JP3868166B2 - Inter-vehicle wireless communication system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a wireless communication technology between vehicles in a road traffic system.
[0002]
[Prior art]
As a wireless communication system between vehicles, for example, there is a wireless communication system using a centralized control station (base station) such as JP-A-7-115422.
[0003]
Further, in order to perform communication between vehicles without using a base station, it is common to adopt a contention method.
[0004]
[Problems to be solved by the invention]
The development of wireless communication technology between vehicles is highly expected to be applied to road traffic systems and railway vehicle systems. Specifically, reporting the speed and position of the preceding vehicle on the same route to the following vehicle and obtaining the abnormality information of the other vehicle is very valuable information for vehicle control during traveling.
[0005]
However, the wireless communication system using the base station has a problem in terms of cost such that a large amount of money is required for the maintenance of base stations, backbone devices and facilities. In addition, 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.
[0006]
In addition, if the contention method is introduced as it is to perform communication between vehicles without using a base station, there is a problem that it becomes impossible to design a system in consideration of the number of vehicles and the operation mode.
[0007]
On the other hand, as a communication means between vehicles, it is desired to construct a wireless system that can be easily used without requiring an advanced backbone such as a device that performs wireless communication control with each vehicle on the track or road side. In the construction of such a simple wireless communication system, there is a demand on wireless communication technology such as communication reliability, effective use of frequency, hidden terminal problem and securing of communication channel because it is wireless communication.
[0008]
The present invention has been made for the purpose of solving the problems and requirements of the above-described conventional technology, and an object thereof is to provide a wireless communication system in which each vehicle can freely communicate without a base station. In addition, means for improving communication efficiency by grouping a special communication control frame and each vehicle, means for reconfiguring a group, and the like are also provided.
[0009]
[Means for Solving the Problems]
In order to solve the above-described problem, the inter-vehicle wireless communication system according to the first invention has a plurality of vehicle groups equipped with wireless communication devices for each vehicle, and each vehicle group is uniquely assigned to its own group. At least one representative vehicle equipped with a representative wireless communication device equipped with storage means for storing the received group ID information, beacon information transmission / reception means for transmitting / receiving beacon information, clock means and control means, and the representative wireless communication device A storage means for storing group ID information uniquely assigned to the own group, a beacon information receiving means for receiving the beacon information, another vehicle equipped with a wireless communication device including a clock means and a control means; The beacon information includes time information of the clock means, transmission interval information of the beacon information, group of representative wireless communication devices. Each wireless communication device capable of period information communication belonging to, and includes the group ID information indicating the group capable of communicating in the period indicated this period information,
Each representative wireless communication device determines priority based on group ID information included in the beacon information or beacon reception timing when the beacon information transmitting / receiving means receives beacon information, and the priority is determined. If it is high, the next beacon information transmission time is corrected in accordance with the time information of the beacon information received by its own clock means, the time synchronization with other groups is performed by the corrected beacon information transmission time, and each representative radio Each wireless communication device belonging to a group of communication devices compares the group ID information when the beacon information is received, and is included in the beacon information when the received beacon information is the beacon information of the group to which the wireless device belongs. For the period specified by the specified period information In Only wireless communication.
[0010]
Further, according to a second aspect of the present invention, in the inter-vehicle wireless communication system of the first aspect, each wireless communication device belonging to each representative wireless communication device group compares the group ID information when receiving the beacon information, and receives the beacon information. If the received beacon information is the beacon information of the group to which the self belongs, the next beacon information reception time is corrected according to the time information of the beacon information received by the own clock means, and the corrected beacon information reception time It is characterized by time synchronization with other wireless communication devices.
[0011]
According to a third aspect of the present invention, in the inter-vehicle wireless communication system according to the first aspect, the vehicles in the vehicle group move in substantially the same direction within a communicable range.
[0012]
According to a fourth aspect of the present invention, in the inter-vehicle wireless communication system according to the first aspect of the invention, each representative wireless communication device performs access according to a random transmission delay time calculation procedure that performs weighting based on the elapsed time from the previous beacon information transmission. Random access means for performing communication channel acquisition by the random access means.
[0013]
According to a fifth aspect of the present invention, in the inter-vehicle wireless communication system according to the first aspect, each representative wireless communication device has 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 the communication channel is acquired by the random access means.
[0014]
According to a sixth aspect of the present invention, in the inter-vehicle wireless communication system according to the first aspect, each representative wireless communication device includes random access means for performing access by a short time slot generation procedure for detecting the presence or absence of communication. The communication channel is acquired by the access means.
[0015]
The seventh invention is the inter-vehicle radio communication system according to the first invention, wherein each representative radio communication device comprises random access means for performing access by a transmission slot generation procedure for sequentially changing the priority of beacon transmission, A communication channel is acquired by the random access means.
[0016]
According to an eighth aspect of the present invention, in the inter-vehicle wireless communication system according to the first aspect of the invention, each representative wireless communication device accesses the random transmission means according to a random transmission delay time calculation procedure based on an elapsed processing time related to beacon information transmission. The communication channel is acquired by the random access means.
[0017]
According to a ninth aspect of the present invention, in the inter-vehicle wireless communication system according to the first aspect of the invention, each representative wireless communication device includes acquisition equalization control means for the communication channels of each group according to the communication channel suspension procedure. The communication channel is acquired by the communication channel acquisition equalization control according to the above.
[0018]
According to a tenth aspect of the present invention, 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. .
[0019]
The eleventh invention is the inter-vehicle wireless communication system according to the first invention, wherein each representative wireless communication device measures beacon information reception and data reception intervals from each wireless communication device, and observes the communication state The communication state observation means is provided.
[0020]
Further, a twelfth aspect of the invention is the inter-vehicle wireless communication system according to the first aspect of the invention, wherein each representative wireless communication device includes transmission control means for enabling or disabling its own beacon information transmission function, beacon information reception, A group for measuring the data reception interval from the wireless communication device and observing the communication state, and a group for separating and combining the groups according to the reception state of the group beacon information observed by the communication state monitoring unit And a construction means.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
[Overview]
The present invention provides wireless communication means between vehicles as shown in the schematic explanatory diagram of FIG. In FIG. 1, the vehicles 1-1, 1-2, 1-3, 2-1, 2-2, 3-1, 3-2 are grouped into a plurality of groups 1, 2, 3.
In the present invention, as a wireless communication means when there are a plurality of vehicles grouped in this way and a group thereof, a wireless communication device configured as shown in FIG. 2 and a communication procedure shown in FIG. 3 are provided. In addition, the conditions of the vehicles constituting the group are that at least two vehicles equipped with the wireless communication devices exist in a short distance (communication 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 configured as shown in FIG. In addition, as will be described later, each group can be configured by one vehicle on which the wireless communication device is mounted.
[0023]
[Wireless communication equipment]
FIG. 2 is a block diagram illustrating a configuration of an embodiment of a wireless communication device mounted on each vehicle in the wireless communication system between vehicles of the present invention. The wireless communication device 100 includes an antenna 11, a wireless communication unit 12, and a control unit 13. A memory 14 and a vehicle interface 15.
[0024]
The wireless communication unit 12 receives a beacon control frame and transmits / receives a data frame via the antenna 11 according to a predetermined communication procedure under the control of the control unit 13. Note that when the wireless communication device 100 is a representative wireless communication device described later, a beacon control frame and a data frame are transmitted and received.
[0025]
The control unit 13 has a microcomputer configuration including a CPU, a ROM (not shown), a program storage memory such as a ROM, an internal clock 131 and peripheral circuits. The control unit 13 controls the entire apparatus and means described below (in the embodiment, a program). Configuration) performs execution control such as comparison of group ID information, determination of priority, correction based on the beacon time of the internal clock, and time synchronization with other groups. In addition to the control program and communication protocol for controlling the entire wireless communication device, the program storage memory includes a program for performing communication control and necessary processing in the inter-vehicle wireless communication system of the present invention, as shown in FIG. The beacon information table 40 value and various set values are stored.
[0026]
The memory 14 stores the beacon control frame and data frame received via the wireless communication unit 12 and the vehicle data (vehicle speed, direction of travel, current position (coordinate), etc.) acquired via the vehicle interface 15. Remember me under the control of
[0027]
The vehicle interface 15 converts vehicle data such as vehicle speed, direction of travel, current position (coordinates), and the like acquired by a sensor provided in the vehicle into digital data and stores it in the memory 14 under the control of the control unit 13. Or data converted from the data read from the memory 14 and sent to the vehicle side (for example, when driving system control data is read from the memory 14, a driving system control unit (not shown) provided in the vehicle) To send).
[0028]
[Vehicle communication procedure]
FIG. 3 is an explanatory diagram of the inter-vehicle communication procedure, and shows the communication procedure of each group on the time axis. Here, the inter-vehicle communication in FIG. 3A indicates a period in which the wireless communication devices of the vehicles belonging to the groups 1, 2, 3, 4. The communication channels of each group 1, 2, 3, 4... Acquire a communication channel using a special control frame called a beacon (reference signal) control frame.
[0029]
This beacon control frame has a function of assigning communication channels of the wireless communication devices in the group. This communication channel assignment function is a data slot (data slot) assigned to each wireless communication device after receiving a beacon control frame having a data slot assignment group ID (in the example of FIG. 3B, 10 data slots). This is a function for calculating an allocation time for transmitting a data frame in a slot slot1 to slot10) period.
[0030]
Accordingly, each wireless communication device in the group has a right to transmit a data frame only to a specific wireless communication device in each assigned data slot period slot 1 to slot 10, so that there is a data frame collision with another wireless communication device. Does not occur. By using the beacon control frame in this way, it is possible to secure a communication channel and realize a data communication environment in which no collision occurs.
[0031]
Moreover, the opportunity to transmit the same data several times is given by setting the communication channel acquisition frequency by the beacon control frame to be equal to or higher than the data generation frequency. Transmitting the same data a plurality of times contributes to further improvement in communication reliability.
[0032]
The beacon control frame is a special function given to the 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 regardless of the group to which the beacon belongs, and includes a content (information transmitted by a beacon) as shown in FIG. 4 as a specific example.
[0033]
[Beacon information table]
FIG. 4 shows an example of a beacon information table in which information included in a beacon control frame is tabulated. Each wireless communication device includes a beacon information table 40 and is not normally used (table inactive state). As will be described later, when a certain wireless communication device is assigned as a representative wireless communication device according to the priority order of the subgroup ID, a beacon control frame is generated using this beacon information table 40 (table active state).
In the beacon information table 40, the time is the time when the beacon control frame is transmitted obtained 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. A device (representative wireless communication device) indicates a time interval (hereinafter, beacon interval) at which a beacon control frame is transmitted, and a period indicates a time (period) in which a group to which the representative wireless communication device belongs can communicate.
The group ID is an ID indicating a group to which the representative wireless communication device that has transmitted the beacon control frame belongs, and the sub group ID is an in-group that identifies the representative wireless communication device that is transmitting the beacon control frame. This ID is unique within the group. This subgroup ID has an important role, and indicates a priority order to be a representative wireless communication device that transmits a beacon control frame.
For example, if numbers are assigned in order from the top wireless communication device in the group and set as the subgroup ID, the top wireless communication device has the highest priority beacon control frame transmission right. Also, if any problem occurs in the wireless communication device of the leading vehicle, the right to transmit a beacon frame is given to the wireless communication device of the second vehicle having the next highest priority. 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 group.
In addition, individual information necessary for the operation of the application destination system can also be added to the beacon control frame.
[0034]
Here, if the wireless communication device in each group is a beacon control frame of its own group, the internal clock is set according to the time information included therein. With this operation, time synchronization of 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.
[0035]
[Representative wireless communication equipment]
The representative wireless communication device of each group is determined by the priority order of the subgroup IDs as described above, and is calculated from the internal clock 131 and the beacon interval at the start of operation based on the beacon information table 40 as shown in FIG. It has a function of transmitting a beacon control frame at the time.
The hardware configuration of the representative wireless communication device may be the same as that in FIG. 1, and the beacon control frame transmission function of the wireless communication unit 12 is activated according to the priority order of subgroup IDs to be described later with other wireless communication devices in the group. It is different in that it is in a state and the function of the control unit 13 as a representative wireless communication device to be described later is in an 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 the subgroup ID as described above. Determined by priority.
[0036]
[Synchronous acquisition by beacon control frame]
Next, a method of using this beacon control frame as the entire system will be described. As is clear from the procedure explanatory diagram of FIG. 3, the beacon control frame indicates a communication time (period) of a specific group as one of its roles. That is, by receiving a beacon control frame, it can be seen that a certain fixed time (indicated by the received beacon control frame) is a communication time (period) used by the group indicated by the beacon control frame. Thereby, the collision of communication can be reduced by grouping a plurality of wireless communication devices and assigning the communication time to the group unit.
[0037]
In this way, the beacon control frame also considers channel acquisition control between groups, so that the channel acquisition operation can be synchronized as a whole system, and inadvertent data communication or communication collision between groups can occur. It works so as not to occur.
[0038]
The beacon control frame is used for synchronization acquisition 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 means having a beacon control frame transmission function) based on the information on the beacon control frame, Perform processing.
[0039]
(1) 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 the own group, (2) 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, (2) is executed according to the beacon reception timing.
[0040]
(2) Set the internal clock to the time information of the received beacon control frame.
[0041]
(3) The communication allocation time of the own group is calculated from the time information of the received beacon control frame and the group ID.
[0042]
(4) Each representative wireless communication device corrects the transmission time (scheduled time) of the beacon control frame to be transmitted next from the calculated value.
[0043]
By performing these processes, time synchronization of each group is performed, and it is possible to assemble a schedule without overlapping communication time allocation of each group. This is a very effective solution to the problem that communication time allocation of each group is overlapped by simple group division, which prevents communication collision avoidance.
[0044]
[Channel acquisition control]
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.
[0045]
(1) Method using a random access method within the beacon transmission period
(1) In this method, transmission of a beacon control frame is performed using a random access method within a beacon transmission period calculated from the beacon period (FIG. 3C). That is, during this period, contention for channel acquisition by the beacon control frame is performed. By this means, for example, even if the number of groups increases, a channel can be acquired by a beacon control frame transmitting wireless communication device (representative wireless communication device) in each group by a simple random delay.
[0046]
(2) The random delay occurrence rate can be weighted as shown in the example of FIG. 5 (an explanatory diagram of a weighting method for random delay generation). In the example of FIG. 5A, the weighting factor is α and the frequency y is expressed by a linear expression of the delay time x. In the example of FIG. 5B, the weighting factors are α and β, and the frequency y Is represented by a quadratic expression of the delay time x. It is also possible to control the random delay time to be in inverse proportion to the elapsed time from the previous beacon control frame transmission time and the number of beacon control frame transmission attempts.
By doing so, it is possible to prevent a specific group from acquiring channels continuously, and to provide an equivalent channel acquisition rate to each group.
[0047]
(2) Method of dividing the beacon period into slots
FIG. 6 is a diagram illustrating a position example of priority order and slot allocation within a beacon period.
(1) In this method, the beacon period (beacon transmission period) is cut into time slots shorter than the radio frame as shown in FIG. 6B (= (FIG. 3C)), and each group beacon is assigned to each time slot. When a representative wireless communication device receives a beacon control frame transmitted from another group before its own time slot, the representative wireless communication device accepts the beacon control frame and determines the transmission timing of its own beacon control frame. Since the time slot width during this beacon transmission period is sufficient for detecting the presence / absence of communication from each representative wireless communication device, a very short time allocation may be used.
[0048]
Therefore, even if the number of groups increases, this time slot (slot) does not significantly affect the system performance (in the example of FIG. 6 (b), the beacon period is divided into 9 time slots and 9 groups are divided into 9 groups). (Corresponding to numbers 1 to 9).
(2) The transmission timing of this beacon control frame can be provided with an even channel acquisition rate without bias in each group by sequentially changing the priority order as shown in FIG. 6 (c). it can. For example, in the first beacon period, group 1 (Group 1) has the highest priority as shown in FIG. In the next beacon period, as shown in FIG. 6C, group 2 has the highest priority and group 1 is the last allocation.
Further, as shown in FIG. 6D, the number of slots to be allocated and the priority order may be changed according to the communication frequency of the group.
[0049]
(3) Acquisition of communication channel by random delay time calculation procedure
FIG. 7 is a flowchart showing an embodiment of a random delay time calculation procedure, taking into account the elapsed time from the start of the beacon period.
[0050]
In FIG. 7, when the communication channel is released (S1), a beacon period is started (S2), and the control unit 13 starts a timer. At this time, the random delay time Tr held in the memory 14 (initial value is held in the memory 14, but the value calculated in step S10 is held from the next cycle) is set. (S3).
[0051]
Next, the control unit 13 checks whether or not the wireless communication unit 12 has received a beacon control frame from another group. If it has been received, the control unit 13 transitions to S5, and if not, transitions to S7 (S4).
[0052]
When receiving a beacon control frame from another group, the control unit 13 calculates an elapsed time Tw from the start of the beacon period (S5), and then delay time Tr from the start of the beacon period = previous delay time The random delay time Tr is updated as Tr−elapsed time Tw, and the process returns to S1 (S6).
[0053]
If a beacon control frame from another group is not 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 beacon control for this group. A frame 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 held in the memory 14, and returns to S1 (S10).
[0054]
In this procedure, the once calculated random delay time is subtracted from the elapsed time in the next beacon period by receiving a beacon control frame from another wireless communication device (representative wireless communication device of another group), and again as a random delay time. By using it, the maximum communication channel acquisition delay time can be clarified. Thereby, in any case, the communication channel can be acquired within the time determined by the maximum random delay time determined by the system.
[0055]
(4) Communication channel acquisition by communication channel suspension procedure
Next, when handling transmission of beacon control frames from another viewpoint, for example, when two groups exist in a certain wireless communication area, it is most efficient for each group to acquire communication rights in order. It is. In such a situation, in order to acquire the optimum communication right, it is effective to temporarily stop the transmission of the beacon control frame during the beacon period subsequent to a certain group once acquiring the communication right. That is, when the group that has acquired the communication right pauses the communication right acquisition operation after the end of the communication, the other group can independently transmit the beacon control frame, and the acquisition of the communication right is successful. This is because even when there are three or more groups in a wireless communication area, if one of those groups suspends beacon control frame transmission, the number of competitors will be reduced for other groups. This results in a decrease in the acquisition collision probability and an increase in the communication channel acquisition probability.
[0056]
Furthermore, as shown in the flowchart (beacon control frame reception request operation) of FIG. 8B, efficient channel acquisition control is realized by monitoring the number of groups (peripheral groups) existing in the wireless communication area. it can.
[0057]
B: Acquire a group ID from the received beacon control frame.
B: Count the type of this group ID. That is, the number of groups (peripheral groups) other than the own group existing in the wireless communication area is acquired.
C: The number of other groups existing in the vicinity is acquired every update time (for example, 1 second).
D: This acquired value is set as the number of beacon control frame transmission pauses. That is, when a beacon control frame is transmitted and a communication channel is acquired, the communication channel acquisition is stopped for a time corresponding to the beacon period corresponding to the number of beacon control frame transmission suspensions.
By performing such control, each group is given equal opportunities to acquire communication channels, and each group can acquire communication channels while avoiding communication channel acquisition competition as much as possible while being random access. .
[0058]
A specific procedure example of the above process will be described with reference to a flowchart of a beacon control frame transmission procedure example in consideration of the number of neighboring groups in FIG. Further, FIG. 9 shows a specific setting example of the number of suspension times of transmission of beacon control frames.
I: Frame reception processing: (FIG. 8A)
FIG. 8A is a flowchart showing one embodiment of the peripheral group number acquisition processing operation when a new frame is received.
In FIG. 8A, when the representative wireless communication device (100) receives a new beacon control frame (T1), the peripheral group ID table developed in the memory 14 is checked, and the group on the new beacon control frame is stored in the table. If there is no ID that matches the ID, the process proceeds to T3, and if there is a matching ID, the beacon control frame reception process ends (T2). If there is no ID that matches the group ID on the new beacon control frame at step T2, the group ID on the new beacon control frame is additionally registered in the peripheral group ID table (T3), and 1 is stored in the group ID counter. To update the number of registered IDs.
[0059]
II: Beacon control frame reception request: (FIG. 8B)
FIG. 8B is a flowchart showing an embodiment of the beacon control frame reception request processing operation. The beacon control frame reception request processing is performed by making a beacon control frame transmission request for every beacon period.
In FIG. 8B, the control unit 13 uses the pause counter to select whether or not to start transmission of a beacon control frame.
That is, when the control unit 13 obtains the group ID from the received beacon control frame, the control unit 13 checks the value of the pause counter. If the pause counter = 0, the control unit 13 transitions to U3, and if the pause counter ≠ 0, the control unit 13 transitions to U5 (U1). .
When the pause counter = 0 in step U1, the control unit 13 counts the types of acquired group IDs. That is, the number of neighboring groups is counted, the number of other groups existing in the vicinity is obtained every update time (for example, 1 second) (U2), and this obtained value is set as a beacon control frame transmission suspension number in the suspension counter. (U3) The beacon control frame is transmitted to the wireless communication unit 12, and the beacon control frame transmission request is terminated (U4). If the pause counter is not equal to 0 in step U1, the control unit 13 subtracts 1 from the pause counter and then ends the beacon control frame transmission request (U5).
With the above operation, if a beacon control frame is transmitted and a communication channel is acquired, the acquisition of the communication channel can be stopped for a time corresponding to the beacon period corresponding to the number of beacon control frame transmission suspensions.
[0060]
III: Update group ID: (Fig. 8 (c))
FIG. 8C is a flowchart showing an example of the group ID update operation. In the process started periodically (for example, every second), the number of neighboring groups is set using the generated group ID counter. .
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), and clears the peripheral group ID table and the group ID counter (V2, V3). The group ID is updated.
[0061]
As described above, even if any of the above-described means (1) to (4) or a combination thereof is used, the channel acquisition opportunities can be made equal in each group, and unnecessary channel acquisition can be eliminated. This means that a group that needs to acquire channels can acquire more communication channels. In addition, it is possible to reduce degradation of system performance due to an increase in the number of groups.
[0062]
[Group synchronization time]
Next, the “group time synchronization by the beacon control frame” described above will be described in more detail by taking, as an example, an inter-vehicle wireless communication system including three vehicle groups shown in FIG.
[0063]
In FIG. 10 (an explanatory diagram of the group time synchronization acquisition procedure), group 1 and group 2 show a case where they are in an area where they can wirelessly communicate with each other, and group 3 shows a case where there is no other group which can wirelessly communicate within the wireless communication area. Is shown.
In this example, the wireless communication devices of group 1 and group 2 can receive the beacon control frame transmitted by the representative wireless communication device of each other group. As a result, the representative wireless communication devices of groups 1 and 2 are synchronized using the received beacon control frame according to the procedures (1) to (4) described above, and further, information on the synchronized beacon control frame is displayed. The wireless communication devices in groups 1 and 2 that receive a beacon control frame that is newly transmitted based on the synchronization are 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. Thus, when the vehicle group carrying each wireless communication device moves and enters the same wireless communication area, the entire system is synchronized.
[0064]
In addition, for example, in a vehicle group that is left out of the wireless communication area like the group 3, the inter-vehicle wireless communication system is operated alone in the group without being synchronized, In this case, since the wireless communication of this group does not affect other groups (and is not affected by other groups), no problem occurs in the operation of the inter-vehicle wireless communication system.
[0065]
<Example of Beacon Transmission Procedure (1)>
The first beacon procedure in the channel acquisition control is described as “(1) Method using a random access method within the beacon transmission period”. This will be described with reference to a time chart.
[0066]
10 and 11, the entire inter-vehicle wireless communication system is composed of three groups. The IDs 1 to 3 are assigned to each group. Further, 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 makes a beacon transmission plan from its own internal clock (131) at the start of operation. The beacon planning standards are shown below.
b: The communication time allocated to each group is 10 msec.
c: The internal clock is in units of 10 μsec.
d: In the beacon period, access using a random delay is performed. For this delay time generation, the number of beacon control frame transmission attempts is used as a parameter. This parameter is cleared when a beacon control frame can be transmitted, and is incremented by 1 every time a random delay is generated during this beacon period. For example, the number of trials “0” indicates that this is the first beacon period when the system is initialized or immediately after the communication channel is acquired.
e: As a procedure for using the number of attempts to transmit a beacon control frame, for example, when the number of trials is “0”, the maximum delay time is generated, and the maximum value of the delay time decreases as the number of trials increases. Random value.
As the priority of the group ID, the smaller the value, the higher the priority.
[0067]
Thus, system group synchronization works as follows.
i: Each group representative wireless communication device makes a beacon transmission plan from its internal clock (131), and transmits a beacon control frame at a predetermined time.
ii: At this time, since the group 3 is a single radio communication area, the beacon control frame is independently transmitted without performing the synchronization work.
iii: Since the group 1 and the group 2 can receive each other's beacon control frame, the synchronization operation is performed. In this case, the channel acquisition of the group 1 is performed during the communication period of the group 2, but synchronization is taken at the time of the group 1 from the group ID priority order (group 1> group 2).
iv: Thereafter, in FIG. 10, group 1 and group 2 move in the direction of group 3 (or group 3 moves in the direction of group 1 and group 2), and groups 1, 2, and 3 are in the same wireless communication area. Once inside, a mutual beacon control frame can be received. Here, the synchronization work of the groups 1, 2, and 3 is performed.
v: The synchronization work of group 1, group 2, and group 3 is synchronized at the time of group 1 based on the priority order of group IDs (group 1> group 2> group 3). Further, in FIG. 11, since the group 3 has received the beacon control frame of the group 2, the beacon control frame is transmitted after the channel acquisition period ends to acquire the communication channel.
vi: In this way, each group is synchronized with the movement of the vehicle equipped with the wireless communication device, and the synchronization of the entire system is uniquely determined.
[0068]
<Example of beacon transmission procedure (2)>
The second beacon procedure in the channel acquisition control is described as “(2) a method of dividing the beacon period into slots”. FIG. 10 and FIG. 12 (description of the time chart of the second beacon procedure) regarding a specific operation example thereof This will be described with reference to FIG.
10 and 12, the entire inter-vehicle wireless communication system is composed of three groups. Each is assigned an ID of 1 to 3. Further, the number of wireless communication devices in each group is not limited to the example of FIG.
[0069]
a: The representative device of each group makes a beacon transmission plan from the internal clock (131) of its own station when the operation starts. The beacon planning standards are shown below.
b: The communication time allocated to each group is 10 msec.
c: The internal clock is in units of 10 μsec.
d: In the beacon period, while referring to the priority order table, it waits for its own group slot. This order is time-controlled. For example, the transmission right is given in order in units of an internal clock (10 μsec). Since the beacon control frame can be transmitted when the transmission right of the own group is given, the group that wants to acquire the channel transmits the beacon control frame according to the priority table.
[0070]
In addition, 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: This priority table is rotated every beacon period, and the priority is switched. It is also possible for the group that has acquired the communication channel to have the lowest priority (FIG. 6C).
Further, as the ID priority, the smaller the value, the higher the priority.
Thus, system group synchronization works as follows.
i: Each group representative wireless communication device makes a beacon transmission plan from its internal clock (131), and transmits a beacon control frame at a predetermined time.
ii: In FIG. 10, since group 3 is in the single wireless communication area, it independently transmits a beacon control frame without performing synchronization work.
iii: Since the group 1 and the group 2 can receive each other's beacon control frame, the synchronization operation is performed. In this case, since the group 2 has acquired the channel first, the representative wireless communication device of the group 1 transmits the beacon control frame of the group 1 according to the priority within the beacon period after the end of the communication period of the group 2. Further, synchronization is taken at the time of group 1 by the priority order of group IDs (group 1> group 2).
iv: After that, if group 1 and group 2 move in the direction of group 3 (or if group 3 moves in the direction of group 1 and 2 and enters the same wireless communication area, the beacon control frame of each other At this point, the synchronization work of groups 1, 2, and 3 is performed.
v: The synchronization work of groups 1, 2, and 3 is synchronized at the time of group 1 according to the priority order of group IDs (group 1> group 2> group 3).
Further, in the acquisition of the communication channel, after the communication period of group 2 ends, group 3 has the highest priority according to the priority order within 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 a beacon control frame from another group and the group 1 attempting to acquire the channel.
vi: In this way, when the vehicle equipped with the wireless communication device moves, the groups are synchronized, and the synchronization of the entire system is uniquely determined.
[0071]
[Expansion of this system]
Although not specified in the above description, in the inter-vehicle wireless communication system of the present invention, if communication channels are all the same (there is only one), communication within the group that acquired the communication channel is performed in the vicinity (wireless It can also be received by other groups (in the communication area). By utilizing this, intra-group communication can be easily extended to inter-group communication.
In other words, even when communication channels acquired by other groups can be received between groups existing in the wireless communication area, it is possible to receive groups without being aware of inside or outside the group. It can be used over and over, and such use does not cause any problems in the 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-sharing control of the communication channel and does not specify the communication partner or group.
[0072]
[Other examples of group structure]
Next, another specific example of the group structure is shown.
In the present invention, a plurality of vehicles equipped with wireless communication devices configured as shown in FIG. 2 are handled as a group. However, there is no need for a plurality of wireless communication devices in the group, and a single group can be configured. The same applies to the above-described embodiments. Examples of communication procedures in this case are shown in FIGS.
FIG. 13 is a diagram showing an example of slot assignment in the case where there is one vehicle constituting the group. Since the number of wireless communication devices constituting the group is one, it is based on the procedure explanatory diagram of FIG. In this example, the number of slots is changed to a predetermined procedure (FIGS. 13B and 13C). The example of FIG. 14 is a diagram showing an example of slot allocation when communication data of a wireless communication device is embedded in the beacon control frame (FIG. 14B) itself (FIG. 14C). This is an example considering efficiency.
[0073]
In this way, using the communication channel acquisition procedure by the beacon control frame, the application form of the application (for example, the group 1 is composed of three vehicles at a certain time in addition to the case where the entire group is composed of one vehicle). When group 2 is composed of one vehicle and group 3 is composed of four vehicles, group 1 is composed of one vehicle, group 2 is composed of five vehicles, and group 3 is composed of three vehicles. The vehicle-to-vehicle wireless communication system can be more appropriately operated in a case where the vehicle is composed of a single vehicle and the groups 4 and 5 are composed of a single vehicle.
[0074]
[Modification (1)]
In the above description, the case where all the vehicles equipped with the wireless communication device configured as shown in FIG. 2 are moving vehicles has been described as an example, but it is not necessary that all the vehicles equipped with the wireless communication devices are moving vehicles. As such an example, FIG. 15 (a diagram showing an embodiment of a vehicle-to-vehicle wireless communication system when a fixed vehicle is considered) shows a specific example using a fixed vehicle that does not move and a wired backbone.
[0075]
In FIG. 15, three mobile vehicle groups 1, 2, 3 and three fixed vehicles (fixed stations) A, B, C are shown. Furthermore, the fixed moving vehicles A, B, and C are respectively moving vehicles 1-, 1-2, 1-3 (group 1), 2-1, 2-2 (group 2), 3-1, 3-2. It is assumed that 3-3 (group 3) is arranged on the moving route 150 and connected by other communication means, for example, an optical network.
[0076]
In such an application, priority is given to receiving the beacon control frame from the fixed stations A, B, and C by using the beacon control frame synchronization process (1) to (4) in the above-mentioned [acquisition of synchronization by beacon control frame]. This can be realized by setting the degree to a high level and by operating the entire system in synchronization by the synchronization processing between the fixed stations A, B, and C by the optical network. Further, 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 moving vehicle, and the synchronization processing of the entire system can be performed.
[0077]
In the case of this application, even group information outside the wireless communication area can be communicated via a fixed station. For example, when the groups 1, 2 and 3 are in different wireless communication areas (indicated by broken circles in FIG. 15) 1 ′, 2 ′ and 3 ′, the communication information of the group 1 is fixed station A Can be received, and relayed to the fixed station C. Further, the fixed station C can perform a process of performing wireless communication channel acquisition control using a beacon control frame and relaying to the group 3.
[0078]
For example, if the vehicle 1 in the group 3 fails and stops, the information on the failed vehicle can be instantaneously transmitted not only to the wireless communication area 3 in the group 3 but also to all vehicles in other wireless communication areas. I mean. In other words, any mobile vehicle station can communicate data to the target mobile vehicle regardless of whether it is inside or outside the wireless communication area. Can communicate.
[0079]
[Modification (2)]
Next, a description will be supplemented regarding the procedure for enabling the beacon control frame transmission function, the procedure for detecting the radio link state, and the procedure for group configuration.
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 the group is divided with the vehicle as a break because a vehicle in a certain group breaks down can be considered. That is, in the wireless communication procedure described above, there is a vehicle representing the group (a vehicle equipped with a representative wireless communication device) in a certain group, and a communication channel is acquired by a beacon control frame from the vehicle. Is doing. Therefore, there may be a case where the radio link is disconnected and the group is divided due to the vehicle failure in the group or the influence of the communication environment. Therefore, in order to prevent such a problem, a procedure for enabling a beacon control frame transmission function, a radio link state detection procedure, and a group configuration procedure are configured as follows.
[0080]
I: Radio link state detection procedure (FIG. 16)
FIG. 16 is an explanatory diagram of the proposed radio link state detection procedure. According to the wireless communication procedure described above, a communication channel can be acquired at certain intervals using a beacon control frame. Therefore, in order to grasp the wireless status with each vehicle (wireless communication device) in the group,
a: Detects whether or not a channel is acquired within a certain time range and that the elapsed time after receiving the beacon control frame of the group to which the own wireless communication device belongs exceeds the time set by the system.
This is important information related to the Beacon transmission function validation procedure and group configuration procedure described below.
[0081]
b: The reception status of the data frame of the wireless communication device corresponding to each data slot in the acquired channel is grasped. For example, a link counter is provided for each wireless communication device in the group, and processing is performed such that the counter is cleared if there is reception from the corresponding wireless communication device, and the counter is incremented by 1 if there is no reception.
[0082]
In the wireless procedure described above, 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 by the system for wireless communication, the frequency of data generation, and the like, and determines system parameters such as the beacon interval and the amount of random delay when transmitting a beacon control frame. The channel acquisition interval is determined by these parameters. If a limit time (link counter value) is set based on this parameter, communication with the corresponding wireless communication device becomes impossible if this 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 communication status within the group, that is, the wireless link status can be determined. it can.
[0083]
II: Beacon transmission function valid procedure:
The beacon control frame is a control frame transmitted from the representative wireless communication device in the group. However, if the beacon control frame cannot be received for a certain period of time due to some reason, that is, the elapsed time is exceeded by the above-described determination of Ia. When the communication is detected, communication is disabled, and it is necessary to try to acquire the communication channel by itself.
FIG. 17 is a flowchart (showing a flowchart of an embodiment of a procedure for switching between valid / invalid of the beacon control frame transmission function).
[0084]
In FIG. 17, the control unit (13) of each wireless communication device (100) has received the beacon control frame within the scheduled reception time of the beacon control frame of the own group, focusing on receiving the beacon control frame for the own group. Sometimes the state transits to W2, and when the scheduled time has not been received, the state transits to W4 (W1).
In addition, when a beacon control frame is received within the scheduled time in the above step W1, it is checked whether or not it is a beacon control frame of its own group. If it is a beacon control frame of its own group, a transition is made to W3. Return to W1 (W2).
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 the beacon control frame cannot be received within the scheduled time in step W1, the beacon control frame transmission function is enabled (for example, the beacon control frame transmission flag is turned on) (W4).
If the beacon control frame of the own group is received when the transmission function of the beacon control frame is valid, the process proceeds to W6. Otherwise, the group separation process is performed according to the 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. When the subgroup ID of the local station is small, the beacon frame transmission right is returned to W4, and when the subgroup ID of the local station is large, the process shifts to W7 (W6). Return to W1 as no beacon control frame transmission right (W7).
[0085]
III: Group configuration procedure
Next, in configuring a vehicle (vehicle with a wireless communication device) group, a procedure for separating and combining groups will be described.
In the design and operation of a wireless communication system, the occurrence of a situation in which a beacon control frame cannot be temporarily received due to the deterioration of the communication environment, or measures to detect such a situation and recover from the situation (recovery) Necessary. Assuming such a case, the procedure for separating and combining groups is shown below.
[0086]
1: Group separation procedure
The separation procedure is executed when a beacon control frame cannot be received for a predetermined time or longer as described above (see “I: detection of wireless link state”) or when data from each corresponding wireless communication device cannot be received. That means
a: Inability to receive the beacon control frame indicates that communication with the group to which the own wireless communication device belongs is interrupted and separated from the group. Therefore, the separated wireless communication devices spontaneously transmit a beacon control frame to form a group using a new subgroup ID.
b: A wireless communication device detects that communication with a wireless communication device in the group has been interrupted based on the wireless link information (the elapsed time since receiving the beacon control frame of the group to which the wireless communication device belongs). Indicates that the wireless communication device is separated from the group. The wireless link information is valid information indicating the wireless communication devices constituting the current group, and becomes system operation information.
[0087]
2: Joining groups
Next, as described above (see “II: Beacon control frame transmission function procedure”), when a beacon control frame having the same group ID is received (W5, W6) when the beacon control frame transmission function is enabled (W4). However, when the subgroup IDs are different, for example, when the wireless communication state is recovered, it is desirable to return to the original group configuration in terms of system operation. This is a concept called combining, 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 the beacon control frame transmission right is determined by determining this value. 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).
[0088]
As mentioned above, although one Example of this invention was described, this invention is not limited to the said Example, It cannot be overemphasized that various deformation | transformation implementation is possible.
[0089]
【The invention's effect】
As described above, in order to realize communication between vehicles without using a base station, it is common to adopt a contention method. However, introducing a contention method as it is is the number of vehicles and It becomes impossible to design the system in consideration of the operation form. On the other hand, according to the inter-vehicle wireless communication system of the present invention, since beacon information (beacon control frame) for controlling grouping and group synchronization of vehicles is used, it is simple and inexpensive, and operational efficiency. It is possible to provide a good wireless communication means between vehicles.
In addition, since the group can be reconfigured, it is possible to prevent the entire group from being stopped by disconnecting the vehicle from the group or separating the group when the vehicle stops due to a failure. In addition, a vehicle group reorganization can be automatically performed in the case of a vehicle failure or when it is necessary for operation, such as returning a vehicle in which the failure has been corrected to the original group.
[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 showing an embodiment of a random delay time calculation procedure.
FIG. 8 is a flowchart of an example of a procedure for transmitting a beacon control frame in consideration of the number of neighboring groups.
FIG. 9 is a diagram showing an example of a suspension number correspondence table according to the number of neighboring 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 an example of slot assignment when there is one vehicle constituting a group.
FIG. 14 is a diagram showing an example of slot assignment when vehicle data is embedded in a beacon control frame.
FIG. 15 is a diagram illustrating an example of an inter-vehicle wireless communication system when a fixed vehicle is considered.
FIG. 16 is an explanatory diagram of a radio link state detection procedure.
FIG. 17 is a flowchart illustrating an example 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 transmitting / receiving means, beacon receiving means, random access means)
13 Control unit (control means, transmission control means, communication state observation means, group construction means)
100 wireless communication equipment
131 Internal clock (clock means)

Claims (12)

Each vehicle has a plurality of vehicle groups equipped with wireless communication devices,
Each vehicle group
Storage means for storing group ID information uniquely assigned to the own group, beacon information transmission / reception means for transmitting / receiving beacon information, at least one representative vehicle equipped with a representative wireless communication device provided with clock means and control means; ,
Equipped with a storage means for storing group ID information uniquely assigned to its own group belonging to the representative wireless communication apparatus, a beacon information receiving means for receiving the beacon information, a clock means and a control means equipped with a control means With other vehicles,
The beacon information is
Time information of the clock means, transmission interval information of beacon information, period information in which each wireless communication device belonging to the group of representative wireless communication devices can communicate, and a group indicating a group communicable in the period indicated by the period information Including ID information,
Each of the representative wireless communication devices is
When the beacon information transmission / reception means receives beacon information, the priority is determined based on the group ID information included in the beacon information or the beacon reception timing, and the own clock means is used. Correct the next beacon information transmission time according to the time information of the received beacon information, take time synchronization with other groups by the corrected beacon information transmission time,
Each wireless communication device belonging to the group of each representative wireless communication device compares the group ID information when receiving the beacon information, and when the received beacon information is beacon information of a group to which the self belongs, inter-vehicle radio communication system just wireless communication, characterized in that during the period designated by the period information included in the beacon information.   Each wireless communication device belonging to the group of each representative wireless communication device compares the group ID information when receiving the beacon information, and when the received beacon information is the beacon information of the group to which the wireless communication device belongs, The next beacon information reception time is corrected in accordance with the time information of the beacon information received by the means, and time synchronization with other wireless communication devices in the group is achieved by the corrected beacon information reception time. The inter-vehicle wireless communication system according to claim 1.   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.   Each of the representative wireless communication devices includes random access means for performing access according to a random transmission delay time calculation procedure that performs weighting based on the elapsed time from the previous beacon information transmission, and obtains a communication channel by the random access means. The inter-vehicle wireless communication system according to claim 1.   Each of the representative wireless communication devices includes random access means for performing access by a random transmission delay time calculation procedure that performs weighting based on the number of beacon transmission attempts, and obtains a communication channel by the random access means. The inter-vehicle wireless communication system according to claim 1.   2. The representative wireless communication device includes random access means for performing access by a short time slot generation procedure for detecting presence / absence of communication, and obtains a communication channel by the random access means. Vehicle-to-vehicle wireless communication system.   Each of the representative wireless communication devices includes random access means for performing access by a transmission slot generation procedure for sequentially changing the priority of beacon transmission, and obtains a communication channel by the random access means. The inter-vehicle wireless communication system according to 1.   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 related to beacon information transmission, and obtains a communication channel by the random access means. The inter-vehicle wireless communication system according to claim 1.   Each of the representative wireless communication devices includes a communication channel acquisition equalization control unit based on a communication channel suspension procedure, and acquires a communication channel by communication channel acquisition equalization control by the acquisition equalization control unit. The inter-vehicle wireless communication system according to claim 1.   2. The inter-vehicle wireless communication system according to claim 1, wherein each of the representative wireless communication devices includes a transmission control unit that enables or disables its own beacon information transmission function.   The said each representative radio | wireless communication apparatus is equipped with the communication state observation means to measure a data reception interval from each beacon information reception and each said radio | wireless communication apparatus, and to observe a communication state. Vehicle-to-vehicle wireless communication system.   Each representative wireless communication device has a transmission control means for enabling or disabling its own beacon information transmission function, communication for receiving beacon information and measuring a data reception interval from each wireless communication device and observing a communication state. 2. The vehicle according to claim 1, further comprising: a state observing unit; and a group constructing unit that separates and combines the groups according to the reception state of the group beacon information observed by the communication state monitoring unit. Wireless communication system.

Images