JP2006042221A - Radio communication system, way side radio communication device, mobile station, control method of way side radio communication deice, control method of mobile station, control program of way side radio communication device, and control program of mobile station - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To be able to effectively avoid transmission collision and efficiently acquire a communication channel. <P>SOLUTION: In this system, where two or more groups 1, 2 comprising two or more mobile stations are set and at least one mobile station in the groups 1, 2 is set at a beacon station, respectively, a way side radio communication device is equipped. The way side radio communication device sends way side beacon packet B2 when it receives vehicle beacon packet B1 transmitted from the beacon station existing in a communication area. The beacon station halts transmission of the vehicle beacon packet B1 before acquiring the communication channel when it receives either the vehicle beacon packet B1 or the way side beacon packet B2. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a radio communication system, a roadside radio communication device, a mobile station, a roadside radio communication device control method, a mobile station control method, a roadside radio communication device control program, and a mobile station control program.

  With the development of wireless communication technology, it has become possible to perform wireless communication between moving bodies in a moving body (for example, a vehicle). This technology is expected to be applied to, for example, road traffic systems and railway vehicle systems. In such a wireless communication system, an application for forming a platoon by autonomous running is conceivable, and a mobile station (wireless communication apparatus) used for this requires broadcast and real-time processing. As a communication means of such a mobile station, an inter-vehicle wireless communication system has been proposed (see, for example, Patent Document 1).

In this type of wireless communication system, a plurality of groups composed of a plurality of mobile stations are set, a representative mobile station of each group is set as a beacon station, and each beacon station is configured to acquire a communication channel. Yes. When acquiring this communication channel, the beacon station is configured to acquire a communication channel by transmitting a beacon signal (beacon packet) to a mobile station in a neighboring group, and each group in turn obtains communication rights. The communication channel acquisition collision probability is reduced and the communication channel acquisition probability is increased by the communication channel pause procedure.
JP 2001-118191 A

  However, in the above wireless communication system, when beacon stations in each group are shielded, each beacon station communicates at the same time depending on the initial state during synchronization between groups and the group configuration (number of mobile stations in the group). There is a problem that a situation where a channel is acquired exists and a communication collision cannot be avoided.

  Therefore, an object of the present invention is to solve the problems of the above-described conventional technology, effectively avoid a communication collision, and efficiently acquire a communication channel, a roadside wireless communication apparatus, a mobile station, A roadside wireless communication apparatus control method, a mobile station control method, a roadside wireless communication apparatus control program, and a mobile station control program are provided.

  In order to solve the above-described problem, the present invention sets a plurality of groups each composed of a plurality of mobile stations, and at least one mobile station in each group transmits a first beacon signal to acquire a communication channel. Mobile stations in a group to which the beacon station that has transmitted the first beacon signal belongs to a wireless communication system in which the communication channel is acquired and data signals can be transmitted and received. A roadside wireless communication device installed in the movement path, the roadside wireless communication device receiving the first beacon signal transmitted from a beacon station existing in the communication area of the roadside wireless communication device; When the receiving unit receives the first beacon signal, the second beacon signal is transmitted to the mobile station existing in the communication area. The beacon station receives the beacon signal of the first beacon signal and the second beacon signal before acquiring the communication channel. The transmission of the beacon signal is paused.

  In this wireless communication system, a first beacon period in which transmission of the first beacon signal is permitted, and a second beacon in which transmission of the first beacon signal is prohibited following the first beacon period And the transmission means of the roadside wireless communication device transmits the second beacon signal in the first beacon period when the reception means receives the first beacon signal. If the receiving means does not receive the first beacon signal, the second beacon signal is transmitted during the second beacon period, and each mobile station receives the second beacon signal received. The start timing of the data period during which the data signal is transmitted and received may be synchronized based on the beacon signal.

  Further, in the wireless communication system, each beacon period includes a plurality of slots each having a predetermined time interval, and the transmission unit of the roadside wireless communication device receives the first beacon signal. The second beacon signal is transmitted in a slot in the first beacon period, and when the receiving means does not receive the first beacon signal, the second beacon signal is The second beacon signal is transmitted in a slot in the second beacon period, and the second beacon signal includes slot information indicating a slot for transmitting the second beacon signal. Based on the slot information included in the second beacon signal, the start timing of the data period in which the data signal is transmitted and received is synchronized. It may be.

  In the wireless communication system, the beacon station may transmit the first beacon signal in a randomly selected slot among a plurality of slots in the first beacon period.

  In the wireless communication system, the roadside wireless communication device may transmit the second beacon signal in a randomly selected slot among a plurality of slots in the second beacon period.

  In the wireless communication system, the first beacon period, the second beacon period, and the data period constitute one cycle, and each mobile station of the group that has acquired the communication channel releases the communication channel. Thereafter, the beacon stations belonging to the group may suspend transmission of the first beacon signal for a predetermined period.

  In the wireless communication system, the predetermined period may be a period corresponding to the number of groups existing around the roadside wireless communication apparatus.

  In the wireless communication system, the first beacon signal includes a group ID assigned to a group to which a beacon station that transmits the first beacon signal belongs, and is transmitted by the roadside wireless communication device. The means transmits the group ID included in the received first beacon signal in the second beacon signal, and each beacon station is based on the group ID included in the second beacon signal. The number of groups existing around the roadside wireless communication device may be specified.

  In addition, a plurality of groups including a plurality of mobile stations are set, and at least one mobile station in each group is set as a beacon station that transmits a first beacon signal to acquire a communication channel. The mobile station in the group to which the beacon station that transmitted the beacon signal belongs is used in a wireless communication system that can transmit and receive data signals by acquiring the communication channel, and is installed on the mobile path of the mobile station. In the communication device, the receiving means for receiving the first beacon signal transmitted from the beacon station existing in its own communication area, and when the receiving means receives the first beacon signal, the communication is still in progress. A second beacon that causes a beacon station belonging to a group that has not acquired a channel to stop transmitting the first beacon signal. It is characterized in further comprising a transmission means for transmitting the items.

  In this roadside wireless communication apparatus, a first beacon period during which transmission of the first beacon signal is permitted, and a second period during which transmission of the first beacon signal is prohibited following the first beacon period. A beacon period is set, and when the receiving unit receives the first beacon signal, the transmitting unit transmits the second beacon signal in the first beacon period, and the receiving unit If the means does not receive the first beacon signal, the second beacon signal may be transmitted during the second beacon period.

  Further, in the roadside wireless communication device, each beacon period includes a plurality of slots each having a predetermined time interval, and the transmission unit receives the first beacon signal when the reception unit receives the first beacon signal. When the second beacon signal is transmitted in the slot in the first beacon period and the receiving means does not receive the first beacon signal, the second beacon signal is transmitted to the second beacon signal. Transmission is performed in a slot in a beacon period, and the second beacon signal may include slot information indicating a slot for transmitting the second beacon signal.

  In the roadside wireless communication apparatus, the second beacon signal may be transmitted in a randomly selected slot among a plurality of slots in the second beacon period.

  In addition, in order to obtain a communication channel in a mobile station used in a wireless communication system having a roadside wireless communication device installed on a mobile route of the mobile station in which a plurality of groups including a plurality of mobile stations are set. Before acquiring the communication channel, a second beacon signal that is set in a beacon station that transmits a first beacon signal and that the roadside wireless communication apparatus transmits after receiving the first beacon signal from another beacon station It is characterized by comprising determination means for determining whether or not the first beacon signal has been received, and pause means for stopping transmission of the first beacon signal when the second beacon signal is received.

  In addition, a plurality of groups including a plurality of mobile stations are set, and at least one mobile station in each group is set as a beacon station that transmits a first beacon signal to acquire a communication channel. The mobile station in the group to which the beacon station that transmitted the beacon signal belongs is used in a wireless communication system that can transmit and receive data signals by acquiring the communication channel, and is installed on the mobile path of the mobile station. In the control method of the communication apparatus, when receiving the first beacon signal transmitted from the beacon station existing in its own communication area, and receiving the first beacon signal, the communication channel is still A second beacon signal that causes a beacon station belonging to a group that has not acquired the transmission to pause transmission of the first beacon signal It is characterized in that and a transmission process of transmitting.

  In addition, a communication channel is obtained in a method for controlling a mobile station used in a wireless communication system including a roadside wireless communication device installed on a mobile route of the mobile station in which a plurality of groups including a plurality of mobile stations are set. A second beacon signal that is set in a beacon station that transmits a first beacon signal and that the roadside wireless communication device transmits after receiving the first beacon signal from another beacon station to the communication channel. A judging means for judging whether or not the signal is received before acquisition, and a pause means for pausing the transmission of the first beacon signal when the second beacon signal is received. It is.

  In addition, a plurality of groups including a plurality of mobile stations are set, and at least one mobile station in each group is set as a beacon station that transmits a first beacon signal to acquire a communication channel. The mobile station in the group to which the beacon station that transmitted the beacon signal belongs is used in a wireless communication system that can transmit and receive data signals by acquiring the communication channel, and is installed on the mobile path of the mobile station. A control program for controlling a communication device by a computer, receiving the first beacon signal transmitted from the beacon station existing in its own communication area, and receiving the first beacon signal The first beacon signal is transmitted to a beacon station belonging to a group that has not yet acquired the communication channel. It is characterized in that to transmit transmitting a second beacon signal to pause.

  Also, a control for controlling by a computer a mobile station used in a wireless communication system including a plurality of groups configured of a plurality of mobile stations and including a roadside wireless communication device installed on the mobile route of the mobile station. A second program that is set in a beacon station that transmits a first beacon signal to acquire a communication channel, and that the roadside wireless communication device transmits after receiving the first beacon signal from another beacon station. It is determined whether or not the beacon signal is received before acquiring the communication channel, and when the second beacon signal is received, transmission of the first beacon signal is suspended. It is.

  According to the present invention, a communication collision can be effectively avoided, and a communication channel can be acquired efficiently.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic explanatory diagram of an inter-vehicle radio communication system 100 as a radio communication system according to the present embodiment.

  In the inter-vehicle wireless communication system 100 shown in FIG. 1, a wireless communication device 10 (hereinafter referred to as “vehicle”) as a mobile station mounted on the vehicles 1-1 and 1-2 and the vehicles 2-1 and 2-2 as moving bodies. And a radio communication device 20 (hereinafter referred to as a “roadside radio communication device”) as a fixed station installed at a fixed position on a vehicle movement route such as a roadside. Vehicle wireless communication devices 10 of 1, 1-2, vehicles 2-1, 2-2 are grouped into a plurality of vehicle groups 1, 2. Each of the vehicle groups 1 and 2 has a representative vehicle equipped with a representative vehicle wireless communication device (hereinafter referred to as a “beacon station”). That is, in each of the vehicle groups 1 and 2, the vehicle wireless communication device 10 of one vehicle (vehicles 1-1 and 2-1 in this embodiment) is assigned to the beacon station, and the remaining vehicles 1-2 and 2- Two vehicular radio communication apparatuses 10 are assigned to the slave stations. In addition, each vehicle constituting each vehicle group 1 and 2 moves along the same route, and exists in a range where the vehicle wireless communication devices 10 in the vehicle group 1 and 2 can communicate with each other. And

  The outline of the operation of the inter-vehicle wireless communication system 100 will be described. The beacon station 10 of the representative vehicle belonging to each of the vehicle groups 1 and 2 is a beacon (Beacon: first beacon signal for acquiring a communication channel). A communication channel is acquired using a reference signal) control frame (hereinafter referred to as “vehicle beacon packet”). Each vehicle wireless communication device 10 in the vehicle groups 1 and 2 transmits a data frame (hereinafter, “data packet”) only to the vehicle wireless communication devices 10 in the vehicle groups 1 and 2 during the assigned data slot period described later. The right to perform transmission of the data packet is prevented so that a data packet collision with the vehicle wireless communication devices 10 in the vehicle groups 1 and 2 does not occur.

  That is, the beacon station 10 of the vehicle group other than the vehicle group that acquired the communication channel pauses the operation of acquiring the communication channel until the communication channel is released, and the vehicles of the vehicle group other than the vehicle group that acquired the communication channel. The wireless communication device 10 pauses transmission / reception of data packets until the communication channel is released.

  Further, the roadside wireless communication device 20 uses a roadside beacon packet as a second beacon signal corresponding to the vehicle beacon packet to drive each vehicle 1-1, 1-2, 2 running in the communication area of the roadside wireless communication device 20. It is comprised so that it may transmit to the vehicle radio | wireless communication apparatus 10 of -1,2-2.

  FIG. 2 is a block diagram showing the configuration of the vehicle radio communication device 10 mounted on each vehicle in the inter-vehicle radio communication system 100 of the present invention.

  The vehicular radio communication device 10 is roughly provided with an antenna 11, a radio communication unit 12, a control unit 13, a memory 14 (mobile station storage means), and a vehicle interface 15.

  When the vehicle wireless communication device 10 is a beacon station, the wireless communication unit 12 transmits and receives beacon packets via the antenna 11 according to a predetermined communication procedure under the control of the control unit 13 (that is, transmission and reception of vehicle beacon packets, Reception of roadside beacon packets) and transmission / reception of data packets. In addition, when the vehicle wireless communication device 10 is a slave station, the wireless communication unit 12 receives beacon packets (that is, reception of vehicle beacon packets and reception of roadside beacon packets) and transmission / reception of data packets.

  The control unit 13 is a microcomputer including a CPU 131, a ROM 132 as a program storage memory for storing control programs and the like in advance, an internal clock 133, and a peripheral circuit (not shown), and controls the entire vehicle radio communication apparatus 10. That is, the control unit 13 controls the entire vehicle radio communication device 10 based on the control program stored in the ROM 132. Specifically, the control unit 13 performs execution control such as comparison of group ID information, determination of priority, correction based on the beacon time of the internal clock 133, time synchronization with other vehicle groups, and the like.

  The ROM 132 includes a control program for performing overall control of the vehicle radio communication apparatus 10 and a communication protocol, a program for performing communication control in the inter-vehicle radio communication system 100 and necessary processing, and a vehicle beacon packet to be transmitted. A beacon information table in which information is tabulated and various setting values are stored.

  The memory 14 stores beacon packets and data packets received via the wireless communication unit 12 and vehicle data (vehicle speed, direction of travel, current position (coordinates), etc.) acquired via the vehicle interface 15. Remember me under the control of Specifically, the memory 14 stores the vehicle beacon packet received from each beacon station 10 and the roadside beacon packet received from the roadside wireless communication device 20, and the other in the vehicle group to which the vehicle wireless communication device 10 belongs. The data packet received from the vehicle radio communication apparatus 10 is stored.

  In addition, the vehicle interface 15 converts vehicle data such as a vehicle speed, a direction of travel, a current position (coordinates) acquired by a sensor provided in the vehicle into digital data, and sends the digital data to the memory 14 under the control of the controller. Or the data read from the memory 14 is converted into a signal and sent to the vehicle.

  Next, FIG. 3 is a block diagram illustrating a configuration of the roadside wireless communication device 20.

  As shown in FIG. 3, the roadside wireless communication device 20 includes an antenna 21, a wireless communication unit 22, a control unit 23, and a memory 24 (roadside storage unit).

  The wireless communication unit 22 transmits and receives only beacon packets (that is, reception of vehicle beacon packets and transmission of roadside beacon packets) via the antenna 21 under the control of the control unit 23 according to a predetermined communication procedure. That is, the data packet is not transmitted in the data slot. Also, the number of pauses control described later is not performed.

  The control unit 23 is a microcomputer including a CPU 231, a ROM 232 as a program storage memory for storing a control program and the like in advance, an internal clock 233, and a peripheral circuit (not shown), and controls the roadside wireless communication device 20 as a whole. That is, the control unit 23 controls the entire roadside wireless communication device 20 based on the control program stored in the ROM 232. More specifically, the control unit 23 performs execution control such as comparison of group ID information, determination of priority, correction based on the beacon time of the internal clock 233, time synchronization with the vehicle group, and the like based on the control program.

  In addition, the ROM 232 includes a control program and a communication protocol for controlling the entire roadside radio communication apparatus 20, a program for performing communication control and necessary processing in the inter-vehicle radio communication system, and information included in the roadside beacon packet to be transmitted. Is stored as a beacon information table (not shown) and various setting values.

  The memory 24 stores the vehicle beacon packet received via the wireless communication unit 22 under the control of the control unit 23. Specifically, the memory 24 stores a vehicle beacon packet received from each beacon station 10.

  The roadside wireless communication device 20 has a hardware configuration different from that of the vehicle wireless communication device 10, but is not limited thereto, and may have a hardware configuration similar to that of the vehicle wireless communication device 10 shown in FIG.

  FIG. 4 is an explanatory diagram for explaining a communication protocol in the inter-vehicle wireless communication system.

  As shown in FIG. 4, a time period divided beacon period 61 and a data period 62 following the beacon period 61 are combined as one unit (one period) T, and this is used as one communication channel. . That is, one beacon period 61 and one data period 62 are alternately repeated. Further, in the vehicle wireless communication device 10 and the roadside wireless communication device 20 of each vehicle 1-1, 1-2, 2-1, 2-2 (FIG. 1), the beacon period 61 is a predetermined first time. The predetermined time interval t1 is set, and the data period 62 is set to a predetermined second predetermined time interval t2.

  In the wireless communication devices 10 and 20, the beacon period 61 includes a first beacon period 61A in which the transmission of the vehicle beacon packet is permitted and a second beacon period 61B in which the transmission of the vehicle beacon packet is prohibited. The first beacon period 61A and the second beacon period 61B are each composed of a plurality of slots (beacon slots) at a predetermined third predetermined time interval t3, and the data period 62 is determined in advance. Each slot is composed of a plurality of slots (data slots) at a fourth predetermined time interval t4.

  That is, if the communication timings of the wireless communication devices 10 and 20 are synchronized, the start and end of the beacon period 61 and the start and end of the data period 62 are the same timing.

  Further, if the communication timings of the wireless communication devices 10 and 20 are synchronized, the vehicle beacon packet transmitted by the beacon station 10 is transmitted to the beacon station in the other vehicle wireless communication device 10 and the roadside wireless communication device 20. 10, the vehicle beacon packet is received in the same beacon slot as the transmitted beacon slot. Similarly, the roadside beacon packet transmitted by the roadside radio communication device 20 is received by the vehicle radio communication device 10 in the same beacon slot as the beacon slot in which the roadside beacon packet is transmitted by the roadside radio communication device 20. The

  Further, if the communication timing of each vehicle radio communication device 10 is synchronized within the vehicle group, the data packet transmitted by the vehicle radio communication device 10 within the vehicle group is transmitted to another vehicle radio communication device within the vehicle group. 10, the vehicle radio communication apparatus 10 receives the data packet in the same data slot as the data slot to be transmitted.

  Here, in the present embodiment, slot numbers are assigned in order from the top to a plurality of beacon slots in the beacon period 61, and slot numbers are assigned in order from the top to a plurality of data slots in the data period 62. Yes.

  A group ID and a subgroup ID are associated with the vehicle wireless communication devices 10 of the vehicles 1-1, 1-2, 2-1, and 2-2, respectively. The group ID and subgroup ID are stored in advance in the ROM 132 of the control unit 13 (FIG. 2).

  The group ID is an ID indicating a vehicle group to which the own vehicle wireless communication device 10 belongs, and is a unique number for each vehicle group. The sub group ID is a unique number for each vehicle wireless communication device 10 in each vehicle group.

  This subgroup ID has shown the priority which becomes a beacon station which transmits a vehicle beacon packet. Specifically, as the sub group ID, a number is sequentially assigned to each wireless communication device 10 in the vehicle group, and a transmission right is given to the wireless communication device 10 with the highest priority number to the beacon station. It is set. Thereby, the beacon station 10 of each vehicle group is determined by the priority of the subgroup ID.

  If any problem occurs in the vehicle radio communication device 10 with the highest priority number, the right to transmit a vehicle beacon packet to the vehicle radio communication device 10 of the second vehicle with the next highest priority is given. Given. Various means for assigning the subgroup ID are conceivable, and assignment from the tail or random assignment may be used. The condition is that the value is unique within the vehicle group.

  Further, the subgroup ID indicates the priority order for transmitting the data packet in the data period 62. That is, in each vehicle wireless communication device 10 of the vehicle group that has acquired the communication channel, the data packets are transmitted in the descending order of priority. Thereby, it is possible to avoid a collision of communication when transmitting a data packet.

  Next, the configuration of the beacon packet will be described with reference to an explanatory diagram showing the configuration of the beacon packet shown in FIG. 5A shows the vehicle beacon packet B1, and FIG. 5B shows the road side beacon packet B2.

  First, as shown in FIG. 5 (a), the vehicle beacon packet B1 transmitted by the beacon station 10 of each vehicle group includes the group ID of the own vehicle group, the subgroup ID of the beacon station 10, and the beacon. Among the plurality of beacon slots in the period 61, slot information (slot number) indicating a beacon slot in which the beacon station 10 transmits the vehicle beacon packet B1 is included. The vehicle beacon packet B1 is generated by the control unit 13. The control unit 13 generates the group ID and subgroup ID of the vehicle beacon packet B1 with reference to the ROM 132 of the control unit 13, and the slot information is generated by calculation.

  Further, as shown in FIG. 5B, the roadside beacon packet B2 transmitted by the roadside wireless communication device 20 corresponds to the group ID of the vehicle, and the group ID unique to the roadside wireless communication device 20 A group ID of all vehicle groups (peripheral groups) existing in the communication area of the roadside wireless communication device 20 and a beacon slot in which the beacon station 10 transmits a beacon packet among a plurality of beacon slots in the beacon period 61 are shown. Slot information (slot number) and the like. The roadside beacon packet B2 is generated by the control unit 23. The control unit 23 generates the group ID of the roadside beacon packet B2 with reference to the ROM 232 of the control unit 23, and the group IDs of the surrounding groups are present in the communication area of the roadside wireless communication device 20. The vehicle beacon packet B1 received from the existing beacon station 10 and stored in the memory 24 is generated with reference to the vehicle beacon packet B1. The slot information is generated by calculation. Here, each vehicle wireless communication device 10 can determine whether the received vehicle beacon packet or the roadside beacon packet belongs to the vehicle group to which the vehicle belongs, based on the group ID of the received beacon packet.

  By the way, as shown in FIG. 1, the beacon station 10 mounted on the vehicle 1-1 of the vehicle group 1 and the slave station 10 mounted on the vehicle 1-2, and the vehicle 2-2 of the vehicle group 2 are mounted. The slave station 10 is in a situation where communication is possible because there is no shielding object, but the beacon station 10 mounted on the vehicle 1-1 of the vehicle group 1 and the beacon station mounted on the vehicle 2-1 of the vehicle group 2. 10 is a situation in which, although they are close to each other, they cannot communicate with each other due to shielding by a shielding object.

  Therefore, in the present embodiment, the roadside wireless communication device 20 is a beacon station existing in the communication area of the roadside wireless communication device 20 in order to avoid simultaneously acquiring communication channels in both vehicle groups 1 and 2. When the vehicle beacon packet B1 transmitted from 10 is received, the roadside beacon packet B2 is transmitted to each vehicle wireless communication device 10 existing in the communication area of the roadside wireless communication device 20, and the beacon station 10 Transmission of the vehicle beacon packet B1 is suspended when any one of the vehicle beacon packet B1 and the roadside beacon packet B2 is received before the communication channel is acquired (that is, when the communication channel is not acquired). .

  Below, the specific operation | movement of the roadside radio | wireless communication apparatus 20 and the vehicle radio | wireless communication apparatus 10 is demonstrated.

  FIG. 6 is a flowchart showing a control operation of the roadside wireless communication device 20 and corresponds to an operation based on a beacon transmission control program executed by the control unit 23.

  In FIG. 6, when the communication channel of the vehicle group (or roadside wireless communication device 20) is released (ST1), the control unit 23 starts a timer simultaneously with the start of the beacon period 61 (ST2). At this time, the control unit 23 reads the random delay time Tr held in the memory 24 (ST3). Here, the memory 24 holds an initial value of the random delay time Tr. That is, the roadside wireless communication device 20 randomly selects one beacon slot among the plurality of beacon slots in the second beacon period 61B. The beacon station 10 prepares to transmit the roadside beacon packet B2 with the selected beacon slot as a transmission slot.

  Next, the control unit 23 determines whether or not the vehicle beacon packet B1 from the beacon station 10 of the vehicle group is detected (ST4).

  When it is determined in step ST4 that the vehicle beacon packet B1 has not been detected (ST4; No), the control unit 23 controls the wireless communication unit 22 to control the roadside beacon packet after the random delay time Tr has elapsed (ST5). B2 is transmitted (ST6), and a communication channel is acquired (acquired) (ST7). That is, the control unit 23 causes the wireless communication unit 22 to transmit the roadside beacon packet B2 in the transmission slot.

  Here, each vehicle wireless communication device 10 of each vehicle group that has received this roadside beacon packet B2 pauses inter-vehicle communication (specifically, transmission / reception of data packets in the data period 62) until the data period 62 ends. To do. This avoids communication conflicts.

  Next, the control unit 23 calculates a random delay time Tr for selecting a beacon slot (ST8), and overwrites the previous random delay time Tr held in the memory 24.

This random delay time Tr is
Tr = (M + N−L + Rand (L)) × t3
Is calculated as Here, Rand (L) indicates a random value that randomly generates any number from 1 to L among the maximum integer values L, and M is a number equal to or less than the total number of beacon slots in the beacon period 61. A predetermined constant integer value, M + N, is a maximum random delay time (total number of beacon slots), and L is a predetermined integer value (where N> L). That is, the beacon slot having the slot number corresponding to the calculated random delay time Tr is selected as the beacon slot for transmitting the roadside beacon packet B2.

  This random delay time Tr is set to be within the second beacon period 61B shown in FIG. That is, when the roadside wireless communication device 20 does not receive the vehicle beacon packet B1 in the first beacon period 61A, the roadside beacon packet B2 is transmitted in a randomly selected beacon slot in the second beacon period 61B. That is what I am trying to do.

  Next, the control unit 23 of the roadside wireless communication apparatus 20 that has acquired the communication channel returns to the process of step ST1 and releases the communication channel simultaneously with the end of the data period 62.

  In step ST4, when the control unit 23 detects the vehicle beacon packet B1 (step ST4; Yes), the control unit 23 determines whether or not the reception of the vehicle beacon packet B1 from the beacon station 10 of the vehicle group is finished. Judgment is made (ST9). When the reception of the vehicle beacon packet B1 from the beacon station 10 of the vehicle group has not ended (ST9; No), the process of step ST9 is repeated, and the reception of the vehicle beacon packet B1 from the beacon station 10 of the vehicle group is completed. In the case (ST9; Yes), that is, when the vehicle beacon packet B1 is received, the control unit 23 immediately controls the wireless communication unit 22 to transmit the road side beacon packet B2 (ST10), and proceeds to the process of step ST1. .

  That is, when the wireless communication unit 22 receives the vehicle beacon packet B1, the control unit 23 of the roadside wireless communication device 20 immediately transmits the roadside beacon packet B2 in the first beacon period 61A. When the vehicle beacon packet B1 is not received, the wireless communication unit 22 is controlled to transmit the roadside beacon packet B2 in the second beacon period 61B. As a result, the roadside wireless communication device 20 transmits the roadside beacon packet B2 for each repeated beacon period 61.

  Therefore, the control unit 13 of the vehicle wireless communication device 10 that has received the roadside beacon packet B2 controls to synchronize the start timing of the data period 62 based on the slot information (slot number) included in the roadside beacon packet B2. (Slot synchronization).

  That is, since the number of beacon slots and the time interval in the beacon period 61 are determined in advance in all the vehicle radio communication devices 10 and the roadside radio communication devices 20, the control unit 13 of each vehicle radio communication device 10 Which beacon slot is transmitted from among the beacon slots can be identified from the received roadside beacon packet B2. Accordingly, the control unit 13 performs control to synchronize the start timing of the data period 62 based on the slot information (slot number) included in the roadside beacon packet B2 received from the roadside wireless communication device 20. Even if there is a shield between the beacon stations of the vehicle group, it is possible to effectively avoid a communication collision caused by the synchronization being lost.

  Next, FIG. 7 is a flowchart showing an operation of communication channel acquisition control when the beacon station 10 acquires a communication channel, and corresponds to an operation based on a beacon transmission control program executed by the control unit 13.

  In FIG. 7, when the communication channel of another vehicle group (or roadside wireless communication device 20) is released (ST21), the control unit 13 of the beacon station 10 sets a timer simultaneously with the start of the beacon period 61 (ST22). to start. At this time, the controller 13 reads the random delay time Tr held in the memory 14 (ST23). Here, the memory 14 holds an initial value of the random delay time Tr.

  That is, when one beacon station 10 existing in each vehicle group intends to acquire a communication channel, one beacon slot is randomly selected from among a plurality of beacon slots in the first beacon period 61A. The beacon station 10 uses the selected beacon slot as a transmission slot and prepares to transmit the vehicle beacon packet B1.

  Next, the control unit 13 determines whether or not a beacon packet has been detected (ST24). Specifically, the control unit 13 determines whether the wireless communication unit 12 has detected a vehicle beacon packet B1 from the beacon station 10 of another vehicle group or a roadside beacon packet B2 from the roadside wireless communication device 20. .

  If it is determined in step ST24 that a beacon packet has not been detected (ST24; No), the control unit 13 controls the wireless communication unit 12 to transmit the vehicle beacon packet B1 after the random delay time Tr has elapsed (ST25). Transmit (ST26) and acquire (acquire) a communication channel (ST27). That is, the control unit 13 causes the wireless communication unit 12 to transmit the vehicle beacon packet B1 in the transmission slot.

  Thereby, when the beacon station 10 transmits the beacon packet before receiving the beacon packet of the beacon station 10 of another vehicle group, the vehicle group to which the beacon station 10 belongs is acquired. Become.

  That is, when one vehicle group acquires a communication channel, data communication is performed in the data period 62 following the beacon period 61 between the vehicle wireless communication devices 10 in the vehicle group, and the other vehicle groups The inter-vehicle communication is suspended until 62 ends. This avoids communication conflicts.

  Next, the control unit 13 calculates a random delay time Tr for selecting a beacon slot (ST28) and overwrites the previous random delay time Tr held in the memory 14.

This random delay time Tr is
Tr = (M + Rand (N−L)) × t3
Is calculated as That is, the beacon slot having the slot number corresponding to the calculated random delay time Tr is selected as the beacon slot for transmitting the vehicle beacon packet B1.

  Next, each vehicle wireless communication device 10 of the vehicle group that acquired the communication channel transmits / receives a data packet between the vehicle wireless communication devices 10 in the vehicle group, specifically, at the same time as the end of the data period 62. Returning to the process of step ST21, the communication channel is released.

  In step ST24, when the control unit 13 detects a beacon packet (step ST24; Yes), that is, before the beacon station 10 of its own vehicle group transmits the beacon packet, the beacon station 10 of another vehicle group is transmitted. When the vehicle beacon packet B1 is received or when the roadside beacon packet B2 is received, the communication channel is acquired by another vehicle group. Therefore, the control unit 13 of each vehicle wireless communication device 10 of the vehicle group performs inter-vehicle communication (specifically, the beacon station 10 transmits the vehicle beacon packet B1 and the data packet until the communication channel is released. The transmission / reception and slave stations are controlled to pause transmission / reception of data packets.

  Next, the control unit 13 of the beacon station 10 calculates the elapsed time Tw between the start time of the beacon period 61 and the time point when the vehicle beacon packet B1 of the other vehicle group is detected (ST29). Next, the delay time from the start of the beacon period 61 (corresponding to the beacon slot number) Tr = the previous delay time Tr−the elapsed time Tw, and the random delay time Tr stored in the memory 14 is updated (step ST30). The process returns to step ST21.

  FIG. 8 is an explanatory diagram of a communication channel acquisition operation for each of the vehicle groups 1 and 2 in the inter-vehicle wireless communication system 100 of FIG. 8A shows a time chart of the vehicle group 1, FIG. 8B shows a time chart of the vehicle group 2, and FIG. 8C shows a time chart of the roadside wireless communication device 20. Show.

  As shown in FIG. 8, when the beacon station 10 of the vehicle group 1 transmits the vehicle beacon packet B1, the roadside wireless communication device 20 that has received the vehicle beacon packet B1 is in the first beacon period 61A. Even immediately, the roadside beacon packet B2 is transmitted (S1). When the beacon station 10 of the vehicle group 2 receives the roadside beacon packet B2, the beacon station 10 stops the transmission of the vehicle beacon packet B1 (S2). That is, even if there is an obstacle between the beacon station 10 of the vehicle group 1 and the beacon station 10 of the vehicle group 2, the vehicle group 2 that has received this roadside beacon packet B2 Is suspended, transmission of the vehicle beacon packet B1 is suspended. As a result, since the communication channel is not occupied by two or more vehicle groups at the same time, it is possible to avoid collision of communication (specifically, transmission / reception of data packet D in FIG. 8) between the vehicle groups. The communication channel can be acquired efficiently.

  Here, the control unit 23 of the roadside wireless communication apparatus 20 extracts the group ID from the received vehicle beacon packet B <b> 1 and stores it in the memory 24. And when transmitting roadside beacon packet B2, with reference to memory 24, group ID of a peripheral group is added to roadside beacon packet B2. The data in the memory 24 is updated every predetermined time (for example, 1 second).

  Therefore, the beacon station 10 of each vehicle group is shielded by the group ID of the vehicle group existing in the periphery of the communication area of the roadside wireless communication device 20, that is, the shielding object, by receiving this roadside beacon packet B2. The group ID of the vehicle group can be acquired. And the beacon station 10 of each vehicle group can specify the number of groups existing around its own vehicle group by counting the number of acquired group IDs.

  As shown in FIG. 4, each vehicle wireless communication device 10 forms one cycle T with a beacon period 61 and a data period 62, and each vehicle wireless communication device 10 of the vehicle group that acquired the communication channel sets the communication channel. After the opening, the beacon stations 10 belonging to the vehicle group are subjected to suspension frequency control for stopping transmission of the vehicle beacon packet B1 for a predetermined period.

  Specifically, as described above, each beacon station 10 acquires a group ID of a vehicle group around the roadside wireless communication device 20 from the received roadside beacon packet B2, and counts the number of types of group IDs. That is, the number of vehicle groups (peripheral groups) other than the own vehicle group existing around the own beacon station 10 is acquired. Note that the group ID of the roadside wireless communication device 20 included in the roadside beacon packet B2 is not included in the number of neighboring groups. The number of peripheral groups is acquired every update time (for example, 1 second).

  That is, the beacon station 10 that has acquired the communication channel performs communication to acquire the communication channel at least for a predetermined period corresponding to the number of groups existing around the roadside wireless communication device 20 after releasing the communication channel. Pause. Further, each beacon station 10 may directly acquire the group ID of the vehicle beacon packet B1 received from another beacon station 10 and add it to the number of types of group IDs. This further improves the accuracy of the number of vehicle groups (peripheral groups) other than the own vehicle group existing around the own beacon station 10. In the present embodiment, as shown in FIG. 8, since the vehicle group 2 exists around the vehicle group 1, the suspension period by controlling the number of suspensions of the vehicle group 1 is two cycles.

  Therefore, once the communication channel acquisition timing can be shifted, communication collision between the vehicle group 1 and the vehicle group 2 can be avoided according to the control of the number of pauses.

  Here, as shown in FIG. 8, the first beacon period 61A includes a first period 71A corresponding to the slot number M (step ST28 in FIG. 7) and the first period 71A. N-L), and the first period 71A is preferentially used in the vehicle beacon slot B1 when the communication channel cannot be acquired in the period after the suspension period ends. The second period 71B is a period allocated to transmit the vehicle beacon slot B1 in the period after the end of the pause period.

  For example, as shown in FIG. 8, the beacon station 10 of the vehicle group 2 that has not acquired the communication channel in the second period 71B in step S2 performs the next cycle by the processing in step ST29 and step ST30 (FIG. 7). The vehicle beacon packet B1 is transmitted in the first period 71A (S3). Thereby, each vehicle group 1 and 2 can acquire a communication channel equally, and the stability of communication is ensured.

  As mentioned above, although this invention was demonstrated based on one Embodiment, this invention is not limited to this.

  For example, in the above-described embodiment, the case where the control program is stored in the ROMs 132 and 232 has been described. However, the control program is recorded in advance on recording media such as various magnetic disks, optical disks, and memory cards, and is read from these recording media. It can also be configured to install. It is also possible to provide a communication interface, download the control program via a network such as the Internet or a LAN, install and execute the control program.

It is an outline explanatory view of the radio communications system concerning this embodiment. It is a block diagram which shows the structure of the vehicle radio | wireless communication apparatus as a mobile station mounted in each vehicle. It is a block diagram which shows the structure of a roadside radio | wireless communication apparatus. It is explanatory drawing for demonstrating the communication protocol in a radio | wireless communications system. It is explanatory drawing which shows the structure of a beacon packet. It is a flowchart which shows the control operation of a roadside radio | wireless communication apparatus. It is a flowchart which shows the operation | movement of communication channel acquisition control when a beacon station acquires a communication channel. It is explanatory drawing of the communication channel acquisition operation | movement of each group in a radio | wireless communications system.

Explanation of symbols

1, 2 Vehicle group (group)
1-1, 1-2, 2-1, 2-2 Vehicle 10 Vehicle wireless communication device (mobile station, beacon station)
11 Antenna 12 Wireless Communication Unit 13 Control Unit (Judgment Unit, Pause Unit)
14 memory 20 roadside wireless communication device 21 antenna 22 wireless communication unit (reception means, transmission means)
23 Control unit (reception means, transmission means)
61 Beacon period 61A First beacon period 61B Second beacon period 62 Data period 100 Inter-vehicle wireless communication system (wireless communication system)
B1 Vehicle beacon packet (first beacon signal)
B2 Roadside beacon packet (second beacon signal)
D Data packet (data signal)

Claims (17)

Multiple groups consisting of multiple mobile stations are set up,
At least one mobile station in each group is set to a beacon station that transmits a first beacon signal to obtain a communication channel;
The mobile station of the group to which the beacon station that transmitted the first beacon signal belongs, in the radio communication system that can acquire and transmit the data signal by acquiring the communication channel,
A roadside wireless communication device installed in the movement path of the mobile station,
This roadside wireless communication device
Receiving means for receiving the first beacon signal transmitted from a beacon station existing in the communication area of the roadside wireless communication device;
A transmission means for transmitting a second beacon signal to the mobile station existing in a communication area when the receiving means receives the first beacon signal;
The beacon station
Before acquiring the communication channel, if any one of the first beacon signal and the second beacon signal is received, the transmission of the first beacon signal is suspended. Wireless communication system. The wireless communication system according to claim 1, wherein
A first beacon period during which transmission of the first beacon signal is permitted;
A second beacon period in which transmission of the first beacon signal is prohibited following the first beacon period is set,
The transmission means of the roadside wireless communication device,
When the receiving means receives the first beacon signal, the second beacon signal is transmitted in the first beacon period,
If the receiving means has not received the first beacon signal, the second beacon signal is transmitted during the second beacon period;
Each mobile station is
A wireless communication system, wherein the start timing of a data period in which the data signal is transmitted and received is synchronized based on the received second beacon signal. The wireless communication system according to claim 2,
Each beacon period includes a plurality of slots each having a predetermined time interval,
The transmission means of the roadside wireless communication device,
When the receiving means receives the first beacon signal, the second beacon signal is transmitted in a slot in the first beacon period;
If the receiving means does not receive the first beacon signal, the second beacon signal is transmitted in a slot in the second beacon period;
The second beacon signal includes slot information indicating a slot for transmitting the second beacon signal,
Each mobile station is
A wireless communication system, wherein the start timing of a data period in which the data signal is transmitted and received is synchronized based on slot information included in the received second beacon signal. The wireless communication system according to claim 3,
The wireless communication system, wherein the beacon station transmits the first beacon signal in a randomly selected slot among a plurality of slots in the first beacon period. The wireless communication system according to claim 3 or claim 4,
The roadside wireless communication device transmits the second beacon signal in a randomly selected slot among a plurality of slots in the second beacon period. The wireless communication system according to any one of claims 2 to 5,
The first beacon period, the second beacon period, and the data period constitute one cycle,
After each mobile station of the group that has acquired the communication channel releases the communication channel, a beacon station belonging to the group pauses transmission of the first beacon signal for a predetermined period. Communications system. The wireless communication system according to claim 6.
The wireless communication system, wherein the predetermined period is a period corresponding to the number of groups existing around the roadside wireless communication apparatus. The wireless communication system according to claim 7,
The first beacon signal includes a group ID assigned to a group to which a beacon station that transmits the first beacon signal belongs,
The transmission means of the roadside wireless communication device,
The group ID included in the received first beacon signal is transmitted by being included in the second beacon signal,
Each of the beacon stations specifies the number of groups existing around the roadside wireless communication device based on a group ID included in the second beacon signal. A plurality of groups composed of a plurality of mobile stations are set, and at least one mobile station in each group is set as a beacon station that transmits a first beacon signal to obtain a communication channel, and the first beacon A roadside wireless communication apparatus used in a wireless communication system in which a mobile station of a group to which a beacon station that has transmitted a signal belongs can acquire the communication channel and transmit and receive data signals is installed in the mobile path of the mobile station In
Receiving means for receiving the first beacon signal transmitted from the beacon station existing in its communication area;
When this receiving means receives the first beacon signal, a second beacon signal for suspending transmission of the first beacon signal is transmitted to a beacon station belonging to a group that has not yet acquired the communication channel. A roadside wireless communication apparatus comprising: a transmission unit; The roadside wireless communication device according to claim 9,
A first beacon period during which transmission of the first beacon signal is permitted;
A second beacon period in which transmission of the first beacon signal is prohibited following the first beacon period is set,
The transmission means includes
When the receiving means receives the first beacon signal, the second beacon signal is transmitted in the first beacon period,
The roadside wireless communication apparatus, wherein the second beacon signal is transmitted during the second beacon period when the receiving means does not receive the first beacon signal. The roadside wireless communication device according to claim 10,
Each beacon period includes a plurality of slots each having a predetermined time interval,
The transmission means includes
When the receiving means receives the first beacon signal, the second beacon signal is transmitted in a slot in the first beacon period;
If the receiving means does not receive the first beacon signal, the second beacon signal is transmitted in a slot in the second beacon period;
The roadside wireless communication apparatus, wherein the second beacon signal includes slot information indicating a slot for transmitting the second beacon signal. The roadside wireless communication device according to claim 11,
The roadside wireless communication apparatus characterized in that the second beacon signal is transmitted in a randomly selected slot among a plurality of slots in the second beacon period. In a mobile station used in a wireless communication system provided with a roadside wireless communication device that is set in a plurality of groups composed of a plurality of mobile stations and is installed in the mobile route of the mobile station
Set to a beacon station that transmits a first beacon signal to obtain a communication channel;
Determining means for determining whether or not the roadside wireless communication apparatus has received a second beacon signal transmitted from another beacon station after receiving the first beacon signal before acquiring the communication channel;
A mobile station, comprising: a pause unit that pauses transmission of the first beacon signal when the second beacon signal is received. A plurality of groups composed of a plurality of mobile stations are set, and at least one mobile station in each group is set as a beacon station that transmits a first beacon signal to obtain a communication channel, and the first beacon A roadside wireless communication apparatus used in a wireless communication system in which a mobile station of a group to which a beacon station that has transmitted a signal belongs can acquire the communication channel and transmit and receive data signals is installed in the mobile path of the mobile station In the control method of
A receiving process of receiving the first beacon signal transmitted from the beacon station existing in its communication area;
When the first beacon signal is received, a transmission process of transmitting a second beacon signal for suspending transmission of the first beacon signal to a beacon station belonging to a group that has not yet acquired the communication channel; A method for controlling a roadside wireless communication apparatus, comprising: In a method for controlling a mobile station used in a radio communication system including a roadside radio communication device, in which a plurality of groups each composed of a plurality of mobile stations are set and installed on a mobile path of the mobile station,
Set to a beacon station that transmits a first beacon signal to obtain a communication channel;
Determining means for determining whether or not the roadside wireless communication apparatus has received a second beacon signal transmitted from another beacon station after receiving the first beacon signal before acquiring the communication channel;
A mobile station control method comprising: a pause unit that pauses transmission of the first beacon signal when the second beacon signal is received. A plurality of groups composed of a plurality of mobile stations are set, and at least one mobile station in each group is set as a beacon station that transmits a first beacon signal to obtain a communication channel, and the first beacon A roadside wireless communication apparatus used in a wireless communication system in which a mobile station of a group to which a beacon station that has transmitted a signal belongs can acquire the communication channel and transmit and receive data signals is installed in the mobile path of the mobile station Is a control program for controlling by a computer,
Receiving the first beacon signal transmitted from the beacon station existing in its own communication area;
When the first beacon signal is received, a beacon station belonging to a group that has not yet acquired the communication channel is allowed to transmit a second beacon signal that pauses transmission of the first beacon signal. A control program for a roadside wireless communication device. A control program for controlling, by a computer, a mobile station used in a wireless communication system having a roadside wireless communication device installed in a mobile route of a plurality of groups each including a plurality of mobile stations. There,
Set the beacon station to transmit the first beacon signal to obtain the communication channel,
Determining whether or not the roadside wireless communication device has received the second beacon signal transmitted after receiving the first beacon signal from another beacon station before acquiring the communication channel;
When receiving the second beacon signal, the mobile station control program suspends transmission of the first beacon signal.

Images