Fujitsu Corporation

Jingmin Xin

Kazuo Shirakawa

Yasushi Seike

Masataka Tsuchihashi

In an environment of spatially correlated additive noise, the direction estimation apparatus for coherent signals calculates (M&#x2212;q&#x2212;1) instantaneous cross-correlations between some array data, and selecting multiple pairs each of which is consisted of p instantaneous correlations from the (M&#x2212;q&#x2212;1) instantaneous cross-correlations to form a Hankel correlation matrix, where a length of a spatial correlation in terms of antenna elements is assumed to be q. Next, the apparatus divides that Hankel matrix into an upper submatrix and a lower submatrix, and then calculates a linear operator at time n by using the adaptive LMS algorithm with a fixed or time-varying step-size parameter. Then a noise subspace is estimated from that linear operator. Finally the directions of incident signals at a predetermined time is estimated and tracked by using that noise subspace with Newton approximation.

Method and apparatus for adaptive direction estimation of radio waves

An incoming wave number estimation device for receiving incoming radio waves by an array antenna in which a plurality (=M) of antenna elements are linearly arrayed with a same element spacing, and estimating the number of the incoming radio waves, including: a correlation matrix creation section for removing a diagonal element from a predetermined row or column constituting an M&#xd7;M array covariance matrix, and creating a correlation matrix by extracting a predeterminednumber of correlations from (M&#x2212;1) number of correlations after the diagonal element is removed while sequentially shifting one element at a time, and arraying thenumber correlations in a matrix; an estimation matrix creation section for creating an estimation matrix for estimating the incoming wave number using the correlation matrix; a QR decomposition section for performing QR decomposition on the estimation matrix; and an incoming wave number determination section for determining the number of incoming radio waves based on each row element of an upper triangular matrix factor obtained by the QR decomposition.

Incoming wave number estimation method, incoming wave number estimation device, and radio device

In an environment of temporally and spatially uncorrelated white additive noise, the direction estimation apparatus for coherent signals calculates (M&#x2212;1) instantaneous cross-correlations between some array data, and selecting multiple pairs each of which is consisted of p instantaneous correlations from the (M&#x2212;1) instantaneous cross-correlations to form a Hankel correlation matrix. Next, the apparatus divides that Hankel matrix into an upper submatrix and a lower submatrix and then calculates a linear operator at time n by using the adaptive LMS algorithm with a fixed or time-varying step-size parameter and or using the adaptive NLMS algorithm from the two submatrices. Then a noise subspace is estimated from that linear operator. Finally the directions of incident signals at time n is estimated and tracked by using that noise subspace with Newton approximation.

A radio wave direction-of-arrival estimation apparatus and method that can estimate, at high speed and with good accuracy, the direction of arrival of a plurality of incoming waves having high correlation. The radio wave direction-of-arrival estimation apparatus includes: an array antenna constructed from a plurality of antenna elements; a receiver for receiving an incoming wave via each of the antenna elements; a correlation matrix calculator for calculating a correlation matrix from each received signal; a correction matrix adder for adding a correction matrix having a suitable correction value only at a specific matrix element to the calculated correlation matrix; an inverse matrix calculator for calculating the inverse matrix of the correlation matrix to which the correction matrix has been added; a weight vector calculator for calculating a weight vector based on the calculated inverse matrix; an angular spectrum calculator for calculating an angular spectrum by using the calculated weight vector; and a direction-of-arrival estimator for estimating the direction of arrival of the incoming wave from the peak waveform of the calculated angular spectrum.

Apparatus and method for estimating direction of arrival of radio wave

A direction tracking method is proposed for quickly tracking directions-of-arrival of radio waves even in an environment where trajectories of the directions-of-arrival intersect. With the tracking method, the state vectors of directions-of-arrival (composed of a direction-of-arrival and the angular velocity and acceleration of the direction-of-arrival) at the current direction updating time are predicted with an observer by using state vectors of directions-of-arrival at the previous direction updating time to calculate provisional estimates of the directions-of-arrival, and furthermore, the state vectors at the current direction updating time are calculated based on the provisional estimates, the predicted state vectors, and predicted values of the directions-of-arrival to calculate estimates of the directions-of-arrival from the state vectors.

Method and apparatus for direction-of-arrival tracking and their application to beamforming at base-station

L overlapping forward subarrays with {overscore (q)}(&#x2267;q) antenna elements are formed with, where q is the number of desired signals, a cyclic correlation matrix is formed from the cyclic correlations between the received signals of L forward subarrays and a received signal of the first predetermined antenna element, the cyclic correlated matrix is divided into two upper and lower submatrices, an orthogonal projection operator in the noise subspace is calculated by performing a linear operation on these two upper and lower cyclic correlation matrices, then by calculating a spatial spectrum or a polynomial by using the estimated orthogonal projection operator, the directions are estimated from of the position of q highest peaks of the spatial spectrum or the phases of q roots of the polynomial closest to the unit circle in z-plane.

Method and device for tracking the directions-of-arrival of radio waves

An incoming radio wave is received by array antenna elements which constitute an array antenna, and the correlation between the received data of some array antenna elements is calculated to form a correlation matrix which is not affected by the additive noise at each antenna element. Then a noise subspace is obtained from the correlation matrix by a simple linear operation based on the partition of an array response matrix and is used to estimate the direction of signal (i.e., radio wave) impinging on the array antenna. Because the evaluation of all correlations between the array data received by array antenna elements is not needed, and the eigendecomposition process is avoided, the computational load of the proposed direction estimation technique is reduced, and the noise insensitivity is improved.

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Kawasaki, Japan

Jingmin Xin