WO2007117026A1

WO2007117026A1 - Moving speed detecting apparatus for mobile terminal

Info

Publication number: WO2007117026A1
Application number: PCT/JP2007/057997
Authority: WO
Inventors: Akinori Ohashi; Kazuaki Ishioka; Takuya Sakaishi; Shinsuke Uga; Hiroo Omori
Original assignee: Mitsubishi Electric Corporation; Ntt Docomo, Inc.
Priority date: 2006-04-11
Filing date: 2007-04-11
Publication date: 2007-10-18
Also published as: JPWO2007117026A1; JP4876124B2

Abstract

A moving speed detecting apparatus for a mobile terminal is composed of: a pilot signal extracting section (1) for extracting a pilot signal from the received signal transmitted from a base station; a frequency analyzing section (2) formed by an octave division filter bank for computing the value of power for each frequency band according to the pilot signal extracted by the pilot signal extracting section (1); a maximum Doppler frequency estimating section (3) for estimating the maximum Doppler frequency on the basis of the power value for each frequency band computed by the frequency analyzing section (2); and a moving speed computing section (4) for computing moving speed from the maximum Doppler frequency estimated by the maximum Doppler frequency estimating section (3) and the carrier frequency of the pilot signal extracted by the pilot signal extracting section (1). The frequency can be analyzed with a small amount of computation to detect the moving speed by using the octave division filter bank for the frequency analyzing section (2).

Description

Moving speed detection device for mobile terminal

Technical field

The present invention relates to a moving speed detection apparatus for a mobile terminal that detects the moving speed of the mobile terminal from a received signal transmitted from a base station.

Background art

[0002] Conventional mobile terminal moving speed detection devices include a pilot signal extraction unit that extracts a pilot signal from a received signal, a frequency analysis unit that performs a fast Fourier transform in accordance with the extracted pilot signal, and a high-speed Based on the sample data after Fourier transform, it is composed of a maximum Doppler frequency estimator that estimates the maximum Doppler frequency and a moving speed calculator that calculates the moving speed from the estimated maximum Doppler frequency and the carrier frequency. There is something to do.

[0003] Further, the maximum Doppler frequency estimation unit detects the frequency at which the power value of the pilot signal is maximum on the frequency axis based on the sample data after fast Fourier transform corresponding to the pilot signal, and performs maximum Doppler frequency estimation. A force that estimates frequency The differentiation circuit that performs differentiation on sample data after high-speed Fourier transform, and the minimum value detector that detects the minimum value from the output of the differentiation circuit and estimates the maximum Doppler frequency (For example, see Patent Document 1).

[0004] Patent Document 1: Japanese Patent Laid-Open No. 7-140232

[0005] A conventional mobile terminal moving speed detection apparatus is configured as described above! Therefore, the frequency analysis unit performs fast Fourier transform in accordance with the pilot signal. This is one of the means for performing frequency analysis. In addition, it is generally desired that a mobile terminal moving speed detection device be realized with as little calculation as possible for reasons such as power consumption and circuit scale. However, there is a problem that the amount of calculation increases by performing fast Fourier transform.

[0006] The present invention has been made to solve the above-described problems. It is an object of the present invention to obtain a moving speed detection device for a mobile terminal that detects a moving speed by performing frequency analysis with a small amount of calculation. Target.

Disclosure of the invention

[0007] A moving speed detection apparatus for a mobile terminal according to the present invention includes a pilot signal extraction unit that extracts a pilot signal from a reception signal transmitted from a base station, and an octave division filter bank, and the pilot signal extraction unit A frequency analysis unit that calculates a power value for each frequency band corresponding to the extracted pilot signal, and a maximum Doppler frequency estimation unit that estimates the maximum Doppler frequency based on the power value for each frequency band calculated by the frequency analysis unit. And a moving speed calculating unit that calculates a moving speed from the maximum Doppler frequency estimated by the maximum Doppler frequency estimating unit and the carrier frequency of the pilot signal extracted by the pilot signal extracting unit.

[0008] According to the present invention, by using an octave division filter bank in the frequency analysis unit, there is an effect that frequency analysis can be performed with a small amount of calculation and a moving speed can be detected. Brief Description of Drawings

FIG. 1 is a block diagram showing a moving speed detection device for a mobile terminal according to Embodiment 1 of the present invention.

FIG. 2 is an explanatory diagram showing an example when the frequency analysis unit divides the octave into eight bands.

FIG. 3 is a block diagram showing a filter bank corresponding to octave division.

FIG. 4 is a block diagram showing a specific example of HPF and LPF.

FIG. 5 is a graph showing an example of frequency band selection for calculating the maximum Doppler frequency.

FIG. 6 is a flowchart showing processing of a maximum Doppler frequency estimation unit.

FIG. 7 is a block diagram showing a moving speed detection device for a mobile terminal according to Embodiment 2 of the present invention.

FIG. 8 is a block diagram showing a moving speed detection device for a mobile terminal according to Embodiment 3 of the present invention.

FIG. 9 is a block diagram showing a moving speed detection apparatus for a mobile terminal according to Embodiment 4 of the present invention. FIG. 10 is a flowchart showing processing of a maximum Doppler frequency estimation unit.

FIG. 11 is a block diagram showing a moving speed detection device for a mobile terminal according to Embodiment 6 of the present invention.

FIG. 12 is a configuration diagram showing details of a filter with a clip.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, in order to describe the present invention in more detail, the best mode for carrying out the present invention will be described with reference to the accompanying drawings.

Embodiment 1.

FIG. 1 is a configuration diagram showing a moving speed detection apparatus for a mobile terminal according to Embodiment 1 of the present invention. In the figure, a pilot signal extraction unit 1 extracts a pilot signal from a received signal transmitted from a base station. To do. The frequency analysis unit 2 divides the extracted pilot signal into a predetermined frequency band by using an octave division filter bank, and calculates a power value for each frequency band. The maximum Doppler frequency estimation unit 3 estimates the maximum Doppler frequency from the calculated power value for each frequency band. The moving speed calculation unit 4 calculates the moving speed based on the estimated maximum Doppler frequency and the carrier frequency of the received signal.

Next, the operation will be described.

In FIG. 1, a pilot signal extraction unit 1 extracts a pilot signal from a received signal that has also been transmitted with a base station power.

[0012] The frequency analysis unit 2 includes a filter bank that performs octave division of a pilot signal and a power calculation unit that calculates a power value for each divided frequency band. In the frequency analysis unit 2, the pilot signal is divided into octaves and the power value of each frequency band is calculated.

[0013] Fig. 2 is an explanatory diagram showing an example of octave division into eight bands in the frequency analysis unit. In the example shown in Fig. 2, the frequency band divided into octaves is 3.75 (kHz). It is. In this example, since the carrier frequency fc = 2.174 (GHz), the moving speed v (mZs) can be obtained from v = c XfdZfc, so it can be detected up to the maximum moving speed 1863 (kmZ h). It becomes. However, the speed of light c = 3. OX 10 ⁸ (mZs), the maximum Doppler frequency fd (Hz), and the carrier frequency fc (Hz). FIG. 3 is a block diagram showing a filter bank corresponding to octave division. In the figure, the octave division filter bank in the frequency analysis unit 2 includes the next high-pass filter (H PF) 21 and the first-order low-pass filter (LPF) 22 By connecting HPFZLPF in a tree shape as shown in Fig. 3, an octave division filter bank is realized. The frequency analysis unit 2 divides the pilot signal into predetermined frequency bands in the octave division filter bank, calculates the power value for each frequency band in the power calculation unit 23, and then calculates the power value for each frequency band in the regularity processing unit 24. Perform regular processing to match the bandwidth. (1) to (8) shown in FIG. 3 correspond to the frequency bands (1) to (8) shown in FIG. 2, and the calculated power value for each frequency band is the maximum Doppler frequency estimation unit. Output to 3

[0015] Fig. 4 is a block diagram showing a specific example of HPF and LPF. In this figure, in order to reduce the processing amount, in this example, the first-order high-pass filter (HPF) 21 and the first-order low-pass filter (L PF ) 22 is the storage element 25 provided on one path where the input is branched, the downsampler 26 provided on both paths and the rate 1Z2 of each path, and the value of the other path provided on both paths. It consists of an adder 27 that adds and subtracts the value of this path.

The maximum Doppler frequency estimation unit 3 estimates the power value force maximum Doppler frequency for each frequency band obtained by the frequency analysis unit 2.

The maximum Doppler frequency estimation unit 3 calculates a candidate maximum Doppler frequency after selecting a plurality of frequency bands, and sequentially performs a check until the calculated frequency meets a condition. In addition, when multiple frequency bands are selected, the maximum Doppler frequency can be estimated more accurately by sequentially selecting higher frequency band forces in order to suppress the influence of direct waves in the rice fading environment.

FIG. 5 is a graph showing an example of selection of a frequency band for calculating the maximum Doppler frequency. In the figure, when the pilot signal is frequency-divided into the frequency bands (1) to (8), In this example, the frequency bands (4) to (6) are selected from (1) to (8). After selecting multiple frequency bands, the candidate maximum Doppler frequency is obtained from the power value of each frequency band. As a method for determining the maximum Doppler frequency as a candidate, for example, a center of gravity point is obtained by weighting the power value of each frequency band, and this center of gravity point is determined as the maximum Doppler frequency. The method of making a candidate for If the calculated frequency is not within the selected frequency band, select a different band and calculate again.

FIG. 6 is a flowchart showing processing of the maximum Doppler frequency estimation unit. The maximum Doppler frequency estimation unit 3 performs the following processing (ST1) to (ST3).

(ST1) Select multiple frequency bands. For example, select three bands in order of higher frequency band power.

(ST2) A candidate maximum Doppler frequency is calculated.

(ST3) If the calculated frequency is within the selected band, the maximum Doppler frequency is set. If it is not within the selected band, the process returns to (ST1) to reselect a band having a low frequency.

The movement speed calculation unit 4 calculates the movement speed using the maximum Doppler frequency estimated by the maximum Doppler frequency estimation unit 3 and the carrier frequency of the pilot signal extracted by the pilot signal extraction unit 1. The moving speed calculation unit 4 uses the following formula when moving speed v (mZs), light speed c = 3. OX IO ⁸ (m / s), maximum Doppler frequency fd (Hz), carrier frequency fc (Hz) Calculate the moving speed.

v = c X fd / fc

[0020] As described above, according to the first embodiment, by using the octave division filter bank in the frequency analysis unit 2, it is possible to perform frequency analysis with a small amount of calculation and detect the moving speed.

In addition, the maximum Doppler frequency estimation unit 3 sequentially selects the power value of a high frequency band, thereby suppressing the influence of the direct wave in the rice fading environment and estimating the more accurate maximum Doppler frequency.

[0021] Embodiment 2.

FIG. 7 is a block diagram showing a moving speed detection apparatus for a mobile terminal according to Embodiment 2 of the present invention. In the figure, a pilot signal extraction unit 1 is used in a CDMA mobile terminal by using a multipath detection function. Then, the pilot signal is extracted from the received signal for each path or each antenna, and the frequency analysis unit 2 performs the frequency band according to the pilot signal extracted by the pilot signal extraction unit 1 for each path or each antenna. The power value is calculated, and the power combiner 5 combines the calculated power values for each frequency band. In the configuration example shown in FIG. 7, the number of fingers is 8 and the number of antennas is 2. The other configurations are the same as those in FIG.

Next, the operation will be described.

In Fig. 1, pilot signal extraction unit 1 extracts a pilot signal from the received signal for each path and each antenna, and frequency analysis unit 2 applies to each pilot signal extracted for each path and each antenna. Divide the frequency band using the octave division filter bank and calculate the power value of each frequency band. The power combiner 5 combines the obtained power values for each frequency band. The maximum Doppler frequency estimation unit 3 estimates the maximum Doppler frequency from the power in each frequency band, and the moving speed calculation unit 4 detects the moving speed from the estimated maximum Doppler frequency and the carrier wave frequency.

As described above, according to the second embodiment, in the case of a CDMA mobile terminal, the pilot signal is extracted from the received signal for each path or for each antenna in the pilot signal extraction unit 1 to perform frequency analysis. In unit 2, the power value for each frequency band corresponding to the pilot signal extracted by the pilot signal extraction unit is calculated for each path or for each antenna, and synthesized in each frequency band in power combining unit 5, The power value of each frequency band can be obtained more accurately.

Embodiment 3.

FIG. 8 is a block diagram showing a moving speed detection device for a mobile terminal according to Embodiment 3 of the present invention. In the maximum Doppler frequency estimation unit 3 in the figure, the low frequency suppression processing unit 31 is a high frequency band as preprocessing. The maximum frequency Doppler frequency calculation unit 32 performs the same processing as the maximum Doppler frequency estimation unit 3 in the first embodiment. Other configurations are the same as those in FIG.

Next, the operation will be described.

In FIG. 8, the maximum Doppler frequency estimation unit 3 includes a low frequency suppression processing unit 31 and a maximum Doppler frequency calculation unit 32. The low frequency suppression processing unit 31 suppresses leakage into the high and frequency bands due to the low frequency band. The leakage due to the low frequency band and the high frequency band is caused by the fact that the frequency analysis unit 2 cannot accurately divide the frequency band by using HPFZLPF. Low frequency suppression As a result, the power value for each frequency band can be accurately obtained, and the maximum Doppler frequency can be estimated appropriately. The maximum Doppler frequency calculation unit 32 performs the same processing as the maximum Doppler frequency estimation unit 3 in the first embodiment.

As described above, according to the third embodiment, the maximum Doppler frequency estimator 3 performs the low frequency suppression process on the high frequency band as a pre-processing, so that the high frequency band by the low frequency band is obtained. The power value for each frequency band corresponding to the pilot signal can be obtained more accurately.

[0027] Embodiment 4.

FIG. 9 is a configuration diagram showing a moving speed detection apparatus for a mobile terminal according to Embodiment 4 of the present invention. In the maximum Doppler frequency estimation unit 3 in the figure, the power value correction unit 33 uses a high frequency band as an interference component. The maximum Doppler frequency calculation unit 32 performs the same processing as the maximum Doppler frequency estimation unit 3 in the first embodiment. It is. Other configurations are the same as those in FIG.

Next, the operation will be described.

In FIG. 9, the maximum Doppler frequency estimation unit 3 includes a power value correction unit 33 and a maximum Doppler frequency calculation unit 32. The power value correcting unit 33 regards the highest frequency component as interference power and corrects power values in other frequency bands. The reason why the highest frequency component is the interference power is that the frequency band divided by the frequency analysis unit 2 is wider than the expected Doppler shift, so there is almost no Doppler shift to the highest frequency band. It is because it is considered. In the example of the frequency band to be divided by the octave in Fig. 2, it is necessary to move in the range of 931.5 to 1863 (kmZh) in order to doppler shift to the highest frequency band, and the speed is detected by the mobile terminal. In the case where the device is mounted, it is considered that there is almost no such moving speed. By performing the power value correction process, the power value for each frequency band can be accurately obtained, and the maximum Doppler frequency can be estimated appropriately. The maximum Doppler frequency calculation unit 32 performs the same processing as the maximum Doppler frequency estimation unit 3 in the first embodiment. Is what you do.

As described above, according to the fourth embodiment, the maximum Doppler frequency estimation unit 3 uses the high frequency band as an interference component, and corrects the power value in the low frequency band according to the interference component. Thus, the power value of each frequency band corresponding to the pilot signal can be obtained more accurately.

[0030] Embodiment 5.

The maximum Doppler frequency estimation unit 3 in Embodiment 5 calculates quality information of the selected frequency bands after selecting a plurality of frequency bands, and determines a threshold value for determining whether the maximum Doppler frequency can be calculated for the quality information. To do. The rest of the configuration is the same as in Figure 1.

Next, the operation will be described.

FIG. 10 is a flowchart showing the processing of the maximum Doppler frequency estimation unit. The maximum Doppler frequency estimation unit 3 performs the following processing (ST1) to (ST5).

(ST4) Quality information corresponding to the selected frequency band is calculated. For example, as the quality information, the signal power to interference power ratio (SIR) of the selected frequency band, the selected band power to total power ratio, etc. are calculated.

(ST5) The obtained quality information is compared with a preset threshold value, and if the obtained quality information is equal to or greater than the preset threshold value, the requested quality information is preset to (ST2). If it is less than the threshold, return to (ST1) and reselect a different frequency band.

(ST2) A candidate maximum Doppler frequency is calculated.

As described above, according to the fifth embodiment, the maximum Doppler frequency estimation unit 3 calculates the quality information of the selected frequency band, and the threshold value for determining whether or not the maximum Doppler frequency can be calculated for the quality information. By making a decision, a more accurate maximum Doppler frequency can be estimated. [0033] Embodiment 6.

FIG. 11 is a block diagram showing a moving speed detection device for a mobile terminal according to Embodiment 6 of the present invention. In the figure, the filter 6 with a clip corresponds to the moving speed calculated by the moving speed calculation unit 4. Appropriate estimation is performed sequentially. The rest of the configuration is the same as in Figure 1.

Next, the operation will be described.

In FIG. 11, the clipped filter 6 operates so as to converge successively to an appropriate estimated value in which the frequency distribution force of the detection speed is also expected.

FIG. 12 is a block diagram showing details of the filter with clip, and is a configuration example of a filter with clip (nonlinear IIR filter) that performs such processing simply and sequentially.

The filter with clip 6 shown in FIG. 12 includes a maximum speed clip processing unit 61, an acceleration clip processing unit 62, a storage element 63, adders 64 and 66, and a multiplier 65. The maximum speed clip processing unit 61 performs a clipping process with a predetermined value when the detected speed as an input value is equal to or higher than a predetermined value. The acceleration clip processing unit 62 performs acceleration clip processing by applying the filter function f (x) to the input value X to the acceleration clip processing unit 62.

[0035] Here, the filter function f (X) is defined as follows.

[Number 1]

CI: Maximum acceleration (positive maximum acceleration)

C2: Minimum acceleration (negative maximum acceleration)

The storage element 63 sequentially stores the filter output.

The flow of the filtering process is shown below.

1.Maximum speed clip processing

In the maximum speed clip processing unit 61, a predetermined speed is detected with respect to the detection speed that is the filter input value. Clip processing is performed for speed detection results that exceed the maximum speed.

2.Acceleration calculation

The adder 64 calculates the acceleration by taking the difference between the result after processing by the maximum speed clip processing unit 61 and the previous filter output result from the storage element 63.

3. Filter coefficient calculation

The multiplier 65 multiplies the acceleration obtained by the adder 64 by a filter coefficient K.

4.Acceleration clip processing

In the acceleration clip processing unit 62, if the calculation result force by the multiplier 65 exceeds a predetermined maximum acceleration or minimum acceleration, clipping processing is performed with each value.

5. Update filter values

The adder 66 adds the acceleration after processing by the acceleration clip processing unit 62 and the previous filter output value from the storage element 63, and updates the value of the storage element 63 using the result as a filter value. As a result.

[0037] As described above, according to the sixth embodiment, since the clipped filter 6 that sequentially performs appropriate estimation on the moving speed calculated by the moving speed calculating unit 4 is provided, the detection is performed. The accuracy of the moving speed can be improved.

Industrial applicability

[0038] As described above, since the moving speed detection device according to the present invention can perform frequency analysis with a small amount of computation by using an octave division filter bank in the frequency analysis unit, it is possible to receive the signal transmitted from the base station. It is suitable for use in a moving speed detection device of a CDMA mobile terminal that detects a moving speed from a signal.

Claims

The scope of the claims

[1] A pilot signal extraction unit that extracts a pilot signal from a received signal transmitted from a base station;

A frequency analysis unit configured by an octave division filter bank, which calculates a power value for each frequency band corresponding to the pilot signal extracted by the pilot signal extraction unit, and a power for each frequency band calculated by the frequency analysis unit A maximum Doppler frequency estimator that estimates the maximum Doppler frequency based on the value;

The moving speed of a mobile terminal comprising a moving speed calculating unit that calculates a moving speed from the maximum Doppler frequency estimated by the maximum Doppler frequency estimating unit and the carrier frequency of the pilot signal extracted by the pilot signal extracting unit. Detection device.

[2] The pilot signal extractor

Extract the pilot signal from the received signal for each path or each antenna,

The frequency analyzer

A power value for each frequency band corresponding to the pilot signal extracted by the pilot signal extraction unit for each path or antenna is calculated, and the calculated power values are synthesized for each frequency band. The apparatus for detecting a moving speed of a mobile terminal according to claim 1.

[3] The maximum Doppler frequency estimator is

2. The moving speed detection apparatus for a mobile terminal according to claim 1, wherein low frequency suppression processing is performed on the high frequency band as preprocessing.

[4] The maximum Doppler frequency estimator is

2. The moving speed detection device for a mobile terminal according to claim 1, wherein the high frequency band is an interference component, and the power value of the low frequency band is corrected according to the interference component.

[5] The maximum Doppler frequency estimator is

2. The moving speed detection apparatus for a mobile terminal according to claim 1, wherein when selecting a plurality of frequency bands, the maximum Doppler frequency is estimated by sequentially selecting the power value of the high frequency band.

[6] The maximum Doppler frequency estimator is The mobile terminal according to claim 1, wherein after selecting a plurality of frequency bands, quality information of the selected frequency bands is calculated, and a threshold value for determining whether or not the maximum Doppler frequency can be calculated is determined for the quality information. Moving speed detection device.

2. The moving speed detection device for a mobile terminal according to claim 1, further comprising a clipped filter that sequentially performs appropriate estimation on the moving speed calculated by the moving speed calculation unit.