KR20020096132A - Method for receiving signal - Google Patents

Abstract

PURPOSE: A method for receiving a signal is provided to obtain a weight value vector by a few calculation quantity so that it is possible to process the signal in real time in mobile communication environment. CONSTITUTION: A random angle(θ1) is estimated as an incident angle of a signal(S10). The random angle(θ1) is updated as a new value(θ2=θ1+Δ)(S11). Steering vectors(a(θ1),a(θ2)) about the random angle(θ1) and the new value(θ2) are obtained(S12). The obtained steering vectors(a(θ1),a(θ2)) are substituted for a criterion vector(f(a(θ))), respectively, and the difference value(f(a(θ2))-f(a(θ1))) of two criterion vectors is calculated(S13). The angle(θ1) is updated as a value(μ(f(a(θ2))-f(a(θ 1))))(S14). It is judged whether the criterion vector(f(a(θ))) is the maximum value(S15). If the criterion vector(f(a(θ))) is the maximum value, the angle is estimated as the incident angle(S16).

Description

Method for receiving signal

The present invention relates to an array antenna system, and more particularly, to a signal receiving method in the system.

In general, when performing wireless communication, a desired signal (hereinafter referred to as an original signal) and an interference signal exist together with a received signal, and a plurality of interference signals exist for one original signal. Since the degree of communication distortion caused by such an interference signal is determined by the sum of the original signal power versus the power of all the interference signals, even if the level of the original signal is significantly higher than the level of each of the interference signals, if the number of interference signals is large, The power increases and communication distortion occurs.

Therefore, the prior art focuses on minimizing such interference signals using an array antenna.

That is, when the moving object moves or the angle of arrival of the signal varies depending on the situation, to locate the remote signal sources using an array composed of several antenna elements or to selectively transmit and receive signals from the antenna elements. By controlling the phase of the arranged antenna to selectively transmit and receive a specific signal (original signal), and minimizes the influence of the interference signal to significantly reduce the interference between subscribers.

In order to selectively transmit and receive the original signal as described above, the weight is changed according to the incident angle of the signals received by the array antenna. The complex weight at this time is called a weight vector.

Signal reception using this weight vector is performed in two ways.

First, in the switching beam method, a weight vector obtained by taking a dot product of several predetermined weight vectors and a received signal and outputting a value which is considered to be optimal among the dot products is used as the weight vector of the array antenna system.

Second, in the tracking beam method, the weight vector is calculated according to a predetermined algorithm using the received signal.

Representative examples include a minimum mean square error (MMSE) method and a maximum signal to noise ratio (SINR) method.

Among these, there are various methods of obtaining a weight vector that maximizes the SINR, but one of them is "Lagrange Multiplier".

This method basically finds the weight vector maximizing the SINR through the following procedure.

First, a signal is received at the array antenna. This received signal is converted into a baseband signal, which is then converted into a digital signal.

The autocorrelation matrix of the digital signal is obtained. Since the weight vector maximizing the SINR is an eigenvector corresponding to the maximum eigenvalue of the autocorrelation matrix, the eigenvector is obtained.

The output of the array antenna system is obtained using the obtained eigenvector as the weight vector.

In this weight vector calculation procedure using the "Lagrange Multiplier", the weight vector is updated in the direction of the gradient vector of f ( w ) in order to maximize the objective function f ( w ).

The gradient vector is " Is calculated as ".

here, Indicates an autocorrelation matrix.

The weight vector " ", Gradient vector Is determined as follows.

In other words, in order to obtain the gradient vector, it is necessary to differentiate the objective function for each element of the weight vector.

Therefore, as the number of antennas increases, the number of differential operations for each weight vector element is inevitably increased.

Such a tracking beam method can obtain an optimal weight vector according to a signal environment that changes with time, but there is a problem in that a great deal of calculation is required.

In addition, although there are some differences depending on the implementation of the tracking beam scheme, in most cases, an inverse matrix of an N × N size matrix is required or eigen value decomposition is required. Where N is the number of antennas.

That is, excessive amount of calculation has been the biggest obstacle to the implementation of the tracking beam antenna system.

Accordingly, an object of the present invention is to provide a method for obtaining a weight vector with a small amount of calculation so as to enable real-time signal processing in a mobile communication environment.

Another object of the present invention is to provide a method for obtaining a weight vector that is suitable for improving the quality of a communication link.

In order to achieve the above object, in the present invention, a method of obtaining an accurate angle of incidence and a weight vector based on the assumption of an angle of incidence of a hand signal is introduced.

According to an aspect of the present invention for achieving the above object, assuming a direction component of the received signal, estimating a weight vector of the received signal from the estimated direction component, the signal according to the calculated weight Decoding is made.

Preferably, estimating the direction vector of the incident angle of the received signal, updating the incident angle by applying an adaptive gain value according to the moving speed of the user to the derivative value of the direction vector, wherein the updated incident angle is the output power Determining whether it is a value that maximizes or maximizes a desired signal power versus noise signal power; and when the updated angle of incidence maximizes the values, determining the updated angle of incidence as the weight of the received signal. It further comprises.

1 is a diagram illustrating a weight update procedure according to the present invention.

The present invention limits the variable to one incident angle estimate and sets the weight vector to be automatically calculated from this estimate of the incident angle. That is, the weight vector is limited to only the direction vector of the incident angle of the incident signal, and only the incident angle of the incident signal is updated to obtain the weight vector.

Hereinafter, a configuration and an operation according to an exemplary embodiment of the present invention will be described with reference to the accompanying drawings.

1 is a diagram illustrating a calculation process of a weight vector according to the present invention.

Referring to FIG. 1, first, an arbitrary angle is estimated as an incident angle of a signal. This random angle It is called. Assuming an incidence angle (S10) may select one of a plurality of angles determined by equally dividing the angle that the beam can direct, or may select one of a plurality of angles determined by analyzing previous incident angle data. This angle of incidence assumption is not entirely arbitrary, and given the information it will be possible to select the closest angle.

this Is randomly estimated so that the original signal (the signal to be received) can enter on the main robe. Or the angle of incidence of the previous received signal Save it, Use as an estimate of. Or estimate from the pilot signal.

Or this Candidates in ), Theta to enable maximum gain Estimate as By way of example, the system monitors the angle at which the previous received signals are incident for a predetermined time period to calculate the probability of occurrence of each angle of incidence. Then, the candidate groups of the incident angle estimation value are determined in the order of the greatest occurrence probability. These candidates will be renewed after a certain time. As another example, the system determines candidate groups around the angle of incidence of the main lobe among a plurality of predetermined weight vectors. That is, it has a predetermined number of candidate group sets.

And, Is the new value Update to. here, Is a positive enough small number near zero (S11).

remind , Steering vectors for, respectively , Obtain (S12)

Each direction vector obtained above is a standard function. Assign to

And, Calculate (S13).

And, in (S14) where Is a positive enough small adaptive gain value, and can be applied differently depending on the moving speed.

By repeating the steps of S10 to S15 sufficiently, Determine whether to maximize (S15), Is estimated by the incident angle (S16).

here, Has a signal As a direction vector at the angle of incidence, assuming that the array antenna system uses a linear array of N antennas, with each antenna element separated by half wavelength, Is as follows.

The standard function Is As a function of, it has the following form depending on the purpose and application of the array antenna system used.

a. Maximize array output power.

here, Is a received signal of the array antenna system Autocorrelation matrix of )to be. In other words, Is the output of the frequency shift portion.

b. Maximize the array output signal to noise ratio (SINR).

here, Wow, Are the autocorrelation matrix of the target user signal and the autocorrelation matrix of the interference signal and noise, respectively.

As described above, the present invention sets the weight vector to be automatically calculated from the estimated angle of incidence, thereby improving the phenomenon in which the number of operations increases explosively as the number of antennas increases, and the weight vector can be obtained by a simple method. It works.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the examples, but should be defined by the claims.

Claims (7)

Estimating a weight from the direction component of the received signal; And decoding the signal according to the calculated weight. 2. The method of claim 1, further comprising: estimating a direction vector of the incident angle; Updating the incident angle by applying an adaptive gain value according to a moving speed of a user to the derivative value of the direction vector; Determining whether the updated incidence angle is a value that maximizes output power or maximizes desired signal power versus noise signal power; And determining the updated angle of incidence as a weight of the received signal when the updated angle of incidence maximizes the values. The signal receiving method of claim 1, wherein the incident angle uses an incident angle of a previous received signal. The method of claim 1, wherein the incident angle is estimated from a pilot signal. The signal receiving method of claim 1, wherein the incident angle uses any one of a predetermined number of incident angles. The method of claim 5, wherein the predetermined number of incident angles is determined according to the number of reception of previous received signals at each incident angle. 6. The method of claim 5, wherein the predetermined number of incident angles is determined based on an incident angle of a main lobe of predetermined weights.