JP3045167B1 - Road-to-vehicle communication system - Google Patents

Abstract

A road-to-vehicle communication system that can use the same frequency for all cells, can prevent inter-carrier interference and inter-symbol interference, and enables stable communication between roads and vehicles. I do. SOLUTION: OFDM subcarriers are classified into two subcarriers S1 and S2, and for a roadside transmitting antenna device arranged in an adjacent cell, data having the same contents for at least one subcarrier S2 among the classified subcarriers S2. B is transmitted. As a result, even when the vehicle 21 passes through the boundary between adjacent cells, the data B having the same content can be continuously obtained without receiving the intersymbol interference.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a road-vehicle communication system in which a roadside antenna is arranged along a road and a series of cells are formed on the road to enable mobile communication with a vehicle-mounted device.

[0002]

2. Description of the Related Art The communication demand between a road manager and a vehicle is:
It is on the rise. Frequent exchanges of roadside information and vehicle information are required, especially on expressways, in order to realize road driving without burdening the driver of the vehicle and avoiding accidents with each other. There is. The development of such a system will lead to an autonomous driving system that covers various sensors and cameras on both the road and the vehicle, and closely contacts and drives the road and the vehicle (for example, JP-A-8-2414
No. 95).

In consideration of future expansion to automatic driving, a driving support system for vehicles (hereinafter referred to as "road-vehicle communication system")
It is necessary to provide continuous cells on the road when building the Therefore, it is conceivable to lay a leaky coaxial cable along the road.However, the laying work becomes large and it is necessary to install the leaky coaxial cable relatively low from the ground. There is a disadvantage that the reach distance is short.

On the other hand, if the on-road antennas are installed at predetermined intervals at various places on the road for communication, a relatively wide cell can be secured with one on-road antenna. In this case, the on-road antennas are respectively coupled to base stations on the road manager side via optical fibers or the like.

[0005]

In the case of a system using the above-mentioned road antenna, communication is usually performed using radio waves having different frequencies for each cell in order to prevent inter-carrier interference and inter-symbol interference. . However, since an automobile moves at high speed and passes through a plurality of cells in a short time, it is necessary to switch the transmission / reception frequency of the vehicle-mounted communication device at high speed. For this reason, it is necessary to take measures such as providing an oscillator capable of high-speed pull-in or a plurality of oscillators, which hinders downsizing and cost reduction of the device.

Therefore, it is desired to construct a system using the same frequency for all cells after taking measures to prevent inter-carrier interference and inter-symbol interference. Therefore, an object of the present invention is to provide the same frequency for all cells and to prevent inter-carrier interference and inter-symbol interference, thereby enabling stable communication between the road and the vehicle. A communication system is provided.

[0007]

According to a first aspect of the present invention, there is provided a road-to-vehicle communication system according to the first aspect of the present invention.
And a control device for transmitting the signal modulated in the transmission line, having a specific directivity, receiving the signal transmitted to the transmission line, based on the received signal, based on the received signal, radio waves of the same frequency A road transmitting antenna device for radiating into the cell, a vehicle receiving antenna for receiving a radio wave radiated from the road transmitting antenna device, and a vehicle receiving unit for receiving and demodulating by the vehicle receiving antenna; An in-vehicle device, the control device classifies the subcarriers into a plurality of types, and has a transmission unit that transmits data to the plurality of types of subcarriers, and the classified at least one type of subcarrier is Transmitting data of the same content as the data of the subcarrier of the type included in the signal transmitted to the on-road transmitting antenna device arranged in the adjacent cell,
The classified other type of subcarrier transmits data having a different content from the data of the other type of subcarrier included in the signal transmitted to the roadside transmitting antenna device arranged in the adjacent cell. The in-vehicle receiving means has a switching means for switching to any type of subcarrier data.

[0008] In the present invention, from the on-road transmitting antenna device,
Radio waves of the same frequency are radiated based on the OFDM-modulated signal. Generally, when radio waves arrive at a vehicle from a plurality of directions, so-called multipath interference may occur. Specifically, a propagation delay time difference occurs between radio waves radiated from the on-road transmitting antenna devices, and intersymbol interference occurs.

However, in the present invention, the OFDM system is adopted, and a guard time is provided for each symbol so that interfering codes can be prevented from overlapping. , It is possible to avoid intersymbol interference caused by delay due to Then, in the present invention, the subcarriers are classified into a plurality of types, and data having the same content is transmitted to at least one type of the subcarriers among the classified subcarriers to a roadside transmitting antenna device arranged in an adjacent cell. I am trying to do it. By cooperating with this and adopting the OFDM method, even when the vehicle passes the boundary between adjacent cells, the data having the same content is continuously obtained without intersymbol interference. be able to. Therefore, no instantaneous interruption of communication occurs.

Here, “at least one” means:
When the subcarriers are classified into N (N ≧ 2) types, the same data is transmitted for at least one type of subcarrier and at most (N−1) types of subcarriers (N number of types). If data of the same content is transmitted for all subcarriers, it is no different from normal OFDM.) On the other hand, for other types of sub-carriers that are classified, since data having contents different from the data of the other types of sub-carriers included in the signal transmitted to the on-road transmitting antenna device arranged in the adjacent cell is received, Then, intersymbol interference occurs between the data having different contents, and the data cannot be reproduced.

[0011] Switching of which type of subcarrier to take in the data transmitted is performed by the on-vehicle receiving means. Although the timing of switching becomes a problem, it is desirable to switch when the reception state is stable. Therefore, the following measures (a) and (b) can be considered. (a) A marker is provided on a road, and switching is performed when the vehicle passes through the marker (claim 3).

(B) The data transmitted on each subcarrier is decoded and switched to the subcarrier of the data with the lowest error frequency (claim 4). (2) When there are two types of sub-carriers to be classified, the transmission means transmits one type of sub-type to the on-road transmitting antenna devices (4a) and (4b) arranged in adjacent cells. Transmitting the same data for the carrier, transmitting different data for other classified sub-carriers,
Roadside transmitting antenna device further arranged in adjacent cells
(4b) For (4c), if the same type of data is transmitted for the other type of subcarrier, and the different type of data is transmitted for the classified one type of subcarrier ( Claim 2) By repeating this configuration in a continuous series of cells, data can always be received without instantaneous interruption even when passing through any cell boundary.

(3) The transmission system for transmitting a signal to the transmission line may be an optical fiber wireless transmission system. According to the present invention, since a high-frequency level signal is supplied from the control device to the roadside transmitting antenna device through the optical fiber, it is not necessary to provide a control device for each roadside transmitting antenna device. Therefore, the configuration of the on-road transmission antenna device can be simplified.

(4) The above-mentioned on-vehicle device is operated according to vehicle data.
It has an in-vehicle transmission antenna for radiating FDM-modulated radio waves, is arranged at different positions along the road, has a unique directivity, receives radio waves radiated from the on-vehicle transmission antenna, A road receiving antenna device for transmitting a signal corresponding to the received radio wave to a predetermined transmission line, and a signal receiving device for demodulating based on a signal transmitted from the road receiving antenna device to the transmission line. Further, it may be included (claim 6).

The present invention proposes a two-way communication system that provides vehicle data from the vehicle to the roadside. (5) There are various ways to classify the sub-carriers into a plurality of types. A method of dividing a subcarrier into a plurality of blocks on the frequency axis (Claim 7) and a method of arranging subcarriers of the same type every K lines on the frequency axis (Claim 8). is there. According to a seventh aspect of the present invention, a plurality of subcarriers are divided into a plurality of groups on a frequency axis and transmitted. In the method described in claim 8, sub-carriers transmitting data of the same content are arranged every K lines. For example, when dividing into two types of subcarriers,
They are arranged alternately one by one.

(6) In the road-vehicle communication system according to the ninth aspect, the data to be transmitted is classified into a plurality of types, and the classified data is arranged in a fixed pattern in the frequency axis direction and the time axis direction. Has a transmission means for transmitting, the at least one type of classified data,
The same type of data included in the signal transmitted to the on-road transmitting antenna device arranged in the adjacent cell is the same as that of the type of data, and the classified other types of data are included in the on-road transmitting antenna device arranged in the adjacent cell. The content is different from that of the other type of data included in the signal transmitted to the in-vehicle receiver, and the in-vehicle receiving unit has a switching unit for switching to any type of data.

In the present invention, data to be transmitted is classified into a plurality of types, and the classified data is transmitted by arranging them in a fixed pattern in the frequency axis direction and the time axis direction. As a result, the classified data is arranged along the frequency axis direction, so that the subcarriers are classified. However, in addition to this, in the present invention, the classified data is also arranged along the time axis direction. Therefore, as a result, it can be said that the manner of classification or the manner of classification of the subcarriers changes over time.

By arranging the classified data in a fixed pattern in the frequency axis direction and the time axis direction, each type of data is switched in the frequency axis direction and the time axis direction. For this reason, the effects of frequency diversity and time diversity appear synergistically. In mobile communication, fading always occurs, but the effect of the fading can be reduced by the effects of the frequency diversity and the time diversity.

The above-mentioned "arranged data items are arranged in a fixed pattern in the frequency axis direction and the time axis direction, respectively".
As a method, after the data including the classified data is temporally rearranged, the data is transmitted by performing an inverse Fourier transform process, and on the vehicle side, the data that has been subjected to the Fourier transform is subjected to an inverse rearrangement process, whereby the data is classified. It is conceivable to obtain various types of data.
0).

[0020]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a conceptual diagram showing a configuration of a road-vehicle communication system according to an embodiment of the present invention. This road-to-vehicle communication system is for performing communication between a ground station 1 and a vehicle-mounted communication device mounted on the vehicle 2.

In the ground station 1, a plurality of cells E
Are continuously formed. Each cell E has a cell E
A road antenna 4 having directivity directed inward is installed. A predetermined frequency (for example, 6 GHz) is output from the road antenna 4.
(z band) radio waves are radiated into the cell E. The height h of the on-road antenna 4 from the ground is, for example, 10 (m), and the length r of the cell E in the longitudinal direction of the road is, for example, 100 (m). When the vehicle 2 passes through the cell E, the vehicle 2 moves forward or backward, or
When the vehicle passes just below the on-road antenna 4, the radio wave is received from above.

The on-road antenna 4 is connected to control devices 6a, 6b,... (Hereinafter, collectively referred to as "control device 6") via a coaxial cable 5. Coaxial cable 5
Is composed of two up / down coaxial cables. Note that an optical fiber can be used as the transmission line instead of the coaxial cable. In this case, as a transmission method for transmitting an optical signal to an optical fiber, a so-called optical fiber wireless transmission method (for example, AJCooper, "FIBER / RAD
IO FOR THE PROVISION OF CORDLESS / MOBILE ELEPHONY
SERVICES IN THE ACCESS NETWORK ", Electron. Lett.,
Vol. 26, No. 24 (Nov. 1990)).

The control device 6 outputs a signal modulated by road traffic data including driving support information such as road information ahead.
It is given to the road antenna 4 via the coaxial cable 5. Further, the vehicle data (including the vehicle ID and data relating to the road surface state detected by various sensors (not shown)) received from the vehicle 2 is acquired from the on-road antenna 4.
The carrier frequency of the radio wave radiated from the control device 6 is
It is the same between adjacent control devices 6. By transmitting a signal using a carrier wave having the same frequency in this manner, it is not necessary to change the frequency of the vehicle-mounted oscillator when the vehicle moves to an adjacent cell. It is not necessary to provide an oscillator, or it is not necessary to provide a plurality of oscillators, so that the cost and size of the device can be reduced.

First Embodiment FIG. 2 is a block diagram showing an electric configuration of the ground station 1. As shown in FIG. The ground station 1 includes a control device 6, a coaxial cable 5, a road antenna 4, and the like. The control device 6 includes a transmission device 7 for providing road traffic data to the road antenna 4. The transmitting device 7 divides data and multiplexes the data using a plurality of orthogonal carrier waves.
l Frequency Division Multiplex) The modulation method is adopted.

The transmitting device 7 includes an inverse Fourier transform circuit 71,
A QPSK modulation circuit 73, an up-converter 74 and the like are provided. In addition, an error correction coding circuit, an interleaving circuit for performing time interleaving and frequency interleaving, a differential coding circuit, and the like may be provided. The inverse Fourier transform circuit 71 performs an inverse Fourier transform on the parallel information, performs parallel-serial conversion on the inverse Fourier transform, returns the serial to serial, time-compresses the serialized symbol sequence, and processes the subsequent symbol. It is a circuit that realizes various functions of setting a guard time by bringing it in advance. In the present embodiment, the parallel signals S1 and S2 respectively corresponding to the two subcarrier blocks on the frequency axis are input and inverse Fourier transformed.

The QPSK modulation circuit 73 performs D / A conversion on the signals corresponding to the phases 0 ° and 180 ° and the signals corresponding to the phases 90 ° and 270 ° output from the inverse Fourier transform circuit 71 to obtain a sine wave, This is a circuit for performing QPSK modulation by adding a cos wave. In this embodiment, QPSK modulation is performed, but other modulation schemes, for example, QAM, BPSK, 8PSK, etc., may be adopted. However, the following description will be given on the assumption that QPSK modulation is performed unless otherwise specified.

The up-converter 74 is a circuit for converting the frequency to a radio frequency. The accuracy of the local oscillator 74a included in the upconverter 74 is determined by taking into account the Doppler effect that occurs between the ground and the traveling vehicle.
A speed on the order of (vehicle speed) / (propagation speed of radio waves) is necessary, but a commercially available oscillator can sufficiently secure such accuracy.

The output signal of the up-converter 74 is radiated as radio waves from the road antenna 4 through the coaxial cable 5. When the above-mentioned optical fiber wireless transmission system is adopted, an electric / optical conversion unit (E / O) for converting the output signal of the up-converter 74 into an optical signal is required. Optical / electrical conversion unit that converts to electrical signals
(O / E) is required.

FIG. 3 shows the state of symbol transmission by OFDM on a frequency axis f and a time axis t. The effective symbol length is represented by TS, and the guard time is represented by Δt. The time compression ratio is represented by (TS + Δt) / TS. Assuming that the number of subcarriers is n and the transmission rate is m (Mbps), TS is represented by TS = 2 n / m (μsec) in the case of QPSK.

In this embodiment, the guard time Δt is longer than the delay time due to multipath. As a result, even if there is a long propagation delay time, demodulation can be performed on the receiving side ignoring symbol overlap. The delay time due to the multipath can be actually measured and obtained in the cell. Alternatively, it may be empirically determined from the size of the cell. In particular,
If the cell size is 100 m, it is expected to be about 500 nsec.

Although not shown, the control device 6 includes a receiving device for acquiring data from the vehicle 2 from the road antenna 4. In the receiving apparatus, the received signal is down-converted, detected, and decoded. As the detection method, the modulation method is QPSK, BPSK, 8PS.
In the case of a phase modulation method such as K, delay detection is performed by multiplying the current signal by one bit before using a delay circuit. QA
In the case of M, synchronous detection is performed using the demodulation carrier.
In the case of delay detection, transmission data needs to be differentially encoded.

FIG. 4 is a conceptual diagram showing the configuration of the vehicle-mounted device 8. The vehicle-mounted device 8 includes a vehicle-mounted receiver 9 and a vehicle-mounted antenna 10.
And The on-vehicle receiving unit 9 is for acquiring road traffic data included in the radio wave radiated from the on-road antenna 4 received by the on-vehicle antenna 10, and includes a down converter 91, a QPSK demodulation circuit 92, a Fourier transform circuit 93, , A changeover switch circuit 94 and a changeover control circuit 95.

In addition, an error correction decoding circuit, a deinterleave circuit, and a differential decoding circuit corresponding to the above-described error correction encoding circuit, interleave circuit, and differential encoding circuit, respectively, may be provided. The Fourier transform circuit 93
A circuit that performs a process reverse to that of the inverse Fourier transform circuit 71 on the transmission side, Fourier transforms the down-converted and QPSK demodulated signal with the window length of the effective symbol length TS to convert the two decoded signals S1 and S2. It is a circuit to get.

The changeover switch circuit 94 is a circuit for changing over to one of the two decoded signals S1 and S2.
Use a semiconductor switch or the like. The switching control of the switching switch circuit 94 is performed by the switching control circuit 95. The switching of the switching control circuit 95 is determined, for example, as follows.

A marker is provided on the road, and the vehicle is switched when the vehicle passes the marker. In this case, a road marker including a magnet for notifying the position on the road, a colored reflector, a light-emitting body, and the like is set at a predetermined position in the cell E. Specifically, the location of the road marker is desirably around the center of the cell E where stable reception of radio waves is possible, but is not limited to the center of the road. On the other hand, the in-vehicle device 8 includes a magnetic sensor for detecting a road marker,
A marker detection unit including a light receiving element is provided.
A reception state detection code is inserted at a predetermined position of the data S1 and S2, and an error frequency is detected by reading the code of the data S1 and S2 transmitted and decoded by each subcarrier, thereby detecting the error frequency. Is switched to the subcarrier of the data having the least number of data.

FIG. 5 is a diagram for explaining the signals transmitted from the control devices 6a, 6b, 6c and the reception state of the vehicle-mounted device 8. Each signal has two subcarriers S1, S2
, Two types of data are included. For example, the signal a sent from the control device 6a is temporally A1, A
Data A that changes to 2, A3, 、, and B1, B
2, B3,... And data B that changes. The signal b transmitted from the adjacent control device 6b is temporally C1,
Data C that changes to C2, C3, ‥ and B1,
B2, B3,... And data B that changes. The signal c transmitted from the adjacent control device 6c includes data C that changes temporally as C1, C2, C3, ‥, and data D that changes temporally as D1, D2, D3, ‥. I have.

The data A of the signal a and the data C of the signal b
And the data C of the signal c are transmitted by the subcarrier S1, and the data B of the signal a, the data B of the signal b, and the signal c
Is transmitted by the subcarrier S2. For example, when the vehicle is at the position 21 (the center of the cell), the signal a sent from the control device 6a is received.
And data B can be received stably. At this point, the on-vehicle receiving unit 9 is
Switches the reception from the subcarrier S1 to the subcarrier S2.

When the vehicle is switched to the subcarrier S2 and the vehicle comes to the position of the cell boundary 22, the on-vehicle receiving unit 9 outputs the signal a sent from the control device 6a and the signal b sent from the control device 6b. Receive at the same time. Data B of signal a;
The data B signal b, but it is transmitted at the same carrier S2, since accept hardly the influence of multipath fading in the cell boundary, as mentioned above, the vehicle-mounted receiving unit 9 passes through the cell boundaries Can continuously obtain stable data B.

On the other hand, the data A of the signal a and the data C of the signal b are transmitted on the same carrier S1, but the data are different, so that the data is mixed at the cell boundary. , The data has no meaning even when decrypted. This meaningless data is not selected by the changeover switch circuit 94. When the vehicle comes to the center position 23 of the adjacent cell, it receives the signal b sent from the control device 6b, so that both the data C and the data B can be received stably. At this point, the in-vehicle receiver 9 switches the reception from the subcarrier S2 to the subcarrier S1 by the changeover switch circuit 94.

As described above, the vehicle-mounted receiving section 9 can sequentially acquire a plurality of types of data while passing through a series of cells. In the above embodiment of the present invention,
The subcarrier was divided into two blocks on the frequency axis. However, in addition to this divided way, mention may be made of how divided as follows.

Second Embodiment FIG. 7 is a block diagram showing an electrical configuration of a ground station 1 according to a second embodiment. The difference from the block diagram of FIG.
This means that the two types of subcarrier signals S1 and S2 input to the inverse Fourier transform circuit 71 are alternately arranged. As a result, in the frequency spectrum of the transmitted radio wave, the subcarriers of data A and the subcarriers of data B are alternately arranged on the frequency axis f, as shown in FIG. When the data to be received is A, the subcarrier indicated by the solid line is used, and the subcarrier indicated by the broken line is not used. Therefore, the detuning frequency Δf between the sub-carriers is substantially doubled as shown in FIG.

In a transmission system using multicarriers such as OFDM, the characteristics deteriorate when the frequency synchronization of each carrier is not completely achieved. In particular, when applied to high-speed mobile communication, Doppler shift occurs, making it difficult to synchronize carriers. Therefore, an AFC circuit for correcting the shifted frequency is required. If the detuning frequency Δf between adjacent subcarriers is narrow, it is necessary to determine whether the frequency of the subcarrier captured by the AFC circuit is that of the upper frequency or that of the lower frequency, which complicates the AFC circuit. Become. If the AFC circuit is not to be complicated, the detuning frequency Δf must be widened, and therefore a band wider than the band required for data to be transmitted must be secured.

Therefore, by alternately interleaving the subcarriers as in this embodiment, the detuning frequency Δf
, The determination process of the AFC circuit becomes easy, and it is not necessary to widen the band, so that the device can be simplified and the frequency can be effectively used. Further, according to the present embodiment, it is possible to provide a system that is resistant to frequency selective fading. FIG. 9 is a diagram in which amplitude fluctuation U for frequency selective fading is written on the frequency axis. FIG. 9B shows a case where the subcarrier is divided into a plurality of blocks on the frequency axis as in the first embodiment, and a case where the subcarriers are arranged alternately and interleaved as in the present embodiment. Is shown in FIG. 9 (a).

As shown in FIG. 9 (b), where the subcarriers of data A are dense, the frequency selective fading U
Occurs, most of the subcarriers used for communication are affected, and a failure occurs. However, by alternately arranging the subcarriers as shown in FIG. 9 (a), only a part of the subcarriers used for communication is affected, and communication failure is less likely to occur, and fading occurs. It becomes a strong system.

Third Embodiment In this embodiment, subcarriers are classified and arranged not only on the frequency axis but also on the time axis. In order to realize such an arrangement, temporal rearrangement of data is performed before performing the inverse Fourier transform processing.

FIG. 10 is an image diagram of a buffer used when performing interleaving used for error correction coding. One measure in the figure has a predetermined number (for example, 8, 16, 3).
2) represents one unit of data composed of bits.
When writing data to the buffer, 1, 2, 3,
Write in the order of ‥‥, and check bits used for error correction are also written at this time. Reading is performed in the vertical direction by
1, 31, ‥‥, 2, 12, 22, ‥‥.

The number of data to be subjected to one inverse Fourier transform or Fourier transform used in OFDM is represented by "FFT
Unit. " The FFT unit may be one unit of data, but is usually composed of several units of data. In FIG.
4 units are shown. In this case, subcarriers are allocated to every four units of data read in the vertical direction. At this time, one subcarrier is not allocated to one data unit, but one subcarrier is allocated to each bit constituting one unit of data. However, the number of bits allocated per subcarrier varies depending on the modulation scheme. For example, in the case of the QPSK method, two bits are assigned to one wave.

Therefore, the data 1, 2, 3,... Which were continuous at the time of writing can be dispersed in time and frequency, so that even if data is lost over a certain time range or a certain frequency is lost. Even if data is lost over the range, the original data can be easily reproduced on the receiving side. The above is a description of general interleaving. In the embodiment of the present invention, there are two types of data A and B to be transmitted. Therefore, if the data A is represented by oblique lines and the data B is represented by white, as shown in FIG. 11, two types of data A and B are dispersedly arranged in a buffer image diagram. The algorithm of this distributed arrangement may be arbitrary, but must be agreed between the transmitting side and the receiving side.

It is not always necessary to perform the distributed arrangement for each unit of data as shown in FIG. For example, they may be finely distributed in bit units. The data distributed as shown in FIG. 11 is read out in units of four in the vertical direction, and subcarriers are allocated. FIG. 12 is an arrangement diagram of data allocated on the frequency axis and the time axis after the inverse Fourier transform. Looking at a certain time, data A and B
Are arranged in a fixed pattern on the frequency axis, and when viewed at a certain frequency, the data A and B are arranged in a fixed pattern on the time axis.

With such an arrangement, the data A and B are switched in the time axis direction and the frequency axis direction, and the effects of time diversity and frequency diversity appear synergistically. When receiving the above data, the data is subjected to Fourier transform by the Fourier transform circuit 93, and then deinterleaving and reverse rearrangement of the data are performed. FIG. 13 is an image diagram of a buffer for allocating received data. The data reading direction and the writing direction are switched as compared with those in FIG. In-vehicle device 8 on the receiving side
Applies the algorithm of the inverse distribution arrangement to the read data string to separate the two types of data A and B. Then, a necessary type of data is selected and read out by the changeover switch circuit 94.

As described above, in the embodiment of the present invention, the classified data A and B are arranged in a fixed pattern in the frequency axis direction and the time axis direction, respectively, so that the frequency diversity and the time diversity are simultaneously performed. At the same time, the correction capability of the error correction code can be used more effectively, and high-quality data communication can be realized. Here, it will be described that if a predetermined algorithm is adopted as the distributed arrangement algorithm, it can be divided into two subcarrier blocks on the frequency axis as described in the first embodiment.

FIG. 14 shows a state in which two types of data A and B are rearranged in a buffer image diagram by a predetermined algorithm. In this algorithm, 2
The distribution repetition period of the types of data A and B is matched to the FFT unit. Therefore, the arrangement of the data after the inverse Fourier transform is divided into two subcarrier blocks on the frequency axis as shown in FIG. 15, and the manner of division is time-invariant.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various design changes can be made within the scope of the present invention. is there. For example, the number of data classifications is not limited to two, and any integer of two or more can be adopted.

In the description of FIG. 1, one on-road antenna 4 forming one cell E is installed at the center of the cell E. However, as shown in FIG. 6, the cell E is divided into a plurality of sub-areas, and the road antennas 41, 42, 4
3 may be provided to supply the same signal. Since the subarea is relatively small, the transmission power of the roadside antenna can be small.

[0055]

According to the present invention, even when a vehicle passes a boundary between adjacent cells, data of the same content can be continuously obtained without being affected by intersymbol interference. Therefore, stable and continuous communication between the road and the vehicle can be performed without causing an instantaneous interruption of communication. Therefore,
For example, when this road-vehicle communication system is applied to an automatic driving system, the automatic driving of the vehicle can be appropriately performed.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a configuration of a road-vehicle communication system according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating an electrical configuration of a ground station.

FIG. 3 is a graph illustrating a state of symbol transmission by OFDM on a frequency axis f and a time axis t.

FIG. 4 is a conceptual diagram illustrating a configuration of an in-vehicle device.

FIG. 5 shows signals transmitted from the control devices 6a, 6b, 6c on a frequency axis f and a time axis t.
FIG. 3 is a conceptual diagram for explaining a reception state of the.

FIG. 6 is a conceptual diagram showing a configuration of a road-vehicle communication system according to another embodiment of the present invention.

FIG. 7 is a block diagram illustrating an electrical configuration of a ground station according to a second embodiment.

FIG. 8 is a frequency spectrum diagram showing a state in which subcarriers of data A and subcarriers of data B are alternately arranged on a frequency axis f.

FIG. 9: Amplitude variation U for frequency selective fading
It is the figure which was written on the frequency axis. (a), when the sub-carriers are interleaved alternately, (b),
The case where the subcarrier is divided into a plurality of blocks on the frequency axis is shown.

FIG. 10 is an image diagram of a buffer used when performing interleaving used for error correction coding.

FIG. 11 is an image diagram showing a state where two types of data A and B are dispersedly arranged in a buffer.

FIG. 12 is a layout diagram of data allocated on the frequency axis and the time axis after the inverse Fourier transform.

FIG. 13 is an image diagram showing a state in which two types of received data A and B are distributed and arranged in a buffer.

FIG. 14 is a buffer diagram showing a state in which two types of data A and B are rearranged by an algorithm in which the distribution repetition period matches the FFT unit.

FIG. 15 is a diagram showing an arrangement of data after inverse Fourier transform on a frequency axis and a time axis.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ground station 2 Vehicle 4 Road antenna 5 Coaxial cable 6 Control device 7 Transmitting device 8 In-vehicle device 9 In-vehicle receiving unit 10 In-vehicle antenna E cell A, B Classified data

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04B ⁷ /24-7/26 H04J 11/00 H04Q 7/00-7/38

Claims (10)

(57) [Claims] A road-to-vehicle communication system in which a plurality of roadside antennas are arranged along a road and a series of cells are formed on the road to enable mobile communication with an on-vehicle device, an orthogonal frequency division multiplexing system (OFDM) ; Orthogonal Frequ
and a control device for transmitting a signal modulated by the ency division multiplex) to a transmission line, having a specific directivity, receiving a signal transmitted to the transmission line, and receiving the same signal based on the received signal. A road-side transmitting antenna device for radiating radio waves of a frequency into the cell, a vehicle-mounted receiving antenna for receiving a radio wave radiated from the road-side transmitting antenna device, and a vehicle mounted for receiving and demodulating with the vehicle-mounted receiving antenna An in-vehicle device having a receiving unit, wherein the control device classifies the subcarriers into a plurality of types, and has a transmission unit for transmitting data to the plurality of types of the subcarriers, and the classified at least one type The sub-carrier transmits the same data as the data of the type of sub-carrier included in the signal transmitted to the on-road transmitting antenna device arranged in the adjacent cell, The classified other type of subcarrier transmits data having a different content from the data of the other type of subcarrier included in the signal transmitted to the roadside transmitting antenna device arranged in the adjacent cell. The road-vehicle communication system, wherein the on-vehicle receiving means has a switching means for switching to any type of subcarrier data. 2. The transmitting means for classifying subcarriers into two types, comprising: a road transmitting antenna device (4a) (4) arranged in an adjacent cell.
In b), data of the same content is transmitted for one type of sub-carrier that is classified, and data of different content is transmitted for another type of sub-carrier that is classified, and further arranged in adjacent cells. Roadside transmitting antenna device
(4b) and (4c), wherein data of the same content is transmitted for the other type of sub-carrier, and data of different content is transmitted for the classified one type of sub-carrier. Item 2. The road-to-vehicle communication system according to Item 1. 3. The road-vehicle communication system according to claim 1, wherein said switching means switches data based on detection of a marker installed on the road. 4. The road-vehicle communication system according to claim 1, wherein said switching means switches the data by managing the decoding quality of the data demodulated by the on-vehicle receiving means. 5. The road-vehicle communication system according to claim 1, wherein a transmission system for transmitting a signal to the transmission line is an optical fiber wireless transmission system. 6. An on-vehicle device according to claim 1, wherein said on-vehicle device is OFD based on vehicle data.
An on-vehicle transmission antenna for emitting M-modulated radio waves, arranged at different positions along the road, having a specific directivity, receiving radio waves radiated from the on-vehicle transmission antenna, A road receiving antenna device for transmitting a signal corresponding to the received radio wave to a predetermined transmission line, and a signal receiving device for demodulating based on a signal transmitted from the road receiving antenna device to the transmission line. The road-to-vehicle communication system according to claim 1, further comprising: 7. The road-vehicle communication system according to claim 1, wherein the classification into the plurality of types of subcarriers is performed by dividing the subcarrier into a plurality of blocks on a frequency axis. 8. The classification into a plurality of types of subcarriers is performed by dividing the same type of subcarriers by K (K is a constant natural number) on a frequency axis.
2. The road-vehicle communication system according to claim 1, wherein the communication is performed by arranging every other book. 9. A road-to-vehicle communication system in which a plurality of roadside antennas are arranged along a road and a series of cells are formed on the road to enable mobile communication with an on-vehicle device. ; Orthogonal Frequ
and a control device for transmitting a signal modulated by the ency division multiplex) to a transmission line, having a specific directivity, receiving a signal transmitted to the transmission line, and receiving the same signal based on the received signal. A road-side transmitting antenna device for radiating radio waves of a frequency into the cell, a vehicle-mounted receiving antenna for receiving a radio wave radiated from the road-side transmitting antenna device, and a vehicle mounted for receiving and demodulating with the vehicle-mounted receiving antenna An in-vehicle device having a receiving unit, wherein the control device classifies the data to be transmitted into a plurality of types,
A transmission unit that transmits the classified data by arranging the data in a fixed pattern in the frequency axis direction and the time axis direction, and the classified at least one type of data is disposed in an adjacent cell. Data of the same type as the data included in the signal transmitted to the on-road transmitting antenna device, and the other types of classified data are included in the signal transmitted to the on-road transmitting antenna device disposed in the adjacent cell. The road-vehicle communication system, wherein the content is different from the other type of data included, and the on-vehicle receiving unit includes a switching unit for switching to any type of data. 10. The transmitting means transmits the data by subjecting the data including the classified data to temporal rearrangement processing and then performing an inverse Fourier transform processing. 10. The road-vehicle communication system according to claim 9, wherein the classified data is subjected to a reverse recombination process to obtain classified data of each type.