JP2009206889A - Signal source position estimation method and arrival angle estimation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To estimate a position of a signal source or an interference source and a state of an arrival angle by utilization of a multi-beam antenna in terrestrial mobile communication using radio. <P>SOLUTION: Beam forming is performed in the horizontal direction and the vertical direction by the multi-beam antenna to detect difference in antenna gain between a set of adjacent beams by every set of beams, an azimuth angle and an elevation angle corresponding to the difference in antenna gain between the detected set of beams are estimated by referring to data in which the preliminarily acquired difference in antenna gain between each set of beams, the azimuth angle, and the elevation angle are associated one to one. Fast Fourier Transform is performed to a received signal to perform channel estimation, inverse Fast Fourier Transform is performed to the signal after the channel estimation to calculate an impulse response, and the direction in which the signal source exists is estimated based on the estimated azimuth angle, elevation angle, and the calculated impulse response. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a signal source position estimation method and an arrival angle estimation method using a multi-beam antenna.

  Conventionally, a method for estimating an arrival direction of an interference wave using a unitary directional beam is known. FIG. 14 is a diagram illustrating a conventional method for estimating the arrival direction of an interference wave. As shown in FIG. 14, conventionally, a unitary directional beam is physically scanned in a horizontal direction and a vertical method to estimate the arrival direction of an interference wave.

  Further, for example, Japanese Patent Application Laid-Open No. 11-266228 (Patent Document 1) discloses a multi-beam antenna system. In this multi-beam antenna system, in a CDMA radio base station, signals received by a plurality of antenna elements of a receiving-side array antenna are subjected to beam forming by a reception beam former RBF to electrically form a plurality of uplink beams. Then, reception is performed based on an optimum beam (for example, a beam having the maximum power) among the plurality of uplink beams. In addition, a transmission beam former TBF that performs beam forming on the transmission signal is provided, and the control unit CNT performs downlink beam forming based on the presence or absence of the uplink reception signal to form a downlink transmission beam in the same direction as the uplink reception beam, Alternatively, it is controlled whether or not downlink beamforming is performed.

  As a method of estimating a propagation path, a method of estimating the state of the propagation path by observing a reception spectrum characteristic in a single wideband signal is known.

Japanese Patent Laying-Open No. 2000-040987 (Patent Document 2) discloses a wireless communication system. In this radio communication system, channel characteristics are estimated by an automatic equalizer provided in the base station apparatus, and based on the estimation result, the inverse characteristics of the channel are added to the downlink transmission data transmitted to the terminal apparatus. The data to which the reverse characteristic of the propagation path is added is transmitted as transmission data to the terminal device.
Japanese Patent Laid-Open No. 11-266228 JP 2000-040987 A

  However, in the method shown in FIG. 14, it takes a long time to scan the beam for estimating the position (direction of arrival) of the signal source (desired wave or interference wave), and the apparatus becomes large. In addition, in the estimation of the propagation path, only the observation of the reception spectrum of a single wideband signal does not reveal a remarkable feature related to the propagation path situation, so that it is not easy to estimate the sufficient propagation path situation.

  The present invention has been made in view of such circumstances, and a signal source position estimation method capable of estimating the position of a signal source or an interference source by using a multi-beam antenna in ground mobile communication using radio. The purpose is to provide. It is another object of the present invention to provide an arrival angle estimation method capable of estimating an arrival angle by monitoring a reception spectrum of a broadband wireless signal.

  (1) In order to achieve the above object, the present invention has taken the following measures. That is, the signal source position estimation method of the present invention is a signal source position estimation method by a position estimation station equipped with a multi-beam antenna capable of beam forming in the horizontal direction and the vertical direction by electronic control. A step of performing beam forming in the horizontal direction to detect a difference in antenna gain between a pair of adjacent beams for each set of beams, and a difference between an antenna gain and an azimuth angle obtained in advance for each set of beams is 1: 1. Referring to the data associated with, the step of estimating the azimuth angle corresponding to the difference in antenna gain of the detected set of beams, and performing beam forming in the vertical direction with the multi-beam antenna, Detecting a difference in antenna gain of each beam set for each set of beams, and an antenna gain of each set of beams acquired in advance. A step of estimating an elevation angle corresponding to a difference in antenna gain of the detected beam pair with reference to data in which a difference and an elevation angle are correlated one-to-one, and performing a fast Fourier transform on a received signal , Performing channel estimation, performing inverse fast Fourier transform on the signal after channel estimation, calculating an impulse response, and based on the estimated azimuth angle, elevation angle and the calculated impulse response, Estimating the direction in which the signal source exists.

  Thus, since the direction in which the signal source exists is estimated based on the estimated azimuth angle, elevation angle, and the calculated impulse response, the direction of the signal source can be estimated with high accuracy even when it is out of sight. it can. Further, since the beam forming can be performed in the horizontal direction and the vertical direction by electronic control, it is possible to instantaneously switch from the antenna pattern beam-formed in the horizontal direction to the antenna pattern beam-formed in the vertical direction. Further, since the azimuth angle and the elevation angle are estimated, the direction in which the signal source exists can be estimated based on the estimated azimuth angle and elevation angle. As a result, unlike the prior art, it is not necessary to scan the beam for detecting the direction of arrival of the signal source, and the position of the signal source can be estimated in a short time. Further, it is possible to promote interference avoidance and effective use of frequency. Further, the use of the software defined radio makes it possible to implement the present invention without greatly changing the conventional hardware.

  (2) In the signal source position estimation method of the present invention, the step of estimating the direction in which the signal source exists uses a minimum delay component with the smallest delay amount in the calculated impulse response. .

  As described above, since the minimum delay component with the smallest delay amount is used in the impulse response, the error can be minimized. That is, when the line of sight is considered to be a multiple propagation path, the profile component with the smallest delay in the impulse response is considered to correspond to the path with the shortest distance between the signal source and the observation station. By using this minimum delay component, the estimation error of the signal source can be minimized.

  (3) Also, the arrival angle estimation method of the present invention is an arrival angle estimation method by a position estimation station having a multi-beam antenna capable of beam forming in the horizontal direction and the vertical direction by electronic control, wherein the multi-beam antenna Performing beam forming in the horizontal direction to detect a difference in antenna gain between a pair of adjacent beams for each pair of beams, and performing beam forming in the vertical direction with the multi-beam antenna to form a pair of adjacent beams. Detecting a difference in antenna gain of each beam for each set of beams, performing fast Fourier transform on the received signal to perform channel estimation, and inverse fast Fourier transform on the signal after channel estimation To calculate an impulse response, and the calculated impulse response For each delay component, the antenna gain difference of each set of beams acquired in advance and the azimuth angle are referenced one-to-one to correspond to the difference in antenna gain of the detected set of beams. With respect to each delay component in the calculated impulse response, the detection is performed with reference to the data obtained by preliminarily associating the antenna gain difference and the elevation angle of each set of beams with respect to each delay component in the calculated impulse response. Estimating an elevation angle corresponding to a difference in antenna gain of the set of beams, and measuring an arrival angle of each delay component based on an azimuth angle and an elevation angle estimated for each delay component, respectively. It is characterized by including.

  Thus, since the arrival angle of each delay component is measured based on the azimuth angle and elevation angle estimated for each delay component, it is possible to estimate the state of the multiple propagation path composed of each delay component.

  According to the present invention, since the direction in which the signal source exists is estimated based on the estimated azimuth angle, elevation angle, and the calculated impulse response, the direction of the signal source is estimated with high accuracy even when it is out of sight. be able to. Further, since the beam forming can be performed in the horizontal direction and the vertical direction by electronic control, it is possible to instantaneously switch from the antenna pattern beam-formed in the horizontal direction to the antenna pattern beam-formed in the vertical direction. Further, since the azimuth angle and the elevation angle are estimated, the direction in which the signal source exists can be estimated based on the estimated azimuth angle and elevation angle. As a result, unlike the prior art, it is not necessary to scan the beam for detecting the direction of arrival of the signal source, and the position of the signal source can be estimated in a short time. Further, it is possible to promote interference avoidance and effective use of frequency. Further, the use of the software defined radio makes it possible to implement the present invention without greatly changing the conventional hardware.

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram illustrating a schematic configuration of a wireless communication system according to the present embodiment. In Figure 1, the radio base station 100 is provided with the receiving-side array antenna ANT _1, the array antenna ANT ₁ has a plurality of antenna elements _AR 1 to Ar _N. The radio base station 100 is provided with an array antenna ANT ₂ on the transmission side, the array antenna ANT ₂ has a plurality of antenna elements _AT 1 to AT _N.

The reception circuits RV _{1 to} RV _N perform high frequency amplification, frequency conversion, and the like of the reception signal. Transmitting circuit _SD 1 to SD _N is frequency conversion, performs high-frequency amplification. The reception beam former RBF performs reception beam forming on the signals received by the _N antenna elements AR _{1 to} ARN to electrically form _M uplink reception beams B _{1 to} B _M. The transmission beamformer TBF can generate a transmission beam having directivity in a predetermined direction by performing transmission beamforming on a transmission signal to generate an antenna element input signal and inputting the input signal to each antenna element. .

  The control unit CNT controls the reception beam former RBF and the transmission beam former TBF to generate a desired beam. The receiving unit RV performs signal detection and error correction, and the transmitting unit SD modulates transmission data. The power monitor PWM observes the received power in an arbitrary beam and is used for estimating the signal source arrival angle. The spectrum monitor SPM observes a signal spectrum received in an arbitrary beam and is used for estimating a transmission path condition. FIG. 1 shows both transmission and reception configurations, but only the reception function is used when estimating the position of the signal source.

  FIG. 2 is a diagram showing the basic concept of the signal source position estimation method of the present invention with respect to the horizontal direction (azimuth angle direction). In the present invention, a difference in received power between two adjacent beams is detected, and a signal source arrival angle is obtained from the difference (= antenna gain difference). That is, in the position estimation station (hereinafter, simply referred to as “estimation station”), the gain difference between adjacent beams is calculated in advance, and the arrival angle is calculated from the difference between the two detected powers. For example, as shown in FIG. 2, the difference between the received power (antenna gain) of the beam 4 and the received power (antenna gain) of the beam 5 is obtained and acquired in advance as shown on the right side in FIG. The azimuth angle corresponding to the difference between the detected antenna gains of the beams 4 and 5 is estimated with reference to the data in which the difference between the antenna gains and the azimuth angles of the sets of beams is one-to-one. The same applies to the vertical direction (elevation direction).

  FIG. 3A shows an example of multi-beam antenna gain characteristics when beam forming is performed in the horizontal direction, which is used when obtaining the signal source arrival angle in the horizontal direction. FIG. 3B shows a vertical beam. FIG. 4 shows multi-beam antenna gain characteristics when beam forming is performed in the vertical direction, which is used when obtaining the signal source arrival angle in the vertical direction. The horizontal direction and the vertical direction in FIG. 3 are interchanged, and four beams in a low elevation angle direction as viewed from the antenna are used.

  In the signal source position estimation method according to the present invention, the position estimation station using these multi-beam antenna systems estimates the signal source position by estimating the horizontal and vertical signal source arrival angles.

  Next, the procedure of the signal source position estimation method of the present invention will be described. In the multi-beam antenna of the position estimation station shown in FIG. 5 (a), horizontal beam forming shown in FIG. 3 (a) is performed. In this state, the received power difference between the beam having the maximum received power of the signal source and the beam having the higher received power among the adjacent beams is obtained. The azimuth angle is calculated from the relationship between the gain difference between the two beams calculated in advance and the azimuth angle to obtain an estimated value of the horizontal signal source arrival angle.

  In the multi-beam antenna of the position estimation station shown in FIG. 5B, vertical beam forming shown in FIG. 4 is performed. In this state, the received power difference between the beam having the maximum received power of the signal source and the beam having the higher received power among the adjacent beams is obtained. The elevation angle is calculated from the previously calculated relationship between the gain difference between the two beams and the elevation angle, and is used as an estimated value of the signal source arrival angle in the vertical direction.

  The position of the signal source is estimated from the estimated values of the signal source arrival angles in the horizontal and vertical directions. When the height of the signal source is unknown, only the direction of the signal source can be estimated. However, when the height of the signal source is known, the position of the signal source can be estimated.

  When position estimation is performed using a multi-beam antenna, a signal propagated in multiple paths cannot be divided for each propagation path as it is. In this case, position estimation must be performed from all of the multiple components. As a result, a signal passing through a propagation path with small propagation attenuation, that is, a signal component having a large received power becomes dominant, and the error becomes large.

  In cognitive radio, it is necessary to measure the surrounding radio environment and perform optimal control of the radio system and antenna. One of the basic characteristics of the wireless environment is the propagation path condition, which is required to be easily measured without the addition of special hardware (such as a measuring instrument or antenna). . For the environmental control as described above, it is necessary to obtain the estimated value in the receiver in real time.

  The present embodiment realizes the following method in order to meet such a demand. First, the transfer function of the propagation path and the impulse response derived from the transfer function will be described. FIG. 6 is a diagram illustrating a schematic configuration of a propagation state monitoring apparatus having a function of obtaining a transfer function from a received signal. For example, in an OFDM communication system such as WiMAX, the RF unit 60 obtains a received wave (received signal), performs analog / digital conversion in the A / D conversion unit 61, and then performs multicarrier demodulation in the FFT circuit 62. Do. Thereafter, the channel estimation unit 63 performs channel estimation in order to compensate for the multipath distorted signal. Then, channel equalization unit 64 performs channel equalization, and decoding unit 65 performs decoding. Channel estimation is performed by using a preamble signal added on the transmission side and comparing it with a known signal held on the receiver side. The propagation state monitoring device 50 outputs the amplitude and phase obtained by the channel estimation unit 63. In FIG. 6, the amplitude and phase are configured to be displayed on a PC.

  FIG. 7 is a diagram illustrating a test configuration example of the propagation state monitoring apparatus. In order to simulate multipath propagation, an equivalent baseband signal is created as waveform data and input to an SG (signal generator) to obtain an RF signal. FIG. 8 is a diagram showing the amplitude and phase of the multipath propagation model. In the upper left and lower left of FIG. 8, an example of the spectrum (transfer function) of the amplitude and phase of each subchannel obtained by the propagation state monitoring apparatus shown in FIG. In addition, examples of the amplitude and phase spectrum (transfer function) of each subchannel calculated from the parameters set in SG shown in FIG. 7 are shown in the upper right and lower right of FIG. As shown in FIG. 8, the amplitude and phase spectrum of each subchannel obtained by the propagation state monitoring apparatus (FIG. 6), and the amplitude and phase spectrum of each subchannel calculated from the parameters set in SG (FIG. 7). ) Is in good agreement.

  FIG. 9 is a diagram illustrating a characteristic (impulse response) obtained by inverse Fourier transform of the transfer function measured by the propagation state monitoring apparatus. This impulse response has a meaning as a delay profile of the propagation path. In FIG. 9, the peak (extreme value) uttered according to the delay time represents each delay component in the multipath. In this way, by performing inverse Fourier transform on the transfer function, it is possible to divide the multiple propagated signal for each delay component.

(Position estimation)
Next, the position estimation method according to the present embodiment will be described. In the case of multiple propagation paths, the profile characteristic with the smallest delay corresponds to the path with the shortest signal source and observation station. For example, in FIG. 9, 0.1 μs corresponds to this. In the delay profile calculated from the signal received by each multi-beam, the arrival angle is estimated using the above-described position estimation method using the same delay component. When this estimation is performed, it is considered that the estimation error is minimized when this minimum delay component is used.

  In order to confirm the effect of this embodiment, a propagation simulation by the ray tracing method was performed. FIG. 10 is a diagram showing a city map of the used propagation path, and FIG. 11 is a diagram showing a simulation result. FIG. 11 shows a case where the center beam (beam # 4) in FIG. 2 is used to face the interference source (angle of the horizontal axis: 0 degree), and further off-beams of 5, 10, 15, and 20 degrees. In this case, the values for each propagation delay value are plotted. “·” Indicates the received power of each path. The solid line indicates the combined power of these signals, and the star-shaped portion indicates the maximum value of the combined power. Since the simulation performed here is a software simulation, the accuracy is infinite. In actual measurements, it is about the reciprocal of the signal bandwidth. If it is 10 MHz, it is about 0.1 μs.

  In the evaluation in FIG. 11, the error becomes smaller as the maximum value approaches 0 degrees. As shown in FIG. 11, the smaller the delay value, the smaller the error. Thereby, the above-mentioned assumption was confirmed by simulation. Furthermore, in the conventional method of position measurement from multi-beams, the power used at that time is the minimum delay component, the total power (sum of all delay components), the maximum power component As shown in FIG. In FIG. 12, interference sources A, B, and C correspond to the three types of signal sources in FIG.

  As shown in FIG. 12, when the component with the smallest delay is used, the estimation error is considerably improved as compared with the conventional method using the total power. For example, in the case of the interference source B, the error is reduced from 18 degrees to 2.5 degrees. In the case of the interference source C, 13 degrees is improved to 1 degree, which shows the superiority of this method.

(Estimation of angle of arrival in multiple channels)
Next, the arrival angle estimation method in the multiple propagation path according to the present embodiment will be described. As described above, when performing position estimation, the minimum delay component is used, but the arrival angle of each delay component can be known by looking at other delay components. Here, since it is a simulation and can be calculated, FIG. 12 also shows the measurement result and true value of the component corresponding to the maximum received power. As is clear from FIG. 12, even in the case of the interference source B with the maximum error, it is 1 degree, and it can be said that the accuracy is quite high. FIG. 13 shows an analytical expression obtained by modeling multiple propagation paths. However, although the two-wave model is shown in the figure, the multipath is also the same. The propagation path delay is reflected in the transfer function and further reflected in the delay profile.

  As described above, according to the present embodiment, position estimation and angle of arrival estimation, which cannot be performed without using a special antenna or measurement apparatus in the prior art, are usually performed without major changes in hardware. It can be implemented by the radio used. In particular, if a software defined radio is used, it can be realized only by changing the software. Furthermore, it has been clarified that the position estimation is more accurate than the prior art, and high accuracy can be obtained even if it is out of sight. Further, this measurement can be performed with the signal itself used for data transmission, and there is a special effect that a special signal for that purpose is unnecessary.

  Note that the signal source position estimation method according to the present invention and the arrival angle estimation method according to the present invention are used for an entrance line to a base station when a mobile phone has been converted to IP, a link between base stations of a cognitive radio system, and the like. It is possible to apply.

It is a block diagram which shows schematic structure of the radio | wireless communications system which concerns on this embodiment. It is a figure which shows the fundamental view of the signal source position estimation method of this invention with respect to a horizontal direction (azimuth angle direction). (A) shows an example of the multi-beam antenna gain characteristic when beam forming is performed in the horizontal direction, which is used when obtaining the signal source arrival angle in the horizontal direction. (B) shows a vertical beam. It is a figure which shows the multi-beam antenna gain characteristic at the time of performing the beam forming in the perpendicular direction used when calculating | requiring the signal source arrival angle of a perpendicular direction. (A) is a figure which shows the mode of the beam forming of the horizontal direction in each position estimation station, when providing one position estimation station. (B) is a figure which shows the mode of the beam forming of the perpendicular direction in each position estimation station, when providing one position estimation station. It is a figure which shows schematic structure of the propagation state monitoring apparatus which has a function which calculates | requires a transfer function from a received signal. It is a figure which shows schematic structure of the propagation state monitoring apparatus which has a function which calculates | requires a transfer function from a received signal. It is a figure which shows the test structural example of a propagation state monitoring apparatus. It is a figure which shows the amplitude and phase of a multipath propagation model. It is a figure which shows the characteristic (impulse response) which carried out the inverse Fourier transform of the transfer function measured with the propagation state monitor apparatus. It is a figure which shows the urban area map of the used propagation path. It is a figure which shows a simulation result. It is a figure which shows the electric power at the time of performing the position measurement using a multi-beam. It is the figure which modeled the multiple propagation path and showed as an analytical expression. It is a figure which shows the outline of the arrival direction estimation method of the conventional interference wave.

Explanation of symbols

100 radio base station ANT ₁ reception array antenna ANT ₂ transmission array antenna _AR 1 to Ar _N receiving antenna elements _AT 1 to AT _N transmit antenna elements CNT controller PWM power monitor RBF receive beamformer RV receiver _RV 1 _{~RV N} receiver circuit SD transmission unit SD _{1 to} SD _N transmission circuit SPM spectrum monitor TBF transmission beamformer

Claims (3)

A signal source position estimation method by a position estimation station equipped with a multi-beam antenna capable of beam forming in a horizontal direction and a vertical direction by electronic control,
Performing beam forming in the horizontal direction with the multi-beam antenna to detect a difference in antenna gain between a pair of adjacent beams for each set of beams;
A step of estimating an azimuth angle corresponding to the difference in antenna gain of the detected beam pair with reference to data in which the difference between the antenna gain and the azimuth angle of each beam pair acquired in advance is one-to-one. When,
Performing beam forming in the vertical direction with the multi-beam antenna and detecting a difference in antenna gain between a pair of adjacent beams for each set of beams;
Estimating the elevation angle corresponding to the difference between the antenna gains of the detected beam set with reference to data in which the difference between the antenna gain and the elevation angle of each beam set acquired in a one-to-one correspondence is obtained;
Performing a fast Fourier transform on the received signal to perform channel estimation;
Performing an inverse fast Fourier transform on the signal after channel estimation to calculate an impulse response;
Estimating the direction in which the signal source exists based on the estimated azimuth angle, elevation angle and the calculated impulse response.   2. The signal source position estimation method according to claim 1, wherein, in the step of estimating the direction in which the signal source exists, a minimum delay component having the smallest delay amount is used in the calculated impulse response. An arrival angle estimation method by a position estimation station equipped with a multi-beam antenna capable of beam forming in a horizontal direction and a vertical direction by electronic control,
Performing beam forming in the horizontal direction with the multi-beam antenna to detect a difference in antenna gain between a pair of adjacent beams for each set of beams;
Performing beam forming in the vertical direction with the multi-beam antenna and detecting a difference in antenna gain between a pair of adjacent beams for each set of beams;
Performing a fast Fourier transform on the received signal to perform channel estimation;
Performing an inverse fast Fourier transform on the signal after channel estimation to calculate an impulse response;
For each delay component in the calculated impulse response, the antenna gain of the detected set of beams is referred to with reference to data in which the difference between the antenna gains and the azimuths of the sets of beams acquired in advance is correlated one-to-one. Estimating an azimuth corresponding to the difference between,
For each delay component in the calculated impulse response, the antenna gain difference of the detected beam set and the elevation angle are referred to in advance in a one-to-one correspondence with the antenna gain difference of each set of beams. Estimating an elevation angle corresponding to the difference;
Measuring an arrival angle of each delay component based on an azimuth angle and an elevation angle respectively estimated for each delay component.