JP2010171575A - Time slot allocation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively secure the transmission time of a mobile communication device by reducing the number of required time slots in allocating a radio transmission time by a plurality of roadside communication devices in a time division manner. <P>SOLUTION: The time slot allocation device generates a time slot T1 for radio transmission by a plurality of roadside communication devices 2 belonging to the same management group and opens a time zone T2 other than the time slot T1 for radio transmission of the mobile communication device 3. The time slot allocation device includes a slot generating means 23D for generating a plurality of time slots T1 so as to periodically repeat slot numbers i of the time slots T1, and a slot allocation means 23E for allocating transmission times for some different roadside communication devices 2 in an overlapping manner to the time slot T1 of a specific slot number i. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a time slot allocating apparatus suitable for allocating radio transmission time to a plurality of roadside communication devices, which is a component of an intelligent transport system (ITS), for example.

In recent years, for the purpose of promoting traffic safety and preventing traffic accidents, advanced road traffic systems that improve the safety of vehicles by receiving information from infrastructure devices installed on the road and utilizing this information have been studied. (For example, refer to Patent Document 1).
Such an intelligent road traffic system is mainly composed of a plurality of roadside communication devices which are wireless communication devices on the infrastructure side and a plurality of in-vehicle communication devices which are wireless communication devices mounted on each vehicle.

  In this case, a combination of communication performed between communication subjects includes road-to-road communication between road-side communication devices, road-to-vehicle (or vehicle-road) communication between road-side communication devices and vehicle-mounted communication devices, and vehicle-mounted communication. Vehicle-to-vehicle communication performed between aircraft.

Japanese Patent No. 2806801

  In the above-mentioned intelligent road transportation system, including communication between vehicles, road-to-vehicle communication, road-to-road communication, and road-to-step communication, in order to coexist these communications, what kind of communication is used effectively The issue is whether to perform control. In view of this, it has been studied that multiple access is used to perform communication between roads, road vehicles, and vehicles within a limited frequency band.

  As this multi-access method, there are frequency division multiplexing (FDMA) and code division multiple access (CDMA), but communication with only a small number of in-vehicle communication devices is assumed in mountainous areas. As a multi-access method for inter-vehicle communication, it is preferable to adopt an autonomous random access method represented by CSMA (Carrier Sense Multiple Access), for example.

However, road-to-vehicle communication, road-to-road communication, and vehicle-to-vehicle communication coexist in an area where roadside communication devices exist. In this case, since the priority of the information handled by the roadside communicator that is the infrastructure side is generally high, a mechanism that gives priority to road-to-vehicle communication and road-to-road communication over vehicle-to-vehicle communication is required. .
Therefore, in order to preferentially transmit information of the roadside communication device, time division multiplexing (TDMA: Time Division) in which the frequency used for communication is time-divided at regular intervals and a time slot dedicated to transmission of the roadside communication device is provided. Multiple access by Multiple Access is enabled.

Therefore, for example, assuming a communication system composed of a plurality of roadside communication device groups installed at each intersection, a time slot transmitted by each roadside communication device is assigned by the TDMA method, and the remaining time slot is assigned to a vehicle by the CSMA method. It is considered to be a rational communication system to be used for inter-vehicle communication.
In this case, in order to control the transmission timing from each roadside communication device, each roadside communication device needs to have a time synchronization function with other roadside communication devices.

However, in an intelligent road traffic system in which the TDMA scheme for roadside transmission control as described above and the CSMA scheme for multi-access between vehicles are mixed, the transmission time preferentially assigned to the roadside communication device is too long. In addition, there is a concern that the transmission time of the in-vehicle communication device becomes too short, or the packet arrival rate between vehicles decreases, which adversely affects vehicle-to-vehicle communication.
On the other hand, as a communication band for ITS, a standard of about 10 MHz in the 700 MHz band has been studied. In such a relatively narrow bandwidth, in a communication area where radio waves of roadside communication equipment reach. The problem is how to effectively secure the transmission time of the in-vehicle communication device.

  In view of such conventional problems, the present invention effectively secures the transmission time of a mobile communication device by reducing the number of necessary time slots when allocating radio transmission time by a plurality of roadside communication devices in a time division manner. It is an object of the present invention to provide a time slot allocating device that can be used.

  The time slot allocating device according to the present invention (claim 1) generates a time slot for wireless transmission by a plurality of roadside communication devices belonging to the same management group, and transmits a time slot other than the time slot to the wireless transmission of the mobile communication device. A time slot allocating device that is opened as trust, wherein a plurality of time slots are generated such that the slot numbers are periodically repeated, and a number of different time slots are assigned to the time slot having a specific slot number. Slot allocation means for allocating redundant transmission times for the roadside communication device.

According to the time slot assigning device of the present invention, the slot assigning means assigns the transmission times for several different roadside communication devices to the time slot having a specific slot number, so that one time The total number of time slots required for a plurality of roadside communication devices can be reduced as much as possible as compared with the case where the transmission time of only a single roadside communication device is assigned to a slot.
For this reason, even in the communication area where the radio waves of the roadside communication device reach, the time zone for wireless communication by the mobile communication device can be increased as much as possible.

On the other hand, when radio wave interference occurs between multiple roadside communication devices, the mobile communication device cannot properly receive transmission signals from the multiple roadside communication devices in the interference area. Should not be assigned to the same time slot.
Therefore, in the time slot allocation device of the present invention, it is preferable that the time slot allocation device further includes a determination unit that determines presence or absence of radio wave interference between the plurality of roadside communication devices. In this case, the slot allocation unit includes the radio wave interference. It is preferable to assign to the time slot based on the determination result of presence / absence.

  In this case, roadside communication devices determined to have no radio wave interference are assigned to time slots with the same slot number, and conversely, for roadside communication devices determined to have radio wave interference, a time slot with a different slot number is assigned. By changing to, it is possible to assign an appropriate time slot that does not cause radio wave interference.

In the time slot allocating device of the present invention, the slot allocating unit sets a plurality of transmission times of the plurality of roadside communication devices so that the number of overlapping of the roadside communication devices for the time slot of one slot number increases. Preferably, the time slot is assigned to the time slot.
In this case, since the transmission time of as many roadside communication devices as possible is assigned to the time slot of one slot number, the number of time slots necessary to secure the transmission time of all roadside communication devices can be reduced, Time slots can be allocated efficiently.

In the time slot allocating device of the present invention, the slot generating means deletes the time slot corresponding to the slot number when there is an empty slot number that does not need to allocate the transmission time of the roadside communication device. (Claim 4).
As a result, the time slot of the deleted time slot is released as the transmission time of the mobile communication device, and the transmission time for the mobile communication device is effectively ensured.

Furthermore, in the time slot allocating device of the present invention, it is preferable that the slot allocating unit has a slot changing function for changing the already assigned transmission time of the roadside communication device to the time slot having a different slot number.
In this case, when there are a plurality of time slots that can be changed when the slot is changed, the time slot having the smallest number of the roadside communication devices included in the time slot that is changed is selected. (Claim 5), it becomes easy to generate an empty slot number that does not require transmission time allocation of the roadside communication device. Therefore, repeating such slot changes increases the possibility that the transmission time of the mobile communication device will increase.
When performing the above time slot selection processing, the selection may be made based on the number of roadside communication devices included in the change source after the slot change, or the roadside communication device included in the change source before the slot change. You may choose based on the number of.

In the time slot allocating device of the present invention, the determination means is based on, for example, a position of the mobile communication device and a reception level of the roadside communication device with respect to a transmission signal transmitted from the mobile communication device at the position. The presence or absence of the radio wave interference can be determined (Claim 6).
Further, the determination means determines the presence or absence of the radio wave interference based on a position of the mobile communication device and a reception level of a transmission signal from the roadside communication device received by the mobile communication device at this position. (Claim 7).

In this case, the geographical range of the communication area of each roadside communication device can be grasped by using the position information of the mobile communication device and the reception level of the mobile communication device or roadside communication device corresponding to this position.
For this reason, the presence or absence of the radio wave interference which arises between roadside communication apparatuses can be correctly determined by the overlapping degree of the geographical range of the communication area of a roadside communication apparatus.

However, the determination means may determine that there is radio wave interference between the roadside communication devices installed at intersections adjacent to each other (claim 8).
In addition, when each of the two roadside communication devices installed at two intersections or more is wirelessly transmitted, the determination means is another third position located on the shortest route connecting the two roadside communication devices. The presence or absence of radio wave interference between the two roadside communication devices can be determined based on the reception level of the transmission signal from each of the roadside communication devices in the roadside communication device.

  In this case, since it is possible to determine the presence or absence of radio wave interference between roadside communication devices without accurately specifying the geographical range of the communication area of each roadside communication device, the calculation load necessary for the determination of the presence or absence should be reduced. Can do.

  As described above, according to the present invention, the number of time slots for wireless transmission by a plurality of roadside communication devices can be reduced, so that the transmission time of the mobile communication device can be effectively ensured.

It is a schematic perspective view which shows the whole structure of an intelligent road traffic system. It is a road top view which shows a part of jurisdiction area of an intelligent road traffic system. It is a block diagram which shows the internal structure of a roadside communication apparatus and a vehicle-mounted communication apparatus. It is a conceptual diagram which shows an example of a time slot. It is a figure which shows an example of the data format which a vehicle-mounted communication apparatus transmits. It is a flowchart which shows an example of the allocation process of a time slot. It is a top view of the road which shows the example of arrangement | positioning of a main | base station and a subunit | mobile_unit. It is a top view of the road which shows the example of arrangement | positioning of a main | base station and a subunit | mobile_unit. It is a conceptual diagram of the time slot for showing an example of a slot change. It is a conceptual diagram of the time slot for showing another example of a slot change. It is a top view of the road for showing the modification of this invention.

[Overall system configuration]
FIG. 1 is a schematic perspective view showing an overall configuration of an intelligent road traffic system (ITS) according to an embodiment of the present invention.
As shown in FIG. 1, the intelligent transportation system of this embodiment is equipped with a traffic signal 1, a roadside communication device 2, an in-vehicle communication device 3 (see FIGS. 2 and 3), a central device 4, and an in-vehicle communication device 3. The vehicle 5 and the monitoring camera 6 are included.

The traffic signal 1 and the roadside communication device 2 are installed at each of a plurality of intersections Ci (i = 1 to 12 in the figure), and are connected to the router 8 via a communication line 7 such as a telephone line. . This router 8 is connected to the central device 4 in the traffic control center.
The central device 4 constitutes a local area network (LAN) with the traffic signal 1 and the roadside communication device 2 of each intersection Ci included in the area under its control. Therefore, the central device 4 can perform bidirectional communication with each traffic signal 1 and each roadside communication device 2. The central device 4 may be installed on the road instead of the traffic control center.

The surveillance cameras 6 are installed at various locations on the road in the jurisdiction area for the purpose of counting the number of vehicles flowing into each intersection Ci. The monitoring camera 6 captures traffic conditions on the road in time series, and the image data is transmitted to the central device 4 via the communication line 7 in almost real time.
In FIG. 1 and FIG. 2, only one signal lamp is depicted at each intersection Ci for simplification of illustration, but each actual intersection Ci is used for ascending and descending roads intersecting each other. At least four signal lamps are installed.

[Central equipment]
The central device 4 has a control unit composed of a workstation (WS), a personal computer (PC), and the like. This control unit includes a roadside communication device 2, a monitoring camera 6, and a vehicle detector (not shown). Collects, processes (calculates) and records various traffic information, controls signals, and provides information.
Specifically, the control unit of the central device 4 performs system control for adjusting the traffic signal group 1 on the same road for the traffic signal 1 at the intersection Ci belonging to its own network, and this system control is applied to the road network. Extended wide area control (surface control) can be performed.

In addition, the central device 4 has a communication unit that is a communication interface connected to the LAN side via the communication line 7, and this communication unit includes a signal control command S1 relating to the lamp color switching timing of the signal lamp, Traffic information S2 including traffic jam information and the like is transmitted to the traffic signal device 1 and the roadside communication device 2 every predetermined time (see FIG. 1).
The signal control command S1 is transmitted every calculation period (for example, 1.0 to 2.5 minutes) of the signal control parameter when performing the system control and the wide area control, and the traffic information S2 is transmitted every 5 minutes, for example. Is done.

  The communication unit of the central device 4 is generated at the time of passing the vehicle information S3 including the current position of the vehicle 5 received from the in-vehicle communication device 3 by the communication device 2 from the roadside communication device 2 corresponding to each intersection Ci. Sensing information S4 of a vehicle sensor (not shown) made up of a pulse signal, image data S5 made up of digital information of the road taken by the monitoring camera 6, etc. are almost real time (for example, 0.1 to 1.0 seconds). The control unit of the central device 4 executes the system control and the wide area control based on these various pieces of information.

[Wireless communication systems, etc.]
FIG. 2 is a road plan view showing a part of the jurisdiction area of the above intelligent road traffic system.
In FIG. 2, each of two roads intersecting each other is illustrated as one lane on one side in the up and down directions, but the road structure is not limited to this.
As shown also in FIG. 2, the intelligent transportation system of this embodiment includes a plurality of roadside communication devices 2 capable of wireless communication with the in-vehicle communication device 3, and other communication devices 2 and 3 using a carrier sense method. And an in-vehicle communication device 3 that is a kind of mobile wireless transceiver that performs wireless communication.

The plurality of roadside communication devices 2 are installed at each roadside intersection Ci, and are attached to the pillars of the traffic signal 1 in the examples of FIGS. 1 and 2. On the other hand, the in-vehicle communication device 3 is mounted on each vehicle 5 traveling on the road.
Each roadside communication device 2 has a communication area A (range in which the transmission signal of the roadside communication device 2 can sufficiently reach) spreading around the roadside communication device 2 and the vehicle-mounted communication device 3 of the vehicle 5 traveling in its communication area A. Wireless communication is possible. Each roadside communication device 2 can also perform wireless communication with other roadside communication devices 2 in which the communication area A overlaps (partially overlaps or all overlaps).

In the intelligent transport system of this embodiment, wireless communication is used between the roadside communication devices 2 (roadside communication), and between the roadside communication device 2 and the vehicle-mounted communication device 3 (from “road” to “car” Wireless communication is also used for both vehicle-to-vehicle communication and vehicle-mounted communication devices 3 (vehicle-to-vehicle communication).
As described above, the central device 4 provided in the traffic control center is capable of two-way communication with each roadside communication device 2 by wire, but wireless communication may be performed between these devices.

Each roadside communication device 2 is assigned a time slot for wireless transmission by itself by the master unit 2A described later by the TDMA method, and wireless transmission is not performed in a time slot other than this time slot. Therefore, the time zone other than the time slot for the roadside communication device 2 is opened as a transmission time by the CSMA method for the in-vehicle communication device 3.
Each roadside communication device 2 has a time synchronization function with other roadside communication devices 2 in order to control its own transmission timing. The time synchronization of the roadside communication device 2 is performed by, for example, GPS synchronization that adjusts its own clock to the GPS time, air synchronization that adjusts its own clock to a transmission signal from another roadside communication device 2, or the like.

[Roadside communication device]
FIG. 3 is a block diagram showing the internal configuration of the roadside communication device 2 and the in-vehicle communication device 3.
The roadside communication device 2 of the present embodiment includes one parent device 2A and a plurality of child devices 2B.
Of these, not only the transmission time of the own device, but also the transmission time of a plurality of child devices 2B belonging to the management group managed by the own device, the parent device 2A assigns time slots to the time slots generated by the parent device 2A. Functions as an allocation device. The assignment information S6 generated by the parent device 2A is notified to each child device 2B belonging to the management group, and the child device 2B broadcasts the assignment information S6 to its own communication area A.

On the other hand, each slave unit 2B performs wireless transmission only in the time slot for the roadside communication device 2 described in the allocation information S6 notified from the master unit 2A. The in-vehicle communication device 3 is connected to the master unit 2A or the slave unit. Wireless transmission is performed only in a time zone other than the time slot described in the allocation information S6 notified from 2B.
In the following description, when the matters common to both of them are described, not the matters specific to the parent device 2A and the child device 2B, they are simply referred to as “the roadside communication device 2”.

The roadside communication device 2 includes a wireless communication unit (transmission / reception unit) 21 connected to an antenna 20 for wireless communication, a wired communication unit 22 that performs bidirectional communication with the central device 4, and a processor (CPU that performs communication control thereof) A central processing unit) and a storage unit 24 connected to the control unit 23, such as a ROM or a RAM.
The storage unit 24 of the roadside communication device 2 stores a computer program for communication control executed by the control unit 23, communication device IDs of the communication devices 2 and 3, and the like.

The control unit 23 of the roadside communication device 2 includes a data transfer unit 23A and an area information generation unit 23B as functional units achieved by executing the computer program.
Among these, the data transfer means 23A temporarily stores the traffic information S2 such as traffic jam information of the central device 4 received by the wired communication unit 22 in the storage unit 24, and the in-vehicle communication device via the wireless communication unit 21. 3 is broadcast. The data transfer unit 23A temporarily stores the vehicle information S3 of the in-vehicle communication device 3 received by the wireless communication unit 21 in the storage unit 24 and transfers the vehicle information S3 to the central device 4 via the wired communication unit 22.

The area information generation unit 23B generates area information S7 for specifying the geographical range of the communication area A corresponding to the roadside communication device 2 using the position information included in the vehicle information S3 of the in-vehicle communication device 3. To do.
The area information S7 includes, for example, the position of the in-vehicle communication device 3 and the reception level in the wireless communication unit 21 of the transmission signal transmitted from the in-vehicle communication device 3 transmitted at this position. Further, when the reception level at the in-vehicle communication device 3 is included in the vehicle information S3, the area information S7 is obtained from the position of the in-vehicle communication device 3 and the roadside communication received by the in-vehicle communication device 3 at this position. It can also be configured from the reception level of the transmission signal from the machine 2.

Note that the data transfer unit 23A of the slave unit 2B sends the area information S7 generated by the area information generation unit 23B of the own device to the wireless communication unit 21 or the wired communication unit 22 of the own device in real time or at regular intervals. To the master unit 2A.
On the other hand, the control unit 23 of the base unit 2A further includes a determination unit 23C, a slot generation unit 23D, and a slot allocation unit 23E as functional units achieved by executing the computer program.

Among these, the determination means 23C determines whether or not radio wave interference has occurred between a plurality of roadside communication devices 2 (including the parent device 2A) belonging to the same management group.
For example, the determination unit 23C determines the presence or absence of radio wave interference based on the area information S7 including the position of the in-vehicle communication device 3 and the reception level corresponding to the position. A specific determination method by the determination unit 23C will be described later.

The slot generation means 23D generates the time slot T1 for the roadside communication device 2 so that the slot number i repeats periodically. FIG. 4 is a conceptual diagram showing an example of a time slot generated by the slot generation means 23D.
As shown in FIG. 4, this time slot includes a first slot T1 and a second slot T2, and these slots T1 and T2 are alternately repeated at a constant period.

The first slot T1 is a time slot for the roadside communication device 2. In this time zone, only wireless transmission by the roadside communication device 2 is allowed, and wireless transmission by the in-vehicle communication device 3 is prohibited. A slot number i is assigned to the first slot T1, and the slot number i is incremented or decremented to repeat periodically.
The second slot T2 is a time slot for the roadside communication device 2. Conversely, in this time zone, wireless transmission by the in-vehicle communication device 3 is allowed, and the roadside communication device 2 does not perform wireless transmission.

The slot generation unit 23D according to the present embodiment generates a slot number i that does not need to be allocated to the transmission time of the roadside communication device 2 due to slot change processing (step ST2 in FIG. 6) by a slot allocation unit 23E described later. Has a function of deleting the time slot T1 for the roadside communication device 2 corresponding to the slot number i.
When the predetermined time slot T1 is deleted in this way, the time slot of the second slot T2 for the in-vehicle communication device 3 increases accordingly.

The slot allocation unit 23E allocates the transmission time of itself (master unit 2A) and the transmission time of the slave unit 2B belonging to its own management group to the first slot T1 generated by the slot generation unit 23D. The allocation information S6 is generated.
For example, the dots ● shown in FIG. 4 indicate the number of roadside communication devices 2 assigned to each first slot T1. In the example of FIG. 4, the transmission time of the parent device 2A and one child device 2B is assigned to the first slot T1 of the slot number (1), and three different child devices are assigned to the first slot T1 of the slot number (2). In this example, 2B transmission time is assigned and the transmission time of one slave unit 2B is assigned to the first slot T1 of slot number (3).

The allocation information S6 generated by the slot allocation unit 23E includes the slot number i, the start time and duration of the time slot T1 corresponding to the slot number i, and the communication device of the slave unit 2B allocated to the slot number i. ID is included.
The data transfer unit 23A of the base unit 2A wirelessly transmits the allocation information S6 generated by the slot allocation unit 23E to its own communication area A via the wireless communication unit 21. The handset 2B that has received the assignment information S6 also wirelessly transmits the assignment information S6 to its own communication area A via the wireless communication unit 21, and transfers the assignment information S6 to the other handset 2B.

Each slave unit 2B that has received the allocation information S6 performs radio transmission only in the time slot T1 of the predetermined slot number i designated for its radio transmission in the allocation information S6, and performs radio communication in other time zones. Do not do.
Further, when the in-vehicle communication device 3 of the vehicle 5 traveling in the communication area A of the parent device 2A or the child device 2B receives the allocation information S6, a time zone other than the first slot T1 described in the allocation information S6 (see FIG. Wireless transmission by the carrier sense method is performed in the second slot T2).

On the other hand, as illustrated in FIG. 4, the slot allocating unit 23E of the present embodiment replaces the plurality of roadside communication devices 2 determined by the determining unit 23C with no radio wave interference with each other in the first slot number i. It has a duplication assignment function that duplicates and assigns to the slot T1.
That is, the slot allocating unit 23E does not simply allocate the first slot T1 and the roadside communication device 2 in a one-to-one correspondence. For example, as in the case of the slot numbers (1) and (2) in FIG. The transmission times of a plurality of roadside communication devices 2 can be assigned to one first slot T1 in an overlapping manner.

For this reason, when the slot allocation unit 23E performs the above-described overlapping allocation, the total number of time slots (first slots) T1 necessary for the roadside communication devices 2 belonging to the same management group is the total number of the roadside communication devices 2. Less than. Therefore, in the communication area A of the roadside communication device 2 belonging to the management group of the parent device 2A, the time zone (second slot) T2 for wireless transmission of the in-vehicle communication device 3 can be set as long as possible.
Note that the slot allocation unit 23E performs allocation to the first slot T1 so that the number of duplications of the roadside communication device 2 for one slot number i increases in the above-described overlapping allocation.

  The slot assigning means 23E of the present embodiment further has a slot changing function for changing the transmission time of the roadside communication device 2 that has already been assigned to the time slot T1 of another slot number i. Specific contents of the process (step ST2 in FIG. 6) will be described later.

[In-vehicle communication device]
Returning to FIG. 3, the in-vehicle communication device 3 includes a communication unit (transmission / reception unit) 31 connected to the antenna 30 for wireless communication, a control unit 32 including a processor that performs communication control on the communication unit 31, and the like. And a storage unit 33 including a storage device such as a ROM or a RAM connected to the control unit 32.
The storage unit 33 stores a computer program for communication control executed by the control unit 32, communication device IDs of the communication devices 2 and 3, and the like.

The control unit 32 of the in-vehicle communication device 3 causes the communication unit 31 to perform wireless communication by a carrier sense method for inter-vehicle communication, and a communication control function in a time division multiplexing method with the roadside communication device 2. Does not have.
Accordingly, the communication unit 31 of the in-vehicle communication device 3 always senses the reception level of a predetermined carrier frequency, and when the value is equal to or greater than a certain threshold, wireless transmission is not performed, and when the value is less than the threshold Only intended to perform wireless transmission.

In addition, the control part 32 of the vehicle-mounted communication apparatus 3 carries out the radio transmission of the vehicle information S3 including the present position, direction, speed, etc. of the vehicle 5 (vehicle-mounted communication apparatus 3) via the communication part 31 by radio. Yes.
For this reason, in the other vehicle 5 or the roadside communication device 2 that has received the vehicle information S3 including the position, speed, and the like, for example, it is possible to perform safe driving support control for avoiding, for example, a right-hand collision or a head-on collision. .

FIG. 5 is a diagram illustrating an example of a data format transmitted by the in-vehicle communication device 3.
As shown in FIG. 5, the transmission signal of the in-vehicle communication device 3 includes a preamble, a header, data, and a CRC (Cyclic Redundancy Check).
Among these, the data includes the position, direction (traveling direction), and speed of the vehicle 5, but can also include a reception level when a transmission signal from the roadside communication device 2 is received. The position and direction of the vehicle 5 are usually information autonomously measured by sensors on the vehicle 5 side such as GPS, but may be acquired from the infrastructure side such as an optical beacon. The speed is information based on a speed sensor of the vehicle 5.

[Time slot allocation processing]
FIG. 6 is a flowchart illustrating an example of time slot allocation processing performed by the control unit 23 of the parent device 2A.
7 and 8 are plan views of a road showing an example of the arrangement of the master unit 2A and the slave units 2B to 2I. In the following, one master unit arranged at each intersection of the road as shown in the figure. Assume that 2A and eight slave units 2B to 2I belong to the same management group.

[Judgment of communication status change]
As shown in FIG. 6, first, the control unit 23 of the base unit 2A always determines whether or not a change in communication status has occurred in its own management group (step ST1 in FIG. 6).
This change in the communication status includes, for example, “occurrence of communication failure (including removal)” in specific slave units 2B to 2I and “change in presence / absence of radio wave interference” between specific roadside communication devices 2. Is included.

[Method for judging the occurrence of communication failure]
For example, when the roadside communication device 2 adjacent to the adjacent roadside communication device 2 cannot receive a transmission signal from a specific slave unit 2B to 2I, the roadside communication device 2 makes a request to increase transmission power. However, it is possible to detect that the transmission signals from the slave units 2B to 2I cannot be received.
When the slave units 2B to 2I detect such a communication failure, the slave units 2B to 2I notify the master unit 2A of the communication device ID of the roadside communication device 2 that has become unable to communicate. .

[Judgment method of presence or absence of radio wave interference (1)]
On the other hand, the latter method for determining the presence or absence of radio wave interference specifically includes the following two variations.
For example, as described above, the determination unit 23C of the parent device 2A acquires the area information S7 from the own device 2A and each of the child devices 2B to 2I, and the area information S7 includes the position of the in-vehicle communication device 3 and The reception level at the in-vehicle communication device 3 or the roadside communication device 2 corresponding to this position is included.

Therefore, the determination unit 23C of the parent device 2A grasps the change in the geographical range of the communication area A between the own device 2A and each of the child devices 2B to 2I based on the area information S7, and When the geographical ranges overlap at a certain level or more, it is determined that there is radio wave interference between the roadside communication devices 2 corresponding to the overlapping communication area A.
Conversely, the determination unit 23C determines that there is no radio wave interference between the roadside communication devices 2 when the communication area A between the specific roadside communication devices 2 is not less than a certain level and does not overlap.

[Judgment method of presence or absence of radio wave interference (2)]
On the other hand, the determination unit 23C of the base unit 2A uses the following determination criteria (a) and (b) as a simple determination method that does not need to grasp the fluctuation of the communication area A of the roadside communication device 2 and performs radio wave interference. Presence / absence can also be determined.
○ Criteria (a)
Roadside communication devices 2 installed at intersections adjacent to each other are determined to have radio wave interference.

○ Criteria (b)
Another third roadside located on the shortest path connecting the two roadside communication devices 2 and 2 when each of the two roadside communication devices 2 and 2 installed at two intersections or more transmits wirelessly When the communication area A of each roadside communication device 2 or 2 is estimated based on the reception level of the transmission signal from each roadside communication device 2 in the communication device 2 and each communication area A overlaps with a certain level or more, 2 When it is determined that there is radio wave interference between the two roadside communication devices 2 and 2 and each communication area A is not less than a certain level, it is determined that there is no radio wave interference between the two roadside communication devices 2 and 2.

  Note that the reason why the determination criterion (a) is valid is that, in the case of roadside communication devices 2 installed at adjacent intersections, it is usual to adjust the transmission level so that the communication areas A overlap to some extent. That's why.

The contents of the determination criteria (a) and (b) will be described more specifically with reference to FIGS. 7 and 8. In FIG. 7, it is assumed that the slave unit 2H is the transmission subject, and in FIG. 8, the slave units 2G and 2F are the transmission subject.
As shown in FIG. 7, when the slave unit 2H is the transmission subject, the slave unit 2G, the slave unit 2E, and the slave unit 2I are all adjacent to the slave unit 2H. It is determined that there is radio wave interference (determination criterion (a)).

Next, with respect to the slave unit 2B, the third slave unit 2E located on the shortest path with the slave unit 2H that is the transmission subject is the transmission subject in a different time slot from the reception level of the transmission signal from the slave unit 2H. The reception level when the slave unit 2B to be wirelessly transmitted is measured.
When the communication areas A of the slave unit 2B and the slave unit 2H estimated from the reception level overlap with each other at a certain level or more, it is determined that the slave unit 2B interferes with the slave unit 2H, and each communication area A is If it is not less than a certain level and does not overlap, it is determined that the handset 2B does not interfere with the handset 2H (determination criterion (b)).

Further, for the slave unit 2D, the shortest route to the slave unit 2H that is a transmission subject is two types, a route of 2H → 2E → 2D and a route of 2H → 2G → 2D. Therefore, in this case, the third slave unit 2E and the slave unit 2G located in these two routes have the slave unit 2D that is the transmission subject in a different time slot from the reception level of the transmission signal from the slave unit 2H. Measure the reception level when transmitting wirelessly.
Then, if any one of the overlapping ranges of the respective communication areas A of the child device 2D and the child device 2H estimated by the child device 2E and the child device 2G from the respective reception levels is equal to or greater than a certain value, When it is determined that the device 2D interferes with the handset 2H and the overlapping range of each communication area A estimated by the handset 2E and the handset 2G is less than a certain value, the handset 2D and the handset 2H It is determined that there is no interference (determination criterion (b)).

Similarly, for the slave unit 2F, the shortest path to the slave unit 2H that is a transmission subject is two types: a route of 2H → 2E → 2F and a route of 2H → 2I → 2F. Therefore, in this case as well, the third slave unit 2E and the slave unit 2I located in these two routes have the slave unit 2F that becomes a transmission subject in a different time slot from the reception level of the transmission signal from the slave unit 2H. Measure the reception level when transmitting wirelessly.
Then, if any one of the overlapping ranges of the respective communication areas A of the child device 2F and the child device 2H estimated by the child device 2E and the child device 2I from the respective reception levels is greater than or equal to a certain value, When it is determined that the handset 2F interferes with the handset 2H and the overlapping range of each communication area A estimated by the handset 2E and handset 2I is less than a certain value, the handset 2F and the handset 2H It is determined that there is no interference (determination criterion (b)).

On the other hand, for the master unit 2A, the shortest path to the slave unit 2H that is the transmission subject is the route 2H → 2E → 2B → 2A, the route 2H → 2E → 2D → 2A, and 2H → 2G → 2D → 2A. There are three types of routes. Therefore, in this case, the four third handset 2B, handset 2D, handset 2E, and handset 2G located in these three routes are different from the reception level of the transmission signal from the handset 2H. The reception level when the base unit 2A that is the transmission subject in the slot transmits wirelessly is measured.
Then, based on each of these reception levels, the overlapping range of each communication area A of the parent device 2A and the child device 2H estimated by the four third child devices 2B, 2D, 2E, and 2G, respectively. If any one of them is more than a certain level, it is determined that the parent device 2A interferes with the child device 2H, and the four third child devices 2B, 2D, 2E, and 2G respectively estimate. When the overlapping range of each communication area A is less than a certain value, it is determined that the parent device 2A does not interfere with the child device 2H (determination criterion (b)).

Similarly, for the slave unit 2C, the shortest path to the slave unit 2H that is the transmission subject is the route 2H → 2E → 2B → 2C, the route 2H → 2E → 2F → 2C, and 2H → 2I → 2F → There are three types with 2C route. Therefore, in this case, the four third handset 2B, handset 2E, handset 2F, and handset 2I located in these three routes are different from the reception level of the transmission signal from the handset 2H. The reception level when the handset 2C, which is the transmission subject in the slot, wirelessly transmits is measured.
Then, the overlapping ranges of the communication areas A of the slave unit 2C and the slave unit 2H estimated by the four third slave units 2B, 2E, 2F, and 2I from the respective reception levels are respectively calculated. If any one of them is above a certain level, it is determined that the handset 2C interferes with the handset 2H, and the four third handset 2B, handset 2E, handset 2F, and handset 2I estimate each. When the overlapping range of each communication area A is less than a certain value, it is determined that the child device 2C does not interfere with the child device 2H (determination criterion (b)).

  On the other hand, as shown in FIG. 8, when two of the slave unit 2F and the slave unit 2G are transmission subjects, the slave unit 2C, the slave unit 2D, the slave unit 2E, the slave unit 2H, and the slave unit 2I are all Since it is adjacent to the slave unit 2F or the slave unit 2G, it is determined that there is radio wave interference between the slave unit 2F and the slave unit 2G that transmit simultaneously (determination criterion (a)).

Next, with respect to the master unit 2A, the shortest distance from the slave unit 2F that is one transmission subject is the route of 2F → 2C → 2B → 2A, route of 2F → 2E → 2D → 2A, and 2F → 2E → There are three types of routes: 2B → 2A, and the shortest route to the other mobile device 2G as the transmission subject is one type of 2G → 2D → 2A.
Therefore, in this case, the four third handset 2B, handset 2C, handset 2D, and handset 2E located in these four routes are transmitted when the handset 2F and handset 2G simultaneously transmit wirelessly. The reception level when the base unit 2A as the transmission subject transmits wirelessly in a time slot different from the reception level is measured.

  Then, the communication areas of the parent device 2A, the child device 2F, and the child device 2G estimated by the four third child devices 2B, the child devices 2C, the child devices 2D, and the child devices 2F from the respective reception levels. If any one of the overlapping ranges of A is greater than or equal to a certain value, it is determined that the parent device 2A interferes with the child device 2F and the child device 2G, and the four third child devices 2B, the child device 2C, and the child device When the overlapping ranges of the communication areas A estimated by the 2D and the slave unit 2F are both less than a certain value, it is determined that the master unit 2A does not interfere with the radio units 2F and 2G (determination criteria (b )).

Furthermore, for the slave unit 2B, the shortest path to the slave unit 2F, which is one transmission subject, is two types of routes: 2F → 2C → 2B and 2F → 2E → 2B route. There are three types of the shortest route to the child device 2G: a route 2G → 2D → 2A → 2B, a route 2G → 2H → 2E → 2B, and a route 2G → 2D → 2E → 2B.
Therefore, in this case, the master unit 2A, the slave unit 2D, the slave unit 2E, and the slave unit 2H located in these five routes are different from the reception levels when the slave unit 2F and the slave unit 2G simultaneously transmit wirelessly. In the time slot, the reception level when the slave unit 2B as the transmission subject transmits wirelessly is measured.

  Then, from the respective reception levels, the overlapping range of each communication area A of the slave unit 2B, the slave unit 2F, and the slave unit 2G estimated by the master unit 2A, the slave unit 2D, the slave unit 2E, and the slave unit 2H, respectively. If any one of them is more than a certain value, it is determined that the slave unit 2B interferes with the slave unit 2F and the slave unit 2G, and each estimated by the master unit 2A, the slave unit 2D, the slave unit 2E, and the slave unit 2H. When the overlapping range of the communication area A is less than a certain value, it is determined that the handset 2B does not interfere with the handset 2F and handset 2G (determination criterion (b)).

[Slot change processing]
Returning to FIG. 6, the control unit 23 of the base unit 2 </ b> A, when a change in communication status such as presence / absence of radio wave interference occurs in its own management group (Yes in step ST <b> 1 in FIG. 6), Slot change processing is performed by 23E (step ST2 in FIG. 6).
Hereinafter, specific contents of the slot changing process performed by the slot allocating unit 23E will be described.

[Basic slot change policy]
First, the slot allocation unit 23E conforms to the following conditions (A) to (C) when changing the transmission time of the roadside communication device 2 to which a specific slot number i has already been allocated to another slot number i. The slot is changed as described above.
(A) The slot is changed so that the number of empty slot numbers i (hereinafter referred to as “empty slots”) that need not be assigned the transmission time of the roadside communication device 2 increases.
(B) Even when an empty slot is not possible, the slot is changed so that the number of roadside communication devices 2 belonging to the slot number i before the change is reduced.
(C) Prevent radio wave interference between the roadside communication devices 2 of the same slot number i.

[Specific example of slot change]
9 and 10 are conceptual diagrams of time slots for showing an example of slot change according to the above conditions (A) to (C).
9 and 10, (a) shows the state before the slot change, and (b) shows the state after the slot change.

First, in the time slot shown in FIG. 9 (a), for example, the parent device 2A and the child device 2C have both interfered with the child device 2I and the child device 2G until now. Is determined from the determination result of the determination means 23C. In this case, there are three possible ways to change slots.
1) The slave units 2I and 2G are moved from the slot number (1) to (2).
2) Move base unit 2A from slot number (2) to (1).
3) Move the handset 2C from the slot number (3) to (1).

Here, among the above three moving methods, even if the handset 2C is moved from the slot number (3) to (1), the slot number (3) before the change is not an empty slot. Therefore, the slot allocation means 23E moves the master unit 2A from the slot number (2) to (1) so that the slot number (2) becomes an empty slot according to the basic policy (A). The state after the movement is shown in FIG.
As described above, when the slot number (2) becomes an empty slot, the slot generation means 23D deletes the first slot T1 corresponding to the slot number (2). The time slot of 2 slots T2 increases.

  In the case of FIG. 9, the slave units 2I and 2G may be moved from the slot number (1) to (2) so that the slot number (1) becomes an empty slot.

On the other hand, in the time slot shown in FIG. 10 (a), for example, the parent device 2A and the child device 2B have both interfered with the child device 2I and the child device 2G until now. Is determined from the determination result of the determination means 23C. In this case, there are two possible ways of changing slots.
1) Move handset 2B from slot number (2) to (1).
2) Move base unit 2A from slot number (3) to (1).

Here, of the above two moving methods, when the master unit 2A is moved from the slot number (3) to (1), two slave units (2E, 2C) are assigned to the slot number (3) before the change. In contrast, when the handset 2B is moved from the slot number (2) to (1), only one handset (2F) remains in the slot number (3) before the change.
Therefore, in such a case, the slot allocating unit 23E determines the slave unit 2B from the slot number (2) so that the number of slave units belonging to the slot number before the change is reduced according to the basic policy (B). Go to 1). The state after the movement is shown in FIG.

In this way, when there are a plurality of time slots that can be changed (slot numbers (2) and (3) in FIG. 10), the time slot that has the smallest number of roadside communication devices included in the changed time slot ( In FIG. 10, if the slot number (2)) is selected, when the next slot change is performed, the possibility of the slot change according to the basic policy (A) increases, and the transmission time of the roadside communication device 2 is increased. It is easy to generate empty slots that do not need to be assigned.
Therefore, by repeating the slot change according to the basic policy (B), the possibility that the transmission time of the in-vehicle communication device 3 increases can be increased.

[Transmission of allocation information after change, etc.]
Returning to FIG. 6, when the slot allocation unit 23E of the parent device 2A executes the slot change, the allocation information S6 after the change is newly generated. The changed allocation information S6 is wirelessly transmitted to the communication area A of the base unit 2A via the wireless communication unit 21 by the data transfer unit 23A (step ST3 in FIG. 6).
The changed allocation information S6 is wirelessly transmitted to other communication areas A by the slave units 2B and 2D that have received the changed allocation information S6, and transferred to the in-vehicle communication unit 3 of the vehicle 5 traveling in each communication area A.

  Thereafter, control unit 23 of base unit 2A determines whether or not the slot change has succeeded (step ST4 in FIG. 6). This determination is made, for example, based on whether or not the determination unit 23C newly observes radio wave interference after a lapse of a certain time after transmission of the new allocation information S6. If no new radio wave interference is observed, the slot is set. The change is a success.

[Modification: Roadside communication device with directivity]
FIG. 11 is a plan view of a road for showing a modification of the present invention.
Each roadside communication device 2 (master device 2A and slave devices 2B to 2I) according to this modification is equipped with a wireless communication unit capable of wireless communication using a plurality of antennas having different directivities.
Each antenna of the wireless communication unit has directivity along the traveling direction of each road flowing into the intersection as indicated by an arrow in FIG. 11, and the wireless communication unit sets transmission / reception timing for each antenna. Can be set.

In the case of the roadside communication device 2 as described above, it can be considered that a single roadside communication device 2 has a plurality of independent communication areas for each antenna.
Therefore, if it is assumed that there is a communication device for each antenna instead of each roadside communication device 2, and determination of presence / absence of radio wave interference and slot allocation are performed, the roadside communication device 2 capable of wireless communication for each directional antenna. Also in this case, the present invention can be applied.

[Other variations]
Each embodiment disclosed this time is an illustration of the present invention and is not restrictive. The scope of the present invention is shown not by the above-described embodiment but by the scope of claims for patent, and includes all modifications within the scope and meaning equivalent to the scope of claims for patent.

  For example, in the intelligent transportation system of the above embodiment, a communication device (portable communication terminal) carried by a pedestrian or the like can be used instead of or in addition to the in-vehicle communication device 3. However, in this case, the mobile communication terminal does not perform wireless transmission during the transmission time (first slot T1) of the roadside communication device 2 as in the case of the in-vehicle communication device 3 of the above embodiment. Need to follow.

DESCRIPTION OF SYMBOLS 1 Traffic signal device 2 Roadside communication device 2A Master device 2B Child device 3 In-vehicle communication device (mobile communication device)
4 Central device 5 Vehicle 6 Monitoring camera 7 Communication line 8 Router 20 Antenna 21 Wireless communication unit 22 Wired communication unit 23 Control unit 23A Data transfer unit 23B Area information generation unit 23C Determination unit 23D Slot generation unit 23E Slot allocation unit 24 Storage unit 30 Antenna 31 Communication unit 32 Control unit 33 Storage unit S1 Signal control information S2 Traffic information S3 Vehicle information S4 Sensing information S5 Image data S6 Allocation information S7 Area information T1 First slot (time slot)
T2 Second slot (Time slot)

Claims (9)

A time slot allocation device that generates a time slot for wireless transmission by a plurality of roadside communication devices belonging to the same management group, and releases a time zone other than the time slot for wireless transmission of a mobile communication device,
Slot generating means for generating a plurality of the time slots so that the slot numbers are periodically repeated;
Slot allocation means for allocating redundant transmission times for several different roadside communication devices for the time slot of a specific slot number;
A time slot allocating device comprising: A determination means for determining presence or absence of radio wave interference between the plurality of roadside communication devices;
The time slot allocation device according to claim 1, wherein the slot allocation unit performs allocation to the time slot based on a determination result of presence / absence of the radio wave interference.   3. The time slot allocation apparatus according to claim 1, wherein the slot allocation unit performs allocation to the time slot so that a plurality of overlapping roadside communication devices with respect to the time slot with one slot number increase.   4. The time slot allocation device according to claim 3, wherein, when an empty slot number that does not need to be allocated to the transmission time of the roadside communication device is generated, the slot generation unit deletes the time slot corresponding to the slot number. . The slot allocation means has a slot change function for changing the transmission time of the roadside communication device that has already been assigned to the time slot of another slot number,
The time slot having the smallest number of the roadside communication devices included in the time slot of the change source is selected when there are a plurality of time slots that can be the change source when performing the slot change. The time slot allocation device according to any one of claims.   The determination means determines the presence or absence of the radio wave interference based on a position of the mobile communication device and a reception level of the roadside communication device with respect to a transmission signal transmitted from the mobile communication device at the position. The time slot allocation device according to any one of 2 to 5.   The determination means determines the presence or absence of the radio wave interference based on a position of the mobile communication device and a reception level of a transmission signal from the roadside communication device received by the mobile communication device at the position. The time slot allocation device according to any one of? 6.   The time slot allocation device according to any one of claims 2 to 7, wherein the determination unit determines that there is radio wave interference between the roadside communication devices installed at intersections adjacent to each other.   When each of the two roadside communication devices installed at two or more intersections wirelessly transmits, the determination means is another third of the above-mentioned, which is located on the shortest route connecting the two roadside communication devices. The roadside communication device according to any one of claims 2 to 8, wherein the presence or absence of radio wave interference between the two roadside communication devices is determined based on a reception level of a transmission signal from each of the roadside communication devices. Time slot allocation device.

Images