JPH07140232A - Device for detecting moving speed of moving body loaded with receiving unit - Google Patents

Abstract

PURPOSE:To detect speeds without providing a speed sensor by extracting pilot signals from signals received by a moving body which receives radio signals that include pattern signals at predetermined intervals, and calculating the speed of movement from the maximum Doppler shift and the carrier frequency of a signal transmitted. CONSTITUTION:A moving-speed detecting device 3 is connected to the output of a pilot sampler 21, together with a pilot interpolation filter 22. The device 3 is provided with an FFT 31 receiving inputs of pilot signals, and a minimum value detecting circuit 33 is connected to the output of the FFT 31 via a differentiator circuit 32. A multiplier 34 is connected to the output of the circuit 33 and the output signal of the multiplier 34 indicates the speed of a moving body. When a pilot signal is transmitted, a frequency shift occurs because of phasing in a propagation course and amplitude is disturbed. Since the maximum Doppler shift by phasing is proportional to the product of a carrier frequency and the speed of the moving body, determining the speed of the moving body through detection of the maximum Doppler shift can be made by predetermining the carrier frequency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a moving speed detecting device for detecting a moving speed of a moving body equipped with a terminal including a receiving device such as a mobile communication system.

[0002]

2. Description of the Related Art The moving speed of a moving body such as an automobile is detected by a speed sensor mounted on the moving body.
The moving speed is displayed by driving the display of the terminal according to the output of the speed sensor.

[0003]

However, when a speed sensor is used for speed detection, there are the following problems. (1) The cost of the speed sensor itself and its mounting cost are required. (2) Since the speed sensor detects the mechanical operation of the moving body, a failure due to mechanical deterioration occurs. (3) It takes time to transmit information between the speed sensor and the terminal. (4) When there are many vehicle types such as automobiles, it is necessary to develop a speed sensor for each vehicle type.

Therefore, since there are various problems as described above, it has been desired to detect the moving speed without using a speed sensor in the moving body. Therefore, an object of the present invention is to provide a moving speed detecting device for detecting the moving speed of a moving body without providing a speed sensor in order to solve the above problems.

[0005]

A moving speed detecting apparatus of the present invention detects a moving speed of a moving body provided with a receiving apparatus for receiving a radio transmission signal containing a pattern signal indicating a predetermined content at predetermined intervals. A moving speed detecting device for detecting,
Extracting means for extracting a pilot signal from the received signal of the receiving device, fast Fourier transforming means for fast Fourier transforming the pilot signal extracted by the extracting means, and maximum Doppler of the pilot signal extracted from the output signal of the fast Fourier transforming means It is characterized by comprising a detecting means for detecting the shift, and a calculating means for calculating the moving speed of the moving body based on the detected maximum Doppler shift and the carrier frequency of the transmission signal.

[0006]

According to the moving speed detecting apparatus of the present invention, when the maximum Doppler shift due to fading is f _D , the pilot signal received by the receiving apparatus has a spectrum width of 2 f _D due to fading, and f _D is Since the carrier frequency f _c is proportional to the product of the carrier frequency f _c and the moving body speed v, if the carrier frequency f _c is predetermined, the moving body speed v is detected by detecting the maximum Doppler shift f _D of the received pilot signal. Can be calculated.

[0007]

Embodiments of the present invention will now be described in detail with reference to the drawings. In a mobile communication system having a configuration used in the moving speed detecting device according to the present invention, the transmitting device may be, for example, a 16QAM (16-level Quadrature Amp).
Litude Modulation) modulation unit, and transmits a modulation signal conforming to the modulation method to the receiving device through the propagation path. In such a propagation path, the transmitted signal is subject to Rayleigh Fading distortion. The transmission signal that has passed through this propagation path is supplied to the 16QAM demodulation unit when received by the reception device. 16QA
The M demodulation unit performs demodulation according to 16QAM on the input signal, and further includes a fading compensation unit for compensating the deterioration of the signal due to the fading distortion.

The transmission data signal is transmitted in units of one frame. As shown in FIG. 1, the transmission data signal is formed by arranging the data signal in sequence at successive symbol strings, that is, at predetermined time slots. Furthermore, a pilot signal (pilot symbol) for detecting fading distortion is inserted for each predetermined number of data signals. Eg 1
Eighteen pilot signals are inserted into the frame every 10 time slots. The pilot signal has a predetermined content and can be represented by a complex number.

FIG. 2 shows a receiving device of a terminal of a mobile communication system including a moving speed detecting device according to the present invention. The RF (high frequency) signal received from the antenna is 16QAM
In the down-conversion / sampling / quantization unit 11 for demodulation, signal processing such as frequency conversion, sampling and quantization for dropping to the base band is performed.
The signal-processed baseband signal is subjected to preprocessing for timing extraction in the symbol rate conversion unit 12 and supplied to the mixer 13. The output signal of the mixer 13 is supplied to a symbol sampler 15 for sampling each symbol in the slot after passing through a pulse shaping filter 14 which is a bandpass filter for removing intersymbol interference.

The pre-processed output of the symbol rate converter 12 is also supplied to the timing extractor 16. The timing extraction unit 16 estimates the frame synchronization based on the pre-processed output and establishes the synchronization, and at the same time, the symbol sampler 1
The sample timing in 5 is generated and is given to the symbol sampler 15. The symbol sampler 15 performs sampling processing based on the given sample timing.

The output signal of the symbol sampler 15 also
It is supplied to the AFC circuit 17 for detecting the offset frequency. The AFC circuit 17 extracts the preamble from the supplied signal, detects the phase shift of the carrier wave (phase shift at the time of transmission and reception), converts the detected phase deviation into a frequency deviation, and outputs this converted output. It is supplied to the mixer 13 via the loop filter. The mixer 13 multiplies the supplied signal by the output baseband signal of the symbol rate conversion unit 12 as an AFC signal, that is, a signal according to the offset frequency. Thereby, the carrier frequency deviation between the transmitter and the receiver is corrected.

The fading compensator 2 is connected to the output of the symbol sampler 15. The fading compensation unit 2 is provided with a pilot sampler 21 that extracts a pilot signal from the output signal of the symbol sampler 15. A pilot interpolation filter 22 is connected to the output of the pilot sampler 21. The pilot interpolation filter 22 is composed of a shift register that holds a plurality of pilot signals in the order of samples, and outputs each held pilot signal of the shift register. The pilot interpolation filter 22 includes a complex conjugate circuit 23 that generates a phase compensation signal by taking the complex conjugate (.) ^{* Of} each of the complex pilot signals output from the pilot interpolation filter 22 and adding them to each other. Squared absolute value of each ||| ² and their reciprocal 1 / |
An absolute value square circuit 24, which generates an amplitude compensation signal by adding | ² , is connected. In addition, “·” indicates a complex number of the pilot signal.

In the fading compensation section 2, further,
A phase compensation circuit 25 and an amplitude compensation circuit 26, which are directly connected to the output of the symbol sampler 15, are provided. Both the phase compensation circuit 25 and the amplitude compensation circuit 26 are composed of multipliers, and the phase compensation circuit 25 multiplies the data signal or pilot signal output from the symbol sampler 15 by the phase compensation signal. The amplitude compensation circuit 26 multiplies the phase-compensated data signal or pilot signal output from the phase compensation circuit 25 by the amplitude compensation signal. The output signal of the amplitude compensation circuit 26 is supplied to the determination circuit 28 as a signal whose fading is compensated by the fading compensation unit 2. The determination circuit 28 compares the supplied data signal with a reference value to determine whether the data signal is logic 0 or 1, and the output signal of the determination circuit 28 becomes a demodulated signal.

To the output of the pilot sampler 21, the moving speed detecting device 3 according to the present invention is connected together with the above pilot interpolation filter 22. The moving speed detection device 3 is provided with an FFT (Fast Fourier Transform) 31 which uses the pilot signal output from the pilot sampler 21 as an input signal. A minimum value detection circuit 33 is connected to the output of the FFT 31 via a differentiation circuit 32. The minimum value detection circuit 33 detects the minimum value from the output signal of the differentiation circuit 32. A multiplier 34 is connected to the output of the minimum value detection circuit 33, and the output signal of the multiplier 34 becomes a speed signal indicating the speed of the moving body.

In the moving speed detecting device 3 having such a configuration, the pilot signal transmitted from the transmitting device of the base station is generated at constant intervals T _S sec and its amplitude is constant, as shown in FIG. 3 (a). . In the spectrum of the pilot signal, as shown in FIG. 3B, only a line perpendicular to the position of 0 Hz in the baseband will occur. When this pilot signal is transmitted from the transmission device and reaches the reception device of the terminal mounted on the mobile body under the influence of fading in the propagation path, for example, a frequency shift as shown in FIG. The generated amplitude is not constant and is disturbed.
Assuming that the maximum Doppler shift due to fading is f _D , the pilot signal received by the receiver is shown in FIG.
As shown in, the spectrum width will be 2f _D. Since f _D is proportional to the product of the carrier frequency f _c and the moving body velocity v, the carrier frequency f _c moves by detecting the maximum Doppler shift f _D of the received pilot signal if it is predetermined. The body speed v can be calculated. The moving speed detecting device 3 of the present invention operates based on this principle.

Next, the operation of the moving speed detecting device 3 according to the present invention will be described. When the pilot signal is extracted by the pilot sampler 21 from the received signal, the extracted pilot signal is supplied to the FFT 31. F
Since the operation of the FT 31 itself is well known, its explanation is omitted here. If the input signal of the FFT 31 is x (n),
It is assumed that X (k) is obtained as the output signal. According to the FFT principle, k is 0, 1, 2, ... N-1, and the angular frequency has a relationship of ω _k = 2πk / NT _S. Where N is the number of pilot signal samples used for FFT calculation, T
_S is a symbol period (sec).

Assuming that the received pilot signal is affected by fading, its spectrum, that is, X (k), exhibits a U shape by the multipath propagation model as shown in FIG. Output signal X of FFT31
When (k) is supplied to the differentiating circuit 32, X (k) −X (k−1) which is the gradient of X (k) is obtained from the differentiating circuit 32. The frequency at ω _k corresponding to k when the slope is maximum with a negative value corresponds to the maximum Doppler shift f _D. Therefore, among the output signals of the differentiating circuit 32, the minimum value is detected by the minimum value detecting circuit 33 as the maximum Doppler shift f.
_It is detected as _D and supplied to the multiplier 34. Multiplier 3
In step 4, the maximum Doppler shift f _D is used to calculate the moving speed v from the equation v = c · f _D / f _c . Here, c is the speed of light.

In the above embodiment, the 16Q is used as a linear modulation system for transmitting digital data.
Although the moving speed detecting device in the mobile communication system using the AM modulation is shown, the present invention is not limited to this modulation system, and the present invention can be applied to mobile communication systems of other modulation systems.

[0019]

As described above, in the moving speed detecting device of the present invention, the pilot signal is received from the receiving signal of the mobile receiving device which receives the radio transmission signal including the pattern signal indicating the predetermined content at every predetermined interval. The signal is extracted, the maximum Doppler shift of the extracted pilot signal is detected by performing a fast Fourier transform on the extracted pilot signal,
The moving speed of the moving body is calculated based on the maximum Doppler shift and the carrier frequency of the transmission signal. Therefore, the moving speed of the moving body can be detected without providing the speed sensor. As a result, even in a moving body in which the speed sensor cannot be easily provided, the moving speed of the moving body can be detected if at least the receiving device of the mobile communication system as described above is provided.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a transmission data signal.

FIG. 2 is a block diagram showing a receiving device of a terminal of a mobile communication system including a moving speed detecting device according to the present invention.

FIG. 3 is a diagram showing a pilot signal on the transmission side and its spectrum for explaining the principle of moving speed detection.

FIG. 4 is a diagram showing a pilot signal on the reception side and its spectrum for explaining the principle of moving speed detection.

FIG. 5 is a diagram showing a spectrum of a received pilot signal.

[Explanation of symbols for main parts]

 2 Fading compensation unit 3 Moving speed detection device 11 Down conversion / sampling / quantization unit 15 Symbol sampler 21 Pilot sampler 22 Pilot interpolation filter 25 Phase compensation circuit 26 Amplitude compensation circuit 31 FFT 32 Differentiation circuit 33 Minimum value detection circuit 34 Multiplier

Claims (3)

[Claims] 1. A moving speed detecting device for detecting a moving speed of a moving body, the moving speed detecting device comprising a receiving device for receiving a radio transmission signal including a pattern signal having a predetermined content at predetermined intervals. Extracting means for extracting a pilot signal from the received signal, a fast Fourier transforming means for performing a fast Fourier transform on the pilot signal extracted by the extracting means, and a maximum of the extracted pilot signal from the output signal of the fast Fourier transforming means. A moving speed detecting device comprising: a detecting means for detecting a Doppler shift; and a calculating means for calculating a moving speed of the moving body based on the maximum Doppler shift and a carrier frequency of the transmission signal. 2. The detecting means has a differentiating circuit, and the differentiating circuit obtains a gradient for each sample of the fast Fourier transforming means, and a minimum value of the gradients for each sample is obtained as the maximum Doppler shift. The moving speed detecting device according to claim 1, wherein: 3. The moving means calculates the moving speed from a formula: v = c · f _D / f _c where v is the moving speed, f _{D is the} maximum Doppler shift, f _{c is} the carrier frequency, and _{c is} the speed of light. The moving speed detecting device according to claim 1, wherein the moving speed is calculated.