JP2018088704A - Communication system, method for transmission used for communication system, and computer program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication system which can suppress a wasteful consumption of time slots if the time slots are allocated in consideration of avoidance of interference of road-to-road communications.SOLUTION: In the communication system according to the present invention, a plurality of road-side communication machines 2 conduct transmission, using a wireless frame in which first slots SL1 are lined. The wireless frame is provided with first slots SL1 for road-to-vehicle communications and first slots SL1 for road-to-road communications. The plurality of road-side communication machines 2 have a communication control device which conducts transmission by sharing the first slots SL1 for road-to-road communications in several time channels in the road-to-road communications.SELECTED DRAWING: Figure 6

Description

  The present invention relates to, for example, a communication system that can be suitably used as a component of an intelligent transport system (ITS).

In recent years, for the purpose of promoting traffic safety and preventing traffic accidents, mobile bodies (vehicles, etc.) receive information from infrastructure devices installed on the road, or exchange information between vehicles, and use these information Thus, an intelligent road traffic system that improves the safety of vehicle travel has been studied (see, for example, Patent Document 1).
A wireless communication system used in such an intelligent road traffic system mainly includes a plurality of roadside communication devices that are infrastructure-side wireless communication devices and a plurality of in-vehicle communication devices (mobile communication devices) that are wireless communication devices mounted on each vehicle. ).

  In this case, the combination of communication performed between each communication subject includes road-to-vehicle (or vehicle-road) communication performed by a roadside communication device and a vehicle-mounted communication device, and vehicle-to-vehicle communication performed between vehicle-mounted communication devices, roadside communication Inter-road communication performed by communication devices is included (see, for example, Patent Document 2).

Japanese Patent No. 2806801 JP 2011-114647 A

  In the above-mentioned intelligent road traffic system, road-to-vehicle communication, road-to-road communication, road-to-road communication, and road-to-step communication, including road-to-vehicle communication, can be carried out between roads within a limited frequency band. In order to perform communication between road vehicles and between vehicles, time division multiplexing (TDMA) that divides radio resources in the time domain and provides time slots that are time zones dedicated to transmission of roadside communication devices. Multi-access method is adopted.

  In the multi-access scheme based on TDMA, a plurality of time slots dedicated to transmission of roadside communication devices are usually arranged in one radio frame. That is, one radio frame includes a plurality of time slots set in different time zones. These multiple time slots are allocated as transmission resources to each roadside communication device.

Roadside communication devices are usually installed at intersections on roads, but there are cases where areas (service areas) that can be transmitted by roadside communication devices installed at intersections overlap each other. If the service areas overlap, the in-vehicle communication device existing in the overlapping portion will receive the transmission signals of both roadside communication devices. That is, interference occurs between the roadside communication devices.
For this reason, different time slots set in different time zones are assigned at least between roadside communication devices in a positional relationship in which interference occurs. Thereby, interference in road-to-vehicle communication can be avoided.

At this time, the plurality of roadside communication devices can be divided into groups of roadside communication devices that can share one or more time slots since no interference occurs between the roadside communication devices in road-to-vehicle communication. Even if roadside communication devices belonging to the same group transmit using the same time slot (group), interference does not occur, and different time slots (group) are assigned to each group. The transmission period assigned for each group is also referred to as a time channel.
If a different time channel (time slot group) is assigned to each group and the time channel assigned to the group to which each roadside communication device belongs is used, assignment capable of avoiding interference can be performed in road-to-vehicle communication.

In the above, the case where only the interference of road-to-vehicle communication was considered was shown, but if the roadside communication device performs road-to-road communication using the time slot allocated only considering road-to-vehicle communication, radio interference is May cause.
There may be a difference in the communication area between road-to-vehicle communication and road-to-road communication, and there is no radio wave interference in road-to-vehicle communication, but there is radio wave interference in road-to-road communication. This is because the interference relationship may be different.

Therefore, when the roadside communication device performs road-to-road communication, each roadside communication device needs time for each roadside communication device in consideration of the interference relationship of both communication so that interference does not occur in both road-to-vehicle communication and road-to-road communication. It is conceivable to allocate slots.
Here, the roadside communication devices are grouped in consideration of both road-to-vehicle communication and road-to-road communication, and the number of time channels to which time slots should be assigned is specified.

FIG. 10 is a graph showing an example of the relationship between the number of time channels necessary for each of a plurality of roadside communication devices arranged in a predetermined area and the intersection interval.
In the figure, the vertical axis indicates the required number of required time channels, and the horizontal axis indicates the intersection interval. A solid line indicates a case where interference between both road-to-vehicle communication and road-to-road communication is considered, and a broken line indicates a case where interference between only road-to-vehicle communication is considered.

  As shown in FIG. 10, as the intersection distance increases, the required number of time channels is relatively greater when road-to-vehicle communication and road-to-road communication are considered than when only road-to-vehicle communication is considered. There is a tendency to increase.

  Then, it is necessary to give more transmission time to road-to-vehicle communication that is communication between in-vehicle communication devices that exist more than roadside communication devices. If allocation that considers both interferences in roadside communication is adopted, time slots (transmission time) must be assigned to the increased time channel in order to avoid interference in roadside communication. Many will be wasted.

  The present invention has been made in view of such circumstances, and even if time slots are allocated in consideration of interference avoidance between roadside communication, the time slots are prevented from being wasted. It is an object of the present invention to provide a communication system that can perform communication, a transmission method used therefor, and a computer program.

[1] The present invention for achieving the above object is a communication system in which a plurality of roadside communication devices perform transmission using a plurality of time slots arranged in a radio frame. A time slot used in road-to-vehicle communication performed between a roadside communication device and a vehicle-mounted communication device, and a time slot used in road-to-road communication performed between the plurality of roadside communication devices are provided. The roadside communication devices are divided into a plurality of first group groups in the road-to-vehicle communication, and the transmission period for simultaneous use by the roadside communication devices in the same group is assigned to be different for each of the plurality of first groups. , The road-to-road communication is divided into a plurality of second group groups, and a transmission period for simultaneous use by roadside communication devices in the same group has a plurality of second groups. To are assigned differently,
The number of the first group is C _RV ,
The number of the second group is C _RR ,
S _RV , the number of time slots for road-to-vehicle communication included in one radio frame,
The number of time slots for the inter-road communication included in one radio frame is set as S _RR ,
The C _RV and the C _RR satisfy the following formula (1),
The plurality of roadside communication devices include a control unit that performs transmission satisfying the following expression (2) by sharing the time slot for roadside communication among the plurality of second groups. .
C _RV <C _RR (1)
S _RV > S _RR (2)

According to the communication system having the above configuration, even when the number C _RR of the second group is larger than the number C _RV of the first group, the time slot for inter-road communication is shared by the second group, The number _SRR of time slots for road-to-road communication included in the radio frame is not set to be larger than the number _SRR of time slots for road-to-vehicle communication.
For this reason, in addition to avoiding interference between road-to-vehicle communications, by assigning time slots in consideration of interference avoidance between road-to-road communications, the number C _RR of the second group is larger than the number C _{RV of} the first group. Even if it becomes, it can suppress that a time slot is consumed wastefully.

[2] The present invention is a communication system in which a plurality of roadside communication devices perform transmission using a plurality of time slots arranged in a radio frame, and the radio frame includes the roadside communication device and an on-vehicle device. A time slot used in road-to-vehicle communication performed with a communication device and a time slot used in road-to-road communication performed between the plurality of roadside communication devices are provided, and the plurality of roadside communication devices are The road-to-vehicle communication is divided into a plurality of ( _CRV ) first group groups, and a transmission period for simultaneous use by roadside communication devices in the same group is assigned to each of the plurality of first groups differently. It is divided into the second group set the plurality (C _RR number) in the road road communication, second glue transmission period of the plurality for simultaneous use in the roadside communication device in the same group They are assigned differently to each
The number of the first group is C _RV ,
The number of the second group is C _RR ,
S _RV , the number of time slots for road-to-vehicle communication included in one radio frame,
The number of time slots for the inter-road communication included in one radio frame is set as S _RR ,
The C _RV and the C _RR satisfy the following formula (3),
The plurality of roadside communication devices include a control unit that performs transmission satisfying the following expression (4) by sharing the time slot for roadside communication among the plurality of second groups. .
C _RV <C _RR (3)
(S _RV −C _RV ) + C _RR ≧ S _RV + S _RR (4)

Note that (S _RV −C _RV ) on the left side of the above equation (3) indicates the difference between the number of time slots allocated to a plurality of first groups and the number of first groups. This is a positive value when there is a first group to which two or more time slots are allocated among the plurality of first groups. In other words, the first group indicates that an extra (S _RV -C _RV ) time slots are required.

Therefore, the left side of the above equation (3) indicates at least the number of time slots necessary for performing road-to-vehicle communication when interference between both road-to-vehicle communication and road-to-road communication is taken into consideration.
On the other hand, the right side shows the number of time slots (S _RV ) necessary for performing road-to-vehicle communication and the time slot necessary for performing road-to-road communication when interference of only road-to-vehicle communication is considered. The total number (S _RR ) is shown.

In other words, the above equation (4) is the sum of the number of time slots for road-to-vehicle communication (S _RV ) and the number of time slots for road-to-road communication (S _RR ), which are necessary when considering interference only in road-to-vehicle communication. It is shown that the value is equal to or less than the number of time slots (left side of Expression (4)) necessary for performing at least road-to-vehicle communication in consideration of interference between both road-to-vehicle communication and road-to-road communication.
By sharing the time slot for road-to-road communication in an environment that considers only road-to-vehicle communication interference so as to satisfy the above equation (4), both road-to-vehicle communication and road-to-road communication interference can be reduced. Compared to the case where both road-to-vehicle communication and road-to-road communication are performed in an environment in consideration, the total number of time slots can be reduced to the same or less.
As a result, it is possible to suppress time slots from being wasted more than when time slots are assigned in consideration of both road-to-vehicle communication and road-to-road communication interference.

[3] The control unit assigns the transmission period of the plurality of second groups to the time slot for inter-road communication included in each of a predetermined number of radio frames arranged adjacent to each other. The transmission periods of the plurality of second groups are preferably distributed and allocated to each of the predetermined number of radio frames.
In this case, transmission periods can be assigned to a plurality of second groups over a predetermined number of radio frames arranged adjacent to each other. The time slots for road-to-road communication included in each of the radio frames adjacent to each other are assigned to each second group because the transmission timing as a radio frame is different even if the position in the radio frame is the same. be able to. For this reason, a transmission period can be allocated to a larger number of second groups.

[4] In addition, the control unit may assign a transmission period to each of the plurality of second groups by dividing and using the time slot for inter-road communication included in a radio frame.

[5] It is considered that the transmission data in road-to-road communication is less than the transmission data in road-to-vehicle communication that communicates with in-vehicle communication devices that exist more than roadside communication devices.
For this reason, the transmission data by the road-to-vehicle communication needs to be transmitted for each radio frame, and requires high transmission frequency, and the transmission data by the road-to-road communication is used as transmission data by the road-to-vehicle communication. It can be transmitted as data having a lower transmission frequency.

[6] Further, the present invention is a transmission method for performing transmission using a plurality of time slots arranged in a radio frame, and the radio frame is transmitted between a roadside communication device and an in-vehicle communication device. A time slot used in road-to-vehicle communication performed and a time slot used in road-to-road communication performed between the plurality of roadside communication devices are provided, and the plurality of roadside communication devices are used in the road-to-vehicle communication. It is divided into a plurality of first group groups, and a transmission period for simultaneous use by roadside communication devices in the same group is assigned differently to each of the plurality of first groups. Divided into groups, the transmission period for simultaneous use by roadside communication devices in the same group is assigned to be different for each of the second groups,
The number of the first group is C _RV ,
The number of the second group is C _RR ,
S _RV , the number of time slots for road-to-vehicle communication included in one radio frame,
The number of time slots for the inter-road communication included in one radio frame is set as S _RR ,
The C _RV and the C _RR satisfy the following formula (5),
Transmission satisfying the following formula (6) is performed by sharing the time slot for roadside communication among the plurality of second groups.
C _RV <C _RR (5)
S _RV > S _RR (6)

[7] Further, the present invention is a computer program for causing a computer to execute a transmission process for transmitting using a plurality of time slots arranged in a radio frame, and the radio frame includes a roadside communication device and Time slots used in road-to-vehicle communication performed with an in-vehicle communication device and time slots used in road-to-road communication performed between the plurality of roadside communication devices are provided, and the plurality of roadside communication devices are provided. Is divided into a plurality of first group groups in the road-to-vehicle communication, and a transmission period for simultaneous use by roadside communication devices in the same group is assigned to each of the plurality of first groups, and the road The communication period is divided into a plurality of second group groups in the inter-communication, and the transmission period for simultaneous use by the roadside communication devices in the same group They are assigned differently to each
The number of the first group is C _RV ,
The number of the second group is C _RR ,
S _RV , the number of time slots for road-to-vehicle communication included in one radio frame,
The number of time slots for the inter-road communication included in one radio frame is set as S _RR ,
The C _RV and the C _RR satisfy the following formula (7),
A computer program that causes a computer to execute transmission processing that performs transmission satisfying the following formula (8) by sharing the time slot for road-to-road communication among the plurality of second groups.
C _RV <C _RR (7)
S _RV > S _RR (8)

[8] The present invention is a transmission method for performing transmission using a plurality of time slots arranged in a radio frame, and the radio frame is performed between a roadside communication device and an in-vehicle communication device. A time slot used in road-to-vehicle communication and a time slot used in road-to-road communication performed between the plurality of roadside communication devices are provided, and the plurality of roadside communication devices include a plurality of time slots in the road-to-vehicle communication. It is divided into first group groups, and a transmission period for simultaneous use by roadside communication devices in the same group is assigned to be different for each of the plurality of first groups, and a plurality of second group groups in the inter-road communication. The transmission period for simultaneous use by roadside communication devices in the same group is assigned to be different for each of the plurality of second groups,
The number of the first group is C _RV ,
The number of the second group is C _RR ,
S _RV , the number of time slots for road-to-vehicle communication included in one radio frame,
The number of time slots for the inter-road communication included in one radio frame is set as S _RR ,
The C _RV and the C _RR satisfy the following formula (9),
Transmission satisfying the following formula (10) is performed by sharing the time slot for inter-road communication among the plurality of second groups.
C _RV <C _RR (9)
(S _RV −C _RV ) + C _RR ≧ S _RV + S _RR (10)

[9] Further, the present invention is a computer program for causing a computer to execute a transmission process for transmitting using a plurality of time slots arranged in a radio frame, the radio frame including a roadside communication device and Time slots used in road-to-vehicle communication performed with an in-vehicle communication device and time slots used in road-to-road communication performed between the plurality of roadside communication devices are provided, and the plurality of roadside communication devices are provided. Is divided into a plurality of first group groups in the road-to-vehicle communication, and a transmission period for simultaneous use by roadside communication devices in the same group is assigned to each of the plurality of first groups, and the road The communication period is divided into a plurality of second group groups in the inter-communication, and the transmission period for simultaneous use by the roadside communication devices in the same group has a plurality of second group groups. They are assigned differently to each
The number of the first group is C _RV ,
The number of the second group is C _RR ,
S _RV , the number of time slots for road-to-vehicle communication included in one radio frame,
The number of time slots for the inter-road communication included in one radio frame is set as S _RR ,
And the C _RV and the C _RR satisfy the following formula (11),
A computer program that causes a computer to execute transmission processing that performs transmission satisfying the following formula (12) by sharing the time slot for roadside communication among the plurality of second groups.
C _RV <C _RR (11)
(S _RV −C _RV ) + C _RR ≧ S _RV + S _RR (12)

  According to the above [6], [7], [8], and [9], in addition to avoiding interference between road-to-vehicle communications, even if time slot allocation is performed in consideration of interference avoidance between road-to-road communications, It is possible to prevent time slots from being wasted.

  According to the present invention, in addition to avoiding road-to-vehicle communication interference, even if time slot allocation is performed in consideration of road-to-road communication interference avoidance, the time slot is prevented from being wasted. Can do.

It is a schematic perspective view which shows one Embodiment of an intelligent road traffic system. It is a block diagram of a roadside communication apparatus. (A) shows a frame, and (b) is a diagram showing the structure (partial) of slots in the frame and how to assign them. It is a figure which shows allocation of the time channel of each intersection. It is a figure which shows an example of the arrangement | positioning model of a roadside communication apparatus. It is a figure which shows an example of the whole structure of the radio | wireless frame used with the communication system of this embodiment. It is a figure which shows the relationship between the slot only for road-to-road communication contained in a 1st radio | wireless frame, and the slot only for road-to-road communication contained in a 2nd radio | wireless frame. It is a figure which shows the extended area | region of the IVC-RVC layer of the transmission packet described in "General corporate judicial person radio wave industry society," 700MHz band intelligent transportation system ARIB-STD T109 1.0 edition "." It is a figure which shows an example of a radio | wireless frame when there is no important intersection. An example of the relationship between the minimum number of time channels required when assigning time channels so that radio wave interference does not occur for each of a plurality of roadside communication devices arranged in a predetermined area and the intersection interval is shown. It is a graph.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
[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. In this embodiment, as an example of the road structure, a grid structure in which a plurality of roads in the north-south direction and the east-west direction intersect with each other is assumed.
As shown in FIG. 1, the intelligent transportation system of this embodiment includes a traffic signal 1, a roadside communication device (radio device) 2, an in-vehicle communication device (radio device) 3 (see FIG. 2), a central device 4, and in-vehicle communication. A vehicle 5 on which the machine 3 is mounted, and a roadside sensor 6 including a vehicle detector, a monitoring camera, and the like are included.

The traffic signal 1 and the roadside communication device 2 are installed at each of a plurality of intersections A1 to A5, B1 to B5, C1 to C5, and D1 to D5, and are connected to the router 8 via a wired communication line 7 such as a telephone line. It is connected. 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 device 1 and the roadside communication device 2 in the area that the central device 4 has jurisdiction over. The central device 4 may be installed on the road instead of the traffic control center.

The roadside sensor 6 is installed in various places on the road in the jurisdiction area for the purpose of counting the number of vehicles flowing into each intersection. The roadside sensor 6 is composed of a vehicle sensor for ultrasonically sensing the vehicle 5 passing underneath, or a monitoring camera for photographing road traffic conditions in time series, and the sensing information and image data are transmitted via the communication line 7. To the central device 4.
In FIG. 1, for simplification of illustration, only one signal lamp is depicted at each intersection. However, at each actual intersection, at least four signal lamps are used for ascending and descending roads that intersect each other. Is installed.

In an intelligent road traffic system, a plurality of roadside communication devices (radio devices) 2 installed at each of a plurality of intersections constituting a wireless communication system are wirelessly communicated with an in-vehicle communication device 3 of a vehicle traveling around the roadside communication device. (Road-to-vehicle communication) is possible.
Each roadside communication device 2 is also capable of wireless communication (inter-road communication) with other roadside communication devices 2 that are located within a predetermined range within which their transmission waves reach.
An in-vehicle communication device (radio device) 3 that also constitutes a wireless communication system performs wireless communication with the roadside communication device 2 and also wirelessly communicates with other in-vehicle communication devices 3 using a carrier sense method (inter-vehicle communication). Is possible.

As shown in FIG. 2, the roadside communication device 2 includes a wireless communication unit (transmission / reception unit) 21 connected to an antenna 20 for wireless communication, and a wired communication for communicating with the central device 4 via a wired communication line 7. The communication part 22 and the communication processing apparatus 25 which performs a communication control process are provided.
The communication processing device 25 includes a control unit 23 and a storage unit 24 that stores necessary information. The control unit 23 performs communication control processing for wireless communication and wired communication. The storage unit 24 stores information necessary for wireless communication and priority communication.

  A part or all of the functions of the communication processing device 25 may be configured by a hardware circuit, or a part or all of the functions may be realized by a computer program. When some or all of the functions of the communication processing device 25 are realized by a computer program, the communication processing device 25 (control unit 23) includes a computer, and the computer program executed by the computer is stored in the storage unit 24. The

[Wireless communication systems, etc.]
FIG. 3A shows a radio frame used in the radio communication system. This radio frame has a time axis length (frame length) set to 100 milliseconds. That is, 10 frames are generated per second.
The frame is generated based on, for example, 1 PPS (signal with a period of 1 second) included in a GPS signal received by a GPS receiver (not shown) included in the roadside communication device 2.

FIG. 3B shows a structure (a part) inside one radio frame. As shown in FIG. 3B, one radio frame includes a first slot SL1 and a second slot SL2.
The first slot SL1 (time slot) is a transmission time slot (road-to-vehicle communication period) of the roadside communication device 2 assigned to the roadside communication device 2. In this time zone, wireless transmission by the roadside communication device 2 is performed. Is acceptable.
On the other hand, the second slot SL2 is a time slot (vehicle communication period) for the in-vehicle communication device 3, and since this time zone is opened for wireless transmission by the in-vehicle communication device 3, the road side communication device 2 is in the second slot. In SL2, wireless transmission is not performed.

The first slots SL1 and the second slots SL2 included in the radio frame are alternately arranged in the time axis direction.
Each first slot SL1 is assigned a slot number i.

One or more first slots SL1 among a plurality of first slots SL1 (for example, 16 first slots) included in the radio frame are allocated to the roadside communication device 2. The roadside communication device 2 recognizes which first slot SL1 is assigned to itself by the slot number i.
When one slot among the plurality of first slots SL1 included in the radio frame is allocated to one roadside communication device 2, for example, the intersection of the first slot SL1 with i = 1 included in the radio frame Assigned to the roadside communication devices 2 of A2, B5, C3, D1, and assigned to the roadside communication device 2 of intersections A3, B1, C4, D2 to the first slot SL1 of i = 2, and the first of i = 3 The slot SL1 is assigned to the roadside communication devices 2 at the intersections A4, B2, C5, and D3, and the i = 4 first slot SL1 is assigned to the roadside communication devices 2 at the intersections A5, B3, C1, and D4. The first slot SL1 with i = 5 is assigned to the roadside communication device 2 at the intersections A1, B4, C2, and D5.

The plurality of roadside communication devices 2 can be divided into groups of roadside communication devices 2 that can use the same slot (transmission period) at the same time because the roadside communication devices 2 do not interfere with each other in road-to-vehicle communication. . In FIG. 3B, the roadside communication device 2 at the intersections A2, B5, C3, D1, the roadside communication device 2 at the intersections A3, B1, C4, D2, the roadside communication device 2 at the intersections A4, B2, C5, D3, and the intersection The roadside communication devices 2 of A5, B3, C1, and D4 and the roadside communication devices 2 of intersections A1, B4, C2, and D5 are divided into five groups.
Even if the roadside communication devices 2 belonging to the same group transmit using the same transmission period, interference does not occur. Therefore, interference is prevented by assigning a different transmission period to each group.

Note that the transmission period assigned differently to each group is also referred to as a time channel. The number of time channels is the same as the number of groups of roadside communication devices 2 that can use the same transmission period.
In FIG. 3B, a different first slot SL1 (i = 1 to 5) is assigned to each time channel (time channel numbers Ch1 to Ch5).

  FIG. 4 shows how time channels are assigned according to FIG. 3 to the plurality of roadside communication devices 2 shown in FIG. In FIG. 4, the numbers in the circles at each intersection indicate the time channel numbers. Each roadside communication device 2 performs road-to-vehicle communication in the first slot SL1 of the time channel number assigned to the own device 2.

  When the same first slot SL1 is assigned to the roadside communication device 2 at the adjacent intersection, the vehicle 5 between the adjacent intersections receives radio waves of road-to-vehicle communication from both roadside communication devices 2, Interference occurs. However, as shown in FIG. 3, the same first slot SL1 is distributed and assigned, so that interference during road-to-vehicle communication by each roadside communication device 2 can be prevented.

[Examination of the number of time channels]
The slot assignment as shown in FIG. 4 is appropriate when only road-to-vehicle communication is considered, but is not appropriate when road-to-vehicle communication is also considered, and radio wave interference may occur in road-to-road communication.
That is, if the slot allocated only considering road-to-vehicle communication is used in road-to-road communication, radio wave interference may occur.

  For example, the first slot SL1 with the time channel number Ch5 is assigned to both the roadside communication device 2 at the intersection C2 and the roadside communication device 2 at the intersection D5 in FIG. And if the building of parts other than a road is considered between the intersections C2 and D5, it will be in the state where an electromagnetic wave cannot reach directly. Therefore, vehicles near the intersection C2 (vehicles in the service area of the roadside communication device 2 at the intersection C2) are almost subject to interference from the roadside communication device 2 at the intersection D5 that transmits radio waves for road-to-vehicle communication at the same timing. It is possible to receive the road-vehicle communication data of the roadside communication device 2 at the intersection C2.

When the roadside communication device 2 at the intersection C2 and the roadside communication device 2 at the intersection D5 perform road-to-road communication at the same timing, the roadside communication device 2 at the intersection D5 communicates with the roadside communication device 2 at the intersection C5. When communication data is transmitted, road-to-road communication or road-to-vehicle communication data transmitted by the roadside communication device 2 at the intersection C2 may directly reach the intersection C5 as an interference wave.
For this reason, the roadside communication device 2 at the intersection C5 may not correctly receive the downlink data of the roadside communication from the roadside communication device 2 at the intersection D5.

Thus, since the communication area is different in road-to-vehicle communication and road-to-road communication, if the time channel allocated only considering road-to-vehicle communication is also used in road-to-road communication, in road-to-road communication, There is a risk of radio wave interference.
Thus, as described above, when the roadside communication device 2 performs both road-to-vehicle communication and road-to-road communication using the same time channel, interference that occurs in both road-to-vehicle communication and road-to-road communication is avoided. It is conceivable to assign a time channel to each roadside communication device 2 in consideration of both interference relationships.

However, when a time channel is assigned to each roadside communication device 2 in consideration of both interference relationships, road-to-vehicle communication and road-to-road communication are considered as the intersection interval increases as shown in FIG. In this case, the required number of slots tends to be relatively larger than when only road-to-vehicle communication is considered.
In FIG. 10, when only road-to-vehicle communication is considered and the intersection interval is 300 m, road-to-vehicle communication and road-to-road communication When 9 is considered, nine time channels are required. That is, when considering road-to-road communication and road-to-vehicle communication, if one first slot SL1 is simply assigned to one time channel, it is about twice as much as when only road-to-vehicle communication is considered. The first slot SL1 may be required.

  As a result, more first slots SL1 must be given to road-to-vehicle communication, which is communication with in-vehicle communication devices that are more numerous than roadside communication device 2, as described above. If allocation that considers both road-to-vehicle communication and road-to-road communication interference is adopted, many first slots SL1 must be assigned to the increased time channel to avoid road-to-road communication interference. Instead, many of the first slots SL1 are wasted.

  On the other hand, in this embodiment, even if the first slot SL1 for roadside communication interference avoidance is assigned by providing a first slot SL1 for road-to-road communication described later, Suppressing one slot SL1 from being wasted.

[Transmission control of roadside communication device 2]
The communication control device 25 of the roadside communication device 2 performs control for wirelessly transmitting road-to-vehicle communication data from the wireless communication unit 21 to the vehicle 5 (vehicle-mounted communication device 3) in the first slot SL1 allocated to the own device 2. Do.
That is, the communication control device 25 of each roadside communication device 2 controls to perform transmission using the plurality of first slots SL1 arranged in the radio frame.

For example, consider an arrangement model of the roadside communication device 2 as shown in FIG. In FIG. 5, 13 roadside communication devices 2 are arranged at intersections where the roads intersect each other so that the arrangement area has a diamond shape.
The intersection located in the center of this area is an important intersection that greatly affects traffic flow improvement and accident prevention, such as intersections where the main roads intersect, which has the highest traffic volume. For roadside communication devices 2 arranged at important intersections, in order to give more communication resources than roadside communication devices 2 arranged at other intersections, roadside communication devices 2 arranged at other intersections Whereas one first slot SL1 is allocated, two first slots SL1 are allocated to the roadside communication device 2 arranged at the important intersection.

In the road-to-vehicle communication of the arrangement model shown in FIG. 5, a plurality (13) of roadside communication devices 2 are grouped by the roadside communication device 2 to which a transmission period that can be used at the same time can be assigned. When divided into groups, it is assumed that the number of these first groups (= C _RV ), that is, the number of necessary time channels is five.
In this case, if five different transmission periods are prepared and assigned to each group, interference in road-to-vehicle communication can be avoided.

Further, in the road-to-road communication of the arrangement model, a plurality of (13) roadside communication devices 2 are grouped by the roadside communication device 2 that can be assigned a transmission period that can be used at the same time, and a plurality of groups (second When divided into groups, it is assumed that the number of these second groups (= C _RR ), that is, the number of necessary time channels is nine.
In this case, if nine different transmission periods are prepared and assigned to each group, interference in road-to-road communication can be avoided.

  FIG. 6 is a diagram illustrating an example of the overall configuration of a radio frame used in the communication system according to the present embodiment. The radio frame of the communication system according to the present embodiment has 16 frames according to “General Radio Industries Association,“ 700 MHz Band Intelligent Transport System ARIB-STD T109 Version 1.0 ””, which is a regulation relating to the roadside communication device 2. One slot SL1 is arranged.

In FIG. 6, the upper first radio frame is, for example, an even-numbered frame (even frame) among 10 radio frames (frame numbers: 0 to 9) generated per second as shown in FIG. The second radio frame is an odd-numbered frame (odd frame) among 10 radio frames (frame numbers: 0 to 9) generated in one second. Accordingly, the first radio frame and the second radio frame are alternately generated periodically.
The allocation of the first slot SL1 to each roadside communication device 2 in the first radio frame and the allocation of the first slot SL1 to each roadside communication device 2 in the second radio frame are a first slot for roadside communication described later. Common except for SL1.
The radio frame shown in FIG. 6 shows a case where the radio frame is applied to the arrangement model shown in FIG.

In FIG. 6, the radio frame is provided with a first slot SL1 (group) for road-to-vehicle communication and a first slot SL1 (group) for road-to-road communication. In this radio frame, six first slots SL1 (= S _RV ) are used for road-to-vehicle communication, and three first slots SL1 are used (= S _RR ) for road-to-road communication. Yes. The remaining seven first slots SL1 are unused.

  In the model shown in FIG. 5, as described above, the number of time channels required for road-to-vehicle communication is five. Therefore, when one first slot SL1 is allocated to these time channels, the first slot SL1 group for road-to-vehicle communication only needs to include at least five first slots SL1.

  In the model shown in FIG. 5, there is a roadside communication device 2 installed at an important intersection among a plurality of roadside communication devices 2. Two first slots SL1 are assigned to the roadside communication devices 2 arranged at the important intersections, and one first slot SL1 is assigned to the other roadside communication devices 2. Therefore, in the present embodiment, the first slot SL1 group for road-to-vehicle communication is composed of a total of six, which is the above-mentioned minimum number of five plus one for the roadside communication device 2 disposed at the important intersection. ing.

In the first slot SL1 group for road-to-vehicle communication, as shown in FIG. 6, two first slots SL1 with slot numbers i = 0 and 1 are assigned to roadside communication devices at important intersections.
A time channel Ch _RV 1 in road-to-vehicle communication is assigned to the two first slots SL1 of slot numbers i = 0 and 1, and the first slot SL1 for road-to-vehicle communication (slot number i = 2) is sequentially assigned. To 5) are assigned time channels Ch _RV 2 to 5 in road-to-vehicle communication.

Thus, a transmission period is assigned to each time channel Ch _RV 1 to 5 of road-to-vehicle communication. In other words, a transmission period is assigned to each of a plurality (five) of first groups grouped in road-to-vehicle communication.

Road-to-vehicle communication data generated by each roadside communication device 2 is arranged in each slot for road-to-vehicle communication.
The road-vehicle communication data includes static information and dynamic information.
Static information refers to information whose information content does not change in a short time, such as road alignment information indicating a road structure or the like, or restriction information indicating the content / period of traffic regulation.
The dynamic information refers to information whose information content can change from moment to moment, such as signal information indicating traffic signal information or sensor information indicating detection by the roadside sensor 6. In other words, the dynamic information is information whose information content varies with time as compared to static information.

The roadside communication device 2 installed at the important intersection assigns static information and dynamic information to each of the two assigned first slots SL1, and transmits both pieces of information for each first slot SL1. To do.
Other roadside communication devices 2 other than the roadside communication device 2 installed at the important intersection transmit both static information and dynamic information by using one assigned first slot SL1.

On the other hand, the first slot SL1 group for inter-road communication includes three first slots SL1 (slot numbers i = 6, 7, 8).
In the model shown in FIG. 5, as described above, the number of necessary time channels in the road-to-road communication is nine. Therefore, when one first slot SL1 is assigned to these time channels, the first slot SL1 group for inter-road communication only needs to include at least nine first slots SL1.

In the present embodiment, there are three first slots SL1 for inter-road communication in one radio frame. Therefore, one first slot SL1 cannot be assigned to each time channel.
Therefore, in the present embodiment, the first slot SL1 for road-to-road communication is configured to be shared by each time channel (a plurality of second groups).
In the present embodiment, two first slots SL1 (slot numbers i = 7, 8) out of the three first slots SL1 constituting the slot for inter-road communication are divided into two sub slots. A slot SS is provided. If the first slot SL1 and the subslot SS are assigned to the time channel as transmission periods, five transmission periods that can be assigned to the time channel can be secured in one radio frame.

Further, using the first slot SL1 for road-to-road communication included in the first radio frame and the first slot SL1 for road-to-road communication included in the second radio frame, the nine roads The transmission period is set to be assigned to each communication time channel.
In this case, the transmission period of the time channel of the road-to-road communication is allocated in a distributed manner to each of the first and second radio frames.
In other words, six first slot SL1 for inter-road communication included in each of two adjacent radio frames are used as one unit, and the transmission period of nine time-channel communication time channels for each unit. Assign.
Thereby, the transmission period of the time channel of the road-to-road communication is assigned over each of two adjacently arranged radio frames.

By setting in this way, since each of the first and second radio frames includes five transmission periods, a total of ten transmission periods that can be allocated to the time channel for inter-road communication are secured. can do.
Thus, in the present embodiment, by sharing the first slot SL1 for road-to-road communication, a transmission period corresponding to the number of time channels for road-to-road communication is secured.

In FIG. 6, the time channel Ch _RR 1 in the road-to-road communication is assigned to the first slot SL1 with the slot number i = 6 of the first radio frame. Time channels Ch _RR 2 to 5 in the inter-road communication are allocated to the subslots SS included in the first slots SL1 of the first radio frame with the slot numbers i = 7 and 8, respectively.
In addition, the time channel Ch _RR 6 in the road-to-road communication is assigned to the first slot SL1 with the slot number i = 6 of the second radio frame. The time channels Ch _RR 7 to 9 in the inter-road communication are assigned to the subslots SS included in the first slots SL1 of the slot numbers i = 7 and 8 of the second radio frame. A time channel is not assigned to one of the two subslots SS included in the first slot SL1 with the slot number i = 8 of the second radio frame.

Thus, a transmission period is assigned to each time channel Ch _RR 1 to 9 of the inter-road communication. In other words, a transmission period is assigned to each of a plurality (9) of second groups grouped in the road-to-road communication.

  As described above, a transmission period is assigned to each of five time channels (a plurality of first groups) in road-to-vehicle communication and each of nine time channels (a plurality of second groups) in road-to-road communication. .

  FIG. 7 is a diagram illustrating the relationship between the first slot SL1 for road-to-road communication included in the first radio frame and the first slot SL1 for road-to-road communication included in the second radio frame. (A) in the figure shows a first slot SL1 (for example, the first slot SL1 with slot number i = 6) for road-to-road communication included in the first radio frame, and (b) in FIG. A first slot SL1 for roadside communication included in a radio frame (for example, a first slot SL1 with a slot number i = 6) is shown.

Since the length of one radio frame is 100 ms, the first radio frame and the second radio frame are switched at a cycle of 100 ms.
Therefore, as shown in the figure, the first slot SL1 for road-to-road communication included in both radio frames appears with a transmission period of 200 ms. The first slot SL1 of the first radio frame and the first slot SL1 of the second radio frame are shifted by 100 ms and have different transmission timings.

  Accordingly, each roadside communication device 2 can reliably obtain a transmission opportunity for roadside communication every 200 ms, so that roadside communication can be reliably performed when each roadside communication device 2 is necessary.

  Each roadside communication device 2 uses 1PPS to identify a frame number and transmit roadway communication data at the timing of the first slot SL1 for roadside communication assigned to each roadside communication device 2. Do.

In FIG. 7, each roadside communication device 2 synchronizes with each other by GPS synchronization using 1PPS, specifies the first radio frame and the second radio frame, and specifies the first slot SL1 for roadside communication. Although the case has been shown, the first radio frame and the second radio frame can be specified even in the case where synchronization is performed by road-to-road communication between the roadside communication devices 2, that is, synchronization by so-called air synchronization.
In this case, it is necessary to share the timing of a radio frame with a specific frame number between the roadside communication devices 2. For example, the roadside communication device 2 that recognizes the timing of the radio frame transmits A frame number of the current wireless frame can be stored in a packet header or the like and notified to another roadside communication device 2.
FIG. 8 is a diagram showing an extended area of the IVC-RVC layer of a transmission packet described in “General Electric Industries Association, 700 MHz Band Intelligent Transport System ARIB-STD T109 Version 1.0”. As shown in the figure, the frame number of the above-mentioned radio frame can be stored in the extension area of the IVC-RVC layer, and the timing of the frame number can be notified to the other roadside communication devices 2.
Further, the synchronization is not limited to GPS synchronization or air synchronization, and synchronization may be performed using a radio clock, or a synchronization signal that can specify a frame number of a radio frame may be transmitted from the central device 4.

  Thus, in this system, the first slot SL1 for road-to-road communication assigned to each roadside communication device 2 is included in the first radio frame and the second radio frame having different transmission timings, respectively. Is set.

  Here, in the case of the present embodiment, the transmission timing of the road-to-road communication by each roadside communication device 2 is every 200 ms, and therefore may be less than the communication resources allocated to the road-to-vehicle communication.

In this regard, road-to-vehicle communication generally requires more communication resources than road-to-road communication because communication is performed with in-vehicle communication devices 3 that exist more than roadside communication device 2.
The inventor conducted an experiment on this system, estimated the amount of transmission data per unit time actually required in road-to-vehicle communication and road-to-road communication, and compared the two.
As a result, it has been confirmed that the amount of transmission data per unit time required in road-to-road communication is sufficient if approximately half is secured as compared with road-to-vehicle communication.

In the present embodiment, based on the above comparison result, between the roads including a predetermined number (three in this embodiment) of the first slots SL1 so as to secure communication resources necessary for the road-to-road communication. A first slot SL1 group for communication is provided.
Therefore, even if the communication resource allocated to road-to-road communication is set to be smaller than the communication resource allocated to road-to-vehicle communication, it is allowed.

[Effect]
In the present embodiment, the radio frame includes a first slot SL1 for road-to-vehicle communication (time slot for road-to-vehicle communication) and a first slot SL1 for road-to-vehicle communication (time slot for road-to-road communication). Is provided.
Also, the number of the first group is included in C _RV (= the number of time channels in road-to-vehicle communication), the number of the second group is included in C _RR (= the number of time channels in road-to-road communication), and one radio frame. when the number of the first slot SL1 for roadside-vehicle communication and the number of S _{RV, 1} one first slot SL1 of road-road communication, which is included in the radio frame and the S _RR, each of these numerical values, It is as follows.

C _RV = 5
C _RR = 9
S _RV = 6
S _RR = 3

Each of the above numerical values satisfies the following formulas (21) and (22).
C _RV <C _RR (21)
S _RV > S _RR (22)

According to the communication system having the above configuration, each roadside communication device 2 performs transmission satisfying the above equation (22) by sharing the first slot SL1 for roadside communication among a plurality of second groups. 25.
Therefore, even when the number C _RR of the second group is larger than the number C _RV of the first group, the first slot SL1 for inter-road communication is shared by the second group, so that it is included in the radio frame. The first slot SL1 for road-to-road communication is not set more than the first slot SL1 for road-to-vehicle communication. For this reason, in addition to avoiding interference in road-to-vehicle communication, even if slot allocation is performed in consideration of interference avoidance in road-to-road communication, it is possible to prevent the first slot SL1 from being wasted.

Further, each of the above numerical values satisfies the following formula (23).
(S _RV −C _RV ) + C _RR ≧ S _RV + S _RR (23)

(S _RV −C _RV ) on the left side of the above equation (23) indicates the difference between the number of first slots SL1 assigned to a plurality of first groups and the number of first groups. This is a positive value when there is a first group to which two or more time slots are allocated among the plurality of first groups. In other words, the number of overlapping first slots SL1 in the case where the first slot SL1 is allocated to one first group among a plurality of first groups is shown. In the case of the above embodiment, (S _RV −C _RV ) is “1”, corresponding to the fact that one extra first slot SL1 is allocated to the roadside communication device 2 arranged at the important intersection. Yes.

In addition, the number C _RR of the second group is the same as the number of groups (the number of required time channels) that can be divided when considering both road-to-vehicle communication and road-to-road communication interference. For this reason, the left side of the above equation (23) is the number of first slots SL1 required when (at least) road-to-vehicle communication is performed in consideration of interference between both road-to-vehicle communication and road-to-road communication.

Therefore, the left side of the above equation (23) indicates the number of time channels (both in both the plurality of first groups and the plurality of second groups when the interference of both road-to-vehicle communication and road-to-road communication is considered. The number of first slots SL1 required when road-to-vehicle communication is performed by assigning a time channel with a larger number of groups) is shown. On the other hand, the right side of the above equation (23) shows the number of first slots SL1 (S _RV ) required for performing road-to-vehicle communication and road-to-road communication, when interference of only road-to-vehicle communication is considered. The total value of the number (S _RR ) of the first slots SL1 required for performing is shown.

In other words, the above equation (23) is obtained when the number of first slots SL1 for road-to-vehicle communication (S _RV ) and the number of first slots SL1 for road-to-road communication that are necessary when considering interference only in road-to-vehicle communication. The total value of (S _RR ) is equal to or less than the number of first slots SL1 (left side of Expression (23)) required when performing road-to-vehicle communication at least in consideration of interference between both road-to-vehicle communication and road-to-road communication. It shows that it becomes.
By sharing the first slot SL1 for road-to-road communication in an environment that considers only interference of road-to-vehicle communication so as to satisfy the above equation (23), both road-to-vehicle communication and road-to-road communication can be performed. Compared to the case where both road-to-vehicle communication and road-to-road communication are performed in an environment that considers interference, the total number of first slots SL1 can be reduced to the same or less.
As a result, wasteful consumption of the first slot SL1 can be suppressed as compared to the case where the first slot SL1 is assigned in consideration of interference between both road-to-vehicle communication and road-to-road communication.

Further, in the present system, as described above, the transmission periods of the plurality of second groups are assigned to the time slots for inter-road communication included in each of a predetermined number of adjacently arranged radio frames. The transmission periods of the plurality of second groups are each distributed and assigned to the predetermined number of radio frames.
In this case, it is possible to assign a transmission period of a time channel for inter-road communication over each of two adjacently disposed radio frames. In addition, the first slots SL1 for road-to-road communication included in radio frames having different transmission timings have different transmission timings as radio frames even if the positions in the radio frame are the same. It can be assigned to the second group. For this reason, a transmission period can be allocated to a larger number of second groups.

Furthermore, in this system, of the three first slots SL1 constituting the slot for road-to-road communication, the sub-slot SS configured by dividing the first slot SL1 into two first slots SL1 is provided. include.
That is, if the communication amount in the inter-road communication is relatively small, the first slot SL1 for the inter-road communication can be divided and used.

  As described above, in the present embodiment, a plurality of subslots SS can be provided by time-sharing the first slot SL1 for road-to-road communication, and a time channel for road-to-road communication (a plurality of second groups ) Can be secured for more transmission periods.

[Other Embodiments]
The present invention is not limited to the above embodiment. In the above embodiment, the description has been made based on the arrangement model (FIG. 5) including the roadside communication device 2 arranged at the important intersection. For example, even if there is no important intersection in the same model, each numerical value described above is used. (C _RV , C _RR , S _RV , S _RR ) satisfies the above formulas (21), (22), and (23).

  FIG. 9 is a diagram illustrating an example of a radio frame when there is no important intersection. When there is no important intersection, each roadside communication device 2 is assigned one first slot SL1 as a time channel for road-to-vehicle communication, so the first slot SL1 group for road-to-vehicle communication is It includes five 1-slot SL1s.

  Therefore, the numerical values in this case are as follows.

C _RV = 5
C _RR = 9
S _RV = 5
S _RR = 3

Each numerical value satisfies the above equations (21), (22), and (23).
Therefore, even when there is no important intersection, it is possible to obtain the effect of suppressing the first slot SL1 from being wasted as in the above embodiment.

Further, the radio frame shown in FIG. 9 shows a case where each of the three first slot SL1 for road-to-road communication includes three sub-slots SS.
In this case, each sub-slot SS can be used as a transmission period that can be assigned to a time channel (a plurality of second groups) for inter-road communication.
Therefore, as shown in FIG. 9, nine time channels Ch _RR 1 to 9 for communication between roads are assigned to each subslot SS.

  Thus, the first slot SL1 for road-to-road communication can be appropriately divided into a plurality of transmission periods (subslots SS) according to the number of time channels for road-to-road communication and the traffic.

  Moreover, although the case where it set so that all said each formula (21), (22), (23) was satisfy | filled was shown in the said embodiment, each said numerical value does not satisfy | fill formula (23). However, it is only necessary to satisfy both the formula (21) and the formula (22), and it is sufficient that both the formula (21) and the formula (23) are satisfied even if the formula (22) is not satisfied. .

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the meanings described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

2 roadside communication device 3 vehicle-mounted communication device 5 vehicle 20 antenna 21 wireless communication unit 23 control unit SL1 first slot (time slot)

Claims (9)

A communication system in which a plurality of roadside communication devices perform transmission using a plurality of time slots arranged in a radio frame,
The radio frame includes a time slot used for road-to-vehicle communication performed between the roadside communication device and the vehicle-mounted communication device, and a time used for roadside communication performed between the plurality of roadside communication devices. A slot is provided,
The plurality of roadside communication devices are divided into a plurality of first group groups in the road-to-vehicle communication, and are assigned so that transmission periods for simultaneous use by roadside communication devices in the same group are different for each of the plurality of first groups. In addition, the road-to-road communication is divided into a plurality of second group groups, and a transmission period for simultaneous use by roadside communication devices in the same group is assigned to be different for each of the plurality of second groups,
The number of the first group is C _RV ,
The number of the second group is C _RR ,
S _RV , the number of time slots for road-to-vehicle communication included in one radio frame,
The number of time slots for the inter-road communication included in one radio frame is set as S _RR ,
The C _RV and the C _RR satisfy the following formula (1),
The plurality of roadside communication devices include a control unit that performs transmission satisfying the following expression (2) by sharing the time slot for roadside communication among the plurality of second groups. Communications system.
C _RV <C _RR (1)
S _RV > S _RR (2) A communication system in which a plurality of roadside communication devices perform transmission using a plurality of time slots arranged in a radio frame,
The radio frame includes a time slot used for road-to-vehicle communication performed between the roadside communication device and the vehicle-mounted communication device, and a time used for roadside communication performed between the plurality of roadside communication devices. A slot is provided,
The plurality of roadside communication devices are divided into a plurality of first group groups in the road-to-vehicle communication, and are assigned so that transmission periods for simultaneous use by roadside communication devices in the same group are different for each of the plurality of first groups. In addition, the road-to-road communication is divided into a plurality of second group groups, and a transmission period for simultaneous use by roadside communication devices in the same group is assigned to be different for each of the plurality of second groups,
The number of the first group is C _RV ,
The number of the second group is C _RR ,
S _RV , the number of time slots for road-to-vehicle communication included in one radio frame,
The number of time slots for the inter-road communication included in one radio frame is set as S _RR ,
The C _RV and the C _RR satisfy the following formula (3),
The plurality of roadside communication devices include a control unit that performs transmission satisfying the following formula (4) by sharing the time slot for roadside communication among the plurality of second groups. Communications system.
C _RV <C _RR (3)
(S _RV −C _RV ) + C _RR ≧ S _RV + S _RR (4) The control unit allocates the transmission period of the plurality of second groups to the time slot for inter-road communication included in each of a predetermined number of radio frames arranged adjacent to each other,
The communication system according to claim 1 or 2, wherein the transmission periods of the plurality of second groups are respectively distributed and allocated to the predetermined number of radio frames.   The communication according to claim 1 or 2, wherein the control unit allocates a transmission period to each of the plurality of second groups by dividing and using the time slot for the inter-road communication included in the radio frame. system. The transmission data by the road-to-vehicle communication is data that requires a transmission frequency that needs to be transmitted for each radio frame,
5. The communication system according to claim 1, wherein the transmission data by the road-to-road communication is data having a lower transmission frequency than the transmission data by the road-to-vehicle communication. A transmission method for performing transmission using a plurality of time slots arranged in a radio frame,
The radio frame includes a time slot used for road-to-vehicle communication performed between a roadside communication device and an in-vehicle communication device, and a time slot used for roadside communication performed between the plurality of roadside communication devices. Is provided,
The plurality of roadside communication devices are divided into a plurality of first group groups in the road-to-vehicle communication, and are assigned so that transmission periods for simultaneous use by roadside communication devices in the same group are different for each of the plurality of first groups. In addition, the road-to-road communication is divided into a plurality of second group groups, and a transmission period for simultaneous use by roadside communication devices in the same group is assigned to be different for each of the plurality of second groups,
The number of the first group is C _RV ,
The number of the second group is C _RR ,
S _RV , the number of time slots for road-to-vehicle communication included in one radio frame,
The number of time slots for the inter-road communication included in one radio frame is set as S _RR ,
The C _RV and the C _RR satisfy the following formula (5),
A transmission method characterized by performing transmission satisfying the following formula (6) by sharing the time slot for roadside communication among the plurality of second groups.
C _RV <C _RR (5)
S _RV > S _RR (6) A computer program for causing a computer to execute transmission processing for performing transmission using a plurality of time slots arranged in a radio frame,
The radio frame includes a time slot used for road-to-vehicle communication performed between a roadside communication device and an in-vehicle communication device, and a time slot used for roadside communication performed between the plurality of roadside communication devices. Is provided,
The plurality of roadside communication devices are divided into a plurality of first group groups in the road-to-vehicle communication, and are assigned so that transmission periods for simultaneous use by roadside communication devices in the same group are different for each of the plurality of first groups. In addition, the road-to-road communication is divided into a plurality of second group groups, and a transmission period for simultaneous use by roadside communication devices in the same group is assigned to be different for each of the plurality of second groups,
The number of the first group is C _RV ,
The number of the second group is C _RR ,
S _RV , the number of time slots for road-to-vehicle communication included in one radio frame,
The number of time slots for the inter-road communication included in one radio frame is set as S _RR ,
The C _RV and the C _RR satisfy the following formula (7),
A computer program that causes a computer to execute transmission processing that performs transmission satisfying the following formula (8) by sharing the time slot for roadside communication among the plurality of second groups.
C _RV <C _RR (7)
S _RV > S _RR (8) A transmission method for performing transmission using a plurality of time slots arranged in a radio frame,
The radio frame includes a time slot used for road-to-vehicle communication performed between a roadside communication device and an in-vehicle communication device, and a time slot used for roadside communication performed between the plurality of roadside communication devices. Is provided,
The plurality of roadside communication devices are divided into a plurality of first group groups in the road-to-vehicle communication, and are assigned so that transmission periods for simultaneous use by roadside communication devices in the same group are different for each of the plurality of first groups. In addition, the road-to-road communication is divided into a plurality of second group groups, and a transmission period for simultaneous use by roadside communication devices in the same group is assigned to be different for each of the plurality of second groups,
The number of the first group is C _RV ,
The number of the second group is C _RR ,
S _RV , the number of time slots for road-to-vehicle communication included in one radio frame,
The number of time slots for the inter-road communication included in one radio frame is set as S _RR ,
The C _RV and the C _RR satisfy the following formula (9),
A transmission method characterized by performing transmission satisfying the following formula (10) by sharing the time slot for inter-road communication among the plurality of second groups.
C _RV <C _RR (9)
(S _RV −C _RV ) + C _RR ≧ S _RV + S _RR (10) A computer program for causing a computer to execute transmission processing for performing transmission using a plurality of time slots arranged in a radio frame,
The radio frame includes a time slot used for road-to-vehicle communication performed between a roadside communication device and an in-vehicle communication device, and a time slot used for roadside communication performed between the plurality of roadside communication devices. Is provided,
The plurality of roadside communication devices are divided into a plurality of first group groups in the road-to-vehicle communication, and are assigned so that transmission periods for simultaneous use by roadside communication devices in the same group are different for each of the plurality of first groups. In addition, the road-to-road communication is divided into a plurality of second group groups, and a transmission period for simultaneous use by roadside communication devices in the same group is assigned to be different for each of the plurality of second groups,
The number of the first group is C _RV ,
The number of the second group is C _RR ,
S _RV , the number of time slots for road-to-vehicle communication included in one radio frame,
The number of time slots for the inter-road communication included in one radio frame is set as S _RR ,
And the C _RV and the C _RR satisfy the following formula (11),
A computer program that causes a computer to execute transmission processing that performs transmission satisfying the following formula (12) by sharing the time slot for road-to-road communication among the plurality of second groups.
C _RV <C _RR (11)
(S _RV −C _RV ) + C _RR ≧ S _RV + S _RR (12)

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