JPH11252633A - Mobile speed detector and mobile speed detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a mobile speed of a mobile body in the CDMA system. SOLUTION: A demodulation and a correlation detection section apply demodulation processing and correlation processing to a transmission wave by the spread spectrum system and output a correlation value. A correlation value sampling section 41 samples a correlation value by the same delay wave from the correlation value A peak detection section 45 detects peaks appearing repetitively at the sampled correlation value. A time difference detection section 46 obtains a time difference between two peaks among the detected peaks. A speed arithmetic section 47 divides a distance coefficient by the time difference obtained by the time difference detection section 46 to device a mobile speed of the mobile body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a moving speed detecting device and a moving speed detecting method in spread spectrum communication such as CDMA.

[0002]

2. Description of the Related Art In mobile communications, one of the techniques for accommodating an increasing number of subscribers is to use a hierarchical cell structure in which a micro cell having a small cell radius is superimposed and arranged in a macro cell having a large cell radius. A method of allocating a moving object to a micro cell and allocating a high-speed moving object to a macro cell can be considered. According to this method, the number of subscribers that can be accommodated per unit area can be increased, and the frequency repetition radius can be reduced so that the frequency can be effectively used. In carrying out the above method, it is essential to detect the moving speed of the moving object for cell allocation.

[0003]

Recently, CDMA (Code Division Multiple Acc.) Has been used as a next-generation mobile communication system.
ess) system is expected, and it is also important to introduce the above-mentioned hierarchical cell configuration into the CDMA system. For this purpose, it is necessary to realize the detection of the moving speed of the moving object in the CDMA system.

[0004] It is an object of the present invention to provide a moving speed detecting device and a moving speed detecting method capable of detecting a moving speed of a moving object from a spread spectrum signal used in a CDMA system.

[0005]

In order to solve the above-mentioned problems, the present invention takes the following measures.

According to a first aspect of the present invention, there is provided a demodulation / correlation processing section for demodulating and correlating a received signal according to a spread spectrum method and outputting a correlation value output, and the correlation value output includes the demodulation / correlation processing section. A time difference detecting unit for obtaining a fluctuation cycle of the correlation value output of the received signal having the same delay time as a time difference, and an operation for calculating a moving speed of the moving body by dividing a predetermined distance coefficient by the time difference obtained by the time difference detecting unit And a processing unit.

According to a second aspect of the present invention, there is provided the moving speed detecting apparatus according to the first aspect, further comprising a peak detecting section for detecting a peak of the correlation value output, wherein the time difference detecting section detects the peak by the peak detecting section. The time difference between the two peaks among the peaks obtained is obtained.

According to a third aspect of the present invention, in the invention of the first or second aspect, the wavelength of the received signal or an integral multiple thereof is used as the distance coefficient.

According to a fourth aspect of the present invention, there is provided the moving speed detecting apparatus according to any one of the first to third aspects, wherein a distance coefficient between the points of the moving object corresponding to the fluctuation cycle of the correlation value output is used as the distance coefficient. This is based on the measured value of the moving distance.

[0010] With these configurations, the demodulation / correlation processing section obtains a correlation value output by demodulating and correlating a signal transmitted from the mobile unit or received by the mobile unit according to the spread spectrum method. The time difference detection unit obtains a fluctuation cycle of the correlation value output of the received signal having the same delay time included in the correlation value output as a difference between reception times of the received signals (hereinafter, referred to as a time difference). The arithmetic processing unit calculates the moving speed of the moving body by dividing the distance coefficient by the time difference. Here, the received signal includes a direct wave and a plurality of delayed waves.

The moving speed detecting device according to the present invention is based on the following principle. Since the received signal undergoes fading as the mobile unit moves, the correlation value output of the received signal having the same delay time fluctuates according to the moving distance of the mobile unit.
The present inventors have measured the distance variation period of the received signal level and found that the distance variation period is substantially constant irrespective of the moving speed. In other words, the distance traveled by the moving body when the correlation value output causes a level change for one cycle (hereinafter, referred to as a movement distance for one cycle) is substantially constant. Here, the distance variation refers to a variation in the received signal level due to a change in the moving distance of the moving object.

[0012] According to this aspect, the time difference corresponds to the time required to move a distance corresponding to one cycle of the received signal level fluctuation. Therefore, the moving speed of the moving object can be obtained by dividing the moving distance for one cycle by this time difference.

As a method of obtaining the time difference, for example,
As described in claim 2, a peak detector for detecting a peak of the correlation value output is provided, and the time difference detector can determine a time difference between two peaks among the peaks detected by the peak detector. Here, the two peaks for which the time difference is calculated may be continuous or discontinuous. In the case of discontinuity, the moving distance of the moving object is two because the other peak is included between the two peaks. It becomes an integral multiple of the case where the peaks are continuous. Therefore, when the receiving speed detecting device is provided on the receiving side, when the receiving signal corresponding to the other peak is received from the position (start point) of the moving object when the receiving signal corresponding to one peak is received. The moving speed can be obtained by dividing the moving distance to the position (end point) of the moving object by the time difference between the peaks. However, the correlation value output obtained from the received signal by the demodulation / correlation processing is usually a direct wave and all The output of the correlation value of the delayed wave is included. For this reason, it is necessary to find the fluctuation cycle of the correlation value output of the received signal having the same delay time from these. Therefore, for example, the peak detection unit detects the peak of the correlation value output of the received signal having the same delay time from the correlation value output of the direct wave and all the delayed waves.

As described above, the moving speed of the moving object can be obtained by dividing the moving distance of the moving object by the time difference. However, since the actual moving distance changes depending on the environment at the time of measurement, an estimated value or an approximate value of the moving distance is used as a distance coefficient for the moving speed of the moving object. As the distance coefficient, for example, a moving distance between points corresponding to the fluctuation cycle of the correlation value output (for example, a point of the moving object corresponding to two peaks) is obtained in advance. The actual measurement value is stored in the storage means and used as a distance coefficient.

The distance coefficient does not completely match the actual moving distance of the mobile unit at the time of reception or transmission, but is an approximate value, and the moving speed of the mobile unit calculated by dividing the distance coefficient by the time difference. Is approximately equal to the actual moving speed.

Further, the present inventors have found that the moving distance for one cycle substantially coincides with the wavelength of the received signal. Therefore,
As described in claim 3, the wavelength of the received signal or an integer multiple thereof can be used as the distance coefficient. In this case, there is no need to actually measure the moving distance.

As described above, since the moving speed of the moving object can be detected only by the transmission / reception system, the moving speed can be easily detected, and the cell allocation of the moving object in the hierarchical cell structure can be realized with an easy and simple system. Can be.

According to a fifth aspect of the present invention, there is provided the moving speed detecting device according to any one of the first to fourth aspects, wherein the moving speed detecting device includes an averaging processing unit for calculating an average value of the moving speed.

According to this configuration, the averaging processing unit averages a plurality of moving speed values, or averages a plurality of time difference values and calculates the moving speed using the average value. By obtaining the value, a more accurate moving speed can be detected.

According to a sixth aspect of the present invention, in the invention of the moving speed detecting device according to any one of the first to fifth aspects,
A configuration including a smoothing processing unit for smoothing the correlation value output is employed.

With this configuration, the peak value can be easily detected because the correlation value output is smoothed by the smoothing processing unit.

According to a seventh aspect of the present invention, there is provided a moving speed processing method comprising the steps of: receiving a received signal according to a spread spectrum system, demodulating the received signal, and performing correlation processing to obtain a correlation value output;
A step of obtaining, as a time difference, a fluctuation cycle of a correlation value output of a received signal having the same delay time included in the correlation value output; and a step of calculating a moving speed of the moving body by dividing a predetermined distance coefficient by the time difference. Are adopted.

According to an eighth aspect of the present invention, in the moving speed detecting method according to the seventh aspect, peaks of correlation value outputs of received signals having the same delay time included in the correlation value output are detected, and these peaks are detected. Of the two peaks is obtained.

According to a ninth aspect of the present invention, in the moving speed detecting method according to the seventh or eighth aspect, a configuration is adopted in which the wavelength of the received signal or an integral multiple thereof is used as the distance coefficient.

The invention according to claim 10 is the same as the invention according to claim 7.
In the invention of the moving speed detecting method according to any one of claims 9 to 9, a configuration is used in which the measured value of the moving distance between the points of the moving object corresponding to the two peaks is used as the distance coefficient.

With these configurations, similarly to the first aspect of the present invention, a correlation value output is obtained by performing demodulation processing and correlation processing on a received signal according to the spread spectrum method transmitted from or received by the mobile unit. . The variation period of the correlation value output of the received signal having the same delay time included in the correlation value output is obtained as a time difference. The moving speed of the moving object is calculated by dividing the preset distance coefficient by the obtained time difference. Therefore, since the moving speed of the moving object can be detected only by the transmission / reception system, the moving speed can be easily detected, and the cell assignment of the moving object in the hierarchical cell structure can be easily performed.

[0027]

Embodiments of the present invention will be described below with reference to the drawings.

(Experimental Results) First, experimental results supporting the principle of the moving speed detecting device and the moving speed detecting method of the present invention will be described.

With the transmitting station fixed and the receiving station mobile, delay profile data was measured. The experimental apparatus used a 2 GHz band DS-SS transmission / reception apparatus. Table 1 shows the specifications of the transmitted and received data.

[0030]

[Table 1] About 10, 20, 30km at the same place in the city
When the receiving station was run at / h, the level fluctuation of the correlation value output of the delayed wave with the change of the moving distance (m) was examined. The result is shown in FIG.

As is apparent from FIG. 1, the period (m) of the level change of the delayed wave (hereinafter referred to as distance change) with the change of the moving distance was substantially constant regardless of the speed. In addition, it was found that this period (m) was substantially equal to the wavelength of the received signal, that is, the wavelength of the transmission wave of the transmission device (= 13.77 mm).

(Embodiment) Hereinafter, a moving speed detecting apparatus according to an embodiment of the present invention will be described with reference to FIGS. FIG. 2 is a block diagram of a system for transmitting and receiving a spread spectrum signal according to the above-described embodiment, and FIG.
FIG. 3 is a block diagram of a moving speed detection unit according to the embodiment.

The transmission device in the upper part of FIG. 2 includes a baseband generator 1 for generating transmission information as baseband data.
A spreading processing unit 2 for performing a spreading process, a spreading code diverging unit 3 for generating a PN code as a spreading code, a modulation processing unit 4 for performing a modulation process, and a power amplification unit 5 for amplifying a transmission signal
And an antenna 6.

The baseband data generated by the baseband generator 1 is sent to the spreading processor 2. Diffusion processing unit 2
, A spreading code is input from the spreading code generator 3. The spreading processor 2 spreads the baseband data with a spreading code and outputs it as a transmission spread signal. In this spreading processing, one baseband data is converted into a spread code data string as it is or a code code inverted spread code data string according to its value. The transmission spread signal is QPSK-modulated by modulation processing section 4 and output as a transmission signal. The transmission signal is amplified to a predetermined power by the power amplifier 5 and transmitted from the antenna 6.

The lower receiving apparatus in FIG. 2 includes an antenna 7 for receiving a transmission signal, and a power amplifier 8 for amplifying the transmission signal.
A demodulation processing unit 9 for demodulating a transmission signal, a correlation detection unit 10 for performing correlation detection on the demodulated received spread signal, and a spread code generation unit 11 for generating the same spread code as that on the transmission side. .

The transmission signal arrives at the receiving device after fading or the like occurs through an outdoor radio path. Antenna 7
Are amplified by the power amplifier 8. The amplified received signal is demodulated by the demodulation processing unit 9 into a received spread signal. This received spread signal is output to the correlation detector 10.
Then, a correlation process is performed using the spreading code from the spreading code generating unit 11 to obtain a correlation value shown in FIG. The correlation detection unit 10 obtains a power-converted correlation value output shown in FIG. 3B by taking the square root of the sum of squares of the correlation value.

The correlation value output shown in FIG. 3B has an amplitude value, and this amplitude indicates the reception level. In this correlation value output, a peak value of a delayed wave including a direct wave (zero delay) is obtained for each baseband length (symbol length). FIG.
Although not seen in (B), when a plurality of delayed waves are received, the peak values of the other delayed waves are also obtained by being separated into symbols. In this embodiment, the transmitting device is fixed,
The receiving device was moved.

Next, the moving speed detecting process will be described. The moving speed detector shown in FIG. 4 samples the correlation value output of one delayed wave (including a direct wave with zero delay) having the same delay time from the correlation value output (power conversion) shown in FIG. 5A. A correlation value sampling unit 41 is provided. The sampling of the correlation value output is performed for each symbol length of the baseband data or for each integral multiple thereof. This allows
The correlation value output of the received signal having the same delay time can be sampled. The timing of the sampling at this time follows the trigger signal generated by the timing generator 42. This trigger signal is generated based on the symbol synchronization timing or the like in the receiving device.

The sampled correlation value output is stored in the correlation value buffer unit 43. The stored correlation values are shown in FIG.
This is obtained as a waveform having an amplitude as shown in FIG.
The time at which the correlation value was sampled is stored in the reception time buffer 44 as the reception time.

In the timing generator 42, a signal having an independent sampling timing longer than an integral multiple of the symbol length of the baseband data is transmitted to the reception time buffer 44, and the reception time buffer 44 receives the signal. And sends the timing of the symbol length of the baseband data that occurs first immediately after the same timing to the correlation value sampling unit 41 as a trigger signal,
The correlation value based on the timing may be stored in the correlation value buffer unit 43.

As shown in FIG. 5C, the peak detection unit 45 calculates the peak value from the correlation value stored in the correlation value buffer unit 43.
The peak position of the fluctuation is detected. For example, when a certain correlation value is larger than both of the correlation values sampled before and after, a position of this correlation value is detected as a peak position. Further, for example, a peak position obtained by smoothing by a smoothing processing unit such as a low-pass filter is detected.

According to the output from the peak detection unit 45, the time difference detection unit 46 determines the reception time between the two peaks based on the reception time stored in the reception time buffer unit 44 as shown in FIG. Find the difference as a time difference.

The speed calculating section 47 calculates the moving speed by dividing the distance coefficient stored in the distance coefficient buffer section 48 by the time difference output from the time difference detecting section 46. In the present embodiment, the wavelength of the transmission signal is used as the distance coefficient.

Using the moving speed detector according to the above embodiment, a simulation was performed using the same measurement data as in the above experimental results. At this time, 13.7 cm, which is the wavelength of the received signal, was used as the distance coefficient. FIG.
FIG. 6 is a characteristic diagram showing a result of estimating a moving speed. In the characteristic diagram of FIG. 6, the horizontal axis indicates the data measurement time, and the vertical axis indicates the moving distance of the receiving station. The results when moving at moving speeds of 10, 20, and 30 km / h are shown. In FIG. 6, the solid line shows the estimation result, and the broken line shows the actual traveling result. The inclination of the solid line and the broken line indicates the moving speed.

As is apparent from FIG. 6, the estimation result and the traveling result are substantially the same, which confirms that the speed can be detected by the moving speed detecting device of the present invention.

In the above embodiment, the wavelength of the transmission signal is used as the distance coefficient, but the distance between the points of the moving object corresponding to the two peaks may be obtained in advance by experiment.

In the above embodiment, the output of the time difference detecting section 46 is used as it is in the calculation processing by the speed calculating section 47, but an averaging processing section is provided between the time difference detecting section 46 and the speed calculating section 47. It is also possible to store a plurality of time differences t _{0 to} t _n , calculate an average value of them, and divide the distance coefficient by the average time difference to obtain an average moving speed. Further, an averaging processing unit may be provided at a stage subsequent to the arithmetic processing unit 47, and the moving speed output from the arithmetic processing unit 47 may be stored in the averaging processing unit, and an average of a plurality of moving speeds may be obtained. In these cases, a more accurate moving speed can be detected.

Further, in the above embodiment, the correlation detection unit 10 performs sampling by the correlation value sampling unit 41.
After the correlation value output of the received signal with the same delay time is sampled from the correlation value output of the direct wave and all the delayed waves from the, the peak detection unit 45 detects the peak of the correlation value output sampled. However, when only the correlation value output of the received signal of the same delay time is included in the correlation value output from the correlation detection unit 10, or when a peak can be directly detected from the correlation value output from the correlation detection unit 10, Sampling by the correlation value sampling unit 41 is unnecessary.

In the above embodiment, the case where the receiving device provided with the moving speed detecting unit is moved and the moving speed is detected has been described. However, the moving speed detecting unit is provided in the receiving device of the base station, and the mobile station is provided. Can also be detected. In the CDMA system, in order to increase the multiplexing efficiency, a power control technique for keeping the signal strength from a plurality of mobile stations received by the base station constant, that is, a technique for changing the transmission power of the mobile station is required. By reading the change in transmission power from the signal and correcting the strength of the received signal, it is also possible to detect the speed at the base station. However, if the control cycle of the power control is longer than the fluctuation cycle of the received signal level, it can be ignored.

In the above embodiment, the peak of the correlation value output having the same delay time included in the correlation value output is detected,
The time difference between two peaks among the detected peaks is obtained, and this time difference corresponds to the fluctuation period of the correlation value output having the same delay time. Accordingly, the fluctuation period of the correlation value output having the same delay time without detecting the peak (unit:
If the time can be obtained, the moving speed can be obtained by dividing the distance coefficient by the fluctuation cycle.

[0051]

As described above, according to the present invention,
In the CDMA system, it is possible to easily detect the moving speed of a mobile using only a transmission / reception system using a spread spectrum signal. As a result, in the hierarchical cell structure,
It is possible to easily and inexpensively allocate cells to mobiles.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram showing a level variation of a correlation value output of a delayed wave with a change in a moving distance.

FIG. 2 is a block diagram of a transmission / reception system of a spread spectrum signal according to an embodiment of the present invention;

3A is a characteristic diagram showing a correlation value obtained by a correlation processing unit, and FIG. 3B is a characteristic diagram showing a correlation value output;

FIG. 4 is a block diagram of a moving speed detecting unit according to the embodiment.

5A is a characteristic diagram showing a correlation value output, FIG. 5B is a characteristic diagram showing a sampled correlation value, FIG. 5C is a schematic diagram showing a result of peak detection, and FIG. 5D is a schematic diagram showing a time difference; Figure

FIG. 6 is a characteristic diagram showing a moving speed estimation result by the moving speed detecting method according to the embodiment.

[Explanation of symbols]

 Reference Signs List 10 correlation detection unit 41 correlation value sampling unit 43 correlation value buffer unit 44 reception time buffer unit 45 peak detection unit 46 time difference detection unit 47 speed calculation unit 48 distance coefficient buffer unit

Claims (10)

[Claims] A demodulator for demodulating and correlating a received signal according to a spread spectrum method and outputting a correlation value output.
A correlation processing unit, a time difference detection unit that obtains, as a time difference, a variation cycle of the correlation value output of the received signal having the same delay time included in the correlation value output, and dividing a predetermined distance coefficient by the time difference obtained by the time difference detection unit. And a calculation processing unit that calculates a moving speed of the moving object by performing the operation. 2. The apparatus according to claim 1, further comprising a peak detector for detecting a peak of the correlation value output, wherein the time difference detector obtains a time difference between two peaks among the peaks detected by the peak detector. 2. The moving speed detecting device according to claim 1. 3. The moving speed detecting device according to claim 1, wherein a wavelength of the received signal or an integral multiple thereof is used as the distance coefficient. 4. The movement according to claim 1, wherein an actual measurement value of a movement distance between points of the moving object corresponding to a fluctuation cycle of the correlation value output is used as the distance coefficient. Speed detector. 5. The moving speed detecting device according to claim 1, further comprising an averaging processing unit for calculating an average value of the moving speed. 6. The moving speed detecting device according to claim 1, further comprising a smoothing processing unit for smoothing a correlation value output. 7. A step of receiving a received signal according to the spread spectrum system, demodulating and correlating the signal to obtain a correlation value output, and changing the correlation value output of the reception signal having the same delay time included in the correlation value output. A moving speed detecting method, comprising: obtaining a period as a time difference; and calculating a moving speed of the moving body by dividing a predetermined distance coefficient by the time difference. 8. The method according to claim 7, wherein peaks of the correlation value output of the received signals having the same delay time included in the correlation value output are detected, and a time difference between two of these peaks is obtained. Moving speed detection method. 9. The moving speed detecting method according to claim 7, wherein a wavelength of the received signal or an integral multiple thereof is used as the distance coefficient. 10. The moving speed according to claim 7, wherein an actual measured value of a moving distance between points of the moving object corresponding to a fluctuation cycle of the correlation value output is used as the distance coefficient. Detection method.