Patent Publication Number: US-2022212701-A1

Title: Ground control device, radio communication apparatus, radio train control system, and train control method

Description:
FIELD 
     The present invention relates to a ground control device, a radio communication apparatus, a radio train control system, and a train control method for train operation control. 
     BACKGROUND 
     There have been radio train control systems in which a ground control device performs radio communication with a train via a radio communication apparatus to control the operation of the train. Patent Literature 1 discloses a technique in train operation control using radio communication in which a radio train control system controls the operation of a train by switching to one of the states of normal operation, degenerate operation, cautious operation, and emergency stop control according to the state of communication between the train and a wireless base station. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: WO98/41435A 
     SUMMARY 
     Technical Problem 
     However, according to the above conventional technique, the radio train control system successively switches an operation control method for a train depending on the real-time communication state of the train. Therefore, when the preceding train enters an area with a deteriorated communication state, the operation control of the preceding train is suddenly switched from normal operation to degenerate operation. This causes a problem in that when trains are under moving-block operation control, the following train can come to an emergency stop due to its stop limit position being suddenly moved toward the train. If the following train that has come to an emergency stop causes the train behind to also come to an emergency stop, there arises a problem in that the effect on the train operation control increases, reducing operation efficiency. 
     The present invention has been made in view of the above. It is an object of the present invention to provide a ground control device capable of preventing a decrease in operation efficiency when there is a train entering or approaching an area with a deteriorated communication state, by avoiding an emergency stop of the following train. 
     Solution to Problem 
     In order to solve the above-stated problem and achieve the object, a ground control device according to the present invention includes: a control unit to determine a control mode of operation control on a train in a communication area of a radio communication apparatus, based on information on a communication level indicating a communication state between the train and the radio communication apparatus determined in a predetermined period, and perform train operation control according to the determined control mode on a train entering or approaching the communication area after the control mode is determined; and a storage unit to store one or more pieces of the information on the communication level for one or more of the radio communication apparatuses. 
     Advantageous Effects of Invention 
     According to the present invention, the ground control device has the effect of being able to prevent a decrease in operation efficiency when there is a train entering or approaching an area with a deteriorated communication state, by avoiding an emergency stop of the following train. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram illustrating an example configuration of a radio train control system according to a first embodiment. 
         FIG. 2  is a block diagram illustrating an example configuration of a radio communication apparatus according to the first embodiment. 
         FIG. 3  is a flowchart illustrating the operation of the radio communication apparatus according to the first embodiment. 
         FIG. 4  is a block diagram illustrating an example configuration of a ground control device according to the first embodiment. 
         FIG. 5  is a diagram illustrating an example of a control mode of operation control on a train performed at communication level A by the ground control device according to the first embodiment. 
         FIG. 6  is a diagram illustrating an example of a control mode of operation control on a train performed at communication level B by the ground control device according to the first embodiment. 
         FIG. 7  is a diagram illustrating a first example of a control mode of operation control on a train performed at communication level C by the ground control device according to the first embodiment. 
         FIG. 8  is a diagram illustrating a second example of a control mode of operation control on a train performed at communication level C by the ground control device according to the first embodiment. 
         FIG. 9  is a diagram illustrating an example of a control mode of operation control on a train performed at communication level D by the ground control device according to the first embodiment. 
         FIG. 10  is a flowchart illustrating the operation of the ground control device according to the first embodiment. 
         FIG. 11  is a flowchart illustrating a control mode management process in the ground control device according to the first embodiment. 
         FIG. 12  is a flowchart illustrating a train control process in the ground control device according to the first embodiment. 
         FIG. 13  is a flowchart illustrating a process of creating a stop limit position based on the rear position of a preceding train in the ground control device according to the first embodiment. 
         FIG. 14  is a flowchart illustrating a process of creating a stop limit position based on a route end in the ground control device according to the first embodiment. 
         FIG. 15  is a diagram illustrating an example where a processor and a memory constitute processing circuitry included in the ground control device according to the first embodiment. 
         FIG. 16  is a diagram illustrating an example where dedicated hardware constitutes processing circuitry included in the ground control device according to the first embodiment. 
         FIG. 17  is a block diagram illustrating an example configuration of a radio communication apparatus according to a second embodiment. 
         FIG. 18  is a flowchart illustrating the operation of the radio communication apparatus according to the second embodiment. 
         FIG. 19  is a block diagram illustrating an example configuration of a ground control device according to the second embodiment. 
         FIG. 20  is a flowchart illustrating a control mode management process in the ground control device according to the second embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, a ground control device, a radio communication apparatus, a radio train control system, and a train control method according to embodiments of the present invention will be described in detail with reference to the drawings. Note that the embodiments are not intended to limit the invention. 
     First Embodiment 
       FIG. 1  is a diagram illustrating an example configuration of a radio train control system  100  according to a first embodiment of the present invention. The radio train control system  100  includes a ground control device  10  and radio communication apparatuses  20 - 1 ,  20 - 2 ,  20 - 3 , and  20 - 4 . The radio communication apparatus  20 - 1  performs radio communication with a train  41  located within a communication area  30 - 1 . The radio communication apparatus  20 - 2  performs radio communication with a train  42  located within a communication area  30 - 2 . The radio communication apparatus  20 - 3  performs radio communication with a train  43  located within a communication area  30 - 3 . The radio communication apparatus  20 - 4  performs radio communication with a train  44  located within a communication area  30 - 4 . In the radio train control system  100 , the communication areas  30 - 1  to  30 - 4  are formed on the route  50  of the trains  41  to  44 . 
     The ground control device  10  controls the operation of the trains  41  to  44  located in the communication areas  30 - 1  to  30 - 4  of the radio communication apparatuses  20 - 1  to  20 - 4 . In the following description, the radio communication apparatuses  20 - 1  to  20 - 4  are sometimes referred to as radio communication apparatuses  20  when not distinguished, the communication areas  30 - 1  to  30 - 4  are sometimes referred to as communication areas  30  when not distinguished, and the trains  41  to  44  are sometimes referred to as trains  40  when not distinguished.  FIG. 1  illustrates an example in which the ground control device  10  is connected to the four radio communication apparatuses  20 , which is an example, and the present invention is not limited to this. The ground control device  10  may be connected to three or less or five or more radio communication apparatuses  20 . 
     The configuration and operation of the radio communication apparatuses  20  will be described.  FIG. 2  is a block diagram illustrating an example configuration of the radio communication apparatuses  20  according to the first embodiment. Each radio communication apparatus  20  includes a radio communication unit  21 , a communication level determination unit  22 , and a ground communication unit  23 . 
     The radio communication unit  21  performs radio communication with the train  40  located in the communication area  30 . The radio communication unit  21  measures the communication quality of the radio communication between the train  40  and the radio communication unit  21 . Examples of the communication quality include, but are not limited to, a reception signal strength, a signal-to-noise ratio, and a packet error rate. The radio communication unit  21  may perform two or more types of measurement and use a combination of the respective measurement results as communication quality. 
     The communication level determination unit  22  determines a communication level indicating the state of communication between the train  40  and the radio communication unit  21 . Specifically, the communication level determination unit  22  determines a communication level, based on information on the communication quality of the radio communication between the train  40  and the radio communication unit  21  measured by the radio communication unit  21 . The communication level is an index used by the ground control device  10  to determine a control mode of operation control on the train  40  when controlling the operation of the train  40 . In the present embodiment, as an example, the communication level determination unit  22  makes a determination to classify the state of communication between the train  40  and the radio communication unit  21  as one of four levels, communication levels A, B, C, and D. Here, communication level A represents the best communication state, communication level B represents the second best communication state, communication level C represents the third best communication state, and communication level D represents the worst communication state. 
     The ground communication unit  23  transmits information on the communication level determined by the communication level determination unit  22  to the ground control device  10 . Specifically, the ground communication unit  23  transmits to the ground control device  10  the communication level information as train information including the communication level information and other control information. Communication between the ground communication unit  23  and the ground control device  10  may be wired communication, wireless communication, or communication combining wired communication and wireless communication. 
       FIG. 3  is a flowchart illustrating the operation of the radio communication apparatuses  20  according to the first embodiment. In each radio communication apparatus  20 , the radio communication unit  21  measures the communication quality of radio communication between the train  40  and the radio communication unit  21  (step S 1 ). The communication level determination unit  22  determines a communication level based on information on the communication quality of the radio communication between the train  40  and the radio communication unit  21  (step S 2 ). The ground communication unit  23  transmits train information including information on the communication level to the ground control device  10  (step S 3 ). 
     Next, the configuration and operation of the ground control device  10  will be described.  FIG. 4  is a block diagram illustrating an example configuration of the ground control device  10  according to the first embodiment. The ground control device  10  includes a communication unit  11 , a storage unit  12 , and a control unit  13 . 
     The communication unit  11  acquires from the radio communication apparatus  20  that performs radio communication with the train  40  information on the communication level determined by the radio communication apparatus  20 . Specifically, the communication unit  11  acquires the communication level information as the train information including the communication level information. When a plurality of radio communication apparatuses  20  are connected to the ground control device  10 , the communication unit  11  acquires communication level information from each radio communication apparatus  20 . The communication unit  11  stores the acquired communication level information in the storage unit  12 . Specifically, the communication unit  11  stores the communication level information included in the train information as train information in the storage unit  12 . 
     The storage unit  12  stores the communication level information acquired by the communication unit  11 . The storage unit  12  stores one or more pieces of communication level information on one or more radio communication apparatuses  20 . The storage unit  12  stores the communication level information included in the train information as train information. 
     The control unit  13  determines a control mode of operation control on the train  40  in the communication area  30  of the radio communication apparatus  20 , based on the communication level information indicating the state of communication between the train  40  and the radio communication apparatus  20  determined in a predetermined period. The control unit  13  performs the operation control according to the determined control mode on the train  40  entering or approaching the communication area  30  of the radio communication apparatus  20  after the control mode is determined. In an unstable communication state in which the communication level frequently changes, if the control unit  13  also changes the control mode of operation control on the train  40  each time the communication level changes, the operation control on the train  40  also becomes unstable. Therefore, the control unit  13  determines a control mode by a method such as periodically determining a control mode, determining a control mode by taking an average of communication levels determined in a past predetermined period, or determining a control mode between the end and start of the operation of the trains  40 . The number of pieces of communication level information determined in the predetermined period may be one or two or more. 
     Next, operation control on the train  40  performed by the ground control device  10  based on each control mode will be described. Since the four communication levels are set as described above, the ground control device  10  controls the operation of the train  40  in four patterns of control modes. The following mainly describes the ground control device  10 , but the actual subject is the control unit  13  unless otherwise specified. 
       FIG. 5  is a diagram illustrating an example of a control mode of operation control on the train  40  performed at communication level A by the ground control device  10  according to the first embodiment. In  FIG. 5 , it is assumed that the communication level of the communication area  30  in which a train to be controlled  45  and the preceding train  46  are located is communication level A. Assume that the ground control device  10  has switched to a control mode corresponding to communication level A before the train to be controlled  45  and the preceding train  46  are located in the communication area  30 . The control mode at communication level A is referred to as a normal mode. 
     For communication level A, the ground control device  10  sets a moving block section based on a position in which the preceding train  46  is located, to control the operation of the train to be controlled  45 . As illustrated in  FIG. 5 , the ground control device  10  sets the stop limit position  60  of the train to be controlled  45  based on the rear position of the preceding train  46 . The train to be controlled  45  acquires information on the stop limit position  60  from the ground control device  10  via the radio communication apparatus  20 , and generates a run curve  61  based on the stop limit position  60  to travel. For communication level A at which the state of communication between the train  40  and the radio communication apparatus  20  is the best, the radio train control system  100  can flexibly set the distance between the preceding train  46  and the train to be controlled  45  for efficient train operation control. In the following description, the train to be controlled  45  and the preceding train  46  are sometimes referred to as trains  40  when not distinguished. 
       FIG. 6  is a diagram illustrating an example of a control mode of operation control on the train  40  performed at communication level B by the ground control device  10  according to the first embodiment. In  FIG. 6 , it is assumed that the communication level of the communication area  30  in which the train to be controlled  45  and the preceding train  46  are located is communication level B. Assume that the ground control device  10  has switched to a control mode corresponding to communication level B before the train to be controlled  45  and the preceding train  46  are located in the communication area  30 . The control mode at communication level B is referred to as degenerate mode  1 . 
     For communication level B, the ground control device  10  sets a block section  62  based on a block in which the preceding train  46  is located, to control the operation of the train to be controlled  45 . As illustrated in  FIG. 6 , the ground control device  10  sets the stop limit position  60  of the train to be controlled  45 , based on the block in which the preceding train  46  is located, that is, the block section  62 . The train to be controlled  45  acquires information on the stop limit position  60  from the ground control device  10  via the radio communication apparatus  20 , and generates a run curve  61  based on the stop limit position  60  to travel. The ground control device  10  may set the block section  62  of the preceding train  46 , based on a track circuit in which the preceding train  46  is located. At communication level B at which the state of communication between the train  40  and the radio communication apparatus  20  is good, the radio train control system  100  can perform train operation control by providing a larger margin in the distance between the preceding train  46  and the train to be controlled  45  than at communication level A. 
       FIG. 7  is a diagram illustrating a first example of a control mode of operation control on the train  40  performed at communication level C by the ground control device  10  according to the first embodiment.  FIG. 8  is a diagram illustrating a second example of a control mode of operation control on the train  40  performed at communication level C by the ground control device  10  according to the first embodiment. In  FIGS. 7 and 8 , it is assumed that the communication level of the communication area  30  where the train to be controlled  45  enters next is communication level C. Assume that the ground control device  10  has switched to a control mode corresponding to communication level C before the train to be controlled  45  enters the communication area  30 . The control mode at communication level C is referred to as degenerate mode  2 . 
     For communication level C, the ground control device  10  sets a block section  62  based on the communication area  30  in which the preceding train  46  is located, to control the operation of the train to be controlled  45 . As illustrated in  FIGS. 7 and 8 , when the preceding train  46  is not located in the communication area  30  where the train to be controlled  45  enters next, the ground control device  10  permits the entry of the train to be controlled  45 . When the preceding train  46  is located in the communication area  30  where the train to be controlled  45  enters next, the ground control device  10  sets the stop limit position  60  of the train to be controlled  45  based on the communication area  30  in which the preceding train  46  is located, that is, the block section  62 . The train to be controlled  45  acquires information on the stop limit position  60  from the ground control device  10  via the radio communication apparatus  20 , and generates a run curve  61  based on the stop limit position  60  to travel. When the state of communication between the train  40  and the radio communication apparatus  20  is communication level C, the radio train control system  100  can perform train operation control by providing an even larger margin in the distance between the preceding train  46  and the train to be controlled  45  than at communication level B. 
       FIG. 9  is a diagram illustrating an example of a control mode of operation control on the train  40  performed at communication level D by the ground control device  10  according to the first embodiment. In  FIG. 9 , it is assumed that the communication level of the communication area  30  where the train to be controlled  45  is scheduled to enter next on the route  50  is communication level D. Assume that the ground control device  10  has switched to a control mode corresponding to communication level D before the train to be controlled  45  enters the communication area  30 . The control mode at communication level D is referred to as an entry prohibition mode. 
     For communication level D, regardless of whether the preceding train  46  is located or not, the ground control device  10  sets the communication area  30  at communication level D as an entry prohibition section  63  where the train to be controlled  45  is prohibited from entering, to control the operation of the train to be controlled  45 . That is, the ground control device  10  sets the communication area  30  corresponding to communication level D that is the lowest of the defined communication levels as the entry prohibition section  63  where the train  40  is prohibited from entering. In this case, the ground control device  10  sets the stop limit position  60  of the train to be controlled  45  based on the communication area  30 , that is, the entry prohibition section  63 . The train to be controlled  45  acquires information on the stop limit position  60  from the ground control device  10  via the radio communication apparatus  20 , and generates a run curve  61  based on the stop limit position  60  to travel. For communication level D at which the state of communication between the train  40  and the radio communication apparatus  20  is the worst, the radio train control system  100  prohibits the train to be controlled  45  from entering the communication area  30 , thereby being able to avoid a possible emergency stop when the train to be controlled  45  enters the entry prohibition section  63 . 
     Here, assume that the ground control device  10  lowers the communication level of the communication area  30  because the state of communication between the preceding train  46  and the radio communication apparatus  20  has deteriorated in the case illustrated in  FIG. 5 or 6 . In this case, if the control mode of operation control on the trains  40  is also changed at the point in time when the communication level is changed, the stop limit position  60  of the train to be controlled  45  is suddenly changed, which can cause a situation in which the train to be controlled  45  goes beyond the stop limit position  60 . 
     Therefore, even when the communication state of the communication area  30  is suddenly changed, the ground control device  10  does not change the control mode of operation control on the trains  40  in the communication area  30  when the trains  40  are located in the communication area  30 . When a determined control mode is different from a current control mode, the ground control device  10  changes the control mode of operation control on the train  40  in the communication area  30  when no train  40  is located in the communication area  30  of the radio communication apparatus  20  of interest. For example, when a determined control mode is different from a current control mode, the ground control device  10  changes the control mode between the end and next start of operation of the trains  40 . That is, using information on a communication level determined based on past communication quality measured between a train  40  located in the communication area  30  and the radio communication apparatus  20 , the ground control device  10  performs operation control on a train  40  entering or approaching the communication area  30  in the future. This allows the ground control device  10  to avoid a situation in which an emergency stop of the preceding train  46  entering or approaching an area with a deteriorated communication state causes an emergency stop of the following train whose communication with the radio communication apparatus  20  is not deteriorated. 
     When the train  40  is located in the communication area  30  as illustrated in  FIGS. 5 to 8 , the ground control device  10  can continuously acquire information on the communication level between the train  40  and the radio communication apparatus  20  from the radio communication apparatus  20 , and can use the information for future operation control on a train  40 . On the other hand, if the entry prohibition section  63  is set as illustrated in  FIG. 9 , the ground control device  10  cannot acquire information on the communication level between a train  40  and the radio communication apparatus  20  from the radio communication apparatus  20 . In this case, in the radio train control system  100 , for example, a worker of a railroad company operating the trains  40  or the like may eliminate the cause of the deteriorated communication state, and then cause a train  40  that has been scheduled to enter the communication area  30  in which the entry prohibition section  63  is set to travel to the communication area  30  by a manual operation or the like to restore a state in which radio communication can be performed between the train  40  and the radio communication apparatus  20 . In the radio train control system  100 , if a train  40  whose on-board wireless device has failed is left in the communication area  30  in which the entry prohibition section  63  is set, the wireless device of the train  40  may be repaired or replaced to restore a state in which radio communication can be performed between the train  40  and the radio communication apparatus  20 . This allows the ground control device  10  to resume acquisition of information on the communication level between the train  40  and the radio communication apparatus  20  from the radio communication apparatus  20 . 
     The operation of the ground control device  10  will be described with reference to a flowchart.  FIG. 10  is a flowchart illustrating the operation of the ground control device  10  according to the first embodiment. In the ground control device  10 , the control unit  13  performs a process of managing the control mode of operation control on the train  40 , based on communication level information acquired from the radio communication apparatus  20  (step S 11 ). The control unit  13  performs operation control on the train  40 , that is, a train control process (step S 12 ). 
     The process in step S 11  of the flowchart illustrated in  FIG. 10  in the ground control device  10  will be described in detail.  FIG. 11  is a flowchart illustrating the control mode management process in the ground control device  10  according to the first embodiment. In the ground control device  10 , the communication unit  11  acquires train information including communication level information from each radio communication apparatus  20  (step S 21 ). The communication unit  11  stores the acquired train information in the storage unit  12 . The control unit  13  selects one radio communication apparatus  20  from the radio communication apparatuses  20  connected to the ground control device  10  (step S 22 ). 
     The control unit  13  acquires from the storage unit  12  the communication level information included in the train information acquired from the selected radio communication apparatus  20  (step S 23 ). If the communication level is different from the previous one (step S 24 : No), the control unit  13  checks whether or not there is a train located in the communication area  30  of the radio communication apparatus  20  (step S 25 ). The control unit  13  can determine whether or not there is a train located in the communication area  30  of interest in normal operation control on the train  40 . If there is no train located in the communication area  30  of the radio communication apparatus  20  (step S 25 : No), the control unit  13  updates the control mode of operation control on the train  40  in the communication area  30  of the radio communication apparatus  20  (step S 26 ). If the communication level is the same as the previous one (step S 24 : Yes) and if there is a train located in the communication area  30  of the radio communication apparatus  20  (step S 25 : Yes), the control unit  13  holds the control mode of operation control on the train  40  in the communication area  30  of the radio communication apparatus  20  (step S 27 ). 
     If there are one or more unselected radio communication apparatuses  20  in the radio communication apparatuses  20  connected to the ground control device  10 , the control unit  13  repeatedly performs the operation of selecting one radio communication apparatus  20  from the unselected radio communication apparatuses  20  until there is no unselected radio communication apparatus  20  (step S 22 ). The control unit  13  performs the operation from step S 23  to step S 27  on the selected radio communication apparatus  20 . 
     The process in step S 12  of the flowchart illustrated in  FIG. 10  in the ground control device  10  will be described in detail.  FIG. 12  is a flowchart illustrating the train control process in the ground control device  10  according to the first embodiment. In the ground control device  10 , the control unit  13  selects one train  40  from the trains  40  located in the communication areas  30  of the radio communication apparatuses  20  connected to the ground control device  10  (step S 31 ). The control unit  13  can determine the trains  40  located from the train information stored in the storage unit  12 . The train  40  selected here is the train to be controlled  45  illustrated in  FIG. 5  and others. 
     The control unit  13  determines the route  50  from the current position of the selected train  40  (step S 32 ). The control unit  13  searches for the preceding train  46  preceding the selected train  40  (step S 33 ). The control unit  13  checks whether or not there is the preceding train  46  in the route  50  from the current position of the selected train  40  (step S 34 ). If there is the preceding train  46  in the route  50  (step S 34 : Yes), the control unit  13  creates a stop limit position  60  based on the rear position of the preceding train  46  (step S 35 ). If there is no preceding train  46  in the route  50  (step S 34 : No), the control unit  13  creates a stop limit position  60  based on the route end (ending end) (step S 36 ). The control unit  13  generates control information including the created stop limit position  60 , and transmits the generated control information to the train  40  via the communication unit  11  and the radio communication apparatus  20  (step S 37 ). 
     If there are one or more unselected trains  40  in the trains  40  located in the communication areas  30  of the radio communication apparatuses  20  connected to the ground control device  10 , the control unit  13  repeatedly performs the operation of selecting one train  40  from the unselected trains  40  until there is no unselected train  40  (step S 31 ). The control unit  13  performs the operation from step S 32  to step S 37  on the selected train  40 . 
     The process in step S 35  of the flowchart illustrated in  FIG. 12  in the ground control device  10  will be described in detail.  FIG. 13  is a flowchart illustrating the process of creating a stop limit position  60  based on the rear position of the preceding train  46  in the ground control device  10  according to the first embodiment. In the ground control device  10 , the control unit  13  checks whether or not there is an entry prohibition section  63  between the selected train  40  and the preceding train  46  (step S 41 ). If there is an entry prohibition section  63  between the selected train  40  and the preceding train  46  (step S 41 : Yes), the control unit  13  sets the start (starting end) of the entry prohibition section  63  as the stop limit position  60  (step S 42 ). 
     If there is no entry prohibition section  63  between the selected train  40  and the preceding train  46  (step S 41 : No), the control unit  13  checks whether or not a block in which the rear position of the preceding train  46  is located is a moving block section (step S 43 ). If the block in which the rear position of the preceding train  46  is located is a moving block section (step S 43 : Yes), the control unit  13  sets the rear position of the preceding train  46  as the stop limit position  60  (step S 44 ). If the block in which the rear position of the preceding train  46  is located is not a moving block section (step S 43 : No), the control unit  13  sets the start of the block in which the rear position of the preceding train  46  is located as the stop limit position  60  (step S 45 ). Thus, if there is the preceding train  46  in the route  50  of the train to be controlled  45  and there is an entry prohibition section  63  between the train to be controlled  45  and the preceding train  46 , the control unit  13  sets the start of the entry prohibition section  63  as the stop limit position  60 . 
     The process in step S 36  of the flowchart illustrated in  FIG. 12  in the ground control device  10  will be described in detail.  FIG. 14  is a flowchart illustrating the process of creating a stop limit position  60  based on the route end in the ground control device  10  according to the first embodiment. In the ground control device  10 , the control unit  13  checks whether or not there is an entry prohibition section  63  between the selected train  40  and the route end (step S 51 ). If there is an entry prohibition section  63  between the selected train  40  and the route end (step S 51 : Yes), the control unit  13  sets the start of the entry prohibition section  63  as the stop limit position  60  (step S 52 ). If there is no entry prohibition section  63  between the selected train  40  and the route end (step S 51 : No), the control unit  13  sets the route end as the stop limit position  60  (step S 53 ). Thus, if there is no preceding train  46  in the route  50  of the train to be controlled  45  and there is an entry prohibition section  63  between the train to be controlled  45  and the end of the route  50  of the train to be controlled  45 , the control unit  13  sets the start of the entry prohibition section  63  as the stop limit position  60 . 
     Next, a hardware configuration of the ground control device  10  will be described. In the ground control device  10 , the communication unit  11  is a communication device. The storage unit  12  is a memory. The control unit  13  is implemented by processing circuitry. The processing circuitry may be a processor for executing programs stored in a memory and the memory, or may be dedicated hardware. 
       FIG. 15  is a diagram illustrating an example where a processor and a memory constitute the processing circuitry included in the ground control device  10  according to the first embodiment. When a processor  91  and a memory  92  constitute the processing circuitry, the functions of the processing circuitry of the ground control device  10  are implemented by software, firmware, or a combination of software and firmware. The software or firmware is described as programs and stored in the memory  92 . In the processing circuitry, the processor  91  reads and executes the programs stored in the memory  92 , thereby implementing the functions. That is, the processing circuitry includes the memory  92  for storing the programs resulting in the execution of the processes in the ground control device  10 . These programs can be said to cause a computer to perform the procedures and methods in the ground control device  10 . 
     Here, the processor  91  may be a central processing unit (CPU), a processing unit, an arithmetic unit, a microprocessor, a microcomputer, a digital signal processor (DSP), or the like. The memory  92  corresponds, for example, to a nonvolatile or volatile semiconductor memory such as a random-access memory (RAM), a read-only memory (ROM), a flash memory, an erasable programmable ROM (EPROM), or an electrically EPROM (EEPROM) (registered trademark), or a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, a digital versatile disc (DVD), or the like. 
       FIG. 16  is a diagram illustrating an example where dedicated hardware constitutes the processing circuitry included in the ground control device  10  according to the first embodiment. When dedicated hardware constitutes the processing circuitry, processing circuitry  93  illustrated in  FIG. 16  corresponds, for example, to a single circuit, a combined circuit, a programmed processor, a parallel-programmed processor, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or a combination of them. The functions of the ground control device  10  may be implemented by the processing circuitry  93  on an individual function basis, or the functions may be collectively implemented by the processing circuitry  93 . 
     The functions of the ground control device  10  may be implemented partly by dedicated hardware and partly by software or firmware. Thus, the processing circuitry can implement the above-described functions by dedicated hardware, software, firmware, or a combination of them. 
     A hardware configuration of the radio communication apparatuses  20  will be described. In each radio communication apparatus  20 , the radio communication unit  21  and the ground communication unit  23  are communication devices. The communication level determination unit  22  is implemented by processing circuitry. The processing circuitry may be a processor for executing programs stored in a memory and the memory, or may be dedicated hardware as is the case with the ground control device  10 . 
     As described above, according to the present embodiment, the ground control device  10  determines a control mode of operation control on a train  40  in the communication area  30  of each radio communication apparatus  20 , based on information on a communication level indicating the state of communication between the train  40  and the radio communication apparatus  20 , and performs the operation control corresponding to the determined control mode on the train  40  entering or approaching the communication area  30  of the radio communication apparatus  20  after the control mode is determined. The ground control device  10  does not switch the control mode while a train  40  is located in the communication area  30 . This allows the ground control device  10  when there is a train with a deteriorated communication state to avoid an emergency stop of the following train to prevent a decrease in operation efficiency. That is, if there is a communication area  30  in which the communication state of radio communication has been deteriorated, the ground control device  10 , which changes the control mode according to the communication level, can localize the range of the impact by setting the control mode to the degenerate mode or the like, and can prevent a decrease in operation efficiency. 
     Second Embodiment 
     In the first embodiment, the radio communication apparatuses  20  determine a communication level. A second embodiment describes a case where the ground control device determines a communication level. In the second embodiment, the radio train control system has a configuration in which the ground control device  10  is replaced with a ground control device  10   a , and the radio communication apparatuses  20  corresponding to the radio communication apparatuses  20 - 1  to  20 - 4  are replaced with radio communication apparatuses  20   a  in the radio train control system  100  of the first embodiment illustrated in  FIG. 1 . 
     The configuration and operation of the radio communication apparatuses  20   a  will be described.  FIG. 17  is a block diagram illustrating an example configuration of the radio communication apparatuses  20   a  according to the second embodiment. Each radio communication apparatus  20   a  includes the radio communication unit  21  and a ground communication unit  23   a . The ground communication unit  23   a  transmits to the ground control device  10   a  information on the communication quality of radio communication between the train  40  and the radio communication unit  21  measured by the radio communication unit  21 . Specifically, the ground communication unit  23   a  transmits to the ground control device  10   a  the communication quality information as train information including the communication quality information and other control information. 
       FIG. 18  is a flowchart illustrating the operation of the radio communication apparatuses  20   a  according to the second embodiment. In each radio communication apparatus  20   a , the radio communication unit  21  measures the communication quality of radio communication between the train  40  and the radio communication unit  21  (step S 61 ). The ground communication unit  23   a  transmits train information including communication quality information to the ground control device  10   a  (step S 62 ). 
     Next, the configuration and operation of the ground control device  10   a  will be described.  FIG. 19  is a block diagram illustrating an example configuration of the ground control device  10   a  according to the second embodiment. The ground control device  10   a  includes a communication unit  11   a , a storage unit  12   a , a communication level determination unit  14 , and the control unit  13 . 
     The communication unit  11   a  acquires from the radio communication apparatus  20   a  that performs radio communication with the train  40  information on the communication quality measured by the radio communication apparatus  20   a . Specifically, the communication unit  11   a  acquires the communication quality information as train information including the communication quality information. When a plurality of radio communication apparatuses  20   a  are connected to the ground control device  10   a , the communication unit  11   a  acquires communication quality information from each radio communication apparatus  20   a . The communication unit  11   a  stores the acquired communication quality information in the storage unit  12   a . Specifically, the communication unit  11   a  stores the communication quality information included in the train information in the storage unit  12   a  as train information. 
     The storage unit  12   a  stores the communication quality information acquired by the communication unit  11   a . The storage unit  12   a  stores one or more pieces of communication quality information on one or more radio communication apparatuses  20   a . The storage unit  12   a  stores the communication quality information included in the train information as train information. 
     The communication level determination unit  14  determines a communication level indicating the state of communication between the train  40  and the radio communication apparatus  20   a . Specifically, the communication level determination unit  14  determines a communication level based on the information on the communication quality of radio communication between the train  40  and the radio communication apparatus  20   a  measured by the radio communication apparatus  20   a . The operation of the communication level determination unit  14  is similar to the operation of the communication level determination unit  22  included in each radio communication apparatus  20  of the first embodiment. 
     The operation of the control unit  13  in the ground control device  10   a  is similar to the operation of the control unit  13  included in the ground control device  10  of the first embodiment. In the second embodiment, the contents of step S 11  of the flowchart illustrated in  FIG. 10  are different from those in the first embodiment.  FIG. 20  is a flowchart illustrating a control mode management process in the ground control device  10   a  according to the second embodiment. In the ground control device  10   a , the communication unit  11   a  acquires train information including communication quality information from each radio communication apparatus  20   a  (step S 71 ). The communication unit  11   a  stores the acquired train information in the storage unit  12   a . The control unit  13  selects one radio communication apparatus  20   a  from the radio communication apparatuses  20   a  connected to the ground control device  10   a  (step S 72 ). 
     The communication level determination unit  14  determines a communication level based on the communication quality included in the train information acquired from the radio communication apparatus  20   a  selected by the control unit  13 , stored in the storage unit  12   a  (step S 73 ). The communication level determination unit  14  notifies the control unit  13  of information on the determined communication level, and stores the information on the determined communication level in the storage unit  12   a . The subsequent process from step S 74  to step S 77  is similar to the process from step S 24  to step S 27  in the flowchart illustrated in  FIG. 11 . 
     Next, a hardware configuration of the ground control device  10   a  will be described. In the ground control device  10   a , the communication unit  11   a  is a communication device. The storage unit  12   a  is a memory. The control unit  13  and the communication level determination unit  14  are implemented by processing circuitry. The processing circuitry may be a processor for executing programs stored in a memory and the memory, or may be dedicated hardware as is the case with the first embodiment. 
     A hardware configuration of the radio communication apparatuses  20   a  will be described. In each radio communication apparatus  20   a , the radio communication unit  21  and the ground communication unit  23   a  are communication devices. 
     As described above, according to the present embodiment, the ground control device  10   a  determines a communication level indicating the state of communication between a train  40  and each radio communication apparatus  20   a . In this case, the effects similar to those of the first embodiment can also be obtained. Further, since the radio communication apparatuses  20   a  do not need to determine a communication level, conventional radio communication apparatuses can be used. That is, replacing only a ground control device with the ground control device  10   a  of the present embodiment allows a shift from an existing radio train control system. 
     Third Embodiment 
     In the first embodiment, the ground control device  10  changes the setting of the block section  62  in the communication area  30  of each radio communication apparatus  20  according to the communication level. In a third embodiment, the ground control device  10  changes the number of trains  40  that are allowed to enter the communication area  30  according to the communication level. Differences from the first embodiment will be described. The description uses the first embodiment as an example, but the present embodiment is also applicable to the second embodiment. 
     In the third embodiment, the control unit  13  of the ground control device  10  sets the number of trains  40  that are allowed to enter the communication area  30  of each radio communication apparatus  20  according to the communication level between the train  40  and the radio communication apparatus  20 . For example, the control unit  13  allows three trains  40  to enter a communication area  30  at communication level A, allows two trains  40  to enter a communication area  30  at communication level B, allows one train  40  to enter a communication area  30  at communication level C, and prohibits the entry of trains  40  into a communication area  30  at communication level D. That is, the control unit  13  sets a communication area  30  corresponding to communication level D that is the lowest of the defined communication levels as an entry prohibition section  63  where trains  40  are prohibited from entering. The flow of operation of the ground control device  10  in the third embodiment is similar to that in the first embodiment. 
     As described above, according to the present embodiment, the ground control device  10  controls the number of trains  40  that are allowed to enter each communication area  30  according to the communication level. This allows the ground control device  10  to perform more flexible control on the track shape of the communication areas  30 , operation conditions for trains  40 , the operation hours of trains  40 , etc. 
     The ground control device  10  may combine the control modes according to the first embodiment and a control mode according to the third embodiment. For example, the ground control device  10  may change the setting of the block section  62  according to the communication level as in the first embodiment for the radio communication apparatuses  20 - 1  and  20 - 3  of the radio communication apparatuses  20 - 1  to  20 - 4  illustrated in  FIG. 1 , and change the number of trains  40  that are allowed to enter the communication area  30  according to the communication level as in the third embodiment for the radio communication apparatuses  20 - 2  and  20 - 4 . That is, according to the control modes, the ground control device  10  may set the block section  62  in the communication area  30  of each appropriate radio communication apparatus  20 , and may set the number of trains  40  that are allowed to be located in the communication area  30  of each appropriate radio communication apparatus  20 . Further, according to the control modes, the ground control device  10  may set the block section  62  in the communication area  30  of a first radio communication apparatus and set the number of trains  40  that are allowed to be located in the communication area  30  of a second radio communication apparatus. The first radio communication apparatus represents the above-described radio communication apparatuses  20 - 1  and  20 - 3 , and the second radio communication apparatus represents the above-described radio communication apparatuses  20 - 2  and  20 - 4 . 
     The configurations described in the above embodiments illustrate an example of the subject matter of the present invention, and can be combined with another known art, and can be partly omitted or changed without departing from the scope of the present invention. 
     REFERENCE SIGNS LIST 
       10 ,  10   a  ground control device;  11 ,  11   a  communication unit;  12 ,  12   a  storage unit;  13  control unit;  14 ,  22  communication level determination unit;  20 ,  20 - 1  to  20 - 4 ,  20   a  radio communication apparatus;  21  radio communication unit;  23 ,  23   a  ground communication unit;  30 ,  30 - 1  to  30 - 4  communication area;  40  to  44  train;  45  train to be controlled;  46  preceding train;  50  route;  60  stop limit position;  61  run curve;  62  block section;  63  entry prohibition section;  100  radio train control system.