JP2004072268A - Inter-vehicle communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inter-vehicle communication system whereby a user can grasp the state of vehicles surrounding its own vehicle. <P>SOLUTION: A vehicle (A) is linked with vehicles a1 to a3 on adjacent lanes through CDMA communication (microwave communication). A vehicle (B) is linked with vehicles b1 to a4 on adjacent lanes through the CDMA communication (microwave communication). Information of its own vehicle and the utilization state of surrounding CDMA channels are basically communicated between CDMA links, and information obtained through the CDMA links is also transmitted between millimeter links in addition to the information of its own vehicle. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for performing communication between vehicles.
[0002]
[Prior art]
2. Description of the Related Art Research and development of inter-vehicle communication in which vehicles directly form a communication link to exchange driving information, road traffic information, and the like are being performed.
(1) Yokosuka Research Park (YRP)
The YRP is conducting research on limiting the communication range to the front and rear vehicles by utilizing the physical characteristics of sharp directivity of millimeter waves (60 GHz band) and oxygen attenuation. Attention is also paid to large-capacity transmission of images and the like.
[0003]
In the communication method studied here, communication is performed only with one vehicle at a time before and after the vehicle on the same lane. The maximum communication distance is 100 m to 150 m. Further, a method of performing communication by relaying (hopping) with a vehicle ahead or behind has been considered. It does not communicate with side and diagonal vehicles.
(2) Automotive Electronics Engineering Association (JSK)
In the inter-vehicle communication protocol (DOLPHINE) studied by JSK, a network is configured by CSMA / CA, assuming eight vehicles around the own vehicle as a communication range. The vehicle to be transmitted first confirms that no other vehicle is transmitting. If there is a transmitting vehicle, it waits, and then transmits if it can transmit. The communication cycle is 20 ms at the fastest.
[0004]
DOLPHINE includes microwave DOLPHINE (5.8 GHz band) and millimeter-wave DOLPHINE (60 GHz band). In microwave DOLPHINE, both transmission and reception take an omnidirectional communication mode. In the millimeter wave DOLPHINE, reception is configured as an omnidirectional type, and transmission is configured as an omnidirectional type using a plurality of antennas and scanning in a limited wireless zone.
[0005]
[Problems to be solved by the invention]
In the vehicle-to-vehicle communication using the millimeter wave (60 GHz band), the communication zone is limited due to the physical characteristics of the millimeter wave, so that a single unit (one antenna) cannot communicate with the side and oblique directions. Further, vehicle information of an adjacent lane required when changing lanes cannot be obtained. Therefore, the arrangement of a plurality of antennas and a scanning technique are required, and the system is considered to be expensive.
[0006]
In the inter-vehicle communication using microwaves (5.8 GHz band), the communication range cannot be limited accurately. In the case of the CSMA system, when the vehicle density increases, communication collisions increase stochastically and under the influence of hidden terminals, and the transmission success rate decreases. When the transmission success rate decreases, the real-time nature of information is applied.
[0007]
[Means for Solving the Problems]
An inter-vehicle communication method according to the present invention is a method for performing data communication between vehicles using a communication device mounted on each vehicle. In this inter-vehicle communication method, a link by microwave communication is formed between vehicles belonging to the first vehicle group. Further, a link by millimeter wave communication is formed between a first vehicle belonging to the first vehicle group and a second vehicle not belonging to the first vehicle group.
[0008]
Preferably, the second vehicle belongs to a second vehicle group. Then, a link by microwave communication is formed between vehicles belonging to the second vehicle group.
[0009]
Preferably, the microwave communication is CDMA communication.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
<Communication link form>
FIG. 1 shows a general form of a communication link formed in an inter-vehicle communication system according to an embodiment of the present invention. Here, it is assumed that nine vehicles A, a1 to a3, B, and b1 to b4 are traveling on a three-lane road, and attention is paid to the vehicles A and B. Vehicle A is linked to vehicles a1 to a3 in adjacent lanes by CDMA communication (microwave communication). Vehicle B is linked to vehicles b1 to b4 in adjacent lanes by CDMA communication (microwave communication). Vehicle A and vehicle B are linked by millimeter wave communication. The vehicles A, a1 to a3 constitute a vehicle group GR1, and the vehicles B, b1 to b4 constitute a vehicle group GR2. Basically, information of the own vehicle and the usage status of surrounding CDMA channels are exchanged between the CDMA links, and information obtained by the CDMA link is transmitted between the millimeter-wave links in addition to the information of the own vehicle.
[0011]
FIG. 2 shows an example of communication performed in the communication link configuration shown in FIG. The vehicle A receives vehicle data periodically transmitted from the vehicles a1 to a3 forming the CDMA link and updates CDMA link information (information obtained by the CDMA link). The vehicle A communicates with the vehicle B via the millimeter-wave link at appropriate time intervals, and obtains information on the vehicle B and information obtained by the vehicle B on the CDMA link. With these, the vehicle A can grasp the operation status of the vehicle in front, rear, left and right (front, rear, side, and oblique directions). The same applies to the vehicle B.
[0012]
<Participation procedure for CDMA link>
Next, a procedure in which a vehicle that does not form a CDMA link with another vehicle participates in the CDMA link will be described. Here, as shown in FIG. 3A, an example is shown in which a vehicle C that does not form a CDMA link with another vehicle participates in a CDMA link formed between vehicles A and a1 to a3. This will be explained. Hereinafter, description will be made with reference to FIG.
[0013]
When a millimeter-wave link is established between any one of the vehicles A and a1 to a3 (for example, the vehicle a2) and the vehicle C, the vehicle C obtains the usage status of the CDMA channel through the millimeter-wave link. (ST41, ST42). When the millimeter wave link has not been established with any of the vehicles A, a1 to a3, the vehicle C accesses any of the vehicles A, a1 to a3 (here, the vehicle a3) through the CDMA link access channel, and The usage status is obtained (ST41, ST43, ST44). The CDMA channel of the own vehicle (vehicle C) is selected from the available channels (unused channels) (ST45), the use channel is transmitted, and the registration status of the own vehicle (vehicle C) channel is determined by the CDMA channel of the communication partner. Confirmation (ST46 to ST48). FIG. 4A shows an example of a communication procedure when an access is made using an access channel, and FIG. 4B shows an example of a communication specification.
[0014]
<Relay of CDMA link>
Next, a process when an abnormality occurs in a normal communication link will be described. Here, as shown in FIG. 5A, a CDMA link A is formed between the vehicle A and the vehicles a1 to a3, and a CDMA link a3 is formed between the vehicle a3 and the vehicles A and a2. And Then, it is assumed that the vehicle a3 becomes unreceivable due to the large transmission power from the vehicle A with respect to the CDMA link a3. The relay process performed in such a case will be described with reference to FIG.
[0015]
The vehicle A can receive data from the vehicle a2. The vehicle a3 requests the vehicle A to relay the vehicle a2. In response to this request, the vehicle A transmits the data of the vehicle a2 currently held to the vehicle a3. The vehicle A transfers the data to the vehicle a3 each time it receives data from the vehicle a2 in the subsequent periodic transmission.
[0016]
<Hidden vehicle detection and handling>
Here, it is assumed that a CDMA link has been established between the vehicle A and the vehicles a1 to a3 and between the vehicle B and the vehicles b1 to b4 as shown in FIG. Further, it is assumed that a millimeter-wave link has been established between vehicle A and vehicle B, between vehicle C and vehicle b2, and between vehicle C and vehicle a2. In the inter-vehicle communication system according to this embodiment, a network is established according to the following rules.
-In the millimeter wave link, vehicle information is transmitted including the vehicle to which the vehicle is linked. -In the CDMA link, vehicle information transmits information of only the own vehicle except hopping and relaying.
The usage status of the CDMA channel transmits the CDMA channel of the vehicle to which the own vehicle is linked.
[0017]
The vehicle information maps and the CDMA channel tables of the vehicles A and B are as shown in FIGS. 6B and 6C. Vehicle information around the own vehicle can be determined by the millimeter wave link and the CDMA link.
[0018]
In FIG. 6A, the vehicle C that does not belong to the CDMA link of the vehicles A and B can visually recognize the driver but cannot directly recognize the information. Such a vehicle is defined as a hidden vehicle. Specifically, when the obtained vehicle information and the CDMA channel information shown in FIGS. 6B and 6C are compared, the presence of a vehicle not included in the vehicle information may be confirmed in the CDMA channel information. This is defined as a hidden vehicle. Taking the vehicle A as an example, when the vehicle information obtained on each link is compared with the CDMA channel information, the presence of the hidden vehicle C is noticed. In this case, the vehicle information of the vehicle C is obtained by relaying the vehicle a2 linked to the vehicle C. Specifically, information is transmitted according to the following procedure.
(1) The existence of a hidden vehicle is grasped by comparing the channel usage status of the CDMA link with the information actually owned.
(2) When a hidden vehicle is found, information is requested from a vehicle linked to the hidden vehicle. (3) When information is requested as a hidden vehicle, information is immediately transmitted to the request source.
(4) Thereafter, the information is transmitted each time the information on the hidden vehicle is updated.
[0019]
Referring to FIGS. 7A and 7B, the hidden vehicle C is linked to the vehicles a2 and b2 by millimeter waves. The vehicle A can recognize the presence of the hidden vehicle C by comparing the vehicle information obtained on each link with the channel information of the CDMA link. In this case, the vehicle A can request information on the vehicle a2 linked to the vehicle C via the CDMA link, and can obtain the vehicle information of the vehicle C from the vehicle a2. The vehicle A immediately transmits the vehicle information of the vehicle C via its own CDMA link. The same applies to the vehicle B.
[0020]
<Communication device>
FIG. 8A shows a configuration of a communication device mounted on each vehicle, and FIG. 8B shows an object model.
[0021]
The millimeter-wave link and the CDMA link are physically and systematically independent of each other and share data at a complex protocol (upper protocol) level. In the composite protocol, control is performed on data and settings of a millimeter-wave link and a CDMA link, a sensor system, and a monitor system. In addition, the obtained vehicle data is analyzed, and mapping, situation determination, and the like are performed. The millimeter-wave link mainly transmits vehicle information (information obtained by the CDMA link and the millimeter-wave link) to which the own vehicle is linked and the use status of surrounding CDMA channels. The CDMA link mainly transmits only the information of the own vehicle and the usage status of the surrounding CDMA channels. The operation status of vehicles around the own vehicle can be grasped from both link information, and mapping is performed.
[0022]
By transmitting code information of the vehicle to which the own vehicle is linked at the same time as communication as an aid to code allocation of the CDMA system, the use status of codes around the own vehicle can be understood, and collision between codes can be avoided.
[0023]
There is a vehicle (hidden vehicle) in which communication becomes impossible due to a near-far problem even if the vehicle is in a short distance from the own vehicle. This can be detected from the usage status of the CDMA channel. For hidden vehicles, vehicle information can be obtained indirectly over a CDMA link.
[0024]
<Millimeter wave link>
Inter-vehicle wireless communication using millimeter waves has the following features.
・ Since the directivity is sharp, it is suitable for linear communication such as vehicles in front and behind.
-The propagation attenuation is large and the communication distance is limited (up to 200 m, practically up to about 120 m).
-Since the carrier frequency is high, large-capacity communication is possible.
[0025]
FIG. 9A shows an object model of the millimeter wave link. The functions required for the millimeter wave link are described below.
(1) Communication system The following functions need to be incorporated.
・ Intermittent communication function of fixed period ・ Function to change communication period and communication speed according to the situation ・ Function to return ACK ・ Resend request function when packet fails due to noise or interference ・ Sending timing of desired station at the time of interference (2) Communication cycle The communication cycle and the contents of support / control are shown in FIG. 9B.
(3) Communication contents and own vehicle ID
・ Vehicle information of the own vehicle ・ CDMA link vehicle information ・ CDMA channel usage status ・ Emergency information
<CDMA link>
The features of the CDMA link are described below.
The radio frequency band is desirably the same as DSRC such as ETC, so that cost reduction can be expected. Therefore, a microwave band (5.8 GHz) is desirable.
-Asynchronous CDMA is adopted, and there is no complicated protocol.
-Basically transmit when you want to transmit at a fixed cycle, but do not transmit when a short-range vehicle is transmitting. This is because information of a short-range vehicle has higher importance. In the case of single-frequency omnidirectional communication, reception is not possible when the own station is in the transmission state.
-Since the communication area is limited to a short distance, communication with a long-distance vehicle is not required, and a transmission signal with a long-distance vehicle is canceled due to a distance problem.
[0027]
FIG. 10A shows an object model of the CDMA link. The functions required for the CDMA link are described below.
[0028]
Retransmission request: If there is an error in the received frame, request retransmission of data to the vehicle.
[0029]
Error determination: Manages the quality of each channel based on the error rate of the received frame or the packet success rate. If the quality is poor and an error occurs, request retransmission.
(2) Communication cycle The communication cycle and the contents of support and control are shown in FIG.
(3) Communication contents and own vehicle ID
・ Vehicle information ・ CDMA channel information ・ Other vehicle information (only when hidden vehicle information is requested)
[0030]
<Composite protocol>
The composite protocol has the function shown in FIG. 11A for each object and controls each object.
(1) Millimeter-wave link communication frame creation In the combined protocol, a millimeter-wave link communication frame is created. As described above, in the millimeter wave link, in addition to the information on the own vehicle, information on the vehicle forming the CDMA link with the own vehicle and information on the CDMA channel to which the own vehicle is linked are transmitted. A communication frame describing these pieces of information is created. FIG. 11B shows an example of a frame format.
(2) Millimeter Wave Link Priority Determination As shown in FIG. 11A, in a millimeter wave link, it is desirable to take a communication cycle corresponding to necessity and reliability in a steady state and an event (application) occurrence. In the multi-mode protocol, an appropriate communication cycle is determined and selected by grasping surrounding conditions.
(3) CDMA Link Communication Frame Creation In the combined protocol, a CDMA link communication frame is created. As described above, since the CDMA link transmits own vehicle information and CDMA channel information, this information is described at a minimum. FIG. 11C shows a frame format example.
(4) CDMA Link Priority Determination Like the millimeter-wave link, the CDMA link takes a communication cycle corresponding to necessity and reliability as shown in FIG. In the multi-mode protocol, an appropriate communication cycle is determined and selected by grasping surrounding conditions.
(5) Surrounding vehicle situation determination function (calculation function)
The surroundings of the information obtained by the millimeter wave link and the CDMA link are determined by calculation. Thus, the coping method of the own vehicle is determined, and a command is issued to the control system and the monitor system. FIG. 12 shows an example of the surrounding situation determination processing.
(6) CDMA channel selection In the CDMA system, reception is impossible unless the code of the communication partner is known, so that surrounding channel information is transmitted during communication to reduce code allocation. In other words, the system is capable of recognizing the use status of the surrounding codes if one surrounding vehicle can be received. The channel selection algorithm is as described in the above <Participation procedure for CDMA link>.
(7) Hidden Vehicle Detection In the CDMA link, it is anticipated that even a vehicle that is relatively close in the adjacent lane may have a vehicle (hidden vehicle) in which communication is impossible due to a perspective problem. However, this can be detected from the usage status of the CDMA channel, and the processing is performed by the hybrid protocol. The processing algorithm is as described in the above <Detection and handling of hidden vehicle>.
[0031]
<Effect>
According to the inter-vehicle communication system according to the embodiment of the present invention, the following effects can be obtained.
・ Adding a microwave link to side-to-side and diagonal vehicle-to-vehicle communication, and transmitting vehicle information obtained through the microwave link of the vehicle using the millimeter-wave link in the front-rear direction. The situation can be grasped.
・ It is not necessary to communicate with long-distance vehicles because information on short-distance vehicles is more important. Therefore, by employing asynchronous CDMA for the microwave link, the communication range can be systematically limited due to the near-far problem.
[0032]
【The invention's effect】
By transmitting the information obtained by the microwave communication using the millimeter wave communication, the situation of the surrounding vehicles centering on the own vehicle can be grasped. This enables two-dimensional vehicle control and driving support such as lane change.
[0033]
By using the CDMA system for microwave communication, interference in communication with surrounding vehicles can be reduced, and the communication range can be systematically limited to a narrow range.
[Brief description of the drawings]
FIG. 1 is a diagram showing a normal form of a communication link formed in an inter-vehicle communication system according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating an example of communication performed in the communication link mode illustrated in FIG. 1;
FIG. 3A is a diagram illustrating a vehicle arrangement situation when a vehicle that does not form a CDMA link with another vehicle participates in the CDMA link; (B) is a flowchart illustrating a procedure in which a vehicle that does not form a CDMA link with another vehicle participates in the CDMA link.
FIG. 4A is a diagram showing an example of a communication procedure when accessing using an access channel. FIG. 3B is a diagram illustrating an example of communication specifications when accessing using an access channel.
FIGS. 5A and 5B are diagrams for explaining processing when an abnormality occurs in a normal communication link, where FIG. 5A shows a vehicle arrangement and FIG. 5B shows a processing procedure;
6A and 6B are diagrams for explaining detection of a hidden vehicle, wherein FIG. 6A shows a vehicle arrangement, and FIGS. 6B and 6C show acquisition information of vehicles A and B.
FIGS. 7A and 7B are diagrams showing a procedure of information transmission with a hidden vehicle.
FIG. 8A is a block diagram illustrating a configuration of a communication device mounted on each vehicle. (B) shows the object model of the communication device shown in (a).
FIG. 9A shows an object model of a millimeter wave link. (B) shows the communication cycle and the contents of support and control in the millimeter wave link.
FIG. 10A shows an object model of a CDMA link. (B) shows the communication cycle and the contents of support and control in the CDMA link.
FIG. 11A shows a function of a composite protocol. (B) shows a frame format example of the millimeter wave link. (C) shows a frame format example of the CDMA link.
FIG. 12 is a diagram illustrating an example of a surrounding situation determination process.

Claims (3)

A method for performing data communication between vehicles using a communication device mounted on each vehicle,
Forming a link by microwave communication between vehicles belonging to the first vehicle group,
An inter-vehicle communication method comprising forming a link by millimeter-wave communication between a first vehicle belonging to the first vehicle group and a second vehicle not belonging to the first vehicle group. In claim 1,
The second vehicle belongs to a second vehicle group,
A vehicle-to-vehicle communication method comprising forming a link by microwave communication between vehicles belonging to the second vehicle group. In claim 1 or claim 2,
The inter-vehicle communication method, wherein the microwave communication is a CDMA communication.

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