JP2008283580A - Communication system and road-side communication system, and road-side communication device, light beacon and on-board communication device for use in them - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a communication system for increasing the probability that an on-board communication device can transmit data to a road-side communication device or another on-board communication device by avoiding the occurrence of collision in an area where the road-side communication device which transmits communication data according to a reservation scheme is installed. <P>SOLUTION: The communication system includes: the on-board communication device mounted in a vehicle; the road-side communication device which is installed near a road and performs, with the on-board communication device, radio communication according to a reservation method in which a communication time slot, in time division multiple access, is assigned beforehand so as not to compete with another device in a predetermined area on the road; and a light beacon which is installed on the road and performs optical communication with the on-board communication device at a spot corresponding to approximately the boundary of the predetermined area. The on-board communication device starts or stops the radio communication according to the reservation scheme in accordance with the optical communication performed with the light beacon. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a communication system for realizing an intelligent transport system (ITS).

  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 a system is mainly realized by a roadside communication device as an infrastructure side communication device and an in-vehicle communication device which is a communication device mounted on each vehicle. As a combination of communication, there are road-to-road communication between roadside communication devices, road-to-vehicle (or roadway) communication between roadside communication devices and vehicle-mounted communication devices, and vehicle-to-vehicle communication between vehicle-mounted communication devices. .

  In general, when a plurality of devices use the same frequency band at the same time in wireless communication, frequency division multiple access (FDMA) that communicates at different frequencies, or time division multiple that divides time into multiple time slots. Access (TDMA: Time Division Multiple Access) or the like can be used. There are also access methods that combine these.

  Among these access methods, in time division multiple access, there are a contention method in which transmission data collision may occur and a non-contention method in which transmission data collision is reliably avoided. The non-contention method includes a polling method and a reservation method. In order to prevent simultaneous transmission of transmission data in the same space, a time slot for wireless communication is exclusively assigned and the time Communicate using slots.

  In this non-contention method, in the polling method, after the sequential inquiry about whether the central device has transmission data to other devices in advance, the transmission data is set so that the device with the transmission data does not compete. Are sent sequentially. In this case, since the prior inquiry is required instead of reliably avoiding the collision of transmission data, the overhead in communication is very large.

  On the other hand, the reservation method is a method in which different unique time slots are assigned to all devices that are likely to communicate wirelessly and data is transmitted only in the slots. Once a time slot is assigned to all devices, data can be transmitted immediately at the timing of the assigned slot.

  In the contention method, transmission data may be transmitted at the same time in the same space. In such a case, the data is lost due to collision, and the data is resent in some way. Although it is necessary to prepare a method, it can be said that this method is suitable for a communication system in which the number of apparatuses that perform wireless communication is relatively small.

  Here, this contention method determines whether or not there is another device that is currently transmitting data by detecting the presence or absence of a carrier signal transmitted from another device before performing data transmission. (Hereinafter, this determination is referred to as carrier sense), regardless of whether other devices are performing data transmission, and an access method with carrier sense that starts data transmission only when it can be determined that it does not exist. It can be roughly divided into an access method without carrier sense for starting data transmission.

  As an access method with carrier sense, for example, CSMA (Carrier Sense Multiple Access), CSMA / CA (Carrier Sense Multiple Access / Collision Availidance), ISMA (Idle Signal Multiple SCT). As an access method without carrier sense, there are methods such as Pure ALOHA and Slotted ALOHA.

  The access method with carrier sense has an advantage that the probability of occurrence of collision is lowered and the certainty of arrival of data is improved because data transmission is started avoiding the timing at which other devices perform data transmission. However, since carrier sense is performed every time before the start of data transmission, there is a problem that overhead occurs and real-time performance is lowered.

  One access method without carrier sense performs data transmission regardless of other devices, so the overhead is smaller than the access method with carrier sense, but when data transmission is performed at the same timing as other devices Since the data is lost due to the occurrence of the collision, there is a problem that the certainty of reaching the destination is lowered. For this reason, in the access method without carrier sense, a backup procedure such as data retransmission is indispensable.

Japanese Patent No. 2806801

  In order to effectively use the limited communication band of radio waves and reduce the number of communication devices to be provided in roadside communication devices and in-vehicle communication devices as much as possible, between roads, between roads, between roads, and It is desirable to use the same communication band and communication procedure for wireless communication between vehicles, but in this case, road-to-vehicle communication and vehicle-to-vehicle communication may be performed simultaneously in the same space. It is better to perform some kind of communication control.

Since the roadside communication device is fixed in position, even when a plurality of roadside communication devices transmit data to each other, two or more roadside communication devices do not transmit data to the same space at the same time. Thus, the data transmission timing can be set differently. In other words, a reservation method for statically assigning slots can be easily applied to inter-road communication between roadside communication devices. Also, in the case of road-to-vehicle communication in which data is transmitted from the roadside communication device to the in-vehicle communication device, if the communication is broadcast-type communication in which the same data is transmitted to an unspecified number of in-vehicle communication devices, the same A reservation method can be adopted.
However, it is virtually impossible to statically set the transmission timing in advance as exclusive between all the in-vehicle communication devices that may communicate.

For this reason, when the in-vehicle communication device transmits communication data, an access method with carrier sense such as CSMA is used, and when the roadside communication device transmits communication data, a reservation method is adopted. It is done.
This method is effective because the number of in-vehicle communication devices is relatively small and vehicle-to-vehicle communication is considered to be successful with a very high probability in suburbs where roadside communication devices are not installed.

  However, if the in-vehicle communication device wants to reliably transmit data to the roadside communication device within a limited communication area, the overhead due to carrier sense impairs the real-time nature of communication and stays in that communication area. Data transmission may not be completed within a limited period of time. In particular, in urban areas where there is a lot of traffic, a large number of in-vehicle communication devices transmit data at random, which increases the probability that data cannot be transmitted. This is more noticeable when the carrier sense-less access method is adopted. Collision chains occur when a lot of in-vehicle communication devices repeat data re-transmission processing to back up data loss due to collision. There arises a problem that the throughput decreases at a stretch.

  If it is desirable to reliably avoid such collisions, it is desirable to use the non-contention method even when the in-vehicle communication device transmits data, but the overhead is too large for the polling method among the non-contention methods. Therefore, it is difficult to apply to mobile communication with a limited communication time.

Here, the present inventors pay attention to the fact that when the communication area of the roadside communication device is limited, the in-vehicle communication device that can transmit data to the specific roadside communication device is constantly changing dynamically. did.
In other words, even if the reservation method is adopted when the in-vehicle communication device transmits data, a slot is statically assigned to all the in-vehicle communication devices that may transmit data to a specific roadside communication device. It has been found that there is no need to assign, and it is only necessary that the data transmission slots of the in-vehicle communication devices existing in the road-to-vehicle communication area at that time be exclusively assigned.

  Therefore, the present invention avoids the occurrence of collision in an area where the in-vehicle communication device is installed with a roadside communication device that transmits communication data by a reservation method, and transmits data to the roadside communication device and other in-vehicle communication devices. An object of the present invention is to provide a communication system that increases the probability of transmission.

  The present invention relates to a time-division multiple access in a predetermined area on the road between an in-vehicle communication device mounted on a vehicle traveling on a road and the in-vehicle communication device installed near the road. A roadside communication device that performs wireless communication by a reservation method that is assigned in advance so that a communication time slot does not compete with other devices, and the vehicle-mounted vehicle at a location that is installed on the road and corresponds to the approximate boundary of the predetermined area A communication system including an optical beacon that performs optical communication with a communication device, wherein the in-vehicle communication device starts wireless communication by a reservation method according to optical communication performed with the optical beacon or It has the wireless communication means to stop, It is characterized by the above-mentioned.

  According to the present invention, it is possible to grasp that an in-vehicle communication device has entered or exited the communication area of a roadside communication apparatus that performs wireless communication by optical communication with an optical beacon, so communication using a reservation method is started. Or the timing which should be stopped can be made accurate. Since the optical beacon can set the optical communication area in a narrow range, the optical beacon is suitable for making the in-vehicle communication apparatus know where the boundary of the communication area of the roadside communication apparatus is.

  Further, in the communication system, the wireless communication means is a point corresponding to an approximate boundary of the predetermined area, and an entrance optical beacon installed on a lane in a direction of entering the predetermined area. An exit light beacon installed on a lane in a direction corresponding to an approximate boundary of the predetermined area and exiting from the predetermined area, starting wireless communication by a reservation method at the time of performing optical communication; Wireless communication using the reservation method can be stopped at the time when optical communication is performed between the two.

  By installing optical beacons at both the entrance and exit of the communication area of the roadside communication device, it becomes possible to accurately grasp that the vehicle has entered the communication area of the roadside communication device and has left the communication area. .

Further, in the communication system, the wireless communication means is a point corresponding to an approximate boundary of the predetermined area, and an entrance optical beacon installed on a lane in a direction of entering the predetermined area. Wireless communication by the reservation method may be started when optical communication is performed, and wireless communication by the reservation method may be stopped when at least one of the following applies.
(1) When the elapsed time from the start time exceeds a predetermined first threshold (2) When the travel distance from the start time exceeds a predetermined second threshold (3) After the start time When the elapsed time from the last data reception from the roadside transmitter exceeds the predetermined third threshold

  In this case, once the entrance light beacon has accurately grasped that the vehicle has entered the communication area of the roadside communication device, the exit light can be determined based on the elapsed time from that point, the travel distance, or the record of communication with the roadside communication device. Even if a beacon is not installed, it is advantageous in that it can be grasped that the roadside communication device has left the communication area.

  Further, in the communication system, when the wireless communication means has started the wireless communication by the reservation method, the wireless communication means performs the wireless communication by the reservation method even with an in-vehicle communication device mounted on another vehicle, When wireless communication using the reservation method is stopped, communication time slots may compete with other devices in time-division multiple access with in-vehicle communication devices installed in other vehicles. Communication using a contention method may be performed.

  In the communication area of the roadside communication device, since the in-vehicle communication device cannot transmit communication data during the time zone in which the roadside communication device transmits communication data, the time zone in which the in-vehicle communication devices can communicate with each other is limited. Therefore, communication efficiency can also be improved by avoiding competition by a reservation method for communication methods between in-vehicle communication devices. On the other hand, when it is not necessary to communicate with the roadside communication device, the time zone in which the in-vehicle communication devices can communicate with each other is not necessarily limited, and therefore the contention method can be adopted.

  Further, in the communication system, when the wireless communication means stops wireless communication by the reservation method with the roadside communication device, the vehicle-mounted communication device notification means for notifying the roadside communication device of the stoppage. You may make it have.

  Once the time slot assigned for the in-vehicle communication device by the reservation method remains assigned until the in-vehicle communication device leaves the communication area of the roadside communication device, for example, it remains in the communication area. If it is no longer necessary to transmit communication data, the in-vehicle communication device may stop the wireless communication by the reservation method at that time, and in this case, immediately notifies the roadside communication device to that effect. As a result, the time slot can be assigned to another in-vehicle communication device, and the use efficiency of the time slot can be increased.

  Moreover, in the communication system, the roadside communication device can perform wireless communication by a reservation method with another roadside communication device in the vicinity.

  If the roadside communication device can communicate with other roadside communication devices in the vicinity, the communication band can be used more efficiently by adopting the reservation method for the roadside communication. It becomes.

  Further, in the communication system, the optical beacon or the roadside communication device communicates with the in-vehicle communication device that starts wireless communication with the roadside communication device according to the optical communication according to the reservation method. There may be provided time slot notifying means for notifying time slot information related to the time slot used in the communication, and the wireless communication means of the in-vehicle communication device may transmit data to the outside based on the time slot information.

  By notifying the information on the available time slots to the in-vehicle communication device that the optical beacon or the roadside communication device enters the communication area, it becomes possible to dynamically assign the time slots according to the demand. The time slot information refers to information for the in-vehicle communication device to know the time slot that can be used by itself, and may be a combination of the start time and end time of the usable time slot. It may be an identification number.

  In the communication system, the time slot information includes a combination of vehicle ID information assigned to the in-vehicle communication device and a time slot according to the vehicle ID information. The communication means may transmit data to the outside using a time slot corresponding to the vehicle ID information assigned to itself included in the notified time slot information.

  Since the time slot information may be received simultaneously by a plurality of in-vehicle communication devices, each in-vehicle communication device itself can be associated by associating the vehicle ID information unique to the in-vehicle communication device with an available time slot. It is possible to accurately grasp which time slot can be used. The vehicle ID information refers to a unique character string or numerical value string assigned to each in-vehicle communication device. For example, vehicle ID information generally used with optical beacons can be used. .

  Further, in the communication system, the time slot notification means prepares a plurality of time slots to be assigned to the in-vehicle communication device, and starts in-vehicle communication with the roadside communication device in accordance with the optical communication in accordance with the reservation method. An empty time slot that is not assigned to another in-vehicle communication device among the prepared time slots may be assigned to the device.

  By preparing a plurality of time slots, a plurality of in-vehicle communication devices can communicate within the communication area of the roadside communication device. In addition, for in-vehicle communication devices that newly enter the communication area, an empty time slot that has not yet been assigned to any in-vehicle communication device is assigned, so communication conflicts with other in-vehicle communication devices can be reliably avoided. It becomes possible to do.

Further, in the communication system, the time slot notification means determines that the assigned time slot is an empty time slot when the in-vehicle communication device to which the time slot is assigned can be determined to be in a state corresponding to at least one of the following: You may make it.
(1) A state in which the in-vehicle communication device to which the time slot is assigned has stopped wireless communication by the reservation method. (2) A state in which the in-vehicle communication device to which the time slot is assigned has left the predetermined area.

  Further, in the communication system, the time slot notification means may be configured such that an exit light beacon installed on a lane in a direction corresponding to a substantially boundary of the predetermined area and exiting from the predetermined area is the time. When optical communication is performed with an in-vehicle communication device to which a slot is assigned, the assigned time slot may be an empty time slot.

  Further, in the communication system, the time slot notifying unit is configured such that an entrance optical beacon installed on a lane in a direction corresponding to the approximate boundary of the predetermined area and entering the predetermined area is the time slot. When the elapsed time from the time when optical communication is performed with the in-vehicle communication device to which the slot is assigned exceeds a predetermined fourth threshold, the assigned time slot may be set as an empty time slot. .

  Further, in the communication system, the time slot notifying means is assigned when the elapsed time from the last data reception from the in-vehicle communication device to which the time slot is assigned exceeds a predetermined fifth threshold value. The time slot may be an empty time slot.

  According to these methods, a time slot once allocated can be made an empty time slot at an appropriate time. As a result, it is possible to efficiently use the communication band by eliminating the waste of time slot allocation after the time point when the time slot allocation is no longer necessary.

  In the communication system, the contention method may be a CSMA method or a slotted aloha method.

  On the other hand, the roadside communication system of the present invention is installed in the vicinity of a road so that a communication time slot does not compete with other devices in time-division multiple access in a predetermined area on the road with an in-vehicle communication device. An optical beacon that performs optical communication between a roadside communication device that performs wireless communication by a reservation method assigned in advance to the vehicle and the vehicle-mounted communication device that is installed on the road and corresponds to a substantially boundary of the predetermined region The optical beacon includes optical beacon notification means for notifying the start and stop of wireless communication by the reservation method with the roadside communication device during optical communication with the in-vehicle communication device. It is characterized by having.

  According to the present invention, for an in-vehicle communication device that enters or leaves a communication area of a roadside communication device that performs wireless communication, an optical beacon accurately determines when to start or stop communication in a reservation method. Notification can be made. Since the optical communication area of the optical beacon is limited to a narrow range, it can be set at the boundary of the communication area of the roadside communication device, and thus is suitable as a means for notifying the in-vehicle communication device.

  Further, in the roadside communication system, the optical beacon or the roadside communication device is configured to wirelessly use the reservation method with respect to an in-vehicle communication device that starts wireless communication with the roadside communication device according to the optical communication. You may make it have a time slot notification means which notifies the time slot information regarding the time slot used in communication.

  Moreover, the roadside communication apparatus, optical beacon, and in-vehicle communication apparatus of the present invention are used in any one of the communication system and the roadside communication system.

  According to the communication system of the present invention, in a region where a roadside communication device that transmits communication data by a reservation method is installed, occurrence of collision is avoided, and data is transmitted to the roadside communication device and other in-vehicle communication devices. Probability can be increased.

  FIG. 1 is a diagram showing a configuration of a communication system according to an embodiment of the present invention as an example of an intelligent road traffic system. The communication system is connected to the traffic control center 1 and installed in a vehicle traveling on the road, and is installed in the vicinity of the road, and between the in-vehicle communication device 3 in a predetermined area on the road. A roadside communication device 2 that performs wireless communication by a reservation method that is assigned in advance so that a communication time slot does not compete with other devices in time division multiple access, and is installed on a road and approximately at a boundary of a predetermined area It is comprised by the optical beacon 4 which performs optical communication between the vehicle-mounted communication apparatuses 3 in the applicable point, and the circuit network which connects between them.

  In the circuit network, the traffic control center 1 and the roadside communication device 2 and the optical beacon 4 are connected by wire (also wireless), and the roadside communication devices 2 (between roads), the roadside communication device 2 and the vehicle-mounted Wireless communication is used between the communication devices 3 (between roads and vehicles / between vehicles) and between the vehicle-mounted communication devices 3 (between vehicles).

  The optical beacon 4 can communicate bidirectionally with the in-vehicle communication device 3 by optical communication using near infrared rays. The optical beacon 4 transmits a near-infrared light signal from one or a plurality of light emitters / receivers installed corresponding to each lane on the road toward a vehicle traveling on the road, and passes through the light transmitter / receiver area. Communication can be performed with the in-vehicle communication device 3 of the vehicle. The light emitting / receiving area of the optical beacon 4 is relatively narrow and spot-like. Therefore, one-to-one communication between the optical beacon 4 and the in-vehicle communication device 3 is possible. Such an optical beacon 4 is installed everywhere on the main trunk road (only one location is shown in FIG. 1).

  Here, the outline | summary of the optical communication performed between the optical beacon 4 and the vehicle-mounted communication apparatus 3 is as follows. The optical beacon 4 continuously transmits lane notification information and the like at a predetermined cycle. The in-vehicle communication device 3 receives the lane notification information when entering the area where optical communication is possible, and transmits uplink information including the vehicle ID information of the in-vehicle communication device 3 to the optical beacon 4 accordingly. When the optical beacon 4 receives the uplink information, the optical beacon 4 transmits information to the in-vehicle communication device 3 including information in which the lane number that received the uplink information and the vehicle ID information are associated with each other in the lane notification information. Thereby, the in-vehicle communication device 3 can also recognize the number of the lane in which the vehicle is traveling. The vehicle ID information indicates a character string or a numerical string uniquely assigned to the in-vehicle communication device or a combination thereof.

  In the communication system as described above, communication between roads, between roads, between roads, and between cars is performed by a time division multiplexing method within a limited frequency band. FIG. 2 shows an example of a frame configuration. One frame is constituted by roads, road vehicles, roadways, and time slots (hereinafter also simply referred to as slots) of vehicles.

  3A is an example of a data format transmitted from the in-vehicle communication device, and includes a header, reception quality, vehicle position, direction (traveling direction), speed, mode, and data. The header includes a preamble, the vehicle ID information, and the like. The reception quality is C / N (Carrier to Noise Ratio), RSSi (Receive Signal Strength Indication), etc. as seen from the in-vehicle communication device. The mode is information indicating whether the vehicle is in the infrastructure mode under the control of the roadside communication device or in the ad hoc mode of autonomous control. Here, the infrastructure mode is an example of a reservation method, and the ad hoc mode is an example of a contention method.

  FIG. 3B is an example of a data format that the roadside communication device 2 transmits to the in-vehicle communication device 3. Here, the service information stores information related to services currently being implemented by the roadside. For example, it is information that information for supporting safe driving is currently sent, current information or video information is provided to the driver. In addition, these include information such as which service is provided among a plurality of services and the quality level of the service (level according to the image transfer speed of video information, information resolution, etc.) Etc. may be included.

  The signal information is information relating to the current and future displays of one or more traffic lights installed in the vicinity of the roadside communication device. For example, the current signal color, the number of continuous seconds, the order of the signal color displayed in the future And the number of continuous seconds, and information on the type of signal control (information on whether or not the point sensitive control is implemented or whether or not the traffic signal controller has a distributed control processing function). The road shape information is information that defines details about the shape of the road in the vicinity where the roadside communication device is installed, such as information on the number of road lanes and gradient, the position of the stop line ahead, and the distance to the stop line, etc. It is included.

The other application data may store image information to be transmitted from the roadside communication device to the in-vehicle communication device, local area information, and the like.
In the road-to-road communication, information such as traffic volume at the vehicle detector and information related to the signal control plan, which should be exchanged between traffic signals, are transmitted and received in the same format.

  FIG. 4 is a block diagram showing the internal configuration of the roadside communication device 2, the in-vehicle communication device 3, and the optical beacon 4. The roadside communication device 2 includes a communication unit (transmission / reception unit) 21 connected to the antenna 20, a control unit 22 that performs control related to communication, and a storage unit 23 that stores necessary information.

  The in-vehicle communication device 3 includes a communication unit (transmission / reception unit) 31 connected to the antenna 30, a control unit 32 that performs control related to communication, a storage unit 33 that stores unique information such as an ID, and light beacon transmission / reception. Part 34. The optical beacon 4 includes one or a plurality of beacon heads 40 attached to a horizontal portion of a support frame 5 (FIG. 1) installed on a road, a light projecting / receiving unit 41 built in the head, and the vicinity thereof, for example, the support frame 5 And a control unit 42 attached to the vertical portion. The control unit 22 of the roadside communication device 2 and the control units 42 of the plurality of optical beacons 4 are connected to each other and also connected to the traffic control center 1 (FIG. 1).

FIG. 5 is a schematic diagram showing a state in plan view of a road in an urban area where roads intersect, for example, east, west, south, and north. The roadside communication device 2 and its antenna 20 are provided at the central intersection, thereby forming a bi-directional road-to-vehicle communication area A (hereinafter simply referred to as communication area A) in the east-west and north-south directions. Yes. The roadside communication device 2 can manage the communication timing of each in-vehicle communication device 3 existing in the communication area A.
The antenna 20 does not necessarily have directivity.

  Optical beacons are provided corresponding to the lanes (up and down) at the area end in the east-west direction and the area end in the north-south direction (may be near the end). Here, for simplification of explanation, it is assumed that a pair of entrance light beacon 4s (entrance of communication area A) and exit light beacon 4e (exit of communication area A) are provided for each road. Hereinafter, mode switching (infrastructure mode / ad hoc mode) using the entrance light beacon 4s and the exit light beacon 4e will be described.

First, the roadside communication device 2 prepares a sufficient number of slots that can be used by the in-vehicle communication device 3 of each vehicle even if there are many vehicles in the communication area A. Here, it is assumed that all available slots are empty.
FIG. 6 is a diagram illustrating an operation of a communication system that performs mode switching. When the vehicle X or Y (in-vehicle communication device 3) in FIG. 5 goes straight in the direction of the arrow and enters the light projecting / receiving area of the entrance light beacon 4s, communication between the entrance light beacon 4s and the in-vehicle communication device 3 is performed ( Steps S31 and S41). Through this communication, the entrance light beacon 4s detects the in-vehicle communication device 3, and the in-vehicle communication device 3 receives a notification that it has entered the communication area A from the entrance light beacon 4s.

  Thereby, the vehicle-mounted communication apparatus 3 performs mode switching from ad hoc mode to infrastructure mode (step S32). On the other hand, the entrance light beacon 4s communicates (wires) with the roadside communication device 2 (steps S21 and S42), and provides the roadside communication device 2 with information related to the in-vehicle communication device 3. On the other hand, the roadside communication device 2 notifies the in-vehicle communication device 3 of the identification number of one or more time slots assigned to the in-vehicle communication device 3 by using the entrance light beacon 4s as a notification means (step) S43). Thus, the in-vehicle communication device 3 knows the timing at which it can be transmitted in the infrastructure mode (step S33). The above processing is performed substantially instantaneously while the in-vehicle communication device 3 is in the light projecting / receiving area of the entrance light beacon 4s. Thereafter, the in-vehicle communication device 3 traveling in the communication area A can immediately communicate between the roads and between the vehicles using the assigned time slot (steps S34 and S22).

  Here, when notifying the slot to be assigned in step S43, the vehicle ID information of the in-vehicle communication device 3 included in the uplink information transmitted from the in-vehicle communication device 3 to the entrance light beacon 4s corresponds to the slot identification number and the like. It is preferable to create and transmit the attached time slot information. In particular, when a plurality of in-vehicle communication devices can receive time slot information, the in-vehicle communication device 3 can accurately know which time slot is allocated to itself.

  When assigning a plurality of time slots to one in-vehicle communication device 3, even if the in-vehicle communication device 3 is assigned as a time slot that can transmit data (a time slot that can be used for both inter-vehicle communication and inter-vehicle communication). The time slot dedicated to inter-vehicle communication and the time slot dedicated to inter-vehicle communication may be assigned respectively (b in FIG. 7). When the time slots used between the roadways and between the vehicles are separated, it is possible to easily recognize whether the device on the information receiving side is the information addressed to itself.

  Next, when the in-vehicle communication device 3 tries to leave the communication area A, it enters the light projecting / receiving area of the exit light beacon 4e (FIG. 5). Thereby, communication with the exit light beacon 4e and the vehicle-mounted communication apparatus 3 is performed (step S35, S45), the exit light beacon 4e detects the vehicle-mounted communication apparatus 3, and the vehicle-mounted communication apparatus 3 is a communication area from the exit light beacon 4e. Get notified that you have gone out (or are about to leave).

  Thereby, the vehicle-mounted communication apparatus 3 performs mode switching from infrastructure mode to ad hoc mode (step S36). On the other hand, the exit light beacon 4e communicates (wires) with the roadside communication device 2 (steps S23 and S46), and provides the roadside communication device 2 with information related to the in-vehicle communication device 3. On the other hand, the roadside communication device 2 cancels the slot assignment to the in-vehicle communication device 3 to make the slot empty.

  The mode switching process as described above is performed on the in-vehicle communication devices 3 of all the vehicles that have entered the communication area A. The roadside communication device 2 performs allocation so that slots do not compete each time a new in-vehicle communication device 3 enters. Further, the slot assigned to the in-vehicle communication device 3 that has left the communication area A can be assigned to another in-vehicle communication device 3 that enters the communication area A thereafter by releasing the assignment.

  As described above, the in-vehicle communication device 3 that moves together with the vehicle, based on the one-to-one communication with each of the optical beacons 4s and 4e, the time when the communication device A enters the communication area A and the communication area A. Since it is possible to accurately grasp the time of departure, switching between the ad hoc mode / infrastructure mode can be performed in a timely and reliable manner.

  Basically, it is possible to always perform the above processing, but in the event of entering or leaving the communication area A, the communication between the in-vehicle communication device 3 of the vehicle and the optical beacons 4s and 4e fails. When finished, the following exceptional processing may be performed.

  First, in order to enable mode switching to the infrastructure mode when the in-vehicle communication device 3 enters the communication area A without receiving a signal (in-area notification signal) from the entrance light beacon 4s. The vehicle-mounted communication device 3 may always use a method of measuring the radio wave intensity from the infrastructure side at the current location and switching to the infrastructure mode if the intensity is greater than a predetermined level.

When switching from the ad hoc mode to the infrastructure mode based on such determination, the in-vehicle communication device 3 transmits data requesting time slot allocation to the roadside communication device 2 by a method such as CSMA or Slotted Aloha. . In response to this request, the roadside communication device 2 assigns a time slot to the in-vehicle communication device 3 and notifies it.
In this case, what is assigned is a slot (empty slot) that is not assigned to another in-vehicle communication device or roadside communication device at the time of assignment (see a in FIG. 7). In addition, the transmission slot of the roadside communication apparatus 2 is used for transmission between roads or between road cars, and is assigned statically and semipermanently in principle. The transmission slot of the in-vehicle communication device 3 is used for transmission between vehicles or between roads, and in principle is dynamically assigned with a time limit from the road side.

  On the other hand, when the vehicle exits outside the communication area A without receiving the signal (out-of-area notification signal) from the exit light beacon 4e, or when the exit light beacon 4e is not installed in the first place. The mode may be switched when the elapsed time after entering the communication area A (after starting the reservation-type communication) becomes a predetermined time or longer (for example, 1 minute). Mode switching may be performed by providing a timeout value in the no-communication state. For example, the vehicle-mounted communication device 3 does not receive a signal from the exit light beacon 4e as a timeout when a predetermined time (for example, 10 seconds) elapses since the last time the information provision from the roadside communication device 2 is received. However, it is only necessary to automatically switch to the ad hoc mode. Moreover, when the geographical information regarding the boundary of the communication area A on the said map can be acquired with the information applicable to the road shape near a roadside communication apparatus and a detailed map, the said vehicle position and the acquired said Based on the information, it may be determined whether or not the own vehicle remains in the communication area A.

  In addition, the in-vehicle communication device 3 independently manages the travel distance after entering the communication area A, not the time (timeout value) as described above, and switches to the ad hoc mode when the travel distance reaches a predetermined value. You may do it. In this case, even when a traffic jam or an accident occurs in the communication area A, it is possible to almost accurately grasp the exit timing from the communication area A. Note that the exit timing from the communication area A may be captured in consideration of both time and travel distance.

In the above embodiment, both mode switching and slot allocation are basically performed by optical communication using an optical beacon. However, only mode switching and slot allocation are performed by optical communication using an optical beacon, and slot allocation is performed. Can also be performed by wireless communication from the roadside communication device 2.
In other words, optical communication using an optical beacon is used to inform the in-vehicle communication device side of entry into or out of communication area A, and actually notifies the in-vehicle communication device side of the slot identification number. With regard to the process of doing, another communication means such as wireless communication of the roadside communication device 2 may be used.
It is also possible to use GPS information instead of an optical beacon. However, at present, optical beacons have higher positional accuracy than GPS.

  When one roadside communication device 2 receives a notification from the in-vehicle communication device 3 to stop the wireless communication by the reservation method or to exit out of the communication area A, the in-vehicle communication device 3 at that time The time slot can be canceled. If the exit light beacon e is installed, the exit light beacon e may be canceled when it is confirmed that the uplink information including the vehicle ID information of the in-vehicle communication device 3 is received in the exit light beacon e. If the exit light beacon e is not installed, it may be canceled when communication using the time slot allocated to the in-vehicle communication device 3 is not performed for a predetermined time or longer. Further, a timeout time may be provided for the elapsed time after the time slot is allocated, and the time slot may be canceled when the timeout time has elapsed. These conditions can also be used in combination.

In addition, it is desirable that the information regarding the time slot dynamically allocated to the in-vehicle communication device 3 is shared with other roadside communication devices.
This is because the radio wave arrival area of the in-vehicle communication device that uses the time slot assigned by the roadside communication device is wider than usual and may reach the communication area of the adjacent roadside communication device. By sharing information between neighboring roadside communication devices, it is possible to prevent adjacent roadside communication devices from using time slots allocated to in-vehicle communication devices as much as possible, and further avoid communication conflicts. It will be a thing.

  Further, in the above embodiment, the explanation is made assuming that the vehicle travels straight through the intersection in FIG. 5, but also when turning at the intersection, the communication from the communication area A by the communication between the light beacon at the exit and the in-vehicle communication device is similarly performed. Exit can be detected. Since the roads in the city area are clearly divided into up and down, optical beacons can be placed at the entrance and exit regardless of whether going straight, turning right or turning left.

  In addition, after entering the communication area A, it may be possible that the vehicle enters a side road / small path other than the intersection and does not pass through the originally expected exit, but even in such a case, by using the above timeout value, etc. Operation without problems is possible.

  Further, in the above embodiment, the slot allocation is performed by the roadside communication device 2, but it is performed by the central control unit (for example, in the traffic control center 1) located above the roadside communication device 2 and the optical beacon 4. Also good.

  In this embodiment, the vehicle-mounted communication device 3 that has been switched to the infrastructure mode transmits data to the roadside communication device 2 (inter-vehicle communication) and data transmission to other vehicle-mounted communication devices in a time slot that is permitted to be used. (Vehicle-to-vehicle communication) is performed by the non-contention method, but only the vehicle-to-road communication may be performed by the non-contention method. You may make it use the time slot for vehicle-to-vehicle communication prepared in order to perform vehicle-to-vehicle communication. In this case, the vehicle-to-vehicle communication time slot may be configured so that each in-vehicle communication device competes and uses a so-called contention method (c in FIG. 7). In the case of this method, the time slot information notified to the in-vehicle communication device 3 includes the information on the time slot that the in-vehicle communication device 3 can use for inter-road communication, and the inter-vehicle communication that can be used in the contention method. Time slot information may be included.

In other words, the time slot related to transmission / reception of the roadside communication device is a non-contention method that reserves in advance so as not to compete, and for inter-vehicle communication, one or more slots that may compete may be prepared and configured. It is also possible to use a method of using the tension method. As described above, the time slots used in the non-contention method and the contention method in the communication area A can be divided and used in a mixed manner.
According to this method, in the case where the importance of inter-vehicle communication is low compared to the communication with the roadside communication device 2 or the case where the frequency of inter-vehicle communication is relatively small, time slots assigned between the roads are set. There is an advantage that more can be secured.

Alternatively, a method in which a part of the time slot for inter-road communication is a contention method may be used. For in-vehicle communication devices that have failed in optical communication with the entrance light beacon 4s when entering the communication area A, a roadside communication device is used by using a time slot for inter-road communication that is allowed to be used in this contention method. 2 may be directly requested to assign a non-contention time slot.
As described above, in addition to non-contention-type time slots, preliminarily mixing contention-type time slots improves system flexibility and flexibility, and executes exception handling Can be used.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined not by the above-mentioned meaning but by the scope of claims for patent, and is intended to include all modifications within the scope and meaning equivalent to the scope of claims for patent.

It is a figure which shows the structure of the communication system by one Embodiment of this invention. It is an example of a frame structure. It is an example of the data format transmitted from a vehicle-mounted communication apparatus, and an example of the data format which a roadside communication apparatus transmits to a vehicle-mounted communication apparatus. It is a block diagram which shows the internal structure of a roadside communication apparatus, a vehicle-mounted communication apparatus, and an optical beacon. It is the schematic which shows the state which planarly viewed the road of the urban area where the road crossed east, west, south, and north. It is a figure which shows operation | movement of the communication system which performs mode switching. It is a figure which shows the structural example of a time slot.

Explanation of symbols

2 Roadside communication device 3 Carside communication device 4 Optical beacon 4s Entrance light beacon 4e Exit light beacon A Roadside communication area

Claims (19)

An in-vehicle communication device mounted on a vehicle traveling on a road;
A reservation method that is installed in the vicinity of the road and is allocated in advance with the in-vehicle communication device in a predetermined area on the road so that a communication time slot does not compete with other devices in time division multiple access. A roadside communication device that performs wireless communication with
A communication system including an optical beacon installed on the road and performing optical communication with the in-vehicle communication device at a point corresponding to a substantially boundary of the predetermined region;
The in-vehicle communication device is
A communication system, comprising: wireless communication means for starting or stopping wireless communication according to a reservation method in accordance with optical communication performed with the optical beacon. The wireless communication means includes
Wireless communication by the reservation method is performed at the time when optical communication is performed with an entrance optical beacon installed on a lane in a direction that enters the predetermined area at a point corresponding to the approximate boundary of the predetermined area. Start,
Wireless communication by a reservation method is performed at the time when optical communication is performed with an exit light beacon installed on a lane in a direction corresponding to the boundary of the predetermined area and exiting from the predetermined area. The communication system according to claim 1, wherein the communication system is stopped. The wireless communication means includes
Wireless communication by the reservation method is performed at the time when optical communication is performed with an entrance optical beacon installed on a lane in a direction that enters the predetermined area at a point corresponding to the approximate boundary of the predetermined area. Start,
2. The communication system according to claim 1, wherein wireless communication according to the reservation method is stopped when at least one of the following applies.
(1) When the elapsed time from the start time exceeds a predetermined first threshold (2) When the travel distance from the start time exceeds a predetermined second threshold (3) After the start time When the elapsed time from the last data reception from the roadside transmitter exceeds the predetermined third threshold The wireless communication means includes
If you have started wireless communication with the reservation method, perform wireless communication with the reservation method even with in-vehicle communication devices mounted on other vehicles,
When wireless communication using the reservation method is stopped, communication time slots may compete with other devices in time-division multiple access with in-vehicle communication devices installed in other vehicles. The communication system according to any one of claims 1 to 3, wherein communication is performed by a contention method. The wireless communication means includes
The vehicle-mounted communication device notifying means for notifying the roadside communication device that the communication has been stopped when wireless communication by the reservation method with the roadside communication device is stopped. The communication system according to any one of the above. The communication system according to any one of claims 1 to 5, wherein the roadside communication device performs wireless communication by a reservation method with another roadside communication device in the vicinity. The optical beacon or the roadside communication device is
Time slot notifying means for notifying an in-vehicle communication device that starts wireless communication by the reservation method with the roadside communication device according to the optical communication, time slot information related to a time slot used in the wireless communication by the reservation method. Have
The communication system according to any one of claims 1 to 6, wherein the wireless communication means of the in-vehicle communication device transmits data to the outside based on the time slot information. The time slot information includes a combination of vehicle ID information assigned to the in-vehicle communication device and a time slot corresponding to the vehicle ID information,
The wireless communication means of the in-vehicle communication device is:
8. The communication system according to claim 7, wherein data is transmitted to the outside using a time slot corresponding to the vehicle ID information assigned to itself included in the notified time slot information. The time slot notification means includes:
Several time slots to be allocated to in-vehicle communication devices are prepared.
For the in-vehicle communication device that starts wireless communication with the roadside communication device in accordance with the optical communication, an available time slot that is not assigned to another in-vehicle communication device among the prepared time slots The communication system according to claim 7 or 8, wherein The time slot notification means includes:
10. The communication according to claim 9, wherein when it is determined that the in-vehicle communication device to which the time slot is assigned has become a state corresponding to at least one of the following, the assigned time slot is set as an empty time slot. system.
(1) A state in which the in-vehicle communication device to which the time slot is assigned has stopped wireless communication by the reservation method. (2) A state in which the in-vehicle communication device to which the time slot is assigned has left the predetermined area. The time slot notification means includes:
The exit light beacon installed on the lane in a direction corresponding to the approximate boundary of the predetermined area and exiting the predetermined area performs optical communication with the in-vehicle communication device to which the time slot is assigned. The communication system according to claim 9, wherein, when performed, the assigned time slot is an empty time slot. The time slot notification means includes:
Optical communication with an in-vehicle communication device to which an entrance optical beacon installed on a lane in a direction corresponding to the boundary of the predetermined area and entering the predetermined area is assigned the time slot. 10. The communication system according to claim 9, wherein when the elapsed time from the time of the execution exceeds a predetermined fourth threshold, the assigned time slot is set as an empty time slot. The time slot notification means includes:
When the elapsed time from the last data reception from the in-vehicle communication device to which the time slot is assigned exceeds a predetermined fifth threshold, the assigned time slot is set as an empty time slot. The communication system according to claim 9.   The communication system according to any one of claims 1 to 13, wherein the contention method is a CSMA method or a slotted aloha method. Wireless communication based on a reservation method that is installed in the vicinity of a road and is allocated in advance so that a communication time slot does not compete with other devices among time-division multiple access in a predetermined area on the road with an in-vehicle communication device A roadside communication device for performing
A roadside communication system including an optical beacon that is installed on the road and performs optical communication with the in-vehicle communication device at a point corresponding to a substantially boundary of the predetermined region,
The optical beacon is
A roadside communication system, comprising: an optical beacon notification means for notifying the start or stop of wireless communication by a reservation method with the roadside communication device during optical communication with the in-vehicle communication device. The optical beacon or the roadside communication device is
Time slot notifying means for notifying an in-vehicle communication device that starts wireless communication by the reservation method with the roadside communication device according to the optical communication, time slot information related to a time slot used in the wireless communication by the reservation method. The roadside communication system according to claim 15, comprising: a roadside communication system according to claim 15.   A roadside communication device used in any one of the communication system according to claim 1 and the roadside communication system according to claims 15 and 16.   An optical beacon used in any one of the communication system according to claim 1 and the roadside communication system according to claims 15 and 16.   An in-vehicle communication device, which is used in any one of the communication system according to claim 1 and the roadside communication system according to claims 15 and 16.

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