JP2008233017A - Radio communication apparatus and road-vehicle communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio communication technology capable of detecting the arrival direction of a vehicle with a simple method. <P>SOLUTION: This radio communication apparatus for performing radio communication between it and on-vehicle terminal comprises a plurality of receiving antennas for receiving a known signal transmitted from the on-vehicle terminal, a position estimating means for estimating the azimuth of the on-vehicle terminal based on the phase difference of the known signal received by the plurality of receiving antennas, a travel direction estimating means for estimating whether the on-vehicle terminal approaches or separates from one's own device based on frequency transition of the known signal received by the plurality of receiving antennas, and a determining means for determining whether radio communication with the on-vehicle terminal is performed based on the estimation result by the position estimating means and travel direction estimating means. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a wireless communication technology, and more particularly to a wireless communication technology capable of detecting the direction of arrival of a vehicle.

  In recent years, a wireless communication device is mounted on a vehicle, and wireless communication is performed between vehicles or roads. An example of such wireless communication is a safe driving support system that notifies information related to an out-of-sight vehicle on a road with poor visibility such as an intersection or a curve. In such a system, information required by a certain vehicle is information about a vehicle that is facing the host vehicle. That is, depending on the traveling direction of the opponent vehicle, whether information about the vehicle is necessary or not changes. Therefore, if the traveling direction of another vehicle is known, unnecessary information need not be received and processed.

  Thus, in vehicle-to-vehicle communication and road-to-vehicle communication, each wireless communication device can communicate only with necessary terminals by grasping the positions and traveling directions of surrounding terminals. Thereby, the reliability of communication can be improved and unnecessary radio wave radiation can be reduced. Moreover, unnecessary radio wave radiation can be further suppressed by limiting the communication area on the transmission side using adaptive array technology.

Therefore, a technique has been proposed in which each terminal periodically transmits GPS position information, a terminal ID, a velocity vector, an acceleration vector, and the like to the surroundings. In Patent Literature 1, each vehicle transmits a traveling state obtained from a GPS or a vehicle speed sensor together with a terminal ID, so that traveling information of surrounding vehicles can be grasped.
JP 2000-348299 A

  However, in the technique described in Patent Document 1, each vehicle needs a GPS system and a vehicle speed sensor in order to acquire the traveling state of the vehicle. Moreover, since each vehicle transmits these information regularly, communication volume will increase. In particular, when a traffic jam occurs, the amount of communication becomes extremely large, and radio wave interference occurs, making communication difficult.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a wireless communication technique capable of detecting the arrival direction of a vehicle by a simple method.

  The present invention is characterized by using a plurality of receiving antennas to estimate the direction of the vehicle and whether the vehicle is approaching or moving away based on the phase difference or frequency shift of a known signal transmitted from the in-vehicle terminal. To do.

  A wireless communication device according to the present invention performs wireless communication with an in-vehicle terminal, and is received by a plurality of receiving antennas that receive known signals transmitted from the in-vehicle terminal and the plurality of receiving antennas. Based on the phase difference of the known signal, the position estimating means for estimating the azimuth of the in-vehicle terminal and the in-vehicle terminal based on the frequency shift of the known signal received by the plurality of receiving antennas. A traveling direction estimation unit that estimates whether the vehicle is approaching or moving away from the vehicle, and a determination that determines whether to perform wireless communication with the in-vehicle terminal based on estimation results by the position estimation unit and the traveling direction estimation unit Means.

  As described above, since the azimuth and traveling direction of the vehicle are estimated based on the phase differences and frequency shifts of known signals received by a plurality of receiving antennas, it is necessary to provide equipment such as a GPS device and a sensor on the vehicle side. Absent. In addition, since a short signal is sufficient for the known signal transmitted from the in-vehicle terminal, the amount of information to be transmitted can be reduced, and the use band and power consumption can be reduced.

  In the wireless communication apparatus according to the present invention, the receiving antenna is a directional antenna, and a configuration in which each has directivity in a different direction can be employed.

  In the wireless communication apparatus according to the present invention, the receiving antenna itself does not have directivity, but a shielding means for shielding radio waves is provided, and the receiving antenna is shielded from radio waves from a predetermined direction by the shielding means. Therefore, it is possible to employ a configuration in which each has directivity in different directions. More specifically, the shielding means is a polygonal columnar or columnar wave absorber, and a plurality of receiving antennas are arranged close to the wave absorber to block radio waves from a predetermined direction. Can be adopted.

  As described above, since the receiving antenna has directivity so as to receive radio waves from a predetermined direction, the rough direction of the vehicle can be estimated. And it is possible to estimate a more detailed azimuth based on the phase difference of the received signals at a plurality of receiving antennas.

  The wireless communication device according to the present invention is arranged at an intersection, the plurality of receiving antennas have directivity with respect to the road direction, and the determination means is used when the in-vehicle terminal approaches the device from a predetermined road direction. It is preferable to determine that wireless communication is performed with the in-vehicle terminal.

  According to such a configuration, it is possible to appropriately estimate the traveling direction of the vehicle at intersections where the vehicle passes in various directions, and to transmit information only to the necessary vehicle.

  The present invention can be understood as a wireless communication apparatus having at least a part of the above means. Moreover, this invention can also be grasped | ascertained as the road-vehicle communication system comprised from the said radio | wireless communication apparatus (roadside machine) and the said vehicle-mounted terminal. The present invention can also be understood as a wireless communication method including at least a part of the above processing or a program for realizing the method. Each of the above means and processes can be combined as much as possible to constitute the present invention.

  For example, a road-to-vehicle communication system as one aspect of the present invention is a road-to-vehicle communication system that performs wireless communication between a roadside device and a vehicle-mounted terminal, and the vehicle-mounted terminal has a transmission unit that transmits a known signal. The roadside device includes a plurality of reception antennas that receive the known signals, and a position estimation unit that estimates the azimuth of the in-vehicle terminal based on a phase difference between the known signals received by the plurality of reception antennas. A traveling direction estimating unit that estimates whether the in-vehicle terminal is approaching or moving away from the roadside device based on a frequency shift of the known signal received by the plurality of receiving antennas; and the position estimating unit And determining means for determining whether or not to perform wireless communication with the in-vehicle terminal based on the estimation result by the traveling direction estimating means.

  According to the present invention, it is possible to detect the arrival direction of a vehicle by a simple method.

  Preferred embodiments of the present invention will be exemplarily described in detail below with reference to the drawings.

<System configuration>
FIG. 1 is a diagram illustrating a system overview of a road-to-vehicle communication system according to the present embodiment. A roadside device 1 (corresponding to a wireless communication device in the present invention) set at an intersection provides information to a vehicle approaching the device from a predetermined road direction. In the present embodiment, the predetermined road direction is the left side in FIG. 1, and the service providing area 3 is in a range as shown.

  For example, when the information provided by the roadside device 1 is traffic light information in the right direction in the figure, the vehicle that needs this information is a vehicle that enters this intersection from the left side in the figure. Therefore, the service providing area 3 has a range as shown in the figure. In other words, whether or not a vehicle exists in the service providing area 3 can be determined by whether or not the vehicle approaches the roadside device 1 from the left side in the figure. And the roadside machine 1 performs radio | wireless communication with such a vehicle. In the example of FIG. 1, the roadside device 1 performs wireless communication with the vehicle A and does not perform wireless communication with the vehicles B and C.

<Configuration of roadside machine>
FIG. 2 is a diagram illustrating the configuration of the antenna portion of the roadside machine 1. The roadside machine 1 has four antennas ANT1-4. The four antennas ANT1 to ANT4 are arranged to form a square. The antennas ANT1 to ANT4 are omnidirectional antennas. However, each antenna ANT1-4 is arrange | positioned around the column-shaped electromagnetic wave absorber 3 which shields an electromagnetic wave, and does not receive the electromagnetic wave from the electromagnetic wave absorber 3 direction. Therefore, each has directivity with respect to a different direction.

  As shown in FIG. 1, the roadside machine 1 is provided at an intersection (crossroad). And each antenna ANT1-4 is prescribed | regulated by the electromagnetic wave absorber 3 so that the electromagnetic wave from each road direction may be received strongly. In other words, as a result of radio waves from a predetermined direction being shielded by the radio wave absorber 3, the antennas ANT1 to ANT4 each have a directivity with respect to the road direction.

  FIG. 3 is a diagram illustrating a functional configuration of the roadside machine 1. The roadside device 1 includes antennas ANT1 to ANT4, a combiner 11, an arrival direction estimation unit 12, a frequency detection unit 13, a communication control unit 14, and a communication data processing unit 15.

  The synthesizer 11 calculates complex weights (weighting coefficients) for controlling the amplitude and phase for the reception signals of the plurality of antennas ANT1 to ANT4, and synthesizes signals adjusted by these weights. As for the weight calculation method, for example, an intrinsic modulation signal (known signal) may be used, or a waveform periodically inserted into the transmission signal such as a guard interval may be used.

  The arrival direction estimation unit 12 estimates the position of the vehicle based on the received signal strength and the phase difference of the intrinsic modulation signal from the vehicle (on-vehicle terminal) received at each antenna. Details of the vehicle position estimation process performed by the arrival direction estimation unit 12 will be described later.

  The frequency detector 13 calculates the frequency shift amount of the intrinsic modulation signal received at each antenna. Based on this frequency shift amount, the communication control unit 14 can estimate whether the vehicle approaches or moves away from the own device, and further, the moving speed of the vehicle. Details of processing for detecting the frequency shift amount performed by the frequency detector 13 will also be described later.

The communication control unit 14 performs control related to the overall communication of the roadside device 1, and in particular, performs wireless communication with the vehicle based on the position and moving direction of the vehicle estimated from the arrival direction estimation unit 12 and the frequency detection unit 13. It is determined whether or not to perform. The communication data processing unit 15 processes received data.

  In addition, in FIG. 3, although only the function part which concerns on reception of the roadside machine 1 was demonstrated, the roadside machine 1 also has the function which concerns on transmission. However, the radio transmission function of the roadside device 1 may be specifically realized in any way. For example, there may be only one transmission antenna, and a plurality of transmission antennas may be provided so as to transmit radio waves only in the vehicle direction using adaptive array technology.

<Direction of arrival estimation processing>
The arrival direction estimation unit 12 estimates the position of the vehicle based on the intrinsic modulation signal transmitted from each vehicle. Each vehicle, when receiving a beacon periodically transmitted from the roadside device 1, transmits a unique modulation signal (a packet preamble or the like) for identifying the type of the terminal itself.

  Hereinafter, vehicle position estimation processing performed by the arrival direction estimation unit 12 will be described with reference to FIGS. An example in which the position of the vehicle A is estimated based on the inherent modulation signal received from the vehicle A in FIG. 1 will be described.

  Of the four antennas of the roadside device 1, the intrinsic modulation signal transmitted from the vehicle A has the highest reception intensity at the antenna ANT1. Therefore, it can be roughly determined that the vehicle A is located on the left side of the roadside machine 1. The arrival direction estimation unit 12 estimates a more detailed azimuth of the vehicle A based on the phase difference of the reception signal at each reception antenna. Here, as shown in FIGS. 1 and 4, the angle θa from the direction along the road on the left side in the figure is estimated.

  The arrival direction estimation unit 12 detects the phase difference between the received signals at ANT2 and ANT3 with reference to the antenna ANT1 having the largest received power. The angle α shown in FIG. 4 can be calculated from the phase difference between the received signals of the antennas ANT1 and ANT2. Further, the angle −β shown in FIG. 4 can be calculated from the phase difference between the received signals of the antennas ANT1 and ANT3. 1 and 4, the phase difference when the antenna ANT1 is used as a reference is as shown in FIG.

  Here, since α = π / 4 + θa and −β = π / 4−θa, it can be seen that θa = (α + β) / 2. In other words, it is possible to estimate the azimuth of the vehicle based on the phase difference of the inherent modulation signal (known signal) received at each receiving antenna.

<Frequency shift detection processing>
Next, the process which the frequency detection part 13 detects the frequency shift amount of the intrinsic | native modulation signal which a vehicle transmits is demonstrated. The frequency of the intrinsic modulation signal transmitted from each vehicle is fixed, but is affected by Doppler shift and the like because the vehicle is moving. And the frequency of the received signal received in the roadside machine 1 shifts. The frequency detector 13 detects this frequency shift amount.

  FIG. 6 shows detailed functional blocks of the frequency detection unit 13. The frequency detection unit 13 includes a quadrature demodulator 131, a detection circuit 132, and a phase difference calculator 133.

  The quadrature demodulator 131 performs quadrature demodulation on a received signal at the antenna having the highest received intensity among the plurality of antennas ANT1 to ANT4, and divides the quadrature demodulated signal into an I signal (in-phase component) and a Q signal (quadrature component). Output. The detection circuit 132 detects (demodulates) the received signal from the I signal / Q signal.

  The phase difference calculator 133 calculates a deviation amount of the frequency of the demodulated received signal from the frequency of the transmitted intrinsic modulation signal. First, it is assumed that the intrinsic modulation signal V is expressed as follows.

ここで、ｆ_ｃは搬送波周波数、θ_ｃは初期位相である。

Here, f _c is the carrier frequency, and θ _c is the initial phase.

  The reception signal Vr demodulated by the detection circuit 132 is expressed as follows.

ここで、Δθが周波数偏移量である。

Here, Δθ is the frequency shift amount.

  The frequency shift amount Δθ is determined by the Doppler shift and the phase change due to multipath.

ここで、２πｆ_ｄｔはドップラー偏移量を表し、θ_ｍはマルチパスによる位相変化量を表す。

Here, 2πf _d t represents a Doppler shift amount, and θ _m represents a phase change amount due to multipath.

  In the antenna having the strongest reception strength, the amount of frequency deviation is dominated by the amount due to Doppler deviation. Therefore, Δθ represented by the following expression represents the Doppler shift amount.

  It is possible to estimate whether the vehicle is approaching or moving away from the roadside device 1 depending on whether the frequency shift amount thus obtained is positive or negative.

FIG. 7 is a diagram showing the frequency shift of the received signal from the vehicle A received by the antennas ANT1 to ANT4 in the situation of FIG. Here, since the reception intensity at antenna ANT1 is the strongest, the amount of frequency shift of the received signal at antenna ANT1 is obtained. As shown in FIG. 7A, since the Doppler shift amount f _d = f _ra1 −f _c > 0, it can be determined that the vehicle A is approaching the roadside device 1.

  Note that the traveling direction of the vehicle may be estimated in consideration of not only the reception signal of the antenna having the strongest reception intensity but also the frequency shift in another antenna.

<Communication target vehicle determination processing>
As described above, the direction of arrival of the vehicle and the traveling direction (whether approaching or moving away) can be acquired by the arrival direction estimation unit 12 and the frequency detection unit 13. The communication control unit 14 performs a process of determining a vehicle to be communicated based on these results. Hereinafter, this process will be described.

  As shown in FIG. 1, when there are three vehicles A to C, the processing results of the arrival direction estimation unit 12 and the frequency detection unit 13 obtained from the reception results of the inherent modulation signals transmitted from these vehicles. Is as shown in FIG.

  The vehicle A is estimated to be present in the direction of 0 to π / 2 from the phase difference of the received signals, and is estimated to be approaching the roadside unit 1 from the Doppler shift. The vehicle B is estimated to be present in the direction of 0 to π / 2 from the phase difference of the received signals, and is estimated to be away from the roadside device 1 from the Doppler shift. The vehicle C is estimated to exist in the direction of π / 2 to π from the phase difference of the received signals, and it is estimated that the vehicle C is approaching the roadside unit 1 from the Doppler shift.

  Since the service providing area 3 of the roadside machine 1 is as shown in FIG. 1, it can be determined that the vehicle approaching the roadside machine 1 from the left in the figure is the vehicle to be communicated. Therefore, the communication control unit 14 determines whether or not each vehicle is a communication target according to the flowchart shown in FIG.

  That is, the communication control unit 14 targets a vehicle whose arrival direction is in the range of 0 to π / 2 and whose Doppler shift is positive (close to the roadside device 1) as a communication target. Here, the vehicle A is in the range of 0 to π / 2 (S1-YES), and the Doppler shift is positive (S2-YES), and therefore becomes a communication target. On the other hand, although the vehicle B is located in the range of 0 to π / 2 (S1-YES), the Doppler shift is negative (S2-NO), so the vehicle B is not a communication target. In addition, since the vehicle C is not located within the range of 0 to π / 2 (S1-NO), it is not a communication target.

<Operation / Effect of Embodiment>
In this way, the roadside machine 1 can estimate the vehicle location and the traveling direction, and can easily determine the vehicle to be communicated.

  Here, the vehicle side merely transmits the intrinsic modulation signal (preamble), and it is not necessary to provide a GPS device or other sensors, and the vehicle can be configured simply and at low cost. In addition, the vehicle side does not transmit a packet with the payload of position information or its own ID, but only transmits a short intrinsic modulation signal, so that the communication amount can be reduced and the use band, power consumption, etc. It becomes possible to reduce.

(Modification)
In addition to the configuration shown in FIG. 2, various configurations can be adopted in consideration of the shape of the road, the service providing area, and the like as the specific configuration regarding the antenna of the roadside device 1. Some examples are shown in FIG. For example, as shown to Fig.10 (a), the shape of the electromagnetic wave absorber 3 may be square column shape instead of cylindrical shape. The same effect can be obtained also by this. Also, the number of antennas need not be four, and may be three or five or more. When there are three antennas, it is preferable to use a triangular pole wave absorber as shown in FIG. When there are five antennas, it is preferable to use a pentagonal wave absorber as shown in FIG. Further, the shape of the radio wave absorber is not limited to a cylindrical shape or a polygonal column shape, and a configuration in which a plate-like radio wave absorber is provided behind each antenna as shown in FIG. . The antenna itself may have directivity.

In the above description of the embodiment, the service providing area 3 is an area approaching from one of the intersections, but is not limited to such a configuration. For example, in FIG. 1, a vehicle that approaches the roadside device 1 from the left direction and the right direction may be a communication target. Which other vehicle is to be used for communication can be appropriately set according to information provided by the roadside machine 1.

  Moreover, in description of said embodiment, the roadside machine 1 was equipped with the antenna which has directivity with respect to all the road directions in an intersection, respectively. However, the antenna may not be provided for some directions. For example, the antenna ANT4 may be omitted in the above description.

  In the above description of the embodiment, the wireless communication device according to the present invention is configured as the roadside device 1, but the wireless communication device according to the present invention may be an in-vehicle terminal. That is, also in the inter-vehicle communication, the presence direction and the traveling direction of the opponent vehicle can be determined based on the unique modulation signal as described above.

It is a figure which shows the outline | summary of the whole system of the road-vehicle communication system which concerns on this embodiment. It is a figure which shows the structure of the antenna which a roadside machine has. It is a figure which shows the function structure of a roadside machine. It is a figure which shows the phase difference in the arrival direction of each received signal and each antenna. It is a figure which shows the phase difference of the received signal received with each antenna. It is a detailed functional block diagram of the frequency detection part which a roadside machine has. It is a figure which shows the Doppler shift amount of the received signal received with each antenna. It is a figure which shows the detection result of the arrival direction of a vehicle, and a Doppler shift amount. It is a flowchart which shows the flow of the process which determines whether a vehicle is made into communication object. It is a figure which shows another example of the structure of the antenna which a roadside machine has.

Explanation of symbols

ANT1, ANT2, ANT3, ANT4 Antenna 1 Roadside unit 11 Synthesizer 12 Arrival direction estimation unit 13 Frequency detection unit 131 Quadrature demodulator 132 Detection circuit 133 Phase difference calculator 14 Communication control unit 15 Communication data processing unit

Claims (6)

A wireless communication device that performs wireless communication with an in-vehicle terminal,
A plurality of receiving antennas for receiving known signals transmitted from the in-vehicle terminal;
Position estimation means for estimating the azimuth of the in-vehicle terminal based on the phase difference of the known signals received by the plurality of receiving antennas;
Based on frequency shifts of the known signals received at the plurality of receiving antennas, a traveling direction estimation unit that estimates whether the in-vehicle terminal is approaching or moving away from the own device;
A determination unit for determining whether to perform wireless communication with the in-vehicle terminal based on the estimation result by the position estimation unit and the traveling direction estimation unit;
A wireless communication apparatus comprising:   The wireless communication apparatus according to claim 1, wherein the receiving antennas are directional antennas, each having directivity in a different direction. The wireless communication device has shielding means for shielding radio waves,
The radio communication apparatus according to claim 1, wherein the plurality of receiving antennas have directivities in different directions by shielding radio waves from a predetermined direction by the shielding unit. The shielding means is a polygonal columnar or cylindrical wave absorber,
The wireless communication apparatus according to claim 3, wherein the plurality of receiving antennas are installed in proximity to the radio wave absorber. The wireless communication device is installed at an intersection,
The plurality of receiving antennas have directivity with respect to a road direction,
5. The determination unit according to claim 1, wherein the determination unit determines to perform wireless communication with the in-vehicle terminal when the in-vehicle terminal approaches the own apparatus from a predetermined road direction. The wireless communication device described. A road-vehicle communication system that performs wireless communication between a roadside device and an in-vehicle terminal,
The in-vehicle terminal is
Having transmission means for transmitting a known signal;
The roadside machine
A plurality of receiving antennas for receiving the known signal;
Position estimation means for estimating the azimuth of the in-vehicle terminal based on the phase difference of the known signals received by the plurality of receiving antennas;
Based on frequency shifts of the known signals received by the plurality of receiving antennas, a traveling direction estimation unit that estimates whether the in-vehicle terminal is approaching or moving away from the roadside device;
A determination unit for determining whether to perform wireless communication with the in-vehicle terminal based on the estimation result by the position estimation unit and the traveling direction estimation unit;
A road-vehicle communication system characterized by comprising:

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