WO2001006690A1

WO2001006690A1 - On-board receiver

Info

Publication number: WO2001006690A1
Application number: PCT/JP2000/004123
Authority: WO
Inventors: Takashi Maehata; Keiji Tanaka
Original assignee: Sumitomo Electric Industries, Ltd.
Priority date: 1999-07-14
Filing date: 2000-06-22
Publication date: 2001-01-25
Also published as: JP2001028576A

Abstract

An on-board receiver which provides no-interruption stable communication even if the reception frequency varies because of the Doppler effect in a vehicle-to-roadside communication system for communication between roadside communication stations installed in a cell and an on-board mobile station in the cell. A frequency control unit (72) measures the temporal shifts of the reception frequencies of the radio waves received by two receiving antennas (61, 62) having different directivities, calculates an average of the shifts, and performs common frequency control of down converters (66, 67) of receiving units according to the average.

Description

Specification

Technical field

The present invention relates to an on-vehicle receiving device used in a road-vehicle communication system that enables mobile communication between a road and a mobile station by forming a cell on the road by arranging a plurality of road antennas along the road. It is. Background art

The demand for communication between road managers and vehicles is likely to increase in the future. Especially on expressways, if roads are to be run without burdening the driver of the vehicle and avoiding accidents with each other, information on the road and information on the vehicle are frequently exchanged. There is a need. By developing such a system, various sensors and cameras will be covered on both the road and the vehicle, and the road and the vehicle will be in close contact with each other, leading to an automatic driving system in which the vehicle runs. (See, for example, Japanese Patent Application Laid-Open No. Hei 8-242495).

In consideration of the future expansion to autonomous driving systems, when building a driving support system using communication with vehicles (hereinafter referred to as “road-vehicle communication system”), a communication area (cell ) Must be provided.

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. The shortcoming is that it has a short reach.

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 by one on-road antenna. In this case, the on-street antennas are respectively connected to control stations on the road manager side via optical fibers or the like.

If a large car approaches a small car when a roadside antenna is installed, May not be able to see the antenna on the road. In particular, high-frequency microphone mouth and millimeter waves have small diffraction angles and are easily shielded. For this reason, communication is interrupted between roads and vehicles, and communication becomes impossible.

Therefore, in order to enable continuous communication between the road and the vehicle, multiple road antennas with unique directivity are arranged along the road, and radio waves of the same frequency and the same content are transmitted from each road antenna in the same cell. Proposal of multi-station communication has been made.

In the case of a multi-station communication system, there are multiple propagation paths for radiated radio waves, so even if the vehicle is running near a large vehicle such as a truck, shielding of radio waves can be avoided and communication with mobile stations on the road can be achieved. There is an advantage that continuous communication with the station can be performed well.

By the way, in a multi-station communication system, when a vehicle travels, a Doppler phenomenon occurs as the vehicle travels, and the receiving antennas with forward directivity and backward directivity respectively transmit radio waves of different frequencies based on the Doppler shift. receive.

Fig. 7 (a) shows the arrangement of three on-road antennas a, b, and c of a multi-station communication system and a vehicle traveling under the antenna. The vehicle consists of a front-directional receiving antenna 61 and a rear-facing antenna. It is equipped with a directional receiving antenna 62. The receiving antenna 6 1 and the receiving antenna 6 2 are respectively connected to a receiving unit.

FIG. 7B is a graph showing a change in the reception frequency received by the reception antenna 61 and a change in the reception frequency received by the reception antenna 62. The transition of the reception frequency deviation received by the receiving antenna 61 from the road antenna b is represented by b1, the transition of the reception frequency received by the receiving antenna 61 from the road antenna c is represented by c1, and the reception antenna 62 is transmitted by the road antenna a. The transition of the received frequency shift received is indicated by a 2, and the shift of the received frequency received by the receiving antenna 62 from the on-road antenna b is indicated by b 2.

A numerical example of the deviation of the reception frequency received from the road antenna a will be described. If the transmission frequency is f0 and the vehicle speed is V, the Doppler shift Δf is Δf = f0v / c (c is the speed of light). The vehicle travels on the road, and the height of the road antenna from the ground H, and the horizontal distance from the vehicle to the antenna on the road is L,

Δ f = f 0 (v / c) L (L ² + H ² )- ^{, / 2}

Becomes Assuming f 0 = 5.8 GH z, v = 10 Okin / h, H = 10 (m), the Doppler shift Δ f is

Δ f = 53 7L (L ² + H ² ) " ^{, / 2} (H z)

Becomes Assuming that the distance between road antennas is 50 (m), L ranges from 0 (m) to a maximum of 50 (m), so the Doppler shift Δ を ranges from 0 to 527 (Hz). . At the middle L = 25 (in) position, the Doppler shift A f becomes 4 99 (H z).

In the arrangement shown in Fig. 7 (a), as shown in Fig. 7 (b), each time the vehicle passes directly below the on-road antenna, the two reception frequencies jump at the same time. .

Because of this jump, when performing automatic frequency control (AFC), it became difficult for any receiver to follow the frequency control, and during that time, the communication was interrupted.

It is considered that this is because the two receivers independently performed frequency control so as to follow the reception frequency.

Therefore, from the viewpoint that the numerical example of the Doppler shift △ f is not so large as shown above, it is conceivable that the automatic frequency control (AFC) may be stopped. Automatic frequency control is necessary because there is a problem in that it cannot withstand temporal fluctuations in frequency (for example, chronological fluctuations or sudden fluctuations) due to causes other than the Doppler effect of radio waves.

Thus, the present invention provides a road-to-vehicle communication system for performing communication between a plurality of road communication stations arranged in a cell and an on-vehicle mobile station in the cell, while having an automatic frequency control (AFC) function. No matter where the vehicle passes in the cell, communication based on the Doppler effect is not interrupted and stable communication can be performed. It is intended to realize an in-vehicle receiving device. Disclosure of the invention

(1) The on-vehicle receiving device according to claim 1 for achieving the object includes a plurality of receiving antennas having different directivities, an equal number of receiving units connected to these receiving antennas, and a frequency control unit, The frequency control unit calculates a mean of the frequency shift detected by the first detection unit and the first detection unit that respectively detects a time shift of the reception frequency of each reception unit, and calculates an average of the shift. Frequency control means for performing frequency control common to each of the receiving units based on the frequency. In the present invention, the average of the deviation of the receiving frequency for each receiving antenna having different directivity is averaged, and the common frequency control of each receiving unit is performed based on the average of the deviation. Therefore, continuous frequency control can be performed no matter where the vehicle passes through the cell.

As described above, according to the in-vehicle communication device of the present invention, continuous frequency control is performed, so that if the reception frequency changes suddenly based on the Doppler effect, it cannot follow the change. As a result, the quality of the signal received by the receiver and demodulated and decoded is slightly degraded.However, since the change in the reception frequency that fluctuates due to the Doppler effect is not so large, such deterioration in the quality is within an acceptable range. is there.

Rather, it has a greater effect that continuous frequency control is performed to prevent instantaneous interruptions in communication and that communication can always be performed stably.

(2) The on-vehicle receiving device of the present invention further includes a second detecting unit that detects a received power or a received electric field strength of each receiving unit, and the frequency control unit detects each of the detected powers by the second detecting unit. It is desirable to take the average of the frequency shift detected by the first detection means according to the received power or the weight of each received electric field strength (claim 2).

In the present invention, the average of the frequency shift is calculated according to the reception power of each reception antenna having different directivity or the weight of each reception field strength. Therefore, it follows the shift of the frequency of the radio wave with the larger received power or received electric field strength more quickly.

Normally, the on-vehicle receiving device receives a radio wave having a large received power or a large received electric field strength from the on-road communication station when the vehicle is passing immediately near the on-road communication station. When a vehicle passes very close to the on-road communication station, the angle at which the on-road communication station is looked up becomes large, so that the frequency shift based on the Doppler effect is relatively small.

Therefore, with the configuration of the present invention, the in-vehicle receiving apparatus has an advantage that the frequency can be controlled in a range where the frequency shift is relatively small, and the control is facilitated.

(3) The receiving section may receive an OFDM-modulated radio wave (claim 3).

In multi-station communication, multiple radio waves are radiated at the same transmission power in the same cell, so multipath fading occurs, and inter-carrier interference and inter-symbol interference appear strongly. Necessary for system construction.

Generally, a mobile communication system using a single carrier (single carrier) is susceptible to intersymbol interference due to multipath delay waves.

Therefore, it has been proposed to employ an OFDM modulation scheme that can divide a carrier into a plurality of subcarriers and transmit the divided subcarriers. This OFDM modulation method can eliminate the effects of delayed waves by setting the guard time. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a conceptual diagram showing the configuration of a road-vehicle communication system.

FIG. 2 is a block diagram showing an internal configuration of the transmitting device 2b and the receiving device 2a of the transmitting / receiving station 2.

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 showing the internal configuration of the transmitting device 4b of the vehicle-mounted mobile station 4. FIG. 5 is a conceptual diagram showing the configuration of the receiving device 4a of the vehicle-mounted mobile station 4.

FIG. 6 (a) is a diagram showing an arrangement of three on-road antennas a, b, and c of the multi-station communication system, and a vehicle 4 traveling thereunder. (B) is a graph showing the transition of the average frequency deviation <Δf> received by the on-vehicle receiver.

Figure 7) is a diagram showing the arrangement of three on-road antennas a, b, and c of a multi-station communication system and a vehicle traveling under it. (B) is a graph showing the transition of the reception frequency shift. It is. Explanation of reference numerals

1 is a central base station, 2 is a transmitting / receiving station, 2a is a receiving device, 2b is a transmitting device, 4 is an on-vehicle mobile station, 4a is a receiving device, 2 2 is a downcomer, 2 3 is a quadrature demodulation circuit, 24 is a Fourier transform circuit, 26 is? 5 conversion circuit, 27 is a detection unit, 31 is an SZP conversion circuit, 33 is an inverse Fourier conversion circuit, 34 is a quadrature modulation circuit, 35 is an upconverter, 41 is a first reception unit, and 42 is 2nd receiver, 4 7 is 5? Conversion circuit, 49 is an inverse Fourier transform circuit, 50 is a quadrature modulation circuit, 51 is an upcomer, 61 is a receive antenna, 62 is a receive antenna, 63 is a quadrature demodulator circuit, and 64 is Fourier transform. Circuit, 6 5? No. 5 conversion circuit, 66 is a down converter, 67 is a down converter, 68 is a quadrature demodulation circuit, 69 is a Fourier transform circuit, 70 is a PZS conversion circuit, 71 is a sign switching circuit, and 72 is frequency control Department

(Embodiment 1)

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a conceptual diagram showing the configuration of the road-vehicle communication system of the present invention. This road-to-vehicle communication system is a system for transmitting and receiving road traffic information between a road communication station and a mobile station mounted on a vehicle.

Cells are formed along the road. Each cell has its own finger A plurality of directional transceiver stations 2 are installed at intervals. From the antenna of each transmitting and receiving station 2, a radio wave having the same content and the same frequency (for example, 6 (GHz) band) is radiated into the cell. Therefore, at each point in the cell, an electric wave of the same frequency arrives in the longitudinal direction of the road from the front and rear or from above.

The transmission / reception station 2 obtains transmission data from the central base station 1 via a wired transmission line 9 such as an optical fiber or a coaxial cable (a wireless transmission line may be used. Hereinafter, the “wired transmission line 9” is assumed). OFDM modulation is performed using a plurality of orthogonal carriers (subcarriers) and transmitted as radio radio waves within the cell. Further, the transmitting / receiving station 2 receives the OFDM-modulated radio wave from the on-vehicle mobile station 4 in the cell, demodulates it, and transmits the received data to the central base station 1 via the wired transmission line 9 to the central base station. One to send.

The function of the transmitting / receiving station 2 and the function of the central base station 1 are collectively referred to as “road communication station”.

It is assumed that the frequency of the (down) radio wave transmitted from the transmitting / receiving station 2 into the cell and the frequency of the (up) radio wave transmitted from the vehicle-mounted mobile station 4 to the transmitting / receiving station 2 are different from each other. However, if a method is provided in which a separate time slot for communication is provided, the uplink and downlink frequencies may be the same.

The transmission device 2b includes an SZP (serial-parallel) conversion circuit 31, an inverse Fourier conversion circuit 33, a quadrature modulation circuit 34, an up-converter 35, and the like.

The receiving device 2a includes a downcomer 22, a quadrature demodulation circuit 23, a Fourier transform circuit 24, a P / S (parallel serial) transform circuit 26, a detection unit 27, and the like.

The inverse Fourier transform circuit 33 of the transmitting device 2b performs an inverse Fourier transform on the transmission data supplied from the SZP transform circuit 31 to the parallel, and performs an inverse Fourier transform. This is a circuit that realizes various functions such as converting the converted data to serial data, time-compressing the serialized symbol sequence, and setting the guard time by bringing the subsequent symbol to the front.

FIG. 3 is a graph illustrating a 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 + At) ZTS. Assuming that the number of subcarriers is n and the transmission rate is m (Mbps), TS is expressed as TS = 2 n / m (/ sec) in the case of QPSK.

The guard time Δt of the 〇FDM modulation needs to be longer than the delay time due to multipath. As a result, the transmitting / receiving station 2 and the on-vehicle mobile station 4 can accurately recover the received signal by avoiding interference between symbols without being adversely affected by the propagation delay caused by multiple radio wave propagation paths (multipath). can do.

Referring to FIG. 2, quadrature modulation circuit 34 performs D / A conversion on the in-phase component and the quadrature component output from inverse Fourier transform circuit 33, respectively, and generates a sin wave (sinwt) and a cos wave (COS Ot). This is a circuit that performs quadrature modulation by multiplying and adding. In this embodiment, QPSK modulation is performed. However, it goes without saying that other modulation schemes such as QAM, BPSK, and 8PSK may be adopted. However, the following description is based on the assumption that QPSK modulation will be performed unless otherwise specified.

The up-converter 35 is a circuit that converts the frequency into a radio frequency. The output signal of the up-converter 35 is radiated as radio waves from the on-road antenna 36 through a coaxial cable during a short period of time.

The down converter 22 of the receiving device 2a is a circuit that converts a radio frequency to an intermediate frequency.

The quadrature demodulation circuit 23 is a circuit that performs quadrature demodulation in the opposite manner to the quadrature modulation circuit 34, and applies a sine wave to one of the two divided signals and a cos wave to the other, and performs AZD conversion, respectively. Circuit. The frequency difference Δf detection unit 27 calculates the reception frequency based on the in-phase component I (signal after applying a cos wave) and the quadrature component Q (signal after applying a sine wave) of the quadrature demodulation circuit 23. This circuit detects the deviation △ f. The deviation of the reception frequency is calculated by calculating the argument of the complex number I ZQ at each sample time interval, and the argument of the current I ZQ (I / Q), and the argument of the immediately preceding sample (I ZQ). Can be calculated based on the difference between

Δ f = (I / Q),-(I / Q), _,

The Δf detection unit 27 performs a function of correcting the reception frequency deviation Δf by feeding back the reception frequency deviation Δf to the down converter 22.

The Fourier transform circuit 24 is a circuit that performs a process reverse to that of the inverse Fourier transform circuit 33 on the transmission side, and performs a Fourier transform on the demodulated signal with the window length of the effective symbol length TS to convert the decoded signal. It is a circuit to get.

The PZS conversion circuit 26 is a circuit that converts the parallel signal after the Fourier transform into a serial signal.

The data converted into the serial signal is transmitted to the central base station 1. Next, the configuration of the on-vehicle mobile station mounted on the vehicle will be described.

FIG. 4 is a conceptual diagram showing a configuration of the transmitting device 4b of the vehicle-mounted mobile station 4.

The transmission device 4b includes a 57? Conversion circuit 47, an inverse Fourier transform circuit 49, a quadrature modulation circuit 50, an up converter 51, and the like.

The configuration of the transmitting device 4b is the same as the configuration of the transmitting device 2b on the road shown in FIG.

FIG. 5 is a conceptual diagram showing the configuration of the receiving device 4a of the vehicle-mounted mobile station 4.

The receiving device 4 a includes two receiving antennas 6 1 and 6 2 facing the front and rear direction of the vehicle, a first receiving unit 4 1 connected to the receiving antenna 6 1, and a second receiving unit connected to the receiving antenna 6 2 42, a frequency control unit 72 including an automatic frequency control (AFC) function, and a code switching circuit 71.

The first receiver 41 is a down-converter that converts a radio frequency to an intermediate frequency. E 6 6, Quadrature demodulation circuit 63, Fourier transform circuit 64,? The second receiving unit 42 includes a down converter 67, a quadrature demodulation circuit 68, a Fourier transform circuit 69, a PZS transform circuit 70, and the like. The configuration of the first receiving unit 41 and the second receiving unit 42 is the same as the configuration of the receiving device 2a described with reference to FIG.

The frequency control unit 7 2, first receiver 4 1, together with the function of the second receiving portion 4 2 of the number of received frequency deviation Δ ί ,, Δ f ₂ to detect each first receiver 4 1, a function of detecting the second receiving portion 4 2 of the reception power P ,, P _2, respectively, averages Ku delta f> of the frequency shift depending on the weight of the detected received power PP _2, the average device of this deviation A function of performing frequency control common to the first receiving unit 41 and the second receiving unit 42 based on Δf>.

The function of detecting the reception frequency deviation Δf ₂ can be described in the same manner as the function of the Δf detection unit 27 described with reference to FIG. That is, based on the in-phase component I, (the signal after applying the cos wave) and the quadrature component Q, (the signal after applying the sine wave) of the quadrature demodulation circuit 63, the complex number I, / Calculates the declination of Q, based on the difference between the declination of the current I, ZQ, (Ι, ΖΟ,), and the declination of (前, ΖΟ,),, Detect the reception frequency deviation Δf ,.

Δ f, = (Ino Q!),-(Ino Q,), „,

Similarly, based on the in-phase component I ₂ of the quadrature demodulation circuit 68 (the signal after applying the cos wave) and the quadrature component Q ₂ (the signal after applying the sine wave), the reception frequency deviation Δ f Detect ₂

Δ f _; = (INO Q ₂ ),-(INO Q ₂ )

On the other hand, the received power P ₂ of the reception power P ,, the second reception section 4 2 of the first receiver 4 1 detects each at the output of the down comparator Isseki 6 6 6 7. In addition, in addition to the output sections of the down-converters 66 and 67, the detection may be performed between the receiving antennas 61 and 62 and the down-converters 66 and 67. As the power detection method, a known method such as detection with a diode can be used. Frequency control unit 7 2, the shift Δ f ,, Δ ί ₂ of the detected reception frequency, the reception power [rho,, based on the [rho _2, Ru obtains a weighted average tool delta f> of the frequency shift.

<Δ f> = (Ρ, Δ f, + Ρ ₂ Δ f ₂ ) Ζ (Ρ, + Ρ ₂ )

Then, the average frequency deviation <Δf> is fed back to the oscillator of the down converter 22 to perform a function of correcting the reception frequency deviation Δf.

f = f „ _I8- Δ Δ f>

In this formula, f. _fg is the frequency to be oscillated when _Δf > is zero. FIG. 6 is a graph showing the average frequency deviation Δf> thus obtained.

Fig. 6 (a) shows the arrangement of three on-road antennas a, b, and c of the multi-station communication system, and the vehicle 4 traveling under it. As described above, the vehicle 4 is equipped with the forward directional receiving antenna 61, the backward directional receiving antenna 62, and the on-vehicle mobile station 4.

FIG. 6B is a graph showing the transition of the average frequency deviation <Δ <>. Comparing the graph of FIG. 6 (b) with the graph of FIG. 7 (b), <△ f> is a value between the deviations of the receiving frequencies received from the receiving antennas 6 1 and 6 2.

For example, when the vehicle is at an intermediate position between the antennas on the road a and the antenna b on the road, the angle Δ ぐ> is the deviation b 1 of the reception frequency received from the antenna b on the road and the deviation a of the reception frequency received from the antenna a on the road a Take an intermediate value of 2. This is because the received power of the radio wave received by the vehicle from the on-road antenna a is substantially equal to the received power of the radio wave received from the on-road antenna.

When the vehicle is directly below the antenna on the road b, A f> takes a value close to the deviation b1 of the reception frequency received from the antenna on the road b. This is because the received power of the radio wave received by the vehicle from the road antenna b is higher than the received power of the radio wave received from the other road antennas. From the graph in Fig. 6 (b), it can be seen that even when the vehicle is running, Af> changes smoothly and no frequency jump occurs. For this reason, when performing automatic frequency control (AFC), it is possible to follow the frequency control sufficiently, and there is no interruption in communication.

Looking at the graph in Fig. 6 (b), the fluctuation of <Δί> falls within a small range centered on 0 compared to the fluctuation of the receiving frequency shift b1 received from the roadside antenna b. I have. This is considered to be because the received powers P,, P, are weighted to obtain <A f>. In other words, the on-vehicle receiving device receives radio waves with high received power or each received electric field strength from the on-road communication station when the vehicle is passing very close to the on-road communication station. This is because when passing close to a station, the angle at which the station on the road looks up becomes large, and the frequency shift based on the Doppler effect is relatively small.

Therefore, the on-vehicle receiving device 4 only has to control the frequency within a range where the frequency deviation is relatively small, so that the performance requirement for the frequency control unit 72 can be eased.

In FIG. 5, the code switching circuit 71 compares the received power of the radio waves received by the first receiver 41 and the received power of the radio waves received by the second receiver 42, respectively. It is a circuit that switches to the output of the unit. A circuit that synthesizes instead of switching may be used. By such switching or combining, even if the multi-station vehicle is running near a large vehicle such as a truck, the propagation path of the radio wave radiated from the transmitting station can be selected. Can be avoided.

The switching position is? It is not limited to the output points of the 73 conversion circuits 65 and 70, and may be switched at any position after the output sections of the down converters 66 and 67. For example, the output positions of the quadrature demodulation circuits 63 and 68 may be used.

Also, instead of the sign switching circuit 71, instead of switching, both flat It is also possible to make a circuit that averages. ,

Although the embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment. For example, the above-described in-vehicle receiver 4a uses the reception powers P 1 and P ₂ as the weights to obtain the weighted average Δf> of the frequency shift, but may use the reception electric field strength.

In addition, various design changes can be made within the scope of the present invention.

Claims

The scope of the claims

1. An in-vehicle receiver used in a road-vehicle communication system for performing communication between a plurality of on-road communication stations arranged in a cell and on-vehicle mobile stations in the cell,

A plurality of receiving antennas having different directivities, the same number of receiving sections connected to these receiving antennas, and a frequency control section;

The frequency control unit,

A first detection means for detecting a time shift of the reception frequency of each receiving unit, and an average of the frequency shift detected by the first detection means, and each reception is determined based on the average of the shifts. An on-vehicle receiving apparatus, comprising: frequency control means for performing frequency control common to all units.

2. It further comprises a second detection means for respectively detecting the reception power or the reception electric field strength of each reception section,

The frequency control means calculates a weighted average of deviation of the frequency detected by the first detection means according to the weight of each received power or each received electric field strength detected by the second detection means. 2. The in-vehicle receiving device according to claim 1, wherein:

3. The receiving unit performs orthogonal frequency division multiplexing (〇FDM; Orthogonal

The in-vehicle receiving device according to claim 1, wherein the on-vehicle receiving device receives a radio wave modulated by Frequency Division Mu 11 i pi ex).

Claims in the certificate

[January 17, 2000 (17.11.00) Accepted by the International Bureau: Claim 1 as originally filed was amended; other claims remained unchanged. (1 page)]

1. (After correction) An in-vehicle receiver used in a road-to-vehicle communication system that performs communication between on-road communication stations and on-vehicle mobile stations in a cell by using a plurality of on-road antennas arranged along the road in the cell So,

A receiving antenna having forward directivity, a receiving antenna having backward directivity, the same number of receiving sections connected to these receiving antennas, and a frequency control section;

The frequency control unit,

First detection means for respectively detecting a shift based on a temporal Doppler shift of a reception frequency of each reception unit,

An in-vehicle receiving apparatus, comprising: frequency control means for averaging frequency deviations detected by the first detection means, and performing frequency control common to the receiving units based on the average of the deviations.

3. The receiving unit performs orthogonal frequency division multiplexing (OFDM; Orthogonal

The in-vehicle receiving device according to claim 1, wherein the in-vehicle receiving device receives a radio wave modulated by Frequency Division Multiplex).

Reliable paper (Article 19 of the Convention) The amendment to the description based on Article 19 (1) of the Convention clarified that the on-street antennas are along the road, and the receiving antennas have forward directivity and backward directivity. In such a configuration, the Doppler shift is larger than in other configurations, and the Doppler shift fluctuates greatly each time the antenna passes on the road (Fig. 7 (b)). Such problems and their solutions are not disclosed or suggested in the cited references.