JP2001118191A - Vehicle-to-vehicle wireless communication system - Google Patents

Abstract

(57) [Problem] To provide a wireless communication system in which vehicles between vehicles can communicate freely without a base station. SOLUTION: Vehicle groups 1, 2 and 3 which are located in a short distance (a range where wireless communication is possible) and move in almost the same direction, and each have a wireless communication device, and each group has a representative wireless communication device. There is a representative vehicle. At the calculated time, the representative wireless communication device transmits a beacon control frame including time information, a group ID, and a subgroup ID, and synchronizes with another group and each wireless communication device in the group. The group ID is an ID indicating a group belonging to the representative wireless communication device, the subgroup ID is an ID within a group specified by the representative wireless communication device,
The priority order indicating the representative wireless communication device transmitting the beacon control frame is shown.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a wireless communication technology between vehicles in a road traffic system.

[0002]

2. Description of the Related Art As a radio communication system between vehicles, for example, there is a radio communication system using a central control station (base station) such as Japanese Patent Laid-Open No. Hei 7-115422.

In order to perform communication between vehicles without using a base station, a contention system is generally employed.

[0004]

The development of wireless communication technology between vehicles is expected to be applied to road traffic systems, railway vehicle systems, and the like. Specifically, it reports the speed and position of the preceding vehicle on the same course to the following vehicle,
The availability of abnormality information on other vehicles is very valuable information for vehicle control during traveling.

[0005] However, the wireless communication system using the above base station has a problem in terms of cost that maintenance of the base station and the backbone equipment and facilities requires a large amount of cost. Also, the problem that the performance of the base station affects the communication quality of the system, and the problem that the wireless communication system using the base station is not suitable when the main purpose of use is direct communication such as inter-vehicle communication There was a point.

Further, if the contention system is introduced as it is for performing communication between vehicles without using a base station, there is a problem that it is impossible to design a system in consideration of the number of vehicles and the operation form.

On the other hand, there is a demand for a wireless system that can be easily used without requiring an advanced backbone such as a device for performing wireless communication control with each vehicle on a track or road as communication means between vehicles. However, since the construction of such a simple wireless communication system between vehicles is wireless communication, there is a demand for wireless communication technology such as reliability of communication, effective use of frequency, hidden terminal problem and securing of communication channel. is there.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems and needs of the related art, and has as its object to provide a wireless communication system in which vehicles can freely communicate without a base station. Further, a means for improving communication efficiency by grouping each vehicle with a special communication control frame and a means for reconfiguring the group are also provided.

[0009]

In order to solve the above-mentioned problems, a vehicle-to-vehicle wireless communication system according to a first aspect of the present invention provides a vehicle-to-vehicle wireless communication system which includes a wireless communication device for each vehicle.
A wireless communication system in a vehicle group, wherein each vehicle group includes at least one representative vehicle equipped with a representative wireless communication device having beacon information transmitting / receiving means for transmitting / receiving beacon information, a clock means, and a control means, and Belonging to the representative wireless communication device, beacon information receiving means for receiving beacon information, another vehicle equipped with a wireless communication device equipped with a clock means and a control means, the beacon information,
The time information of the clock means, the transmission interval information of the beacon information, the period information in which each wireless communication device belonging to the group of representative wireless communication devices can communicate, the unique group ID for each group, and the wireless communication device in the group When the representative wireless communication device determines the priority based on the group ID information or the beacon reception timing when the beacon information transmitting and receiving means receives the beacon information, the representative wireless communication device includes the unique subgroup ID information and the like. The time of transmission of the next beacon information is corrected in accordance with the time information of the beacon information received by its own clock means, and the time is synchronized with another group based on the corrected time of transmission of beacon information.

According to a second aspect, in the inter-vehicle wireless communication system according to the first aspect, each of the wireless communication devices belonging to each representative wireless communication device group compares the group ID information when receiving the beacon information. Then, when the received beacon information is the beacon information of the group to which the self belongs, its own clock means corrects the next beacon information reception time in accordance with the time information of the received beacon information. Time synchronization with other wireless communication devices in the group is achieved.

A third invention is characterized in that, in the inter-vehicle wireless communication system according to the first invention, the vehicles in the vehicle group move in substantially the same direction within a communicable range.

According to a fourth aspect of the present invention, in the vehicle-to-vehicle wireless communication system according to the first aspect, each representative wireless communication device comprises:
A random access means for performing an access by a random transmission delay time calculating procedure for performing weighting based on an elapsed time from the previous transmission of beacon information is provided, and a communication channel is obtained by the random access means.

According to a fifth aspect of the present invention, in the vehicle-to-vehicle wireless communication system according to the first aspect, each representative wireless communication device comprises:
There is provided random access means for performing access by a random transmission delay time calculation procedure for performing weighting based on the number of beacon transmission attempts, and a communication channel is obtained by the random access means.

According to a sixth aspect of the present invention, in the vehicle-to-vehicle wireless communication system according to the first aspect, each representative wireless communication device comprises:
A random access means for performing access by a short time slot generation procedure for detecting the presence or absence of communication is provided, and a communication channel is obtained by the random access means.

According to a seventh aspect of the present invention, in the vehicle-to-vehicle wireless communication system according to the first aspect, each representative wireless communication device includes:
There is provided random access means for performing access by a transmission slot generation procedure for sequentially changing the priority of beacon transmission, and the communication channel is obtained by the random access means.

According to an eighth aspect of the present invention, in the vehicle-to-vehicle wireless communication system according to the first aspect, each representative wireless communication device comprises:
There is provided random access means for performing access by a random transmission delay time calculation procedure based on an elapsed processing time related to beacon information transmission, and a communication channel is obtained by the random access means.

According to a ninth aspect, in the vehicle-to-vehicle wireless communication system according to the first aspect, each representative wireless communication device includes:
The present invention is characterized in that a communication channel acquisition equal control means is provided for each group by a communication channel suspension procedure, and the acquisition of the communication channels is performed by the communication channel acquisition equal control by the acquisition equal control means.

According to a tenth aspect, in the inter-vehicle wireless communication system according to the first aspect, each representative wireless communication device includes transmission control means for enabling or disabling its own beacon information transmission function. Features.

According to an eleventh aspect, in the inter-vehicle wireless communication system according to the first aspect, each representative wireless communication device communicates by measuring beacon information reception and data reception intervals from each of the wireless communication devices. A communication state observing means for observing a state is provided.

According to a twelfth aspect, in the vehicle-to-vehicle wireless communication system according to the first aspect, each representative wireless communication device includes a transmission control unit for enabling or disabling its own beacon information transmission function; And a communication state observing unit that measures a data reception interval from each of the wireless communication devices to observe the communication state, and separates and combines the groups according to a reception state of the beacon information of the group observed by the communication state monitoring unit. And a group construction means for performing

A thirteenth aspect of the present invention provides a vehicle-to-vehicle wireless communication system which is a vehicle-to-vehicle wireless communication system in which a wireless communication device is mounted for each vehicle. The wireless communication device having the control means is provided, and the beacon information includes time information of the clock means, transmission interval information of the beacon information, information on a period in which each wireless communication device can communicate, and a unique ID for each communication device.
The wireless communication device of each vehicle determines the priority based on the ID information or the beacon reception timing when the beacon information transmission / reception means receives the beacon information, and determines the own priority when the priority is high. The beacon transmission / reception time is corrected in accordance with the time information at which is received, and the time is synchronized with another wireless communication device based on the corrected beacon transmission / reception time.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Overview] The present invention provides a wireless communication means between vehicles as shown in the schematic explanatory view of FIG. In FIG. 1, each vehicle 1-1, 1-2, 1-3, 2-
1,2-2,3-1,3-2 are a plurality of groups 1,2,2
3 groups. In the present invention, a wireless communication device having a configuration as shown in FIG. 2 and a communication procedure as shown in FIG. 3 are provided as wireless communication means when a plurality of such vehicles and a plurality of groups are present. In addition, the condition of the vehicles forming the group is that at least two vehicles equipped with the wireless communication device exist in a short distance (communicable range) and move in substantially the same direction (the destination destination is the same). It is. Each vehicle is equipped with a wireless communication device having a configuration as shown in FIG. In addition, as described later, each group may be configured by one vehicle equipped with the wireless communication device.

[Wireless Communication Device] FIG. 2 is a block diagram showing the configuration of an embodiment of a wireless communication device mounted on each vehicle in the wireless communication system between vehicles according to the present invention. Wireless communication unit 12, control unit 1
3, a memory 14 and a vehicle interface 15 are provided.

The radio communication unit 12 receives a beacon control frame and transmits and receives a data frame via the antenna 11 according to a predetermined communication procedure under the control of the control unit 13.
When the wireless communication device 100 is a representative wireless communication device described later, transmission and reception of a beacon control frame and transmission and reception of a data frame are performed.

The control unit 13 includes a CPU and a ROM (not shown).
And a microcomputer comprising an internal clock 131 and peripheral circuits as described above. The control of the entire apparatus and each unit described later (configured by a program in the embodiment) allow comparison of group ID information and priority. Execution control such as determination of the degree, correction based on the beacon time of the internal clock, and time synchronization with other groups is performed. Also,
The program storage memory includes, in addition to a control program and a communication protocol for controlling the entire wireless communication apparatus, a program for performing communication control and necessary processing in the inter-vehicle wireless communication system of the present invention, and beacon information as shown in FIG. The table 40 stores values and various set values.

The memory 14 stores beacon control frames and data frames received via the radio communication unit 12 and vehicle data (vehicle speed, heading direction, current position (coordinates, etc.)) acquired via the vehicle interface 15. It is stored under the control of the control unit 13.

The vehicle interface 15 converts vehicle data, such as vehicle speed, direction of travel, and current position (coordinates) acquired by a sensor or the like provided on the vehicle, into digital data, and under the control of the control unit 13, The data is sent to the memory 14, or the data read from the memory 14 is signal-converted and sent to the vehicle side (for example, when the drive system control data is read from the memory 14, the drive system control unit (FIG. (Not shown)).

[Inter-Vehicle Communication Procedure] FIG. 3 is an explanatory diagram of the inter-vehicle communication procedure, and shows the communication procedure of each group on a time axis. Here, the inter-vehicle communication in FIG. 3A indicates a period during which the wireless communication devices of the vehicles belonging to groups 1, 2, 3, 4,... Acquire a communication channel. The communication channels of each group 1, 2, 3, 4,... Acquire a communication channel using a special control frame called a beacon (Beacon: reference signal) control frame.

The beacon control frame has a function of allocating a communication channel for each wireless communication device in the group. This communication channel assignment function is a data slot assigned to each wireless communication device after receiving a beacon control frame having a data slot assignment group ID (FIG. 3B).
Is a function of calculating an allocation time for transmitting a data frame during a period of ten slots slot1 to slot10).

Therefore, each wireless communication device in the group:
In each of the allocated data slot periods slot1 to slot10, only a specific wireless communication device has a right to transmit a data frame, so that data frame collision with another wireless communication device does not occur. By using the beacon control frame in this manner, a communication channel can be secured and a data communication environment free from collision can be realized.

Further, by setting the frequency of acquiring the communication channel by the beacon control frame to be equal to or higher than the frequency of data generation, an opportunity to transmit the same data a plurality of times is provided. Transmitting the same data a plurality of times contributes to further improvement in communication reliability.

The beacon control frame is a special function provided to a wireless communication device representing each group, and has a function of managing communication time (setting a reference time). This beacon control frame can be received by all wireless communication devices irrespective of the group to which it belongs, and includes, as a specific example, the content (information transmitted by the beacon) as shown in FIG.

[Beacon Information Table] FIG. 4 shows an embodiment of a beacon information table in which information included in a beacon control frame is tabulated. Each wireless communication device has a beacon information table 40 and is normally used. Although there is no (table inactive state), as described later, when a certain wireless communication device is assigned as a representative wireless communication device according to the priority of the subgroup ID, the beacon information is used using this beacon information table 40 (table active state). Generate a control frame. In the beacon information table 40, the time is the time at which the beacon control frame is transmitted from the internal clock (131) of the wireless communication device (representative wireless communication device) that transmits the beacon control frame, and the interval is the wireless communication time. The time interval (beacon interval) in which the device (representative wireless communication device) transmits a beacon control frame is shown, and the period indicates the time (period) in which the group to which the representative wireless communication device belongs can communicate. Group I
D is an ID indicating the group to which the representative wireless communication device that has transmitted the beacon control frame belongs, and the subgroup ID is an ID within a group that specifies the representative wireless communication device transmitting the beacon control frame. Yes, a unique value within the group. This subgroup ID
Has an important role, and indicates a priority order as a representative wireless communication device that transmits a beacon control frame. For example, assuming that a sub-group ID is assigned by assigning a number in order from the first wireless communication device in the group, the first wireless communication device has the transmission right of the highest priority beacon control frame. Further, if any problem occurs in the wireless communication device of the leading vehicle, the right to transmit the beacon frame to the wireless communication device of the second vehicle having the next highest priority is given. There are various ways of assigning the subgroup ID, and assignment from the end or random assignment may be used.
The condition is that the value is unique within the group.
In addition, individual information necessary for operation of the application destination system can be added to the beacon control frame.

Here, the wireless communication devices in each group are:
In the case of the beacon control frame of the own group, the internal clock is adjusted based on the time information included therein. By this operation, time synchronization of the wireless communication devices belonging to the group can be performed, and further, the reception time of the next beacon control frame of the group can be predicted.

[Representative wireless communication device] The representative wireless communication device of each group is determined by the priority order of the subgroup ID as described above, and based on the beacon information table 40 as shown in FIG. It has a function of transmitting a beacon control frame at a time calculated from the clock 131 and the beacon interval. Note that the hardware configuration of the representative wireless communication device may be the same as that of FIG. 1, and the beacon control frame transmission function of the wireless communication unit 12 is activated with other wireless communication devices in the group according to the priority order of the subgroup ID described later. The state is different from the state described above in that the function of the control unit 13 as the representative wireless communication device described later is in the active state. That is, each wireless communication device has a normal mode that operates as a normal wireless communication device in the group and a representative mode that operates as a representative wireless communication device. Switching between the normal mode and the representative mode is performed by switching the sub-group ID as described above. Determined by priority.

[Synchronization Acquisition by Beacon Control Frame] Next, a method of using the beacon control frame as the whole system will be described. As is clear from the procedure explanatory diagram of FIG. 3, the beacon control frame indicates the communication time (period) of a specific group as one of its roles. That is, by receiving the beacon control frame, it is understood that a certain period of time (indicated by the received beacon control frame) is the communication time (period) used by the group indicated by the beacon control frame. This makes it possible to reduce communication collisions by grouping a plurality of wireless communication devices and allocating communication time to each group.

As described above, since the beacon control frame also considers the channel acquisition control between groups, the channel acquisition operation can be synchronized in the entire system, and the occurrence of careless data communication and communication between groups can be achieved. Operate so that no collision occurs.

The beacon control frame is used for acquiring synchronization between groups. That is, the representative wireless communication device of each group that has received the beacon control frame (each representative wireless communication device has a beacon transmission unit having a beacon control frame transmission function), based on the information on the beacon control frame, Perform processing.

The group ID of the received beacon control frame is compared with its own group ID, and if the group ID of the received beacon control frame has a higher priority than its own group, the process is executed. If the priority is low, a beacon time (scheduled time) to be transmitted next is calculated. When the group ID information is not used, the process is executed according to the beacon reception timing.

The internal clock is adjusted to the time information of the received beacon control frame.

The communication allocation time of the own group is calculated from the time information of the received beacon control frame and the group ID.

Each representative wireless communication device corrects the transmission time (scheduled time) of the next beacon control frame to be transmitted based on the calculated value.

By performing these processes, time synchronization of each group is performed, and it becomes possible to assemble a schedule without overlapping the communication time allocation of each group. This is a very effective solution to the problem that the communication time allocation of each group is duplicated by mere group division, which prevents communication collision avoidance.

[Channel Acquisition Control] The channel acquisition control is performed by the beacon sending means of each representative wireless communication device. Hereinafter, a specific beacon transmission procedure related to channel acquisition control will be described.

(1) Method using a random access method within a beacon transmission period In this method, transmission of a beacon control frame is performed within a beacon transmission period calculated from a beacon period (FIG. 3).
This is performed using the random access method in (c)). That is, during this period, contention for channel acquisition by the beacon control frame is performed. By this means, even if the number of groups increases, for example, a channel can be obtained by a beacon control frame transmitting wireless communication device (representative wireless communication device) in each group simply by a random delay.

The random delay occurrence rate is shown in FIG.
Weighting as shown in the example of (weighting method for generating random delay) is possible. FIG. 5 (a)
Is an example in which the weighting factor is α, and the frequency y is represented by a linear expression of the delay time x. In the example of FIG. 5B, the weighting factors are α, β, and the frequency y is the quadratic of the delay time x. This is an example represented by an expression. Also, control can be performed so that the random delay time is shortened in inverse proportion to the elapsed time from the previous beacon control frame transmission time or the number of trials of beacon control frame transmission. By doing so, it is possible to prevent a specific group from continuously acquiring channels and to provide each group with an equivalent channel acquisition rate.

(2) Method of Dividing Beacon Period into Slots FIG. 6 is a diagram showing an embodiment of priorities and slot allocation positions in a beacon period. In this method, the beacon period (beacon transmission period)
6 (b) (= (FIG. 3 (c))), a time slot shorter than the radio frame is allocated, and a beacon control frame transmission timing of each group is assigned to each time slot. When a beacon control frame transmitted from another group is received before the time slot of the own group, the beacon control frame is accepted, and the transmission timing of the beacon control frame of the own group is postponed to the next beacon period. Since the time slot width may be a time sufficient to detect the presence or absence of communication from each representative wireless communication device, a very short time allocation may be used.

Therefore, even if the number of groups increases, the time slot does not significantly affect the system performance (in the example of FIG. 6B, the beacon period is divided into nine time slots). Nine groups correspond to numbers 1 to 9 in that order). As shown in FIG. 6 (c), the transmission timing of the beacon control frame is changed in order of priority so that each group can be provided with an even channel acquisition rate without bias. For example, in the first beacon period, as shown in FIG.
oup1) has the highest priority, so it is assigned first.
In the next beacon period, as shown in FIG. 6C, group 2 has the highest priority and group 1 has the last assignment. Further, as shown in FIG. 6D, the number of slots to be allocated and the priority may be changed according to the communication frequency of the group.

(3) Acquisition of Communication Channel by Random Delay Time Calculation Procedure FIG. 7 is a flowchart showing one embodiment of the random delay time calculation procedure, taking into account the elapsed time from the start of the beacon period.

In FIG. 7, when the communication channel is released (S1), a beacon period starts (S2), and
3 starts a timer. At this time, the random delay time Tr held in the memory 14 (the initial value is initially held in the memory 14, but the value calculated in step S10 is held from the next cycle) is set. (S3).

Next, the control unit 13 checks whether or not the wireless communication unit 12 has received a beacon control frame from another group. If the beacon control frame has been received, the control unit 13 transits to S5, and if not, transits to S7 (S4). ).

When a beacon control frame from another group is received, the control unit 13 calculates the elapsed time Tw from the start of the beacon period (S5), and then calculates the delay time Tr from the start of the beacon period = previous time The random delay time Tr is updated as the delay time Tr−the elapsed time Tw of
Return to (S6).

If a beacon control frame from another group has not been received in step S4, after the random delay time Tr has elapsed (S7), the control unit 13 controls the wireless communication unit 12 to control this group. Is transmitted (S8), and a communication channel is acquired (S9). Next, the control unit 13 calculates the random delay time Tr, overwrites the previous random delay time stored in the memory 14, and returns to S1 (S10).

In this procedure, the once calculated random delay time is re-randomized by subtracting the elapsed time in the next beacon period by receiving a beacon control frame from another wireless communication device (a representative wireless communication device of another group). By using it as the delay time, the maximum communication channel acquisition delay time can be clarified. Thus, in any case, the communication channel can be acquired within the time determined by the maximum random delay time determined by the system.

(4) Acquisition of Communication Channel by Communication Channel Suspension Procedure Next, from another viewpoint, transmission of a beacon control frame is handled. For example, when two groups are present in a certain wireless communication area, each other's group It is the most efficient that the communication rights are acquired in order. In such a situation, in order to obtain the optimum communication right, it is effective to suspend the transmission of the beacon control frame once in a beacon period after a certain group has once obtained the communication right. That is, when the group that has acquired the communication right suspends the work of acquiring the communication right after the end of the communication, the other group can independently transmit the beacon control frame, and the acquisition of the communication right succeeds. This is because, even when there are three or more groups in the wireless communication area, the suspension of transmission of a beacon control frame by one of the groups reduces the number of competitors for other groups. This has the effect of lowering the acquisition collision probability and increasing the communication channel acquisition probability.

Further, as shown in the flowchart of FIG. 8B (beacon control frame reception request operation), the number of groups (peripheral groups) existing in the radio communication area is monitored, so that efficient channel acquisition is achieved. Control can be realized.

A: A group ID is obtained from the received beacon control frame. B: The type of this group ID is counted. That is,
Groups other than your group that exist in the wireless communication area
(Peripheral group) Get the number. C: Acquire the number of other groups existing in the vicinity every update time (for example, 1 second). D: This acquired value is set as the number of times of beacon control frame transmission suspension. In other words, if the transmission of the beacon control frame is performed and the communication channel is acquired, the acquisition of the communication channel is suspended for a time corresponding to the beacon period corresponding to the number of beacon control frame transmission suspensions thereafter. By performing such control, each group is given an equal opportunity to acquire a communication channel, and each group can acquire a communication channel while avoiding competition for acquiring a communication channel as much as possible while performing random access. .

An example of a specific procedure of the above process will be described with reference to a flowchart of an example of a procedure for transmitting a beacon control frame in consideration of the number of peripheral groups in FIG. FIG. 9 shows a specific setting example of the number of times the transmission of the beacon control frame is suspended. I: Frame Reception Processing: (FIG. 8A) FIG. 8A is a flowchart showing an embodiment of a peripheral group number acquisition processing operation when a new frame is received. When the representative wireless communication device (100) receives a new beacon control frame (T1) in FIG.
Check the peripheral group ID table expanded in No. 4 and
Group I on new beacon control frame in table
When there is no ID that matches D, the process proceeds to T3, and when there is an ID that matches, the beacon control frame reception process ends (T2). If there is no ID matching the group ID on the new beacon control frame in step T2, the group ID on the new beacon control frame is additionally registered in the peripheral group ID table (T3), and 1 is added to the group ID counter. To update the number of registered IDs.

II: Beacon Control Frame Reception Request: (FIG. 8B) FIG. 8B is a flowchart showing one embodiment of a beacon control frame reception request processing operation. This is performed by making a beacon control frame transmission request every period. In FIG. 8B, the control unit 13 uses the pause counter to select whether to start transmitting a beacon control frame. That is, when acquiring the group ID from the received beacon control frame, the control unit 13 checks the value of the pause counter, and when the pause counter = 0, transits to U3, and when the pause counter ≠ 0, transits to U5 (U1). . When the pause counter = 0 at step U1, the control unit 13 counts the types of the acquired group IDs. That is, the number of peripheral groups is counted, and the update time (for example, 1 second)
The number of other groups existing in the vicinity is acquired every time (U2), and the acquired value is set in the suspension counter as the number of beacon control frame transmission suspensions (U3), and the wireless communication unit 12 transmits the beacon control frame. Then, the beacon control frame transmission request is terminated (U4). If the pause counter is $ 0 in step U1, the control unit 13 ends the beacon control frame transmission request after subtracting 1 from the pause counter (U5). By transmitting the beacon control frame by the above operation and acquiring the communication channel, the acquisition of the communication channel can be suspended for a time corresponding to the beacon period corresponding to the number of suspensions of the beacon control frame transmission thereafter.

III: Update of group ID: (FIG. 8
(C)) FIG. 8C is a flowchart showing an embodiment of the group ID update operation, which is a process started periodically (for example, every one second). Number of groups. That is, the control unit 13 sets the number of group ID counter values (see step T4 in FIG. 8A) as the number of peripheral groups (V1), clears the peripheral group ID table and the group ID counter (V2, V3). , The group ID is updated.

As described above, even if any of the above-described means (1) to (4) or a combination thereof is used, the chances of acquiring channels can be equalized in each group, and unnecessary channel acquisition can be eliminated. . This means that a group that needs to acquire a channel can acquire more communication channels. In addition, it is possible to reduce deterioration of system performance due to an increase in the number of groups.

[Group Synchronization Time] Next, regarding the above-mentioned “group time synchronization by beacon control frame”,
An inter-vehicle wireless communication system including three vehicle groups shown in FIG. 10 will be described in more detail as an example.

FIG. 10 (explanatory diagram of the procedure for acquiring the group time synchronization) shows a case where group 1 and group 2 are in an area where wireless communication is possible with each other, and group 3 is where another group capable of wireless communication is within the wireless communication area. Is not shown. In this example, each of the wireless communication devices of the group 1 and the group 2 can receive the beacon control frame transmitted by the representative wireless communication device of the other group. From this, the representative wireless communication devices of the groups 1 and 2 are synchronized by the above-described procedures 1 to 3 using the received beacon control frame, and are newly transmitted based on the information on the synchronized beacon control frame. Each of the wireless communication devices in the groups 1 and 2 that receive the beacon control frame is also synchronized. Thereafter, for example, when the group 3 moves in the direction of the group 1 and the group 2 and enters the same wireless communication area, the groups 1, 2, and 3 are synchronized by the same procedure. As described above, when the vehicle group equipped with each wireless communication device moves and enters the same wireless communication area, the entire system is synchronized.

Further, for example, in a vehicle group that is out of the radio communication area and left behind, such as Group 3, the inter-vehicle radio communication system is operated independently within the group without synchronization. However, in this case, the wireless communication of this group does not affect other groups (and is not affected by other groups), so that there is no problem in operation of the inter-vehicle wireless communication system.

<Embodiment (1) of Beacon Transmission Procedure> The first beacon procedure in the channel acquisition control has been described as "(1) Random access scheme within beacon transmission period". An example will be described with reference to FIGS. 10 and 11 (time chart of a first beacon procedure).

In FIGS. 10 and 11, the entire inter-vehicle wireless communication system is composed of three groups. IDs 1 to 3 are assigned to each group. Also,
The number of wireless communication devices in each group is not limited to the example shown in FIG. a: The representative wireless communication device of each group sets up a beacon transmission plan from its own internal clock (131) at the start of operation. The beacon planning criteria are shown below. b: The communication time allocated to each group is 10 msec.
And c: The internal clock is in units of 10 μsec. d: In the beacon period, access using random delay is performed. For the generation of the delay time, the number of attempts to transmit a beacon control frame is used as a parameter. This parameter is cleared when a beacon control frame can be transmitted, and is incremented by one every time a random delay is generated in the beacon period. For example, the number of trials “0” indicates that this is the first beacon period immediately after system initialization or immediately after acquiring a communication channel. e: As a procedure for using the number of trials of transmitting a beacon control frame, for example, when the number of trials is “0”, a maximum delay time is generated, and as the number of trials increases, the maximum value of the delay time decreases. Use a random value. As the priority of the group ID, the smaller the value, the higher the priority.

Thus, system group synchronization functions as follows. i: The representative wireless communication devices of each group make a beacon transmission plan from their respective internal clocks (131) and transmit a beacon control frame at a predetermined time. ii: At this time, since the group 3 is a single wireless communication area, a beacon control frame is transmitted independently without performing a synchronization operation. iii: Group 1 and Group 2 can receive each other's beacon control frame, so that synchronization is performed. In this case, the channel of the group 1 is acquired during the communication period of the group 2, but the time is synchronized with the time of the group 1 based on the group ID priority (group 1> group 2). iv: Thereafter, in FIG. 10, the groups 1 and 2 move in the direction of the group 3 (or the group 3 moves in the direction of the groups 1 and 2), and
When the devices 3 enter the same wireless communication area, they can receive each other's beacon control frames. Here, the synchronization work of groups 1, 2, and 3 is performed. v: Synchronization work of group 1, group 2, and group 3 is based on group ID priority (group 1> group 2
> Synchronization is performed at the time of group 1 from group 3). In FIG. 11, since the beacon control frame of group 2 has been successfully received in group 3, the beacon control frame is transmitted after the end of the channel acquisition period to acquire the communication channel. vi: In this way, the movement of the vehicle equipped with the wireless communication device synchronizes the groups, and uniquely determines the synchronization of the entire system.

<Embodiment (2) of Beacon Transmission Procedure> The second operation of the channel acquisition control is described as “(2) Method of dividing beacon period into slots”. And FIG.
(Explanation of a time chart of the second beacon procedure) will be described. 10 and 12, the entire inter-vehicle wireless communication system is composed of three groups. Each is
IDs 1 to 3 are assigned. Further, the number of wireless communication devices in each group is not limited to the example in FIG.

A: The representative device of each group sets up a beacon transmission plan from its own internal clock (131) at the start of operation. The beacon planning criteria are shown below. b: The communication time allocated to each group is 10 msec.
And c: The internal clock is in units of 10 μsec. d: In the beacon period, wait for the order (slot) of the own group while referring to the priority order table. This order is time-managed. For example, transmission rights are sequentially given in units of an internal clock (10 μsec). Since the transmission of the beacon control frame is possible when the own group has the transmission right, the group that wants to acquire the channel transmits the beacon control frame according to the priority table.

When a beacon control frame is transmitted from a high-priority group before the transmission right is given to the own group, the high-priority group acquires the communication right. e: In this priority order table, rotation is performed for each beacon period, and the priority order is changed. It is also possible to make the group that has acquired the communication channel have the lowest priority (FIG. 6C). Also, I
As the priority of D, the smaller the value, the higher the priority. Thus, system group synchronization works as follows. i: The representative wireless communication devices of each group make a beacon transmission plan from their respective internal clocks (131) and transmit a beacon control frame at a predetermined time. ii: In FIG. 10, since the group 3 is in the single wireless communication area, the group 3 independently transmits a beacon control frame without performing a synchronization operation. iii: Group 1 and Group 2 can receive each other's beacon control frame, so that synchronization is performed. In this case, since group 2 acquired the channel first,
After the end of the communication period of group 2, the representative wireless communication device of group 1 follows the priority order in the beacon period.
The beacon control frame is transmitted. Group I
Synchronization is performed at the time of group 1 according to the priority of D (group 1> group 2). iv: After that, group 1 and group 2 become group 3
(Or when group 3 moves in the direction of groups 1 and 2 and enters the same wireless communication area, it becomes possible to receive the beacon control frames of each other. V: Synchronization work of groups 1, 2, and 3 is performed by group ID
(Group 1> group 2> group 3), the time is synchronized with the time of group 1. After the communication period of the group 2 ends, the group 3 has the highest priority in obtaining the communication channel according to the priority order in the beacon period. In the example of FIG. 12, the group 1 continues to acquire the communication channel, but this is a result of no transmission of the beacon control frame from another group and the group 1 trying to acquire the channel. vi: As described above, when the vehicle equipped with the wireless communication device moves, the groups are synchronized, and the synchronization of the entire system is uniquely determined.

[Expansion of the present system] Although not specified in the above description, in the inter-vehicle wireless communication system of the present invention,
If the communication channels are all the same (there is only one), the communication in the group that acquired the communication channel can be received in other groups in the vicinity (in the wireless communication area). By utilizing this, the intra-group communication can be easily extended to the inter-group communication. That is,
Between groups existing in the wireless communication area, even if the communication channel is acquired by another group, the group can receive the communication channel. It can be used, and such use does not cause any problem in operation of the inter-vehicle wireless communication system. This is because the communication channel acquired in the beacon control frame is for the purpose of time-division control of the communication channel, and does not specify a communication partner or a group.

[Other Embodiments of Group Configuration] Next, another specific example of the group configuration will be described. In the present invention, a plurality of vehicles having the configuration as shown in FIG. However, the number of wireless communication devices in the group does not need to be more than one, and the group can be constituted by only one. This is the same for each of the above-described embodiments. An example of a communication procedure in this case is shown in FIGS. FIG. 13 is a diagram showing an embodiment of slot assignment when the number of vehicles forming the group is one. Since the number of wireless communication devices forming the group is one, FIG. 13 is based on the procedure explanatory diagram of FIG. Predetermined procedure with the number of slots being 1 (FIG. 13B,
It is an example changed to (c)). Further, the example of FIG. 14 is a diagram showing an embodiment of slot assignment when communication data of the wireless communication device is embedded in the beacon control frame (FIG. 14B) itself (FIG. 14C). This is an example considering efficiency.

As described above, by using the procedure for acquiring the communication channel using the beacon control frame, the application form of the application (for example, in addition to the case where the entire group is made up of one vehicle, the group 1 has three vehicles at a certain point in time) Group 2 is composed of one vehicle, Group 3 is composed of four vehicles, or Group 1 is composed of one vehicle and Group 2 is composed of five vehicles,
Group 3 consists of three vehicles, groups 4 and 5 are 1
(E.g., when there are two vehicles), it is possible to more appropriately operate the inter-vehicle wireless communication system.

[Modification (1)] In the above description, a case has been described as an example where all the vehicles equipped with the radio communication device having the configuration as shown in FIG. 2 are moving vehicles. The vehicle need not be a moving vehicle. As such an example, a specific example using a fixed vehicle that does not move and a wired backbone is shown in FIG. 15 (a diagram illustrating an embodiment of an inter-vehicle wireless communication system in consideration of a fixed vehicle).

In FIG. 15, three moving vehicle groups 1 and
2, 3 and 3 fixed vehicles (fixed stations) A, B, C are shown. Further, the fixed moving vehicles A, B, and C are moving vehicles 1-, 1-2, 1-3 (group 1), 2-1 and 2-2, respectively.
(Group 2), 3-1, 3-2, 3-3 (Group 3)
Is disposed on the route 150 on which the mobile phone moves, and is connected to another communication means, for example, an optical network or the like.

In such an application, the synchronization processing (-) by the beacon control frame in the above-mentioned [Synchronization acquisition by beacon control frame] is performed by the fixed stations A,
The priority of receiving beacon control frames from B and C is set high, and each fixed station A,
This can be realized by operating the entire system while synchronizing it by the synchronization process between B and C. In addition, in the case of such a configuration, it is not necessary to make a high demand for the clock accuracy of the wireless communication device of each mobile vehicle, and it is possible to perform synchronization processing of the entire system.

In the case of this application, even group information outside the wireless communication area can be communicated via the fixed station. For example, groups 1, 2, and 3 have different wireless communication areas (indicated by broken-line circles in FIG. 15).
When the information is in 1 ', 2', 3 ', the communication information of group 1 can be received by the fixed station A, relayed to the fixed station C, and the fixed station C further transmits the radio communication channel by the beacon control frame. Processing such as performing acquisition control and relaying to group 3 can be performed.

This is because, for example, if the vehicle 1 of the group 3 breaks down and stops, the information of the failed vehicle is stored in the group 3.
Means that it can be instantaneously transmitted to all vehicles in other wireless communication areas as well as the wireless communication area 3. In other words, any mobile vehicle station can perform data communication with the target mobile vehicle regardless of inside or outside the wireless communication area, and information important for system operation is transmitted to all mobile vehicles. Can communicate.

[Modification (2)] Next, a supplementary description will be given of the activation procedure of the beacon control frame transmission function, the radio link state detection procedure, and the group configuration procedure. In the cases so far, for example, when a vehicle in a certain vehicle group fails and stops, the following vehicle basically stops, and the vehicle in front of the failed vehicle continues to operate. Such a situation, that is, a case where a vehicle in a certain group breaks down and the group is divided with the vehicle as a break may be considered. That is, in the above-described wireless communication procedure, a vehicle (a vehicle equipped with a representative wireless communication device) representing the group exists in a certain group, and the acquisition of a communication channel is performed by a beacon control frame from the vehicle. I do. Therefore, there may be a case where the wireless link is cut off due to a vehicle failure in the group or the influence of the communication environment, and the group is further divided. Therefore, in order to prevent such a situation, a procedure for enabling a beacon control frame transmission function, a procedure for detecting a radio link state, and a procedure for configuring a group are configured as follows.

I: Wireless Link State Detection Procedure (FIG. 16) FIG. 16 is an explanatory diagram of the wireless link state detection procedure of the present proposal. According to the above-described wireless communication procedure, a communication channel can be acquired at certain intervals by the beacon control frame. Therefore, each vehicle (wireless communication device) in the group
In order to grasp the wireless status of the wireless communication device, the system determines: a: the presence / absence of channel acquisition within a certain time range, and the elapsed time after receiving the beacon control frame of the group to which the wireless communication device belongs. Time is exceeded. This is important information relating to a Beacon transmission function activation procedure and a group configuration procedure to be described later.

B: The reception status of the data frame of the wireless communication device corresponding to each data slot (data slot) in the acquired channel is grasped. For example, a link counter is provided for each wireless communication device in the group, and a process is performed such that the counter is cleared when there is reception from the corresponding wireless communication device, and the counter is incremented by +1 when there is no reception.

In the above-described radio procedure, the maximum channel acquisition interval assumed in the system is determined by the beacon control frame. This is determined from the amount of data required for wireless communication by the system, the frequency of data generation, and the like, and determines system parameters such as beacon intervals and the amount of random delay when transmitting a beacon control frame. Since the channel acquisition interval is determined from these parameters, if a limit time (link counter value) is set based on this, communication with the corresponding wireless communication device becomes impossible if the limit value is exceeded. Can be detected. In other words, from this link counter, each wireless communication device obtains reception status information with each wireless communication device in the group, and from this information,
The state of communication within the group, that is, the wireless link state can be determined.

II: Beacon Transmission Function Validation Procedure: A beacon control frame is a control frame transmitted from a representative wireless communication device in the group. However, if a beacon control frame cannot be received for a certain period of time for some reason, that is, If it is determined that the elapsed time has been exceeded according to the determination of Ia, communication becomes impossible, and it is necessary to try to acquire a communication channel by itself. FIG. 17 is a flowchart (showing a flowchart of an embodiment of a procedure for switching between enabling and disabling the beacon control frame transmission function).
Is shown.

In FIG. 17, the control unit (13) of each wireless communication device (100) pays attention to the reception of the beacon control frame for the own group, and sets the beacon control frame within the scheduled beacon control frame reception time of the own group. Is received, a transition is made to W2, and if reception is not possible even after the scheduled time has elapsed, the transition is made to W4 (W1). Also, if a beacon control frame is received within the scheduled time in step W1, it is checked whether or not it is the beacon control frame of its own group. If it is the beacon control frame of its own group, transition to W3 is made; Return to W1 (W
2). When the beacon control frame of the own group is received in step W2, the scheduled reception time of the beacon control frame of the own group is updated, and the process returns to W1 (W3).
If a beacon control frame cannot be received within the scheduled time in step W1, the beacon control frame transmission function is enabled (for example, a beacon control frame transmission flag is turned on) (W4). If a beacon control frame of the own group is received when the transmission function of the beacon control frame is valid, the process transits to W6, and otherwise, performs a group separation process according to a group separation procedure described later (W5). When the beacon control frame of the own group is received in step W5, the beacon control frame transmission function is controlled by the subgroup ID. Specifically, the subgroup IDs are compared, and when the subgroup ID of the own station is small, the process returns to W4 as having the right to transmit a beacon frame, and when the subgroup ID of the own station is large, the process transits to W7 (W6), The process returns to W1 with no beacon control frame transmission right (W7).

III: Group Configuration Procedure Next, a description will be given of a procedure of group separation and connection in forming a vehicle (vehicle with a wireless communication device) group.
Occasionally, a situation in which a beacon control frame cannot be received due to the deterioration of the communication environment occurs, and it is necessary to detect such a situation and take measures to recover from the situation. Required. Assuming such a case, the procedure of separation and combination into groups will be described below.

1: Group separation procedure As described above (see "I: Radio link state detection"), the separation procedure is performed when a beacon control frame cannot be received for a certain period of time or data from a corresponding wireless communication device is received. Executed when unable. In other words, a: The inability to receive a beacon control frame indicates that communication with the group to which the wireless communication device belongs has been interrupted and the wireless communication device has been separated from the group. Accordingly, the separated wireless communication device voluntarily transmits a beacon control frame and forms a group using the new subgroup ID. b: A wireless communication device detects that communication with a wireless communication device in the group has been interrupted based on wireless link information (elapsed time after receiving a beacon control frame of the group to which the wireless communication device belongs). Indicates that the wireless communication device has been separated from the group. The wireless link information is valid information indicating the wireless communication devices constituting the current group, and is system operation information.

2: Group Combination Next, as described above (see “II: Beacon Control Frame Transmission Function Procedure”), when the beacon control frame transmission function is enabled (W4), a beacon control frame having the same group ID is received. In this case (W5, W6), however, if the subgroup ID is different, for example, when the wireless communication status is restored, it is desirable to return to the original group configuration in system operation. This is a concept called coupling, and can be realized by determining the subgroup ID of the received beacon control frame. Since the wireless communication devices are originally configured as the same group, they have different subgroup IDs, and determine this value to determine the right to transmit a beacon control frame. Further, since the group IDs are the same, even a wireless communication device in a different subgroup can realize an operation corresponding to a beacon control frame indicating the same group in a regular procedure (FIG. 17).

Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and it goes without saying that various modifications can be made.

[0089]

As described above, in order to realize communication between vehicles without using a base station, a contention method is generally adopted, but it is not possible to introduce the contention method as it is. This makes it impossible to design a system in consideration of the number of vehicles and the operation mode. On the other hand, according to the inter-vehicle wireless communication system of the present invention, since the beacon information (beacon control frame) for controlling vehicle grouping and group synchronization is used, it is simple and inexpensive, and operation efficiency is low. Wireless communication means between vehicles can be provided.
Further, since the group can be reconfigured, it is possible to prevent the vehicle from being stopped from being separated from the group or from being separated from the group when the vehicle stops due to a failure in the vehicle. In addition, a vehicle group that has been repaired can be returned to the original group, and vehicle group reorganization can be automatically performed in the event of a vehicle failure or when necessary for operation.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory diagram of the present invention.

FIG. 2 is a block diagram showing a configuration of an embodiment of a wireless communication device mounted on each vehicle.

FIG. 3 is an explanatory diagram of an intra-group communication procedure.

FIG. 4 is an example of a beacon information table.

FIG. 5 is an explanatory diagram of a weighting method for random delay generation.

FIG. 6 is a diagram illustrating an example of priorities and slot allocation within a beacon period.

FIG. 7 is a flowchart illustrating an embodiment of a random delay time calculation procedure.

FIG. 8 is a flowchart of an example of a beacon control frame transmission procedure in consideration of the number of peripheral groups.

FIG. 9 is a diagram showing an example of a suspension number correspondence table according to the number of peripheral groups.

FIG. 10 is an explanatory diagram of a group time synchronization acquisition procedure.

FIG. 11 is a time chart of a first beacon procedure.

FIG. 12 is a time chart of a second beacon procedure.

FIG. 13 is a diagram showing one embodiment of slot assignment in the case where one vehicle forms a group.

FIG. 14 is a diagram showing an embodiment of slot assignment when vehicle data is embedded in a beacon control frame.

FIG. 15 is a diagram showing an embodiment of an inter-vehicle wireless communication system when a fixed vehicle is considered.

FIG. 16 is an explanatory diagram of a wireless link state detection procedure.

FIG. 17 is a flowchart illustrating an embodiment of a procedure for switching between valid / invalid of a beacon control frame transmission function.

[Explanation of symbols]

1,2,3 vehicle group 1-1-3,2-1,2-2,3-1-3 vehicle 12 wireless communication unit (beacon transmission / reception unit, beacon reception unit, random access unit) 13 control unit (control unit) , Transmission control means, communication state observation means, group construction means) 100 wireless communication equipment 131 internal clock (clock means)

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Koichi Kato 5-35-2 Hakusan, Bunkyo-ku, Tokyo Clarion Co., Ltd. (72) Inventor Takeshi Hashimoto 5-35-2, Hakusan, Bunkyo-ku, Tokyo Clarion (72) Inventor Masaki Ashizawa 5-35-2, Hakusan, Bunkyo-ku, Tokyo Clarion Co., Ltd. (72) Inventor Takeshi Sasaki 1 Toyota Town, Toyota City, Aichi Prefecture F-term in Toyota Motor Corporation (Reference) 5H180 AA01 BB04 BB15 CC12 FF13 5K067 AA41 BB36 CC13 DD15 DD17 DD25 EE02 EE25 GG01 GG11

Claims (13)

[Claims] 1. A wireless communication system between or within a plurality of vehicle groups in which a wireless communication device is mounted for each vehicle, wherein each vehicle group includes a beacon information transmitting / receiving means for transmitting / receiving beacon information, and a clock means. And at least one representative vehicle equipped with a representative wireless communication device equipped with a control device, a beacon information receiving device belonging to the representative wireless communication device and receiving the beacon information, a clock device, and a wireless communication device including a control device The beacon information, time information of the clock means, transmission interval information of the beacon information, period information in which each wireless communication device belonging to the representative wireless communication device group can communicate, and , Including a unique group ID for each group and unique subgroup ID information for each wireless communication device in the group, Each representative wireless communication device determines its priority based on the group ID information or the beacon reception timing when the beacon information transmitting / receiving means receives the beacon information, and receives its own clock means when the priority is high. An inter-vehicle wireless communication system wherein the next beacon information transmission time is corrected in accordance with the time information of the beacon information thus obtained, and the time is synchronized with another group based on the corrected beacon information transmission time. 2. When each of the wireless communication devices belonging to each of the representative wireless communication device groups receives the beacon information, the wireless communication devices compare the group ID information and determine whether the received beacon information is the beacon information of the group to which the wireless communication device belongs. In the case, the own clock means corrects the next beacon information reception time in accordance with the time information of the received beacon information, and synchronizes time with other wireless communication devices in the group by the corrected beacon information reception time, The vehicle-to-vehicle wireless communication system according to claim 1, wherein: 3. The inter-vehicle wireless communication system according to claim 1, wherein the vehicles in the vehicle group move in substantially the same direction within a communicable range. 4. Each of the representative wireless communication devices includes random access means for performing access by a random transmission delay time calculation procedure for performing weighting based on an elapsed time since the last transmission of beacon information, and the random access means performs communication channel communication. The vehicle-to-vehicle wireless communication system according to claim 1, wherein acquisition of the vehicle information is performed. 5. Each of the representative wireless communication devices includes random access means for performing access by a random transmission delay time calculating procedure for performing weighting based on the number of beacon transmission attempts, and acquiring a communication channel by the random access means. The inter-vehicle wireless communication system according to claim 1, wherein: 6. Each of the representative wireless communication devices includes random access means for performing access by a short time slot generation procedure for detecting the presence or absence of communication, and acquires a communication channel by the random access means. The inter-vehicle wireless communication system according to claim 1. 7. Each of the representative wireless communication devices includes random access means for performing access according to a transmission slot generation procedure for sequentially changing the priority of beacon transmission, and acquires a communication channel by the random access means. The inter-vehicle wireless communication system according to claim 1, wherein: 8. Each of the representative wireless communication devices includes random access means for performing access by a random transmission delay time calculation procedure based on an elapsed processing time for beacon information transmission, and acquires a communication channel by the random access means. The inter-vehicle wireless communication system according to claim 1, wherein: 9. Each of the representative wireless communication devices includes means for controlling the acquisition of communication channels of each group by a communication channel suspension procedure, and acquires communication channels by means of the acquisition and equalization control of communication channels by the acquisition and equalization control means. The inter-vehicle wireless communication system according to claim 1, wherein: 10. The vehicle-to-vehicle wireless communication system according to claim 1, wherein each of the representative wireless communication devices includes transmission control means for enabling or disabling its own beacon information transmission function. 11. The communication device according to claim 1, wherein each of the representative wireless communication devices includes a communication state observation unit that measures a beacon information reception and a data reception interval from each of the wireless communication devices to observe a communication state. The inter-vehicle wireless communication system according to claim 1. 12. Each of the representative wireless communication devices communicates by controlling transmission / reception means for enabling or disabling its own beacon information transmission function, measuring beacon information reception and data reception intervals from the respective wireless communication devices. A communication state observing unit for observing a state, and a group constructing unit for separating and combining groups according to a reception state of the beacon information of the group observed by the communication state monitoring unit. Item 4. The inter-vehicle wireless communication system according to Item 1. 13. A wireless communication system between vehicles having a wireless communication device mounted on each vehicle, comprising: a wireless communication device having beacon information transmitting / receiving means for transmitting / receiving beacon information, a clock means, and a control means; The beacon information includes time information of the clock means, transmission interval information of beacon information, information on a period in which each wireless communication device can communicate, ID information unique to each communication device, and the like. The control means is configured to control the ID when the beacon information transmitting / receiving means receives the beacon information.
The priority is determined based on the information or the beacon reception timing, and when the priority is high, the beacon transmission / reception time is corrected in accordance with the time information when the own clock means is received, and the corrected beacon transmission / reception time is corrected. A vehicle-to-vehicle wireless communication system which synchronizes time with another wireless communication device.