Receiving device and receiving method as well as program and recording medium

Abstract

Receiving device for receiving radio waves transmitted by a transmitter and for estimating the angle of incidence of a direct wave from the transmitter, comprising: first to Nth (where N is an integer not less than 2) wireless receiving devices, each provided corresponding to first to Nth antenna elements forming a group antenna, and performing frequency conversion and A / D conversion on first to Nth analog signals obtained by receiving the radio waves each through the first to Nth antenna elements to output first to Nth digital signals; First to Nth transmission channel estimation units for estimating transmission channel frequency characteristics based on the first to Nth digital signals, and outputting first to Nth transmission channel estimation results; a delay time estimation unit for estimating, by means of a super-resolution process, delay times of one or more arriving waves contained in the radio waves, based on a transmission channel estimation result within the first to Nth transmission channel estimation results; a delay time grouping unit for comparing the delay times estimated by the delay time estimation unit with a threshold to determine whether the estimated delay times are shorter than the threshold; first to Nth delayed wave removal units, each corresponding to the first to Nth transmission channel estimation units, which remove an incoming wave component from the first to Nth transmission channel estimation results according to the delay time determined by the delay time grouping unit to be equal to or greater than the threshold, and output the first to Nth transmission channel frequency characteristics with respect to the incoming waves of the delay times determined by the delay time grouping unit to be shorter than the threshold; first to Nth incoming wave separation units, each provided corresponding to the first to Nth delayed wave removal units, and each separating incoming wave components contained in the first to Nth transmission channel frequency characteristics from each other to extract first to Nth direct wave components; and an incidence angle estimation unit for estimating an incidence angle of the direct wave based on a phase difference between the first to Nth direct wave components.

Description

Technical field

[0001] The present invention relates to a receiving method and a receiving device and, in particular, to a method for receiving radio waves transmitted from a transmitter and for identifying the direction of incidence of the direct wave based on the received signal. The present invention also relates to a program that causes a computer to execute the processes of the aforementioned receiving device or receiving method and to a computer-readable recording medium on which the aforementioned program is recorded. Background on the state of the art

[0002] When receiving radio waves from a mobile phone, Wi-Fi, terrestrial digital transmission, or similar sources, the reception power is reduced due to the effects of incoming waves (hereinafter referred to as "delayed waves"), which arrive after reflection or scattering by buildings, vehicles, or similar objects, in addition to the incoming wave (hereinafter referred to as "a direct wave") that arrives directly from the transmitter. An environment in which a multitude of incoming waves are present is called a multipath environment.

[0003] A well-known technique for reducing power loss due to multipath reception is directivity control using a multi-element antenna. A multi-element antenna has a multitude of antenna elements and can be tuned to achieve a specific directivity by controlling weighting factors used to combine signals received by the antenna elements. In a multipath environment, the power loss due to the influence of delayed waves can be mitigated by controlling the directivity so that the main lobe is directed towards the direction from which the direct wave arrives. To improve received performance through directivity control of the multi-element antenna, it is necessary to accurately estimate the direction from which the direct wave arrives.

[0004] If the receiver is fixed and the transmitter's direction is known in advance, the directivity factor can be manually adjusted so that the main lobe of the array antenna is directed towards the transmitter. However, if the radio waves are received in a moving object, such as a vehicle, manual adjustment is not feasible in the case of vehicle-to-vehicle communication, as the transmitter's position relative to the receiver changes with the vehicle's movement. Therefore, it is necessary to automatically estimate the direction of arrival of the direct wave from the received signal, in which the direct wave and delayed waves are multiplexed.

[0005] Radio wave environments for wireless communication can be classified into line-of-sight (LOS) connections, where the transmitter has direct line of sight to the receiver, and non-line-of-sight (NLOS) connections, where there is no line of sight between the transmitter and the receiver. The present invention assumes a LOS environment.

[0006] Patent Reference 1 describes a device in which the multipath incidence directions are measured based on signals received by two antennas. In this device, the frequency property (transfer function in the frequency domain) of the transmission channel is estimated from the signal received by each antenna element. The estimated transmission channel frequency property is an inverse Fourier transform used to determine a complex delay profile. The arriving waves with different delay times are separated from the complex delay profile, and the angle of incidence is estimated based on the phase difference between the separated direct waves received by the antenna elements.

[0007] Patent Reference 2 describes the estimation of delay times using a super-resolution process, such as a MUSIC (Multiple Signal Classification) or ESPRIT (Estimation of Signal Parameters via Rotational Invariance Techniques) process. According to the method described in Patent Reference 2, the signals received by a multitude of antennas are converted into a frequency spectrum. The delay time of each incoming wave is estimated using a super-resolution process within this frequency spectrum. The estimation results are used to estimate a coefficient matrix containing the incoming waves. This frequency spectrum is then multiplied by a pseudo-inverse matrix of the coefficient matrix to separate the components of the direct waves. The angle of incidence is then estimated from the phase differences between the separated direct waves. References to the state of the art Patent references Patent reference 1: Patent No. 4, 833, 144 ( Fig. 1) Patent reference 2: Patent publication no. 2010-286403 ( Fig. 1)

[0008] Non-patent reference 1: N. Kikuma, “Adaptive Signal Processing by Array Antenna”, published by Kagaku Gijutsu Shuppan, Nov. 1998.

[0009] Reference will be made later to Non-Patent Reference 1. Summary of the invention: Problems solved by the invention

[0010] The method shown in patent reference 1 addresses a problem where the direct wave and the delayed waves cannot be separated when the delay times are short. For example, if a building, vehicle, or similar object is present near the receiver, there is no significant difference in the propagation path length of the radio waves from the transmitter to the receiver between the direct wave and the delayed waves, resulting in very short delay times. If the delay times are shorter than the delay time resolution of the complex delay profiles, the direct wave and the delayed waves overlap in the estimated complex delay profile and cannot be separated. Consequently, the accuracy of the angle of incidence estimation is significantly reduced.For example, the delay time resolution of the complex delay profile, estimated when receiving a signal with a bandwidth of 10 MHz, is approximately 100 ns, which is the reciprocal of the bandwidth. If a vehicle or similar object is present at a distance of 3 m in the opposite direction to the transmitter from the receiver's perspective, the delay time with respect to the direct wave is... τ=3×2 / c=20ns. Here, c denotes the speed of light (approximately 3×10⁻¹⁰). 8 m / s). The delay time, 20ns, is shorter than the delay time resolution, 100ns, and the direct wave and the delayed wave overlap in the estimated delay profile, resulting in reduced accuracy in estimating the angle of incidence.

[0011] The method shown in patent reference 2 is associated with a problem in that the scope of the processes necessary to separate the incoming wave, in particular the computational scope of the pseudoinverse matrix, is large.

[0012] One objective of the present invention is to provide a receiving device and a method that can accurately estimate the angle of incidence of the direct wave in an environment where delayed waves with short delay times are present, and with which the scope of necessary calculations can be reduced. Means to solve the problem

[0013] A receiving device according to the present invention is for receiving radio waves transmitted from a transmitter and for estimating an angle of incidence of a direct wave from the transmitter, comprising: first to Nth (where N is an integer not less than 2) wireless receiving devices, each provided corresponding to first to Nth antenna elements forming a group antenna, and performing frequency conversion and A / D conversion on first to Nth analog signals obtained by receiving radio waves through the first to Nth antenna elements to output first to Nth digital signals; First to Nth transmission channel estimation units for estimating transmission channel frequency characteristics, based on the first to Nth digital signals, and outputting first to Nth transmission channel estimation results; a delay time estimation unit for estimating, by means of a super-resolution process, delay times of one or more arriving waves contained in the radio waves, based on a transmission channel estimation result within the first to Nth transmission channel estimation results; a delay time grouping unit for comparing the delay times estimated by the delay time estimation unit with a threshold to determine whether the estimated delay times are shorter than the threshold; First to Nth delayed wave distance unit distance units, each provided corresponding to the first to Nth transmission channel estimation units, which remove an incoming wave component from the first to Nth transmission channel estimation results, corresponding to the delay time that the delay time grouping unit has determined to be equal to or greater than the threshold, and output the first to Nth transmission channel frequency characteristics with respect to the incoming waves of the delay times that the delay time grouping unit has determined to be shorter than the threshold; first to Nth incoming wave separation units, each provided corresponding to the first to Nth delayed wave removal units, and each separating incoming wave components contained in the first to Nth transmission channel frequency characteristics from each other to extract first to Nth direct wave components; and an incidence angle estimation unit for estimating an incidence angle of the direct wave based on a phase difference between the first to Nth direct wave components. Effects of the invention

[0014] According to the present invention, the direct wave and the delayed wave are separated after estimating the delay times by a super-resolution process, so that the angle of incidence of the direct wave can be accurately estimated, even in an environment where a delayed wave with a short delay time is present. Furthermore, the calculation of the pseudoinverse matrix, etc., is performed after removing a relatively long delay time, thus reducing the computational scope. Brief description of the drawings Fig. Figure 1 is a block diagram showing a receiving device according to a first embodiment of the present invention. Fig. Figure 2 is a block diagram showing an example of a configuration of the transmission channel estimation unit in Fig. 1 shows. Fig. Figure 3 is a block diagram showing another example of a configuration of the transmission channel estimation unit in Fig. 1 shows. Fig. Figure 4 is a block diagram showing an example of a configuration of the delayed wave distance unit in Fig. 1 shows. Fig. 5 (a) is a diagram showing an example of a delay profile before removal of the delayed waves by the delayed wave removal unit in Fig. 1, and Fig. 5 (b) and Fig. 5 (c) are diagrams showing different examples of delay profiles according to distance. Fig. Figure 6 is a diagram that schematically illustrates the angle of incidence of the direct wave. Fig. Figure 7 is a block diagram that shows an example of a configuration of the angle of incidence estimation unit in Fig. 1 shows. Fig. Figure 8 is a block diagram showing a receiving device according to a second embodiment of the present invention. Fig. Figure 9 is a block diagram showing a receiving device according to a third embodiment of the present invention. Fig. Figure 10 is a flowchart showing the sequence of processes in a receiving procedure according to a fourth embodiment of the present invention. Fig. 11 is a flowchart that illustrates the sequence of processes in an example of the transmission channel estimation step in Fig. 10 shows. Fig. Figure 12 is a flowchart that illustrates the sequence of processes in another example of the transmission channel estimation step in Fig. 10 shows. Fig. Figure 13 is a flowchart illustrating the sequence of processes in an example of the delayed wave removal step in Fig. 10 shows. Fig. 14 is a flowchart that illustrates the sequence of processes in an example of the angle of incidence estimation step in Fig. 10 shows. Fig. Figure 15 is a flowchart showing the sequence of processes in a receiving procedure according to a fifth embodiment of the present invention. Fig. Figure 16 is a flowchart showing the sequence of processes in a receiving procedure according to the sixth embodiment of the present invention. Fig. Figure 17 is a block diagram showing a computer performing the processes according to the first to sixth embodiments. Mode for executing the invention; First embodiment

[0015] Fig. Figure 1 shows a receiving device of the present embodiment.

[0016] The receiver shown is used to receive radio waves sent by a transmitter and to estimate the direction of the transmitter, i.e., the direction of incidence of the direct wave.

[0017] The illustrated receiving device comprises wireless receiving units 11-1, 11-2, transmission channel estimating units 12-1, 12-2, a delay time estimating unit 13, a delay time grouping unit 14, delayed wave distance units 15-1, 15-2, a pseudoinverse matrix generation unit 16, arriving wave separation units 17-1, 17-2 and an angle of incidence estimating unit 18. The wireless receiving units 11-1, 11-2 are each connected to antenna elements 10-1, 10-2.

[0018] The wireless receiving unit 11-1, the transmission channel estimating unit 12-1, the delayed wave distance unit 15-1, and the incoming wave separation unit 17-1 form a first system and are provided to correspond with each other and also correspond with the first antenna element 10-1.

[0019] The wireless receiving unit 11-2, the transmission channel estimating unit 12-2, the delayed wave distance unit 15-2 and the incoming wave separation unit 17-2 form a second system and are provided to correspond with each other and also correspond with the second antenna element 10-2.

[0020] The processes in the first system and the processes in the second system are similar. However, the signals supplied to the respective systems differ (that is, they are the signals received from the antenna elements 10-1 and 10-2, respectively).

[0021] The delay time estimation unit 13, the delay time grouping unit 14, the pseudoinverse matrix generation unit 16 and the angle of incidence estimation unit 18 are provided jointly for the two systems mentioned above.

[0022] The receiving device, shown in Fig. Figure 1 has a configuration for the case where the number of antenna elements is 2. The present invention is applicable even if the number of antenna elements is three or more, so that in the following description the number of antenna elements may sometimes be represented by N.

[0023] The wireless receiving units 11-1, 11-2 in Fig. One each is provided corresponding to the antenna elements 10-1, 10-2 and each performs frequency conversion of the analog signal obtained by receiving the radio waves at the corresponding antenna element into a baseband signal, A / D conversion of the baseband signal to create a digital signal Srn to generate (where n is 1 or 2), and outputs the generated digital signal Sr n out of.

[0024] The transmission channel estimation units 12-1, 12-2 in Fig. 1 are each provided according to the wireless receiving units 11-1, 11-2 and each estimates the frequency property (transmission function in the frequency domain) of the transmission channel based on the digital signal Sr n, output by the corresponding wireless receiving unit. The method for estimating the transmission channel frequency characteristic depends on the transmission scheme adopted by the communication system. The present invention is applicable to any transmission scheme. However, the following description refers to a case in which the OFDM transmission scheme (OFDM: Orthogonal Frequency Division Multiple Access) is used and a case in which the DSSS transmission scheme (DSSS: Direct Sequence Spectrum Spread) is used. The OFDM and DSSS transmission schemes are used in many communication systems.

[0025] First, a case in which the OFDM transmission scheme is applied is described. In the OFDM transmission scheme, symbols are generated by multiplexing a multitude of subcarriers that are orthogonal to each other, and transmission is performed symbol by symbol. In many of the communication systems in which the OFDM transmission scheme is applied, a portion of the subcarriers are used as pilot subcarriers, known on both the transmit and receive sides, to compensate for transmission channel distortion on the receive side. In the present embodiment, the pilot subcarriers are used to estimate the transmission channel frequency characteristic.

[0026] Fig. Figure 2 shows an example of a transmission channel estimation unit 12-n (where n is 1 or 2) that is used when the OFDM transmission scheme is applied.

[0027] The transmission channel estimation unit 12-n, shown in Fig. 2, comprises an FFT unit 20-n, a pilot extraction unit 21-n, a pilot generation unit 22-n, a division unit 23-n and an interpolation unit 24-n.

[0028] The FFT unit 20-n converts the digital signal Sr n , output by the wireless receiving unit 11-n, shown in Fig. 1. Symbol by symbol, from the time axis to the frequency axis, through FFT (Fast Fourier Transform) in order to output subcarriers.

[0029] The pilot extraction unit 21-n extracts pilot carriers from the subcarriers output by the FFT unit 20-n.

[0030] The pilot generation unit 22-n generates pilot carriers that are known in the receiving device.

[0031] The division unit 23-n divides the pilot carriers extracted by the pilot extraction unit 21-n by the pilot carriers generated by the pilot generation unit 22-n in order to output the frequency property of the transmission channel that responds to the pilot carriers.

[0032] The interpolation unit 24-n performs interpolation based on the frequency characteristics of the transmission channel and reacts to the pilot carriers in the symbol direction and the subcarrier direction to obtain frequency characteristics of the transmission channel (transmission channel estimation results) for all subcarriers.

[0033] Next, a case in which the DSSS transmission scheme is applied is described. In the DSSS transmission scheme, signals are spread symbol by symbol using a pseudorandom noise sequence, transmitted, and unspread at the receiving end.

[0034] Fig. Figure 3 shows an example of a transmission channel estimation unit 12-n (where n is 1 or 2) that is used when the DSSS transmission scheme is applied.

[0035] The transmission channel estimation unit 12-n, shown in Fig. 3, has a pseudorandom noise sequence generation unit 25-n, a spreading unit 26-n and an FFT unit 27-n.

[0036] The pseudorandom noise sequence generation unit 25-n generates a pseudorandom noise sequence Ns that is identical to the pseudorandom noise sequence used at the time of spreading on the transmission side.

[0037] The spreading unit 26-n calculates a sliding correlation between the digital signal Sr n , Symbol by symbol issued by the wireless receiving unit 11-n in Fig. 1 and the pseudorandom noise sequence Ns and outputs the calculated sliding correlation.

[0038] The FFT unit 27-n converts the result of the spreading unit 26-n into the frequency domain using FFT in order to obtain the transmission channel frequency property (transmission channel estimation result).

[0039] The transmission channel frequency property (transmission channel estimation result), output by the transmission channel estimation unit 12-n, can be expressed as a column vector consisting of components of the respective frequencies f1 to f M consists, which can be represented by the following equation (1). [Mathematical expression 1] zn=⌊zn(f1)zn(f2)Mzn(fM)⌋

[0040] Here, f is indicated m (where m can be anything from 1 to M) a frequency at a point where the range of the lowest frequency f1 to the highest frequency f M is equally divided into M sections, where the division number M is the number of FFT points at the FFT unit 20-n in Fig. 2 or the FFT unit 27-n in Fig. 3 is.

[0041] Back to Fig. 1, based on the result of one of the transmission channel estimation units 12-1, 12-2, for example the transmission channel estimation unit 12-1, the delay time estimation unit 13 estimates the delay times of one or more incoming waves contained in the radio waves, received by the corresponding antenna element 10-1.

[0042] The delay time estimation is performed using a super-resolution process, such as the MUSIC process (Multiple Signal Classification) or the ESPRIT process (Estimation of Signal Parameters via Rotational Invariance Techniques).

[0043] In the following description, the number of arriving waves is denoted by K, and the delay times of the corresponding arriving waves are denoted by τ1, τ2, ..., τ K , the estimated values ​​of the delay times are denoted by τ(hat)1, τ(hat)2, ..., τ(hat) Kdenoted. Here it is assumed that τ1<τ2<...<τ K .

[0044] The delay time grouping unit 14 compares the delay time estimation results τ(hat)1, ..., t(hat) K , output by the delay time estimation unit 13, with a predefined threshold τ th and determines whether each estimated value τ(has) k is shorter than the threshold τ th The delay time grouping unit 14 then groups the estimated values ​​τ(hat)1, ..., τ(hat) K in those τ(has)1, ..., τ(has) q , which are shorter than the threshold τ th , and other estimated values ​​τ(has) q+1 , ..., τ(hat) K (those that are equal to or longer than the threshold τ th ). Here, it is assumed that the threshold τ th is determined such that the ratio τ(has)1<τ th <τ(has) K is fulfilled.

[0045] The delay time grouping unit 14 gives the estimated values ​​τ(hat)1, ..., τ(hat) q from those that are shorter than the threshold τ th had been determined and does not give the estimated values ​​τ(has) q+1 , ..., τ(hat) K from those that are equal to or longer than the threshold τ th had been determined. The delay time grouping unit 14 can alternatively output information indicating whether each estimated value τ(has) k is shorter than the threshold τ th .

[0046] The delayed wave removal units 15-1, 15-2 are each provided according to the transmission channel estimation units 12-1, 12-2 and each removes the arriving wave components according to the delay times that the delay time grouping unit 14 determines to be equal to or longer than the threshold τ thhas determined, from the result of the corresponding transmission channel estimation unit (transmission channel estimation result). That is, each delayed-wave distance unit 15-n is removed from the estimation result of the transmission channel frequency property, output by the corresponding transmission channel estimation unit 12-n, which has delayed-wave components according to the delay times τ(has) q+1 , ..., τ(hat) K , which defines the delay time grouping unit 14 as equal to or longer than the threshold τ th determined.

[0047] For example, the Delayed Wave Removal Unit 15-n comprises an IFFT Unit 50-n, a Delayed Wave Component Removal Unit 51-n, and an FFT Unit 52-n, as shown in Fig. 4 shown.

[0048] The IFFT unit 50-n applies IFFT (inverse function of the Fast Fourier Transform) to the estimation result z. nThe transmission channel frequency property, shown in equation (1), is used to determine a delay profile. An example of the determined delay profile is shown in Fig. 5 (a) is shown.

[0049] The delayed wave component removal unit 51-n replaces the components according to the estimated delay time values ​​τ(hat) q+1 , ..., τ(hat) K in the delay profile ( Fig. 5 (a)), determined by the IFFT unit 50-n, by 0s. As a result of this process, a delay profile (post-removal delay profile) is generated that does not have the components according to τ(has) q+1 , ..., τ(hat) K includes and that the components according to τ(has)1, ..., τ(has) q includes, as in Fig. 5 (b) shown.

[0050] The FFT unit 52-n performs FFT on the result ( Fig. 5 (b)) of the delayed-wave component distance unit 51-n to re-establish a signal in the frequency domain. As a consequence of this process, a transmission channel frequency property is obtained that does not have the incoming-wave components corresponding to τ(has) q+1 , ..., τ(hat) K includes and the incoming wave components according to τ(hat)1, ..., τ(hat) q includes, generates.

[0051] Furthermore, the delayed wave component removal unit 51-n 0en can be used for all components in the range τ(has) q+1 , ..., τ(hat) K in the delay profile. One result of this process is in Fig. 5 (c) shown. In the example, shown in Fig. 5 (c), not only were the components adjusted according to τ(has) q+1 , ..., τ(hat) K in the delay profile in Fig. 5 (a), but also replace the noise components in the area of ​​these components with zeros.

[0052] The input and output signals of the delayed-wave distance unit 15-n can be represented by matrices. First, the input signal represented by equation (1) above can also be represented by equation (2) below. [Mathematical expression 2] zn=X⋅yn

[0053] In equation (2), X denotes a matrix representing the delay times and can be represented by the following equation (3). [Mathematical expression 3] X=[exp(−j2πf1τ1)Lexp(−j2πf1τk)Lexp(−j2πf1τK)exp(−j2πf2τ1)Lexp(−j2 πf2τk)Lexp(−j2πf2τK)MMMexp(−j2πfMτ1)Lexp(−j2πfMτk)Lexp(−j2πfMτK)]

[0054] In equation (3) K denotes the number of arriving waves, as mentioned above, and M denotes the frequency division number, as mentioned above.

[0055] The distance between the antenna element 10-1 and the antenna element 10-2 is approximately half the wavelength, so it is assumed that there is no difference in the delay time between the antenna elements. y n in equation (2) denotes a column vector consisting of components representing the amplitude and phase of each of the arriving waves (first to K-th arriving waves) and can be represented by the following equation (4). yn=[an,1an,2 Man,K]

[0056] In equation (4) a denotes n,k (n=1, 2; k=1, ...,K) a complex number representing the amplitude and phase of the k-th arriving wave of the signal, received by the n-th antenna element 10-n.

[0057] Next, the output signal of the delayed-wave distance unit 15-n is explained. If the estimated values ​​of the delay times, which the delay time grouping unit 14 considers to be equal to or longer than the threshold τ th Since the delayed wave components have been determined to be equal to the actual delay times, such delayed wave components are eliminated by the delayed wave removal unit 15-n. The result of the delayed wave removal unit 15-n is represented by the following equation (5). [Mathematical expression 5] zn'=X'⋅y'n

[0058] In equation (5), X' denotes what is obtained by removing the components according to the delay times z. q+1 , ..., τ K of X and is represented by equation (6). [Mathematical expression 6] X'=[exp(−j2πf1τ1)Lexp(−j2πf1τq)exp(−j2πf2τ1)Lexp(−j2πf2τq)MMexp(−j2πfMτ1)Lexp(−j2πfMτq)]

[0059] In equation (5) y' denotes n what is obtained by removing the components according to the delay times τ q+1, ..., τ K from y n and is represented by equation (7). [Mathematical expression 7] y'n=[an,1an,2 Man,q]

[0060] When equation (2) (together with equations (3) and (4)) is compared with equation (5) (together with equations (6) and (7)), it will be found that the result of the delayed-wave distance unit 15-n is a transmission channel frequency property belonging to the arriving waves of delay times τ(hat)1, ..., τ(hat) q , which defines the delay time grouping unit 14 as smaller than the threshold τ th has determined, and the size of the matrix X, which represents the delay times, is reduced from MxK to Mxq.

[0061] The pseudoinverse matrix generation unit 16 calculates a matrix, represented by the following equation (8), from the delay times τ(hat)1, ..., τ(hat) q , which defines the delay time grouping unit 14 as shorter than the threshold τ th has determined. X(has) + , represented by equation (8), is called a pseudoinverse matrix of X(hat)'. [Mathematical expression 8] X^=(X^'HX^')−1X^'H

[0062] In equation (8) X(hat)' denotes a matrix of the estimated values ​​of the delay times which the delay time grouping unit 14 is shorter than the threshold τ th has been determined and is represented by the following equation (9). The exponent “H” denotes a complex conjugate and transpose matrix and the exponent “-1” denotes an inverse matrix. [Mathematical expression 9] X'=[exp(−j2πf1τ^1)Lexp(−j2πf1τ^q)exp(−j2πf2τ^1)Lexp(−j2πf2τ^q)MMexp(−j2πfMτ^1)Lexp(−j2πfMτ^q)]

[0063] The matrix, represented by equation (9), is generated on the basis of the delay times τ(hat)1, ..., τ(hat)q, which define the delay time grouping unit 14 as shorter than the threshold τ th has determined, and the process of determining the pseudoinverse matrix in equation (8) is carried out using the matrix of equation (9).

[0064] In equation (8), the size of the matrix X(hat)'HX(hat)', on which the inverse matrix calculation is performed, is qxq. In contrast, when a similar calculation is performed using X in equation (3), the size of the matrix on which the inverse matrix calculation is performed is KxK. Thus, it will become clear that the size of the matrix is ​​reduced as a consequence of the delayed wave removal.

[0065] The incoming wave separation units 17-1 and 17-2 are each provided corresponding to the delayed wave removal units 15-1 and 15-2, and each separates the incoming wave components contained in the result of the corresponding delayed wave removal unit to extract the direct wave component. More precisely, each incoming wave separation unit 17-n multiplies the result z' n (Equation (5)) of the corresponding delayed-wave distance unit 15-n with the pseudoinverse matrix X(hat) + Equation (8)), generated by the pseudoinverse matrix generation unit 16, extracts the direct wave component from the multiplication result. The above multiplication is represented by the following equation (10). [Mathematical expression 10] y^'n=X^+⋅z'n y(hat)' n In equation (10) is the result of the estimation of y' nin equation (7) and denotes a column vector, represented by the following equation (11). [Mathematical expression 11] y^'n=[a^n,1a^n,2Ma^n,q]

[0066] As a result of the calculation of equation (10), complex numbers are obtained that represent the amplitude and phase of the arriving wave components (first to q-th arriving wave components) of the delay times, which the delay time grouping unit 14 is shorter than the threshold τ. th who determined, won.

[0067] Equations (5) to (11) will make it clear that if the estimated delay times are equal to the actual delay times, y(hat)' n equal to y' n will be.

[0068] The incoming wave separation unit 17-n also extracts the value a(has). n,1 at the head of the above-mentioned column vector y(has)' nand outputs it as a direct wave component.

[0069] The incidence angle estimation unit 18 calculates the phase difference between the direct wave component a(hat) 1,1 , extracted by the incoming wave separation unit 17-1, and the direct wave component a(has) 2,1 , extracted by the incoming wave separation unit 17-2, and estimates the direction of incidence of the direct wave based on the calculated phase difference. The direction of incidence of the direct wave is determined to be the direction of the transmitter.

[0070] If, as in Fig. As shown in Figure 6, where the distance between the antenna elements is d[m], the wavelength of the carrier is λ[m], and the angle of incidence θ of the direct wave is, there is a relationship: dp=d×sinθ between the propagation path difference d p between the antenna elements and the angle of incidence θ, and there is a relationship: dp=λ×ϕ / 2π between the propagation path difference d p , the wavelength λ and the phase difference ϕ of the received radio waves.

[0071] Accordingly, the following equation (12) is related: [Mathematical expression 12] ϕ=2π⋅(d / λ)⋅sin θ between the angle of incidence θ and the phase difference ϕ.

[0072] Equation (12) can be rewritten as equation (13). [Mathematical expression 13] θ=arcsin(ϕ2π⋅(d / λ))

[0073] In equation (13), the inter-antenna element distance d and the wavelength λ are known. Accordingly, it will become clear that θ can therefore only be determined by ϕ.

[0074] To perform the processes mentioned above, the angle of incidence estimation unit 18 comprises a phase difference calculation unit 80 and an angle of incidence calculation unit 81, as shown in Fig. 7 shown.

[0075] The phase difference calculation unit 80 calculates the phase difference ϕ between the direct wave component a(hat) 1,1 and the direct wave component a(has) 2,1 If the argument of the direct-wave component a(has) 1,1 Ψ1 is and the argument of the direct-wave component a(has) 2,1 If Ψ2, the phase difference ϕ is determined by the following equation (14). [Mathematical expression 14] ϕ=ψ2−ψ1

[0076] The angle of incidence calculation unit 81 determines the angle of incidence θ from the phase difference ϕ, using the relationship from the above-mentioned equation (13).

[0077] In the embodiment described above, the number of antenna elements is two. However, the invention is also applicable in cases where the number of antenna elements is greater than two. In such a case, the phase difference between the antenna elements is determined for each of a plurality of combination patterns, and an average value of the incidence angles for the respective combinations can be calculated.

[0078] As described above, according to the method shown in patent reference 1, the direct wave and the delayed waves cannot be separated if delayed waves with short delay times are present, and the accuracy of estimating the angle of incidence of the direct wave is lower. In contrast, according to the present embodiment, the direct wave and the delayed waves are separated after estimating the delay times of the arriving waves by a super-resolution process, with the result that the angle of incidence of the direct wave can be estimated with high accuracy, even if delayed waves with short delay times are present.

[0079] Furthermore, after removing the delayed-wave components with long delay times, the incoming waves are separated from the transmission channel estimate result, thus reducing the number of calculations required to determine the inverse matrix needed for incoming-wave separation. That is, if the delayed-wave components are not removed, the number of required multiplications K is... 3 , whereas, when the delayed waves are removed, the number of required multiplications q 3is. Since q <K wird deutlich, dass die Menge an Berechnungen, die für die Berechnung der inversen Matrix nötig ist, reduziert ist. Obwohl die Verzögerte-Welle-Entfernungseinheit 15-n die Prozesse der FFT und IFFT von M Punkten zur Entfernung der verzögerten Wellen ausführt, beträgt die Zahl der für die FFT oder IFFT benötigten Multiplikationen Mxlog(M) und hängt nicht von der Zahl der eintreffenden Wellen ab, so dass die Menge an Berechnungen konstant ist. Folglich kann festgehalten werden, dass der Effekt des Reduzierens der Menge an Berechnungen größer ist in einer Umgebung, in der die Zahl der eintreffenden Wellen groß ist. Second embodiment

[0080] Fig. Figure 8 shows a receiving device of the second embodiment of the present invention. The receiving device, shown in Fig. 8, is generally identical to the receiving device in Fig. 1, but a threshold determination unit 31 was added.

[0081] The threshold determination unit 31 determines the threshold value τ th based on the delay times, estimated by the delay time estimation unit 13.

[0082] The delay time grouping unit 14 in Fig. 8 is generally identical to the delay time grouping unit 14 in Fig. 1, but differs in the following aspects. This includes the fact that the delay time grouping unit 14 in Fig. 1 the specified threshold τ th uses, whereas the delay time grouping unit 14 in Fig. 8 the threshold τ th uses the threshold determination unit 31.

[0083] For example, the threshold determination unit 31 uses an intermediate value between the minimum and maximum values ​​of the delay times, estimated by the delay time estimation unit 13, as the threshold τ. th.

[0084] Alternatively, a sum of the minimum value of the delay times, estimated by the delay time estimation unit 13, and a predefined value as the threshold τ can be used. th can be used.

[0085] Alternatively, a sum of a product of the difference between the maximum and minimum values ​​of the delay times, estimated by the delay time estimation unit 13, and a given value greater than 0 and less than 1, as well as the aforementioned minimum value as the threshold τ, can be used. th can be used.

[0086] The threshold τ th can be any value, provided it is longer than the minimum value and shorter than the maximum value of the delay times estimated by the delay time estimation unit 13, and, with regard to the nature of its calculation, the present embodiment is not limited to the calculations explained above.

[0087] By dynamically determining the threshold, used as described above to group the delay times, even in an environment where the delay times of the delayed waves vary over time, the delay times can be divided into those that are shorter than the threshold τ. th and those that are equal to or longer than the threshold τ th They are grouped and therefore only a portion of the incoming waves, estimated in the transmission channel estimation units 12-1, 12-2, can be removed. Third embodiment

[0088] Fig. Figure 9 shows a receiving device of the third embodiment of the present invention. The receiving device, shown in Fig. 9, is generally identical to the receiving device in Fig. 1, but a delay time number distinction unit 32 was added.

[0089] The delay time number discrimination unit 32 determines whether the number K of delay times (corresponding to the number of arriving waves), estimated by the delay time estimation unit 13, is less than a predetermined threshold K. th , and outputs the result ER of the determination.

[0090] The delay time grouping unit 14 and the delayed wave removal units 15-1, 15-2 in Fig. 9 are generally identical to the delay time grouping unit 14 and the corresponding delayed wave removal units 15-1, 15-2 in Fig. 1, but differ in the following points.

[0091] The delay time grouping unit 14 in Fig. 9 determines whether the delay time grouping process is executed based on the result ER of the determination by the delay time number differentiation unit 32.

[0092] Furthermore, the delayed wave distance units 15-1, 15-2 determine in Fig. 9, whether the delayed wave removal process is carried out based on the result of the determination by the delay time number discrimination unit 32.

[0093] That is, if the result of the determination by the delay time number distinction unit 32 shows that the number K of delay times is smaller than the threshold K th , the delay time grouping unit 14 does not perform the delay time grouping process and outputs all delay times τ1 to τ K , estimated by the delay time estimation unit 13.

[0094] As a result, the pseudoinverse matrix generation unit 16 generates the pseudoinverse matrix X(hat) + equation (8), based on all delay times τ1 to τ K (i.e. by substituting q=K into equation (9)).

[0095] Furthermore, if the result of the determination, output by the delay time count distinction unit 32, shows that the number K of delay times is less than the threshold K th , the delayed wave removal units 15-1, 15-2 do not perform the delayed wave removal processes and output the result z n The transmission channel estimation units 12-1, 12-2 continue without change.

[0096] As a result, the incoming wave separation unit 17-n multiplies the result z. n The transmission channel estimation unit 12-n is combined with the pseudoinverse matrix (equation (8)) in a similar manner to that shown in equation (10) to obtain the column vector (equation (11)). That is, z n is used in the multiplication in equation (10) as z n ' used and has a column vector y' n , represented by equation (11) except for q=K, is obtained. Such a column vector y(has)'n includes the components corresponding to all delay times τ1 to τ K .

[0097] Does the result of the determination by the delay time number distinction unit 32 show that the number K of delay times is equal to or longer than the specified number K th , the delay time grouping unit 14 performs the delay time grouping in the same way as in the first embodiment and the delayed wave removal units 15-1, 15-2 perform the delayed wave removal in the same way as in the first embodiment.

[0098] As described above, the number of delay times corresponds to the number of arriving waves. If the number of arriving waves is small and the effect of reducing the amount of calculations for delay time grouping and delayed wave removal is limited, the number of processes can be reduced by not performing delay time grouping and delayed wave removal.

[0099] The third embodiment was described as a modification of the first embodiment. A similar modification can be applied to the second embodiment.

[0100] A description of the receiving devices according to the present invention has been provided. Receiving methods applied in the receiving devices described above also form part of the present invention.

[0101] Next, receiving methods, corresponding to the first to third embodiments, are described as fourth to sixth embodiments. Fourth embodiment

[0102] The fourth embodiment is a receiving method corresponding to the first embodiment.

[0103] Fig. Figure 10 shows a process flow in the present embodiment.

[0104] The reception procedure, shown in Fig. 10, includes a radio receive step ST11, a transmission channel estimation step ST12, a delay time estimation step ST13, a delay time grouping step ST14, a delayed wave distance step ST15, a pseudoinverse matrix generation step ST16, an arriving wave separation step ST17 and an incidence angle estimation step ST18.

[0105] The processes in radio receiving step ST11 are similar to the processes performed by radio receiving units 11-1 and 11-2 in Fig. 1. The processes in transmission channel estimation step ST12 are similar to the processes performed by transmission channel estimation units 12-1 and 12-2 in Fig. 1. The processes in delay time estimation step ST13 are similar to the processes performed by delay time estimation unit 13 in Fig. 1. The processes in delay time grouping step ST14 are similar to the processes performed by delay time grouping unit 14 in Fig. 1. The processes in the delayed wave removal step ST15 are similar to the processes performed by the delayed wave removal units 15-1 and 15-2 in Fig. 1. The processes in the pseudoinverse matrix generation step ST16 are similar to the processes performed by the pseudoinverse matrix generation unit 16 in Fig. 1. The processes in the incoming wave separation step ST17 are similar to the processes performed by the incoming wave separation units 17-1 and 17-2 in Fig. 1. The processes in the incidence angle estimation step ST18 are similar to the processes performed by the incidence angle estimation unit 18 in Fig. 1.

[0106] In the radio reception step ST11, first and second analog signals, received by receiving radio waves through two antenna elements 10-1, 10-2, are each frequency-converted into baseband signals and then A-converted to generate first and second digital signals Sr1, Sr2.

[0107] In the transmission channel estimation step ST12, transmission channel frequency characteristics are estimated, each from the first and second digital signals generated in the radio reception step ST11, and the first and second transmission channel estimation results z1, z2 are output.

[0108] The method for estimating the transmission channel frequency characteristics depends on the transmission scheme used in the communication system. The present invention is applicable to any transmission scheme. However, the following description refers to a case in which the OFDM (Orthogonal Frequency Division Multiple Access) transmission scheme and a case in which the DSSS (Direct Sequence Spectrum Spread) transmission scheme are used. The OFDM and DSSS transmission schemes are used in many communication systems.

[0109] First, a case is described in which the OFDM transmission scheme is applied. In the OFDM transmission scheme, symbols are generated by multiplexing a multitude of subcarriers that are orthogonal to each other, and transmission is performed symbol by symbol. In many communication systems where the OFDM transmission scheme is applied, a portion of the subcarriers are used as pilot subcarriers, known on both the transmit and receive sides, to compensate for transmission channel distortion on the receive side. In the present embodiment, the pilot subcarriers are used to estimate the transmission channel frequency characteristics.

[0110] Fig. Figure 11 shows a sequence of processes in an example of the transmission channel estimation step ST12, performed in a case where the OFDM transmission scheme was applied.

[0111] The transmission channel estimation step ST12, shown in Fig. 11, includes an FFT step ST20, a pilot extraction step ST21, a pilot generation step ST22, a division step ST23 and an interpolation step ST24.

[0112] In FFT step ST20, the digital signals Sr1, Sr2 are generated, and in radio reception step ST11... Fig. 10, converted symbol by symbol from the time axis to the frequency axis by FFT (Fast Fourier Transform) in order to output corresponding subcarriers.

[0113] In pilot extraction step ST21, the pilot carriers are extracted from the subcarriers output in FFT step ST20.

[0114] The processes in step ST22 are carried out in parallel with the processes in steps ST20 and ST21.

[0115] In the pilot generation step ST22, pilot carriers are generated that are known on the receiving side.

[0116] After steps ST21 and ST22, the processes are carried out in step ST23.

[0117] In division step ST23, the pilot carriers extracted in pilot extraction step ST21 are divided by the pilot carriers generated in pilot generation step ST22 to output the frequency characteristics that respond to the transmission channel for the pilot carriers.

[0118] In interpolation step ST24, interpolation is performed using the frequency characteristics of the transmission channel that respond to the pilot carrier, in the symbol direction and the subcarrier direction, to obtain the frequency characteristics of the transmission channel (transmission channel estimation results) for all subcarriers.

[0119] Next, a case is described in which the DSSS transmission scheme is applied. In the DSSS transmission scheme, signals, spread using a pseudorandom noise sequence, are transmitted symbol by symbol and unspread on the receiving end.

[0120] Fig. Figure 12 shows a sequence of processes in an example of the transmission channel estimation step ST12, performed when the DSSS transmission scheme is applied.

[0121] The transmission channel estimation step ST12, shown in Fig. 12, comprises a pseudorandom noise sequence generation step ST25, an unspreading step ST26 and an FFT step ST27.

[0122] In the pseudorandom noise sequence generation step ST25, a pseudorandom noise sequence Ns is generated that is identical to the pseudorandom noise sequence used in spreading on the transmit side.

[0123] In the spreading step ST26, sliding correlations between the digital signals Sr1, Sr2 are generated in the radio reception step ST11 in Fig. 10, and the pseudorandom noise sequence Ns is calculated symbol by symbol.

[0124] In the FFT step ST27, the results of the calculation in the unspreading step ST26 are transformed into the frequency domain by FFT in order to obtain the transmission channel frequency characteristics (transmission channel estimation results).

[0125] The first and second transmission channel estimation results z1, z2, calculated in transmission channel estimation step ST12, are represented by what was obtained by substituting n=1 or 2 into equation 1.

[0126] Back in Fig. In delay time estimation step ST13, the delay times of one or more incoming waves that are part of the radio waves received by the corresponding antenna are estimated based on one of the first and second transmission channel estimation results z1, z2, for example the first transmission channel estimation result z1.

[0127] The delay time estimation is performed using a super-resolution process, such as the MUSIC or ESPRIT process. Here, the number of arriving waves is denoted by K, and the delay times of the respective arriving waves are denoted by τ1, τ2, ..., τ K , the estimated values ​​of the delay times are denoted by τ(hat)1, τ(hat)2, ..., τ(hat) K Here it is assumed that τ1<τ2<...<τ K .

[0128] In the delay time grouping step ST14, the delay time estimate results τ(hat)1, τ(hat)2, ..., τ(hat) are processed. K compared to a given threshold τ th and a determination is made as to whether each estimated value τ(has) K is shorter than the threshold τ th Then the estimated values ​​τ(hat)1, ..., τ(hat) are calculated. K grouped into those τ(has)1, ..., τ(has) q , which are shorter than the threshold τ thand other estimated values ​​τ(has) q+1 , ..., τ(hat) K (those that are equal to or longer than the threshold τ th ). Here, it is assumed that the threshold τ th is determined such that it has the ratio τ(has)1<τ h <τ(has) K fulfilled.

[0129] In the delayed-wave distance step ST15, the delayed-wave components of each of the results of the transmission channel frequency property in the transmission channel estimation step ST12 are calculated according to the delay times τ(hat) q+1 , ..., τ(hat) K , which were determined to be equal to or longer than the threshold τ th In the delay time grouping step ST14, the first and second transmission channel frequency characteristics z'1, z'2, which consist of the incoming wave components that were not removed, are output.

[0130] Fig. Figure 13 shows a process flow in an example of the delayed wave removal step ST15.

[0131] The delayed wave removal step ST15, shown in Fig. 13, includes an IFFT step ST50, a delayed wave component removal step ST51 and an FFT step ST52.

[0132] In IFFT step ST50, IFFT is applied to the estimation result z. n the transmission channel frequency property, shown in equation (1), carried out to determine the delay profile, shown e.g. in Fig. 5 (a), to obtain.

[0133] In the delayed-wave component removal step ST51, the components are removed according to the delay time estimates τ(hat) q+1 , ..., τ(hat) K in the delay profile, obtained in IFFT step ST50, replaced by zeros, as shown in Fig. 5 (b). As a result, a delay profile (post-removal delay profile) is generated that does not have the components according to τ(has)q+1 , ..., τ(hat) K includes and that the components according to τ(has)1, ..., τ(has) q contains.

[0134] In FFT step ST52, an FFT is performed on the result of the delayed-wave component removal step ST51 to reconstruct a signal in the frequency domain. As a result of this process, a transmission channel frequency property is obtained that does not have the arriving-wave components corresponding to τ. q+1 , ..., τ(hat) K contains and the incoming wave components according to τ(hat)1, ..., τ(hat) q contains.

[0135] In the delayed-wave component removal step ST51 described above, all components in the area τ(has) can be removed. q+1 , ..., τ(hat) K in the delay profile in Fig. 5 (a) are replaced by zeros, as in Fig. 5 (c) shown.

[0136] The processes in the delayed wave removal step ST15 are carried out on the signals z1, z2 (obtained by substituting n=1 or 2 in equation (2)), and signals z'1, z'2 (obtained by substituting n=1 or 2 in equation (5)) are generated as a result of the processes.

[0137] Comparing equation (2) and equation (5) reveals that the signals generated as a result of the delayed-wave distance step processes ST15 represent the transmission channel frequency property, the delay times τ(hat)1, ..., τ(hat) q concerning those that were determined to be shorter than the threshold τ th to be in the delay time grouping step ST14, and that the size of the matrix X representing the delay times is reduced from M×K to M×q.

[0138] Parallel to the processes in the delayed wave removal step ST15, the processes of the pseudoinverse matrix generation step ST16 are carried out.

[0139] In the pseudoinverse matrix generation step ST16, the pseudoinverse matrix X(has) + , represented by the above-mentioned equation (8), calculated on the basis of the delay times which were determined to be shorter than the threshold τ th to be in the delay time grouping step ST14.

[0140] It will become clear that the size of the matrix X(has)' H X(hat)' in equation (8), on which the inverse matrix calculation is performed, is q×q, and that the size of the matrix is ​​reduced by the delayed wave removal step ST15.

[0141] After the delayed wave removal step ST15 and the pseudoinverse matrix generation step ST16, the processes of the arriving wave separation step ST17 are carried out.

[0142] In the incoming wave separation step ST17, each of the first and second transmission channel frequency properties z'1, z'2 (obtained by substituting n=1 or 2 into equation (5)), which are generated in the delayed wave removal step ST15, is multiplied by the pseudoinverse matrix X(has) + , generated in the pseudoinverse matrix generation step ST16, so that the incoming wave components contained in the first to second transmission channel frequency properties z'1, z'2 are separated from each other and the first and second direct wave components are extracted.

[0143] The multiplication mentioned above is represented by the equation (10) mentioned above.

[0144] As a result of the multiplication, column vectors y(hat)' n and y(hat)'2 (obtained by substituting n as 1 or 2 in equation (11)).

[0145] In the incoming wave separation step ST17, the upper values ​​a(has) 1,1 , a(hat) 2,1 from the corresponding column vectors y(hat)'1, y(hat)' n extracted, calculated in the manner described above, and output as first and second direct wave components.

[0146] In the incidence angle estimation step ST18, the phase difference ϕ between the first direct wave component a(hat) is determined. 1,1 and the second direct-wave component a(has) 2,1 , extracted in the incoming wave separation step ST17, calculated and the direction of incidence of the direct wave is estimated based on the calculated phase difference.

[0147] For example, the angle of incidence estimation step ST18 includes a phase difference calculation step ST80 and an angle of incidence calculation step ST81, as shown in Fig. 14 shown.

[0148] In the phase difference calculation step ST80, the phase difference ϕ between the direct wave component a(hat) is calculated. 1,1 and the direct wave component a(has) 2,1 calculated. The calculation is performed according to the equation (14) above.

[0149] In the angle of incidence calculation step ST81, the angle of incidence θ is calculated from the phase difference ϕ, using the relationship from the equation (13) above.

[0150] The fourth embodiments achieve similar effects to the first embodiments. Fifth embodiment

[0151] The fifth embodiment is a receiving method corresponding to the second embodiment.

[0152] Fig. Figure 15 shows a process flow in the fifth embodiment of the present invention.

[0153] The reception procedure, shown in Fig. 15, is generally identical to the receiving procedure of Fig. 10, but a threshold determination step ST31 has been added.

[0154] The processes of the threshold determination step ST31 are similar to the processes performed by the threshold determination unit 31 in Fig. 8.

[0155] The processes of the threshold determination step ST31 are executed after the processes of the delay time estimation step ST13.

[0156] In threshold determination step ST31, the threshold value τ is th determined based on the delay times estimated in delay time estimation step ST13.

[0157] The delay time grouping step ST14 in Fig. 15 is generally identical to the delay time grouping step ST14 in Fig. 10, but differs in the following points.

[0158] This includes the fact that in the delay time grouping step ST14 in Fig. 10 the specified threshold τ th is used while in the delay time grouping step ST14 in Fig. 15 the threshold τ th The value used is the one determined in threshold determination step ST31.

[0159] In the threshold determination step ST31, for example, an intermediate value between the minimum and maximum values ​​of the delay times, estimated in the delay time estimation step ST13, is used as the threshold τ. th used.

[0160] Alternatively, a sum of the minimum value of the delay times, estimated in delay time estimation step ST13, and a predefined value as the threshold τ can be used. th be used.

[0161] Alternatively, a sum of the product of the difference between the maximum and minimum values ​​of the delay times, estimated in delay time estimation step ST13, and a predefined value greater than 0 and less than 1, and the aforementioned minimum value as the threshold τ, can be used. th be used.

[0162] The threshold τ th can be any value as long as it is between the minimum and maximum values ​​of the delay times estimated by the delay time estimation step ST13, and the present embodiment is not limited to the manner of its calculation.

[0163] By dynamically determining the threshold, used to group the delay times as described above, even in an environment where the delay times and the delayed waves vary over time, the delay times can be grouped into those that are shorter than the threshold τ. thand those that are equal to or longer than the threshold τ th , and therefore only a portion of the incoming waves, estimated in the transmission channel estimation step ST12, can be removed. Sixth embodiment

[0164] The sixth embodiment is a receiving method corresponding to the third embodiment.

[0165] Fig. Figure 16 shows a process flow in the sixth embodiment of the present invention. The receiving method, shown in Fig. 16, is generally identical to the receiving procedure in Fig. 10, but a delay time count distinction step ST32 has been added.

[0166] The processes in the delay time count differentiation step ST32 are similar to the processes executed by the delay time count differentiation unit 32.

[0167] The delay time count differentiation step ST32 is executed after the delay time estimation step ST13.

[0168] In the delay time number discrimination step ST32, a distinction is made as to whether the number K of delay times (corresponding to the number of arriving waves), estimated in the delay time estimation step ST13, is smaller than a predefined threshold K. th .

[0169] If, in delay time number discrimination step ST32, the number K of delay times (corresponding to the number of arriving waves), estimated by the delay time estimation step ST13, is determined to be equal to or greater than the threshold K th (If NO is selected in step ST32), the procedure proceeds to step ST14. Subsequent processes are similar to those described in the first embodiment.

[0170] If, in delay time number differentiation step ST32, the number K of delay times (corresponding to the number of arriving waves), estimated in delay time estimation step ST13, is determined to be smaller than the threshold K th (in the case of YES in step ST32), the procedure continues to step ST16.

[0171] As a result, in the pseudoinverse matrix generation step ST16, the pseudoinverse matrix X(has) is generated. + generated from equation (8), based on all delay times τ1 to τ K , estimated in the delay time estimation step ST13 (i.e. substituting q=K into equation (9)).

[0172] In the incoming wave separation step ST17, the first and second transmission channel estimate results z1, z2 (obtained by substituting n=1 or 2 into equation (2)), calculated in the transmission channel estimation step ST12, are multiplied by the pseudoinverse matrix (equation (8)), generated in the pseudoinverse matrix generation step ST16, as in equation (10), to obtain the column vector (equation (11)). That is, in the multiplication of equation (10), z n as z n ' used and as the column vector y(has)' n in equation (11), one of whose results are obtained by substituting q=K. Such a column vector y(has)' n includes the components corresponding to all delay times τ1 to τ K .

[0173] As described above, the number of delay times corresponds to the number of incoming waves. By not performing delay time grouping and delayed wave removal when the number of incoming waves is small, and the effect of reducing the computation scope for delay time grouping and delayed wave removal is therefore limited, the processing scope can be reduced.

[0174] The sixth embodiment was described as a modification of the fourth embodiment. A similar modification can be applied to the fifth embodiment.

[0175] Furthermore, modifications similar to those described in connection with the first and third embodiments can be applied to the fourth and fifth embodiments. Seventh embodiment

[0176] Various parts of the receiving device according to the first, second and third embodiments, shown in Fig. 1, Fig. 8 and Fig. The nine components (shown as functional blocks) can be implemented by a processing circuit. The processing circuit can be dedicated hardware or a processor that executes programs stored in memory.

[0177] For example, the functions of corresponding parts can be in Fig. 1, Fig. 8 and Fig. 9 can be implemented by separate processing circuits, or the functions of a multitude of parts can be implemented by a single processing circuit.

[0178] If the processing circuit is a processor, the functions of different parts of the receiving device can be implemented by software, firmware, or a combination of both. Software or firmware is described as programs and is stored in memory. The processing circuit implements the functions of different parts by reading and executing the programs stored in memory. That is, if the receiving device is implemented by a processing circuit, it includes memory for the stored programs which, when executed, cause the functions of the different parts, as shown in Fig. 1, Fig. 8 or Fig. 9. These programs are considered to be those that cause a computer to execute the processes or their sequence in the receiving procedure, implemented in the receiving device.

[0179] Furthermore, some of the functions of the various parts of the receiving device can be implemented by specific hardware, and other parts can be implemented by software or firmware.

[0180] Consequently, the processing circuit can implement the various functions described above using hardware, software, firmware, or a combination thereof.

[0181] Fig. Figure 17 shows an example of a configuration in which the processing circuit mentioned above is a processor and all functions of the receiving device are implemented by a computer (indicated by the 100 reference symbols) comprising a single processor, together with antenna elements 10-1, 10-2.

[0182] The Computer 100, shown in Fig. 17, comprises a processor 101, a memory 102, input units 103-1, 103-2 and an output unit 104, which are connected to each other via a bus 105.

[0183] Antenna elements 10-1 and 10-2 are connected to the input units 103-1 and 103-2.

[0184] Signals received by the antenna elements 10-1, 10-2 are fed to the processor via the input units 103-1, 103-2.

[0185] The processor 101 operates according to the programs stored in the memory 102 and executes the processes of the various parts of the receiving device of the first, second and third embodiments and outputs the resulting output signals via the output unit 104.

[0186] The contents and sequence of processes of processor 101 are similar to those described in the first, second and third embodiments.

[0187] The cases described are those in which the processes in the receiving devices of the first, second, and third embodiments are executed by a computer. It is also possible for a computer to execute the processes of various steps in the receiving procedures in the fourth, fifth, and sixth embodiments in a similar manner to that described above.

[0188] Effects similar to those described in connection with the receiving device can also be obtained from the receiving method implemented in the receiving device, programs that cause computers to execute the processes carried out by various parts of the receiving device or the processes in the receiving method, and a computer-readable recording medium in which the above-mentioned programs are stored. Reference symbol list

[0189] 10-1, 2: Antenna element; 11-1, 11-2: Radio receiving unit; 12-1, 12-2: Transmission channel estimator; 13: Delay time estimator; 14: Delay time grouping unit; 15-1, 15-2: Delayed wave distance unit; 17-1, 17-2: Incoming wave separation unit; 18: Angle of incidence estimator; 20-n: FFT unit; 21-n: Pilot extraction unit; 22-n: Pilot generation unit; 23-n: Division unit; 24-n: Interpolation unit; 25-n: Pseudorandom noise sequence generation unit; 26-n: Scattering unit; 27-n: FFT unit; 31: Threshold determination unit; 32: Delay time count discrimination unit; 50-n: IFFT unit; 51-n: Delay time component removal unit; 52-n: FFT unit; 80: Phase difference calculation unit; 81: Angle of incidence calculation unit; 101: Processor; 102: Memory; 103-1, 103-2: Input unit; 104: Output unit; 105: Bus.

Claims

[1] Receiving device for receiving radio waves transmitted by a transmitter and for estimating the angle of incidence of a direct wave from the transmitter, comprising: first to Nth (where N is an integer not less than 2) wireless receiving devices, each provided corresponding to first to Nth antenna elements forming a group antenna, and performing frequency conversion and A / D conversion on first to Nth analog signals obtained by receiving the radio waves each through the first to Nth antenna elements to output first to Nth digital signals; First to Nth transmission channel estimation units for estimating transmission channel frequency characteristics based on the first to Nth digital signals, and outputting first to Nth transmission channel estimation results; a delay time estimation unit for estimating, by means of a super-resolution process, delay times of one or more arriving waves contained in the radio waves, based on a transmission channel estimation result within the first to Nth transmission channel estimation results; a delay time grouping unit for comparing the delay times estimated by the delay time estimation unit with a threshold to determine whether the estimated delay times are shorter than the threshold; first to Nth delayed wave removal units, each corresponding to the first to Nth transmission channel estimation units, which remove an incoming wave component from the first to Nth transmission channel estimation results according to the delay time determined by the delay time grouping unit to be equal to or greater than the threshold, and output the first to Nth transmission channel frequency characteristics with respect to the incoming waves of the delay times determined by the delay time grouping unit to be shorter than the threshold; first to Nth incoming wave separation units, each provided corresponding to the first to Nth delayed wave removal units, and each separating incoming wave components contained in the first to Nth transmission channel frequency characteristics from each other to extract first to Nth direct wave components; and an incidence angle estimation unit for estimating an incidence angle of the direct wave based on a phase difference between the first to Nth direct wave components. [2] Receiving device according to claim 1, wherein the super-resolution process is either a MUSIC process or an ESPRIT process. [3] Receiving device according to claim 1 or 2, wherein each of the first to N delayed wave distance units Performs an inverse Fourier transform on the transmission channel estimation result, which was output by the corresponding transmission channel estimation unit, to generate a delay profile. executes a process in which 0 is replaced for the component according to the delay time in the generated delay profile, which was determined to be equal to or longer than the threshold, and Fourier transformation is performed on the result of this process to generate a transmission channel frequency property that affects the incoming waves of the delay times, which have been determined to be shorter than the threshold. [4] Receiving device according to any one of claims 1 to 3 further comprising a pseudoinverse matrix generation unit for generating a pseudoinverse matrix which uses the estimated delay times which the delay time grouping unit has determined to be shorter than the threshold, wherein: Each of the first to Nth incoming wave separation units multiplies the transmission channel frequency property, output by the corresponding delayed wave removal unit, with the pseudoinverse matrix, produces a column vector whose elements include complex numbers representing the amplitudes and phases of the incoming wave components with delay times determined to be shorter than the threshold, extracts the value at the head of the column vector and outputs it as the direct wave component. [5] Receiving device according to claim 4, wherein, if a matrix consisting of the estimated delay times which the delay time grouping unit has determined to be shorter than the threshold is represented by X(hat), the pseudoinverse matrix is ​​represented by: X^+=(X^'HX^')−1X^'H (here the superscript "H" represents a complex conjugate transpose and the superscript "-1" represents an inverse matrix). [6] The receiving device according to any one of claims 1 to 5, further comprising a threshold determination unit for determining of the threshold based on the delay times, estimated by the delay time estimation unit, wherein The delay time grouping unit uses the threshold value determined by the threshold determination unit for comparing delay times, estimated by the delay time estimation unit. [7] Receiving device according to claim 6, wherein the threshold determination unit determines the threshold to be longer than the minimum value of the delay times estimated by the delay time estimation unit and shorter than the maximum value of the delay times. [8] Receiving device according to any one of claims 1 to 7, further comprising a delay time count discrimination unit for determining whether the number of delay times, estimated by the delay time estimation unit, is less than a predetermined number, wherein If the number of delay times is determined to be less than the specified number, the delay time grouping unit does not perform the determination of whether the delay time is shorter than the threshold, and none of the first to N delayed wave removal units perform the wave removal. [9] A receiving method in which radio waves transmitted from a transmitter are received and an angle of incidence of the direct wave from the transmitter is estimated, the method comprising: a radio reception step in which frequency conversion and A / D conversion are performed on first to Nth analog signals obtained by receiving radio waves through first to Nth (where N is an integer not less than 2) antenna elements forming a group antenna to generate first to Nth digital signals; a transmission channel estimation step of estimating transmission channel frequency characteristics based on the first to Nth digital signals to output first to Nth transmission channel estimation results; a delay time estimation step of estimating, by means of a super-resolution process, delay times of one or more arriving waves contained in the radio waves, based on a transmission channel estimation result within the first to Nth transmission channel estimation results; a delay time grouping step of comparing the delay times estimated in the delay time estimation step with a threshold to determine whether the estimated delay times are shorter than the threshold; a delayed-wave removal step of removing, from the first to Nth transmission channel estimate results, an incoming-wave component according to the delay time determined to be equal to or longer than the threshold in the delay time grouping step, and of outputting first to Nth transmission channel frequency characteristics relating to the incoming waves with delay times determined to be shorter than the threshold in the delay time grouping step; an incoming wave separation step of separating from each other incoming wave components contained in the first to Nth transmission channel frequency characteristics in order to extract first to Nth direct wave components; and an incidence angle estimation step of estimating an incidence angle of the direct wave, based on a phase difference between the first to Nth direct wave components. [10] A program for causing a computer to perform the processes in the receiving method according to claim 9. [11] A computer-readable recording medium with which the program according to claim 10 is recorded.

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