position information receiver 52 is stored in the storage unit 55, read out from the storage unit 55 in a timely manner, input to the control unit 4, and used for autonomous traveling.

  The first wireless communication antenna 5 is an antenna corresponding to a communication protocol (920 MHz wireless communication protocol in this embodiment) used for communication with the base station 80. As shown in FIG. 1, the first radio communication antenna 5 is disposed on the upper surface of the roof 26 of the cabin 11. In relation to the base station 80, it can be said that the tractor 1 is a mobile station. The first wireless communication antenna 5 receives a signal including positioning correction information (information used for position correction) distributed from the base station 80 every moment. Note that the bandwidth of the wireless communication protocol is not limited to 920 MHz. For example, the usable band may differ depending on the country, and it is possible to select an appropriate band as appropriate, such as using 860 MHz in Europe and 900 MHz in the United States.

  The mobile station communication device 57 processes the signal including the positioning correction information received by the first wireless communication antenna 5 to acquire the positioning correction information. The positioning correction information acquired by the mobile station communication device 57 is used to correct the positioning information acquired by the position information receiver 52.

  The second wireless communication antenna 48 is an antenna corresponding to a communication protocol (in this embodiment, 2.4 GHz and 5 GHz wireless communication protocols) used for communication with the wireless communication terminal 46 used by the user. As shown in FIG. 1, the second radio communication antenna 48 is disposed on the upper surface of the roof 26 provided in the cabin 11 of the tractor 1. A signal from the wireless communication terminal 46 received by the second wireless communication antenna 48 is subjected to signal processing by the short-range wireless communication device 51 and then input to the control unit 4. A signal transmitted from the control unit 4 or the like to the wireless communication terminal 46 is subjected to signal processing by the short-range wireless communication device 51, then transmitted from the second wireless communication antenna 48 and received by the wireless communication terminal 46.

  The short-range wireless communication device 51 demodulates the signal from the wireless communication terminal 46 received by the second wireless communication antenna 48, extracts information as digital data, and inputs the information to the control unit 4. Thereby, an instruction or the like issued by the user using the wireless communication terminal 46 is input to the control unit 4 and used to control each unit such as the engine 10.

  The camera 56 captures an environment around the tractor 1 (for example, an environment in front of and behind the traveling machine body 2). Although not shown in FIGS. 1 and 2, the camera 56 is attached to the roof 26 of the tractor 1. The moving image data shot by the camera 56 is modulated by the short-range wireless communication device 51 by an appropriate method, and is then transmitted from the second wireless communication antenna 48 on a carrier wave in a predetermined frequency band for wireless communication. It is displayed after reception at the terminal 46.

  The inertial measurement device 54 is a unit that can specify the posture (roll angle, pitch angle, yaw angle) of the traveling machine body 2 of the tractor 1. Information on the posture of the traveling machine body 2 acquired by the inertial measurement device 54 is input to the control unit 4 and used to correct position information or used for other controls.

  The storage unit 55 is a memory that stores a travel route for autonomously traveling the tractor 1 and stores position information of the tractor 1 (strictly speaking, the positioning antenna 6). In addition, the storage unit 55 of the present embodiment stores information related to frequency channels necessary for the tractor (mobile station) 1 to communicate with the base station 80, and the positioning correction information acquired through communication with the base station 80. Remember.

  Furthermore, the storage unit 55 is configured to manage a part of the storage area in units of pages using a page table. Each page is associated with one of the registered base stations 80. The registration of the base station 80 will be described in detail later.

  More specifically, the storage unit 55 of this embodiment includes a local station ID storage unit 61, a position information storage unit 62, a positioning correction information storage unit 63, a base station ID storage unit 711, a channel list storage unit 712, and The used channel storage unit 713 and the like are provided.

  The own station ID storage unit 61 stores an own station ID number which is an identification number of the own apparatus (tractor 1). The local station ID number is an identification number assigned when the tractor 1 is shipped, for example, and is determined not to cover other tractors.

  The position information storage unit 62 stores the position information of the tractor 1 acquired from the position information receiver 52 in association with time.

  The positioning correction information storage unit 63 stores the positioning correction information acquired by the mobile station communication device 57 in association with time.

  The base station ID storage unit 711 stores a base station ID number that is an identification number of the assigned base station 80.

  The channel list storage unit 712 stores the channel list transmitted from the base station 80.

  The used channel storage unit 713 stores a channel used for receiving positioning correction information from the base station 80. The used channel storage unit 713 also stores other information such as a channel change method / rule.

  The base station ID storage unit 711, the channel list storage unit 712, and the used channel storage unit 713 can store information for each registered base station 80. Specifically, the storage unit 55 registers information related to communication with the base station 80 (stored contents of the base station ID storage unit 711, the channel list storage unit 712, and the used channel storage unit 713) in the base station 80. Can be managed in units of base station management pages 71, 72, 73,. Thereby, addition, deletion, switching, and the like of the communication partner base station 80 can be easily performed.

  Next, the configuration of the base station 80 that communicates with the tractor (mobile station) 1 via a medium-distance wireless network such as specific low power will be described in detail with reference to FIG. FIG. 4 is a block diagram illustrating a main configuration of the base station 80.

  The base station 80 of this embodiment includes an antenna and a transceiver (detailed configuration will be described later), and is provided so as not to move easily after installation. The base station 80 is a predetermined location, is located within a range where radio waves from the positioning satellite 105 can sufficiently reach, and is located within a range where radio waves sufficiently reach the tractor 1. As a specific installation location of the base station 80, for example, it is conceivable that the base station 80 is on a hill in the vicinity of a farm field where the tractor 1 performs farm work.

  The base station 80 includes a control unit 82, a positioning antenna 101, a position information receiver 81, two communication antennas 98 and 98, a base station communication device 83, a user interface 99, a storage unit 90, and the like.

  The positioning antenna 101 receives a signal from the positioning satellite 105. The positioning signal received by the positioning antenna 101 is input to the position information receiver 81.

  The position information receiver 81 calculates and acquires the position information of the base station 80 (strictly speaking, the positioning antenna 101) as, for example, latitude / longitude information based on the input positioning signal from the positioning satellite. The position information acquired by the position information receiver 81 is stored in the storage unit 90 and is read out from the storage unit 90 in a timely manner and input to the control unit 82 to be used for calculating positioning correction information. It is done.

  The control unit 82 includes installation location information (position information stored in the installation location information storage unit 96) that is location information of a location where the base station 80 that is known in advance is installed, and location information obtained by the location information receiver 81. And the positioning correction information, which is a correction value for bringing the positioning information, which is the measurement value, closer to the actual position information, is calculated. Further, the control unit 82 sends this positioning correction information to the base station communication device 83 in a timely manner. The above-described installation location information of the base station 80 is set, for example, by the user operating the user interface 99, and is stored in the installation location information storage unit 96.

  Each of the two communication antennas 98 and 98 is an antenna corresponding to a communication protocol (920 MHz wireless communication protocol in the present embodiment) used for communication with the tractor 1. The communication antennas 98 and 98 transmit signals including positioning correction information from moment to moment. In the present embodiment, signals including positioning correction information are alternately transmitted at regular time intervals using two communication antennas 98. It is conceivable that the frequency of transmitting a signal from each communication antenna 98 is a plurality of times per second. Thereby, for example, even if the radio wave from one communication antenna 98 is weakened with the reflected wave due to the influence of so-called multipath or reflection from the ground and the reception level on the tractor 1 side decreases, the other communication antenna Position correction information can be obtained by receiving radio waves from 98 on the tractor 1 side. Thus, the reliability of communication is improved by transmitting the positioning correction information from the plurality of communication antennas 98 a plurality of times.

  The base station communication device 83 acquires the data including the positioning correction information from the storage unit 90, modulates the data, puts it on a carrier wave in a predetermined frequency band, and transmits it from the communication antennas 98 and 98. The radio wave including the positioning correction information is distributed from the communication antennas 98 and 98 at the timing. The base station communication device 83 includes a first transmission module 84 and a second transmission module 85 that are two transmission modules in association with the two communication antennas 98 and 98. The base station communicator 83 is controlled by the control unit 82 so that the second transmission module 85 includes the positioning correction information in the distribution suspension time after the first transmission module 84 distributes the signal including the positioning correction information. The timing of radio wave transmission is adjusted so that the signal is distributed. As a result, the positioning correction information can be transmitted alternately from the two communication antennas 98, 98, and the positioning correction information can be distributed over a plurality of times in one second as a whole, and distributed on the mobile station (tractor 1) side. The frequency of losing information can be reduced.

  When the base station 80 communicates with the tractor 1 by 920 MHz wireless communication, the user interface 99 receives information from the tractor 1 or inputs information to be sent to the tractor 1 when the user is at the base station 80 side. belongs to. The user interface 99 of the present embodiment is configured by a touch panel display or the like, and can input installation location information that is location information of a location where the base station 80 is installed.

  The storage unit 90 is a memory that stores various information such as positioning correction information distributed to the tractor 1 and a plurality of channel lists used for communication with the tractor 1. The storage unit 90 of the present embodiment stores information related to the frequency channel used by the base station (own station) 80 to communicate with the tractor (mobile station) 1 and information related to the tractor 1 acquired through communication with the tractor 1. Remember.

  More specifically, the storage unit 90 of this embodiment includes a local station ID storage unit 91, a positioning correction information storage unit 92, a channel list storage unit 93, a used channel storage unit 94, and a mobile station ID list storage unit 95. Etc. are provided.

  The own station ID storage unit 91 stores an own station ID number which is an identification number of the own device (base station 80). The own station ID number is, for example, an identification number assigned when the base station 80 is registered as being installed in a known location, and is determined not to overlap with other base stations.

  The positioning correction information storage unit 92 stores positioning correction information calculated based on information received by the position information receiver 81 in association with time.

  The channel list storage unit 93 stores in advance a plurality of channel lists obtained by dividing a plurality of channels included in a predetermined frequency band (920 MHz band in the present embodiment) into a plurality of groups. FIG. 5 shows channel lists 1, 2,... That are a plurality of channel lists in the present embodiment. FIG. 5 is a table showing a plurality of channel lists 1, 2,... Stored in the storage unit 55 of the robot tractor 1. FIG. 5 also shows an example of the common channel.

  As can be seen from FIG. 5, each channel included in the plurality of channel lists 1, 2,... Has radio interference with any of the other channels included in the plurality of channel lists 1, 2,. It is set not to occur. Any channel included in this channel list is used when the communication mode between the base station 80 and the tractor 1 is the normal mode (second mode).

  In order to set each channel included in the plurality of channel lists 1, 2,... So as not to cause radio wave interference with any of the other channels included in the plurality of channel lists 1, 2,. For example, the following method can be used.

  That is, for example, when radio wave interference occurs between adjacent channels, by selecting each channel, for example, by skipping one channel so that radio wave interference does not occur, other channels included in the same channel list or different channels It is necessary to set so that it does not cover any of the plurality of channels included in the list and is not adjacent.

  On the other hand, when radio wave interference does not occur between adjacent channels, it is sufficient that each channel is not covered with other channels.

  The used channel storage unit 94 stores one channel selected as a used channel by the base station 80 (from the channels included in the selected channel list). This use channel is used when the communication mode between the base station 80 and the tractor 1 is the normal mode (second mode).

  The mobile station ID list storage unit 95 stores the ID number of the registered tractor (mobile station) 1 acquired by the base station 80 through communication between the base station 80 and the tractor 1 in the registration mode (first mode). It is something to remember. The mobile station ID list storage unit 95 can store the ID numbers of one or more tractors 1 in a list, for example.

  Hereinafter, the communication mode between the base station 80 and the tractor 1 will be described in detail with reference mainly to FIGS. The communication mode between the base station 80 and the tractor 1 of the present embodiment includes a registration mode (first mode) in which the base station 80 and the tractor 1 mutually authenticate and register, and the base station 80 to the tractor 1. In addition to the normal mode (second mode) for delivering positioning correction information, there are also a communication test mode for performing a communication test between each other, but the following description will focus on the registration mode and the normal mode, which are the main communication modes. I do.

  First, the flow of processing performed on the tractor 1 side which is a mobile station will be described with reference to FIGS.

  When the mobile station communication device 57 is activated, the control unit 4 first determines whether or not there is registration information of the base station 80 in the storage unit 55 as shown in FIG. 6 (step S101). Specifically, it is determined whether or not one or more base station management pages 71, 72, 73,. As a result, when registration information of the base station 80 exists, the communication mode is switched to the normal mode in order to attempt to receive positioning correction information from the base station 80, and the subsequent processing (steps S102 to S106) is performed. Done.

  When the mode is switched to the normal mode, the control unit 4 reads out the channel used for receiving the positioning correction information from the used channel storage unit 713 of the base station management page 71 corresponding to the base station 80 registered in the past. . In the following description, it is assumed that the used channel stored in the used channel storage unit 713 is a.

  Then, in order to attempt to receive the positioning correction information from the base station 80, the control unit 4 sets the channel received by the mobile station communication device 57 to a (step S102), and waits for reception from the base station 80 (step S102). Step S103).

  While waiting for reception from the base station 80, if the positioning correction information from the base station 80 is received (step S104, Yes), the control unit 4 stores the received positioning correction information in the positioning correction information storage unit 63. Remember. After that, it returns to the reception standby state and continues to receive positioning correction information from the base station 80 every moment (repeats Step S103 to Step S104).

  On the other hand, when the positioning correction information is not received for a predetermined time or longer when waiting for reception from the base station 80 (step S104, No, step S105, Yes), the base station 80 side uses it for communication for some reason. It is possible that the channel to be changed was changed. Therefore, the control unit 4 reads the channel list specified by the base station 80 from the channel list storage unit 712 of the base station management page 71. In this example, channel list 1 including channel a is read. The control unit 4 refers to the channel list 1 and selects the next channel according to a predetermined channel change method. In the case of the example shown here, “if the channel is changed, the next largest channel in the channel list is set as the next channel (if there is no next largest numeric channel, the channel list The next channel is defined as b (see FIG. 5) in accordance with the change method determined in advance. Although a detailed description is omitted in the present embodiment, as the channel change method / rule, other change methods / rules than the above can be used as long as they are shared between the base station and the mobile station.

  Then, the control unit 4 changes the channel received by the mobile station communication device 57 to b in order to try to receive the positioning correction information from the base station 80 again with the new channel b (step S106). In this state, the control unit 4 waits for reception from the base station 80 (returns to step S103).

  Note that the channel b selected in step S106 is stored in the used channel storage unit 713. That is, the used channel stored in the used channel storage unit 713 is updated from a to b.

  By such a processing flow, the control unit 4 can receive the positioning correction information distributed from the base station 80 every moment. Even when the base station 80 side changes the channel used for distribution for some reason, the next channel is set in accordance with the channel list 1 received from the base station 80 in advance, and the positioning correction distributed from the base station 80 using this channel again. You can try to receive information. That is, the tractor 1 can smoothly communicate with the base station 80 because the channel list 1 and the like indicate which channel the base station 80 uses in the normal mode. Therefore, the tractor 1 can continue to travel and farm work by acquiring accurate positioning information (position information corrected by the positioning correction information acquired every moment) without delay.

  On the other hand, if the result of determination in step S101 is that there is no base station registration information (No in step S101), the communication mode is set to registration mode.

  In the registration mode, as shown in FIG. 7, the control unit 4 sets a channel used by the mobile station communication device 57 and a mobile station transmitter (not shown) as a common channel and waits for reception from the base station 80 ( Step S107). In the following description, it is assumed that channel x is set as the common channel.

  When it is set to the common channel and is waiting for reception from the base station 80, if its own station information (specifically, the ID number of the base station 80) can be received from the base station 80 (Yes in step S108), In order to have the tractor 1 registered as a delivery destination on the base station 80 side, the control unit 4 transmits a registration request to the base station 80 (step S109). The registration request includes information regarding the tractor 1 including the ID number of the tractor 1. In this registration, it is possible to set a time-out as necessary and display an error as appropriate. However, since this is not unique to this patent, a detailed description is omitted.

  The control unit 4 continues the standby state on the channel x until it receives its own station information (base station information) from the base station 80 (No in step S108).

  In response to the registration request transmitted in step S109, when the mobile station communication device 57 receives a response from the base station 80 sent as reception confirmation (step S110, Yes), the control unit 4 subsequently rejects the registration. It is determined whether or not a notification (rejection notification) to the effect is received from the base station 80 (step S111). If a response from the base station 80 has not been received (step S110, No), the process returns to step S108 and the standby on the channel x is continued.

  If a rejection notification is received as a result of the determination in step S111 (step S111, Yes), the mobile station returns to the standby state on channel x in order to try to register at another base station (return to step S108). .

  On the other hand, when the rejection notification is not received (step S111, No), it is considered that the base station 80 permits the registration of the tractor 1. Although details will be described later, the base station 80 is configured to immediately transmit channel list / used channel information to the tractor 1 when the registration of the tractor 1 is permitted.

  When the mobile station communication device 57 receives the channel list / used channel information from the base station 80 (step S112, Yes), the control unit 4 creates the base station management page 71 for the base station 80, and The ID number of the base station 80 is stored in the ID storage unit 711, the channel list received in the channel list storage unit 712, and the used channel received in the used channel storage unit 713 (step S113). In addition, the control unit 4 transmits a response indicating that the information regarding these channels has been received to the base station 80 via the mobile station communication device 57.

  In addition, when the rejection notification is not received, but the channel list / used channel information is not received from the base station 80 for some reason, the control unit 4 is requested to perform authentication registration including other base stations. In order to try, it returns to the standby state on channel x (return to step S108).

  Through such a processing flow, the tractor 1 can perform two-way communication with the base station 80 using a common channel, thereby performing registration with each other. In addition to this registration, the base station 80 informs the tractor 1 in advance of information (channel list / used channel) related to the channel to be used in communication in the normal mode thereafter. Sometimes, two-way communication is not necessary, and it is only necessary to distribute distribution data from the base station to the mobile station in a so-called broadcast type, as will be described later. Therefore, it is possible to suppress the occurrence of a situation where the bandwidth is insufficient, and it is possible to avoid problems such as difficulty in connection of communication and a decrease in communication speed. Further, even when there are a plurality of mobile stations, the positioning correction information can be distributed by the same mechanism as the above-described process without adding a special process.

  Next, the flow of processing performed on the base station 80 side will be described with reference to FIGS.

  When the user on the base station 80 side operates the user interface 99 to set the communication mode to the normal mode, the control unit 82 first uses the channel to be used based on the ID number of the own station as shown in FIG. A list is selected (step S201).

  That is, it is assumed that a plurality of communication systems 100, 100,. In such a case, in order to prevent radio wave interference between the communication systems 100, it is preferable to use channels that do not cause radio wave interference between the communication systems 100 existing in the vicinity. In order to realize this, in the communication system 100 according to the present embodiment, a plurality of channel lists 1, 2,... Are prepared in advance as shown in FIG. (Disconnect).

  Specifically, in this embodiment, the base station 80 of each communication system 100 has a number (order) corresponding to the remainder obtained by dividing its own ID number (base station ID number) by the number of channel lists. Arrange to use channel list for communication.

  In the following description, assuming that the ID number of the base station 80 is 18745, in step S201, the control unit 82 reads 18745, which is the ID number of the own station, from the own station ID storage unit 91. When the remainder obtained by dividing 18745 by the number of channel lists is 1, the control unit 82 selects channel list 1 which is the first channel list. The selected channel list 1 is stored in the channel list storage unit 93 separately from the other channel lists 2, 3,.

  Subsequently, the control unit 82 selects a channel (used channel) to be used during communication in the normal mode from the channels included in the channel list 1 (step S202). In this embodiment, a channel is selected according to a method for determining a channel that has been decided in advance. In the case of the example shown here, a is selected as a channel to be used according to a pre-arranged method of “when selecting a channel for the first time, select the channel with the smallest numerical value in the channel list” (see FIG. 5). reference).

  Subsequently, the control unit 82 determines whether or not the channel a that is a used channel is congested (band is insufficient) (step S203). This determination is performed by a known method such as carrier sense for detecting the usage status of channel a.

  If the channel a is congested as a result of the determination in step S203 (step S203, Yes), communication may be interrupted if communication is performed using this channel. Change to a channel other than a (step S204). Specifically, the control unit 82 refers to the channel list 1 and selects the next channel according to a predetermined channel change method. In the case of the example shown here, “if the channel is changed, the next largest channel in the channel list is set as the next channel (if there is no next largest numeric channel, the channel list The channel is selected (changed) as the next channel in accordance with a change method determined in advance (referred to as FIG. 5). Further, the control unit 82 determines whether or not the channel b selected as the next channel is congested (step S203). Thus, step S203 is repeated until a non-congested channel is found. The changed channel b is stored in the used channel storage unit 94.

  If the used channel is not congested in step S203 (No in step S203), the determination in step S205 is subsequently performed. That is, in step S205, the control unit 82 determines whether or not the communication mode has been switched to the registration mode by operating the user interface 99 or the like. As a result of this determination, when the communication mode is switched to the registration mode (step S205, Yes), the control unit 82 performs a series of processes in the registration mode described later (steps S210 to S218).

  On the other hand, as a result of the determination in step S205, when the communication mode is maintained in the normal mode (step S205, No), the control unit 82 reads the positioning correction information from the positioning correction information storage unit 92, and performs the positioning. An attempt is made to transmit a signal including correction information to the tractor 1 via the base station communication device 83 (step S206). In the present embodiment, the control unit 82 transmits a signal including positioning correction information via the base station communication device 83 by broadcast. Thereby, even when there are a plurality of tractors 1 stored in the mobile station ID list storage unit 95, it is not necessary to transmit positioning correction information to each tractor 1 individually. In other words, the positioning correction information can be transmitted (distributed) to all the tractors 1 at once, the transmission procedure is simplified, and the bandwidth necessary for distribution can be suppressed to the minimum necessary.

  Subsequently, the control unit 82 determines whether or not the transmission of the positioning correction information performed in step S206 has succeeded (has been successfully transmitted) (step S207). In the process of step S206, it is confirmed whether the used channel is not used in another wireless system before transmission, that is, so-called carrier sense is performed. If the channel is free, transmission is actually performed. The control unit 82 determines that transmission is successful. On the other hand, if the channel is busy in another wireless system and is busy, transmission is not performed, and in this case, it is determined that transmission has failed.

  As a result of the determination in step S207, if the transmission is successful (step S207, Yes), the positioning correction information is acquired from the positioning correction information storage unit 92 until the communication mode is switched to the registration mode, and the positioning correction information is stored in the tractor. 1 is repeated every moment (steps S205 to S207 are repeated). For example, the control unit 82 distributes the positioning correction information a plurality of times per second.

  On the other hand, if it is determined in step S207 that the transmission of the positioning correction information performed in step S206 has failed (No in step S207), whether or not the number of consecutive failed transmissions has reached a specified number. Is determined (step S208).

  As a result of the determination in step S208, if the prescribed number of transmissions have failed continuously (step S208, Yes), for example, another system used in the vicinity is using channel a and radio wave interference has occurred. It is considered that this has occurred or the communication band of channel a is insufficient. In that case, in order to switch to another channel and attempt communication again, the control unit 82 changes the channel used in the base station communication device 83 to the next channel with reference to the channel list 1 (step S209). Specifically, the control unit 82 reads the channel list 1 from the channel list storage unit 93 and changes the next channel to b by using a predetermined change method. Note that the change method determined in advance is the same as the change method recognized on the tractor 1 side.

  And the control part 82 tries transmission of positioning correction information anew on this new channel b (step S206). If the number of transmission failures reaches a specified number even if transmission of positioning correction information is attempted on this channel b, the channel is changed to the next channel c and transmission is attempted (see FIG. 5). As described above, the control unit 82 repeats the channel change with reference to the channel list 1 and the change method determined in advance until reaching the communication band where stable communication can be ensured.

  The channel changed in step S206 is stored in the used channel storage unit 94. In other words, the used channel stored in the used channel storage unit 94 is updated from a to b (c from some circumstances).

  By such a processing flow, the control unit 82 can transmit the positioning correction information calculated based on the information received by the position information receiver 81 to the tractor 1 every moment. In addition, as described above, if a channel change method is determined in advance, stable communication cannot be ensured, so that even when the base station 80 changes the channel used for distribution, it is transferred to the tractor 1 side each time. There is no need to inform. If transmission of the positioning correction information fails on the channel a selected first, it transmits on the next channel b according to the channel list 1, and if it fails also on the next channel c according to the channel list 1. It is possible to flexibly change the frequency band used for communication, such as transmission, and generation of radio wave interference with base station systems used in other fields or other wireless systems used in the vicinity It is possible to suppress the communication interruption for a long time. As a result, it is possible to realize distribution with less chipping from the base station 80 to the tractor 1.

  When the user on the base station 80 side operates the user interface 99 to set the communication mode to the registration mode (step S205, Yes), the control unit 82 uses the common channel in the base station communication device 83 as shown in FIG. Using x, the local station information (specifically, the ID number of the base station 80) is transmitted to the tractor 1 within the range where radio waves reach (step S210). In the present embodiment, the ID number information of the base station 80 is distributed by broadcast.

  After the process of step S210, the control unit 82 monitors the reception status at a base station receiver (not shown). As a result, when the registration request from the tractor 1 is received (step S211, Yes), the control unit 82 transmits a response as a reception confirmation to the tractor (mobile station) 1 (step S212).

  Subsequently, the control unit 82 determines whether an operation for permitting registration of the tractor 1 has been performed by the user on the base station 80 side (determination of authentication, step S213). When the user on the base station 80 side determines that registration of the tractor 1 cannot be permitted due to some circumstances such as a contract and performs an operation to that effect, the control unit 82 transmits a rejection notice to the tractor 1 (step S1). S214).

  On the other hand, as a result of the determination in step S213, when the operation for permitting registration of the tractor 1 is performed by the user (step S213, Yes), the control unit 82 reads the base station 80 read from the own station ID storage unit 91. Base station ID number (18745), the channel list 1 used by the own station read from the channel list storage unit 93, and the latest used channel (here, a) read from the used channel storage unit 94, It transmits to the tractor 1 via the station communication device 83 (step S215).

  When a response indicating that information on these channels has been received is received from the tractor 1 by a base station receiver (not shown) (Yes in step S216), the control unit 82 has authenticated the tractor 1 by the base station 80. As an example, the ID number of the tractor 1 included in the response is read out and registered in the mobile station ID list storage unit 95 (step S217).

  In addition, when a predetermined time has elapsed from the start of the registration mode (step S210) (step S218, Yes), the control unit 82 is considered to have completed registration of the neighboring mobile station (tractor 1). Abort mode and switch to normal mode.

  The control unit 82 continues to monitor the reception status from the mobile station until a predetermined time has elapsed from the start of the registration mode (step S211), and registers a plurality of mobile stations in the mobile station ID list storage unit 95. Is also possible. Thereby, it is possible to communicate with a plurality of tractors 1, 1,... Using a single base station 80, and to collectively correct the position information of the plurality of tractors 1, 1,. Can be realized.

  Through such a processing flow, the base station 80 performs two-way communication with the tractor 1 using the common channel, so that the registration of the base station 80 in the tractor 1 and the registration of the tractor 1 in the base station 80 This can be done easily by mutual exchange. In addition, since the tractor 1 is informed in advance of information relating to the channel used for subsequent communication in the normal mode in the registration mode, one-way communication is sufficient in other cases (in the normal mode). Therefore, it is possible to suppress the occurrence of a situation in which the communication bandwidth is insufficient, and it is possible to avoid problems such as difficulty in connection of communication and reduction in communication speed. Thereby, the reliability of communication between the base station 80 and the tractor 1 can be improved, and the occurrence of lack of communication can be suppressed.

  In the case of a mobile station that autonomously travels like the tractor 1 of the present embodiment, the autonomous travel of the tractor 1 is automatically stopped when the reception of positioning correction information is interrupted for a certain time (for example, several seconds). There are many cases. In this regard, in the communication system 100 according to the present embodiment, since it is possible to prevent the communication between the tractor 1 and the base station 80 from being lost for a long time, it is possible to avoid a situation where the tractor 1 stops due to poor communication. .

  As described above, the communication system 100 of the present embodiment is a communication system between the tractor (mobile station) 1 and the base station 80 using a predetermined frequency band (920 MHz). The communication system 100 includes a registration mode (first mode) in which the tractor 1 and the base station 80 can perform bidirectional communication, and a normal mode (second mode) in which the base station 80 distributes positioning correction information. ). The base station 80 stores a plurality of channel lists in which a plurality of channels (a, b,...) Included in the 920 MHz frequency band are divided into a plurality of groups. In the registration mode, the base station 80 transmits predetermined information to the tractor 1. The predetermined information includes a channel list used by the base station 80 in the normal mode and indicating any channel list 1 selected from the plurality of channel lists. The predetermined information indicates a channel used by the base station 80 in the normal mode and included in any of the selected channel lists 1 (a in the example shown in the present embodiment). Contains information.

  Thereby, in the registration mode, information on channel list 1 and channel a used by the base station 80 is transmitted to the tractor 1, and the tractor 1 knows which channel the base station 80 uses in the normal mode. Two-way communication is not necessary in the mode. As a result, it is possible to make it difficult to cause communication interruption due to radio wave interference and the like, and the tractor 1 can acquire accurate positioning information without delay.

  In the communication system 100 of the present embodiment, in the first mode, the base station 80 transmits a base station ID number to the tractor 1, and the tractor 1 transmits a mobile station ID number to the base station 80.

  Thereby, since the other party can mutually be specified and exchanged between the base station 80 and the tractor 1, work such as registration is facilitated.

  Further, in the communication system 100 of the present embodiment, the tractor 1 stores the channel list and used channels received (received) from the base station 80 in association with the base station ID number. In other words, the storage unit 55 of the tractor 1 stores the received channel list and used channels for each base station.

  Thereby, the tractor 1 can change the base station which communicates according to a condition. Further, even when the base station that performs communication is changed, it is possible to know which channel each base station uses in the normal mode, so that communication can be established smoothly in the normal mode.

  In the communication system 100 of the present embodiment, transmission (distribution) from the base station 80 in the normal mode is broadcast.

  Thus, even when a plurality of tractors 1, 1,... Are registered with respect to one base station 80 in the registration mode, it is not necessary to transmit positioning correction information to each tractor 1 individually. In other words, positioning correction information can be transmitted simultaneously to all tractors 1, 1,..., And the transmission procedure is simplified.

  In the communication system 100 of the present embodiment, the base station 80 includes a plurality of first transmission modules (first communication modules) 84 and second transmission modules (second communication modules) 85 that distribute positioning correction information. The transmission module. In the normal mode, in the base station 80, the second transmission module 85 distributes the positioning correction information during the distribution suspension time after the first transmission module 84 distributes the positioning correction information.

  Accordingly, the positioning correction information can be distributed by the second transmission module 85 that is the other communication module by using the distribution suspension time of the first transmission module 84 that is the one communication module. Therefore, it is possible to improve the reliability of distribution of positioning correction information within the limits of the transmission time and the transmission interval for each of the transmission modules 84 and 85.

  The communication system 100 of the present embodiment has the following configuration. That is, the bidirectional communication channels x and y used for bidirectional communication between the base station 80 and the tractor 1 in the registration mode are channels not included in the plurality of channel lists 1, 2,. In addition, the channels included in the bidirectional communication channels x and y and the plurality of channel lists 1, 2,... Are channels that do not cause radio wave interference with each other.

  Thereby, since the channels x and y used for the registration mode are different from the channels in the normal mode, communication necessary for registration and the like can be performed smoothly. In addition, since the channels used in the normal mode do not cause radio wave interference with each other, duplication of communication bands can be avoided and communication failure can be avoided.

  The communication system 100 of the present embodiment has the following configuration. That is, in the normal mode, the base station 80 includes the channel a to be used in the channel list 1 which is one of the selected channel lists when the number of times the positioning correction information distribution has failed reaches a specified number. Change to another channel b. In the normal mode, when the acquisition of the positioning correction information is interrupted for a predetermined time (for example, several seconds), the tractor 1 selects the channel a to be used in the channel list 1 that is one of the selected channel lists. Change to channel b.

  Thus, since the channel list 1 is stored in the base station 80 and the tractor 1, even if information on the used channel is not transmitted from the base station 80 each time, for example, if communication is not performed for a predetermined time, another channel (B, c, etc.) can be changed.

  Further, in the communication system 100 of this embodiment, the base station 80 has a remainder when the ID number (for example, 18745) of the own station is divided by the number of channel lists (for example, 4) stored in advance. The channel list 1 of the number (order) corresponding to the numerical value of is a channel list used by the own station in the normal mode.

  As a result, when a plurality of communication systems 100, 100,... Similar to the communication system 100 are used at the same time in a nearby field, channels are selected according to different channel lists in the communication systems 100 existing nearby. Therefore, it is possible to avoid covering the used channel as much as possible. Therefore, radio interference can be made difficult to occur by such a simple method. In addition, when there is another system using the same frequency band in the vicinity, the channel is automatically changed in the case of interference by the routine shown in steps S208 and S209 in FIG. Interference with the system can be avoided.

  The preferred embodiment of the present invention has been described above, but the above configuration can be modified as follows, for example.

  In the above embodiment, the predetermined frequency band used for communication between the tractor 1 and the base station 80 is 920 MHz. However, as described above, the predetermined frequency band is not necessarily limited to this, and other predetermined frequency bands are used. The present invention can also be applied to a communication system between a mobile station and a base station to be used.

  In the above embodiment, the base station 80 stores channel lists 1, 2,... That divide a plurality of channels (a, b,...) Included in the 920 MHz frequency band into a plurality of groups. However, the number of channel lists can be increased or decreased depending on the situation.

  Each of the channels included in the plurality of channel lists 1, 2,... Shown in the above embodiment can be assumed to be a channel that is one channel away from the adjacent channel. Is not limited to one channel. For example, two channels may be skipped instead.

  In the above embodiment, in the normal mode, the base station 80 sets the channel a to be used when the number of times the distribution of positioning correction information has failed reaches a specified number as a channel that is one of the selected channel lists. The channel is changed to another channel b included in the list 1. However, this is substantially the same as determining the timing of channel change on a time basis, such as changing to another channel when distribution of positioning correction information cannot be performed for a predetermined time. It can be said.

  In the above-described embodiment, the channel changing method determined in advance between the base station 80 and the mobile station (tractor 1) is “if the channel is changed, the next largest channel in the channel list is This is merely an example. That is, the channel changing method previously determined between the base station 80 and the mobile station (tractor 1) may be any other method as long as the channel can be uniquely selected. Specifically, for example, the channel change method is “if the channel is changed, the channel with the next smallest numerical value in the channel list is selected as a candidate channel” or “when the channel is changed, One channel (one channel) may be skipped from the channel list and the next largest numerical channel may be selected as a candidate channel. "

  The base station 80 is a structure that can be carried by the user, and may be appropriately installed in the vicinity of a farm field, or may be permanently installed at a predetermined (known) location.

  In the above embodiment, the base station 80 includes the two transmission modules 84 and 85 and the two communication antennas 98 and 98 corresponding thereto. However, in order to improve the reliability of communication, it is sufficient if it includes a plurality of transmission modules and communication antennas, and the number thereof may be three or more.

1 Tractor (mobile station)
80 base station

Claims (4)

A communication system between a mobile station and a base station using a predetermined frequency band,
A first mode in which the mobile station and the base station can perform two-way communication; and a second mode in which the base station distributes positioning correction information.
The base station stores a plurality of channel lists obtained by dividing a plurality of channels included in the frequency band into a plurality of groups,
In the first mode, the base station transmits predetermined information to the mobile station,
The predetermined information includes
A channel list used by the base station in the second mode, information indicating any channel list selected from the plurality of channel lists;
Information indicating a channel used by the base station in the second mode and included in any of the selected channel lists;
The communication system characterized by including. The communication system according to claim 1,
The base station includes a plurality of transmission modules including a first communication module and a second communication module for distributing the positioning correction information,
In the second mode, the base station distributes the positioning correction information from the second communication module during a distribution suspension time after the first communication module distributes the positioning correction information. Communication system. The communication system according to claim 1 or 2,
The bidirectional communication channel used for bidirectional communication between the base station and the mobile station in the first mode is a channel not included in the plurality of channel lists,
Each channel included in the plurality of channel lists is a channel that does not cause radio wave interference with each other. The communication system according to any one of claims 1 to 3, wherein
In the second mode, when the distribution of the positioning correction information cannot be executed for a predetermined time, the base station changes a channel to be used to another channel included in any of the selected channel lists,
In the second mode, when the acquisition of the positioning correction information is interrupted for a predetermined time, the mobile station changes the channel to be used to the other channel included in any of the selected channel lists. A communication system characterized by the above.

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