KR100955696B1 - Apparatus and method for estimation of channel information using frequency domain and space domain orthogonal transformation in wireless communication systems - Google Patents

Abstract

Disclosed is a channel estimation apparatus and method using frequency and spatial domain orthogonal transformation in a wireless communication system. A channel estimation method according to an embodiment of the present invention is a channel estimation method using frequency and spatial domain orthogonal transformation in an orthogonal frequency division multiplex (OFDM) based wireless communication system using multiple reception antennas. Estimating an initial channel value for each of the subcarrier and the multiple reception antennas based on the received OFDM signal, orthogonally converting the initial channel value into a frequency domain and a spatial domain to generate an orthogonal transform value, the generated orthogonal transform Substituting a predetermined number of lower values of the values with “0” and performing orthogonal inverse transformation of the orthogonal transform values including the predetermined number of “0” s into a spatial domain and a frequency domain for each of the subcarriers and the multiple receive antennas. Estimating the final channel value.

Orthogonal Frequency Division Multiplexing (OFDM), Channel Estimation, Frequency Domain, Spatial Domain, Antenna Correlation

Description

Channel estimating apparatus and method using frequency and spatial domain orthogonal transformation in wireless communication system

The present invention relates to channel estimation, and more particularly, channel estimation using frequency and spatial domain orthogonal transformation to improve channel estimation performance in an orthogonal frequency division multiplex (OFDM) based wireless communication system using multiple receive antennas. An apparatus and a method thereof are provided.

Various multiplexing methods have been proposed for the rapid development of the Internet and wireless communication providing wireless high-speed data service, and a representative method is orthogonal frequency division multiplexing (OFDM).

The advantage of the OFDM scheme is that it is robust to intersymbol interference and has high frequency efficiency.

Meanwhile, a multiple transmit / receive antenna (MIMO) system for transmitting and receiving signals using multiple transmit / receive antennas has an advantage of increasing the capacity of a wireless channel in proportion to the number of antennas.

Due to each of these advantages, the MIMO-OFDM system has received considerable attention and is considered as the most useful technique for the next generation wireless communication.

In the OFDM system, channel information has a great influence on the performance of the system, and channel estimation such as frequency orthogonal transform channel estimation has been actively studied and many techniques have been proposed.

On the other hand, the channel estimation in the MIMO-OFDM system has not been studied much compared to the OFDM system, and the channel estimation in the MIMO-OFDM system is performed by simply applying the results of the system to the MIMO system. There is a situation.

 For example, a method of independently applying two-dimensional channel estimation of two regions in time and frequency for each antenna, one technique of performing one-dimensional channel estimation in each region in time, frequency, and space, and a frequency orthogonal transformation technique in a transmission / reception antenna For each technique.

The frequency domain orthogonal transform technique cuts out portions other than samples where channel power is concentrated in the frequency domain to obtain a noise suppression effect. A fast Fourier transform (FFT) module provided in an OFDM system Although it can be easily implemented using, the channel is estimated independently between the antennas without considering any correlation between the antennas.

An object of the present invention is to provide a channel estimation apparatus using frequency and spatial domain orthogonal transform in a wireless communication system capable of improving channel estimation performance in an OFDM system environment using multiple reception antennas such as SIMO and MIMO, and the like. To provide that method.

In accordance with an aspect of the present invention, a channel estimation method includes a channel estimation method using frequency and spatial domain orthogonal transformation in an orthogonal frequency division multiplex (OFDM) based wireless communication system using multiple reception antennas. Estimating an initial channel value for each of the subcarriers and the multiple reception antennas based on the OFDM signal received by the multiple reception antennas, and orthogonally converting the initial channel values into a frequency domain and a spatial domain to generate an orthogonal transform value. And replacing a predetermined number of lower values according to the magnitude of the generated orthogonal transform values with "0" and orthogonal inverse transforming the orthogonal transform values including the predetermined number "0" into a spatial domain and a frequency domain. Estimating a final channel value for each of the subcarriers and the multiple receive antennas. have.

In addition, estimating the initial channel value may estimate the initial channel value for each of the subcarrier and the multiple receive antennas based on a pilot signal included in each of the subcarriers, and calculates a least squares (LS) channel estimation scheme. The initial channel value may be estimated using.

According to another aspect of the present invention, there is provided a channel estimation method in a channel estimation method using frequency and spatial domain orthogonal transformation in an orthogonal frequency division multiplex (OFDM) based wireless communication system using multiple reception antennas. Estimating an initial channel value for each of the subcarrier and the multiple reception antennas based on the received OFDM signal, orthogonally converting the initial channel value into a frequency domain and a spatial domain to generate an orthogonal transform value, the generated orthogonal transform Calculating an optimal number of values, replacing an orthogonal transform value other than an upper value corresponding to the optimal number according to the magnitude of the value among the orthogonal transform values with "0", and said orthogonality including "0" Orthogonal inverse transform of transform values into a spatial domain and a frequency domain The final value for the channel may comprise the step of estimating.

According to an aspect of the present invention, there is provided a channel estimating apparatus in a channel estimating apparatus using frequency and spatial domain orthogonal transform in an orthogonal frequency division multiplexing wireless communication system using multiple receiving antennas. An initial channel estimator for estimating an initial channel value for each of the subcarrier and the multiple reception antennas based on orthogonality; A substituting unit for substituting a predetermined number of lower values according to the magnitude of the value among the transformed values with "0" and orthogonal inverse transforming of the orthogonal transform values including the predetermined number of "0" into a spatial domain and a frequency domain for the subcarrier and A final channel estimator for estimating a final channel value for each of the multiple reception antennas; .

Furthermore, the substitute unit calculates an optimal number of the orthogonal transform values generated by the orthogonal transform unit, and the difference between the number of the orthogonal transform values according to the magnitude of the value among the generated orthogonal transform values and the calculated optimal number difference You can replace as many lower values as "0".

Other objects and features of the present invention in addition to the above objects will be apparent from the description of the embodiments with reference to the accompanying drawings.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. First of all, in adding reference numerals to the components of each drawing, it should be noted that the same reference numerals are used as much as possible even if displayed on different drawings. In addition, in describing the present invention, when it is determined that the detailed description of the related well-known configuration or function may obscure the gist of the present invention, the detailed description thereof will be omitted.

Hereinafter, an apparatus and method for estimating a channel using frequency and spatial domain orthogonal transformation in a wireless communication system according to an embodiment of the present invention will be described in detail with reference to FIGS. 1 to 7.

SUMMARY OF THE INVENTION The present invention aims to improve channel estimation performance through frequency domain orthogonal transform and spatial domain orthogonal transform in an orthogonal frequency division multiplex (OFDM) based wireless communication system using multiple receive antennas.

Hereinafter, in an embodiment of the present invention, for convenience of description, a channel estimation method in a SIMO-OFDM environment considering only one transmission antenna will be mainly described. It will be appreciated that the channel estimation scheme in < RTI ID = 0.0 >

1 is a block diagram of a channel estimating apparatus according to an embodiment of the present invention.

Referring to FIG. 1, the channel estimating apparatus includes an initial channel estimator 110, an orthogonal transform unit 120, a substitute unit 130, and a final channel estimator 140.

The initial channel estimator 110 estimates an initial channel value for each of the subcarriers of the OFDM signal and the multiple receive antennas based on an OFDM signal that is a received signal received by the multiple receive antennas (not shown).

In this case, the reception signal received by the multiple reception antenna may be represented by Equation 1.

Y _n [k] = H _n [k] X [k] + N _n [k], k = 0, 1,... , K-1, n = 1, 2,... , N

Here, K means the number of subcarriers of the OFDM signal, k means the subcarrier index, n means the receiving antenna index, N means the number of receiving antennas, H _n [k] of the nth receiving antenna The frequency-domain channel value of the k-th subcarrier, X [k] means the transmission signal of the k-th subcarrier, and N _n [k] is additive white Gaussian noise with an average power of N ₀ . ), And Y _n [k] means a k-th subcarrier signal received by the n-th reception antenna.

H _n [k], which is a channel value of the frequency domain shown in Equation 1, may be expressed as Equation 2.

Here, L means the number of multipaths, and h _n [l] means the channel value of the lth multipath for the nth reception antenna.

는 <수학식 3>과 같이 나타낼 수 있다. 여기서, σ_l ²은 주파수 영역 채널 행렬에 대한 상관 행렬의 고유 값들을 의미하는 동시에 l번째 다중 경로의 평균 채널 이득을 의미한다.Where h _n [l] is E {| h _n [l] | ² } = σ _l ² , and if each path is independent, then expressed as a matrix, the (KⅹN) frequency domain channel matrix

Can be expressed as shown in Equation 3. Here, σ _l ² denotes the intrinsic values of the correlation matrix for the frequency domain channel matrix and the mean channel gain of the l-th multipath.

는 주파수 영역 채널 행렬

에 대한 상관 행렬의 고유벡터(eigenvector)로 이루어진 단위행렬인 이산 퓨리에 변환(DFT: discrete Fourier transform) 행렬을 의미하는데,

에 대한 상관 행렬은 <수학식 4>와 같이 나타낼 수 있다.here,

Is the frequency domain channel matrix

A discrete Fourier transform (DFT) matrix, which is a unit matrix of eigenvectors of the correlation matrix for.

The correlation matrix for may be expressed as Equation 4.

는 크기가 (KⅹK)인

의 상관 행렬을 의미하고, ()^H는 행렬의 허미시안(Hermitian) 형태를 의미하고,

는 크기가 (KⅹK)인 상관 행렬의 고유값(eigenvalue)들(즉, σ_l ²)로 이루어진 대각행렬(diagonal matrix)을 의미하고 동시에 채널의 시간 영역의 전력 지연 분포(power delay profile)에서 각 다중 채널의 평균 전력 값과 같다.here,

Is the size (KⅹK)

Means the correlation matrix of, and () ^H means the Hermitian form of the matrix,

Denotes a diagonal matrix of eigenvalues (i.e., σ _l ² ) of a correlation matrix of size (K 하고 K) and at the same time the power delay profile of the channel's time domain. It is equal to the average power value of multiple channels.

는 <수학식 5>와 같이 나타낼 수 있다.The initial channel estimator 110 estimates an initial channel value by using a least square (LS) channel estimating scheme, wherein the transmission signal X [k] is in all frequency domains, that is, in all subcarriers. When included, the initial channel matrix estimated by the initial channel estimator 110 because the pilot signal is known at the transmitting end transmitting X [k] and the receiving end receiving X [k].

Can be expressed as shown in Equation 5.

는 행렬

의 i번째 행, j번째 열의 값을 의미한다.here,

Is a matrix

The i-th row and j-th column of the value.

The orthogonal transform unit 120 generates an orthogonal transform value by orthogonally transforming the subcarrier estimated by the initial channel estimator 110 and initial channel values for each of the multiple reception antennas.

Here, the frequency domain orthogonal transformation may be performed by an Inverse Fast Fourier Transform (IFFT) module. That is, the orthogonal transform unit 120 may include an IFFT module.

First, the orthogonal transform unit 120 generates frequency-domain orthogonal transform values by performing frequency-domain orthogonal transform on the estimated initial channel values, as in the example shown in FIG. 2. That is, the orthogonal transform unit 120 performs inverse fast Fourier transform on the channel average power and the background noise power, which are initial channel values estimated by the initial channel estimator 110, to perform frequency domain orthogonal transform.

를 주파수 영역 직교 변환하여 주파수 영역 직교 변환 행렬을 생성한다.For example, the orthogonal transform unit 120 may determine the initial channel matrix when the initial channel value is estimated by the LS channel estimation method.

Is a frequency domain orthogonal transformation to generate a frequency domain orthogonal transformation matrix.

은 <수학식 6>과 같이 나타낼 수 있다.Where the frequency-domain orthogonal transformation matrix

Can be expressed as shown in Equation 6.

은 (LⅹN) 행렬이고,

는 상술한 <수학식 3>에서 설명한 바와 같이, 주파수 영역 채널 행렬

에 대한 상관 행렬의 고유벡터로 이루어진 단위행렬인 이산 퓨리에 변환 행렬을 의미한다. 이때,

를 곱하는 과정은 고속 퓨리에 변환 연산 과정을 통해 구현 가능하다.here,

Is the (LⅹN) matrix,

Is a frequency-domain channel matrix as described in Equation 3 above.

A discrete Fourier transform matrix, which is a unit matrix of eigenvectors of a correlation matrix for. At this time,

The multiplication process can be implemented by fast Fourier transform operation.

When the orthogonal transform unit 120 generates a frequency domain orthogonal transform value, the orthogonal transform unit 120 generates a orthogonal transform value by performing a spatial domain orthogonal transform on the frequency domain orthogonal transform value as shown in FIG. 3.

을 공간 영역 직교 변환하여 직교 변환 행렬을 생성하는데, 공간 영역 직교 변환에 의해 생성된 직교 변환 행렬

은 <수학식 7>과 같이 나타낼 수 있다.For example, the orthogonal transformation unit 120 is a frequency domain orthogonal transformation matrix generated by Equation (6).

Is orthogonal transform matrix to generate an orthogonal transformation matrix.

Can be expressed as shown in Equation 7.

는 공간 영역에서의 초기 채널 행렬에 대한 상관 행렬의 고유벡터들로 이루어진 단위행렬을 의미하고,

의 각 원소는 무상관되어 있으며

의 전력은

와 같다.here,

Denotes a unit matrix of eigenvectors of the correlation matrix with respect to the initial channel matrix in the spatial domain,

Each element of is unrelated

Power of

Same as

In this case, the correlation matrix for the initial channel matrix in the spatial domain may be expressed as Equation (8).

는 상관 행렬

의 고유값들로 이루어진 대각행 렬을 의미한다.here,

Is a correlation matrix

A diagonal matrix of eigenvalues.

는

인 것이 바람직하다.Of course, when the initial channel estimator 110 estimates the initial channel matrix using the LS channel estimation method,

Is

Is preferably.

Here, the operation of the orthogonal transform unit 120 has been described as sequentially performing the frequency domain orthogonal transformation and the spatial domain orthogonal transformation. However, the present invention is not limited thereto and the frequency domain orthogonal transformation may be performed after performing the spatial domain orthogonal transformation. It may be.

The replacement unit 130 selects a predetermined number, for example, P orthogonal transform values having an upper value among the orthogonal transform values generated by the orthogonal transform unit 120, and selects the remaining orthogonal transform values, that is, the orthogonal transform of the lower values. Replace the values with "0". That is, the replacement unit 130 sequentially leaves only P, starting from the largest average channel power among the LN orthogonal conversion values, and replaces the rest with "0".

은 <수학식 9>와 같이 나타낼 수 있다.An orthogonal transformation matrix in which a predetermined number (LN-P) orthogonal transformation values are replaced with "0" by the replacement unit 130.

Can be expressed as shown in Equation 9.

는 모든

중 P번째로 큰 수를 의미하고, i=1, 2,…, L이고, j=1, 2,…, N이다.here,

Is all

Means the P-th largest number, i = 1, 2,... , L, j = 1, 2,... , N.

Referring to FIG. 4, the substitute unit 130 will be described in more detail. The substitute unit 130 may have a channel value main region (solid line region) having a higher value among the orthogonal transform values generated by the orthogonal transform unit 120. After dividing the main background noise area (dotted area) having the lower and lower values through <Equation 9>, the orthogonal transformation values corresponding to the main background noise area are replaced with "0".

The final channel estimator 140 estimates the final channel value by performing spatial domain orthogonal inverse transform and frequency domain orthogonal inverse transform on the orthogonal transform values replaced by the substitute unit 130. In this case, the final channel estimator 140 sequentially performs the frequency domain orthogonal inverse transform and the spatial domain orthogonal inverse transform when the orthogonal transform unit 120 performs spatial domain orthogonal transform and frequency domain orthogonal transform on the initial channel values. It is desirable to estimate the final channel value.

In this case, the final channel estimator 140 may perform frequency-domain orthogonal inverse transform using a fast Fourier transform (FFT) module. Of course, the final channel estimator 140 is not limited to performing the frequency domain orthogonal inverse transform through the FFT module, and may vary according to the method of performing the frequency domain orthogonal transformation in the orthogonal transform unit 120.

을 <수학식 10>을 이용하여 공간 영역 직교 역변환한 후 <수학식 11>을 이용하여 주파수 영역 직교 역변환을 수행하여 최종 채널 행렬을 추정한다.This, final channel estimator 140 is an orthogonal transformation matrix replaced by substitute 130.

After the spatial domain orthogonal inverse transform using Equation 10, the frequency channel orthogonal inverse transform is performed using Equation 11 to estimate the final channel matrix.

는 대체된 직교 변환 행렬

을 공간 영역 직교 역변환하여 생성된 행렬을 의미한다.here,

Is an orthogonal transformation matrix

Denotes a matrix generated by inverse transform of the spatial domain.

는

을 주파수 영역 직교 역변환하여 추정된 최종 채널 행렬을 의미한다.here,

Is

Denotes the final channel matrix estimated by inverse transform of the frequency domain.

In this case, since the final channel value estimated by the final channel estimator 140 is orthogonally inversely transformed into the spatial domain and the frequency domain by the number P determined by Equation (9), as shown in FIG. While also decreasing, some channel distortion may occur.

In other words, the final channel value estimated by the final channel estimator 140 is P, orthogonal, which is an optimal interval boundary value for distinguishing the main channel value region and the main background noise region, which are set in consideration of not only the frequency domain but also the spatial domain at the same time. Depending on the number of higher values among the transform values, it is desirable to calculate an optimal P value to improve channel estimation performance.

Here, the optimal P value may be calculated by the replacement unit 130 or may be calculated by additionally configuring another block. The optimal P _Popt may be, for example, mean square error (MSE). It can be calculated based on the channel estimation performance.

In this case, the mean square error channel estimation performance mse (P) may be expressed as Equation 12.

는 σ₁ ²λ₁ ²부터 σ_L ²λ_N ²까지의 값들을 큰 값부터 재배열하여 얻어지는 값으로 1부터 L 중 어느 하나의 수를 의미하고,

는 σ₁ ²λ₁ ²부터 σ_L ²λ_N ²까지의 값들을 큰 값부터 재배열하여 얻어지는 값으로 1부터 N 중 어느 하나의 수를 의미한다. 즉, i≥j인 경우

을 만족한다.Here, SNR means signal-to-noise ratio,

Is a value obtained by rearranging values from σ ₁ ² λ ₁ ² to σ _L ² λ _N ² from a large value, and means a number of 1 to L,

Is a value obtained by rearranging the values of σ ₁ ² λ ₁ ² to σ _L ² λ _N ² from a large value, and represents a number of 1 to N. That is, if i≥j

To satisfy.

In Equation 12, the first part represents an error caused by truncation of the channel power sample, and the second part represents an error due to noise remaining after being cut by Equation 9. As can be seen from Equation 12, the smaller the P value, the less the effect of noise, while the power of the portion containing the channel signal is cut off a lot, so the distortion of the signal becomes larger. However, the noise suppression effect can be reduced.

Thus, it is in view of the above noise power suppression as a compromise (trade-off) between the signal distortion to obtain the optimum value of P P _opt preferably, P _opt may be obtained by the <Equation 13>.

As can be seen from Equation 13, P _opt represents all P values, that is, 1, 2,... It can be seen that the mean square error channel estimation performance among the LNs is the P value that is the minimum.

As described above, the channel estimating apparatus according to an embodiment of the present invention calculates an optimal P value for dividing the orthogonal transform values of the frequency domain and the spatial domain orthogonal transform into a channel value main region and a background noise main region, thereby causing distortion of the channel signal. And channel estimation performance can be improved by properly considering the noise suppression effect.

Although the SIMO-OFDM environment has been described in an embodiment of the present invention, it is obvious that the present invention can be applied to the MIMO-OFDM environment. That is, in the MIMO-OFDM environment, the frequency and spatial domain orthogonal transform channel estimation techniques of the SIMO-OFDM environment described above in parallel with each other are performed in parallel between all reception antennas for each transmission antenna.

In addition, in the embodiment of the present invention illustrated in FIG. 1, although the orthogonal transform unit 120 performs the spatial domain orthogonal transformation after performing the frequency domain orthogonal transformation, the frequency after performing the spatial domain orthogonal transformation is performed. It is obvious that the domain orthogonal transformation may be performed. Of course, when the spatial domain and the frequency domain orthogonal transformation are performed sequentially, the final channel estimator 140 preferably performs the frequency domain orthogonal inverse transformation and the spatial domain orthogonal inverse transformation in sequence.

6 is an operation flowchart of a channel estimation method according to an embodiment of the present invention, which is an operation flowchart in a SIMO-OFDM environment.

Referring to FIG. 6, the channel estimation method receives an OFDM signal transmitted from a transmission antenna in a multiple reception antenna through a multipath (S610).

In this case, a signal received by each of the receiving antennas may be represented by Equation 1, and each of the subcarriers may include a pilot signal predefined at the transmitting end and the receiving end.

When the OFDM signal is received by each of the multiple reception antennas, an initial channel value for each of the subcarrier and the reception antenna is estimated based on the received OFDM signal (S620).

In this case, the initial channel value may be estimated by the LS channel estimation method, and the initial channel matrix estimated by the LS channel estimation method may be represented by Equation 5 described above.

An orthogonal transformation matrix is generated by sequentially performing an estimated initial channel value, that is, an initial channel matrix and a frequency domain orthogonal transformation and a spatial domain orthogonal transformation (S630 and S640).

In this case, the initial channel matrix may be orthogonally transformed by the frequency domain by the IFFT, and the orthogonal transformation matrix may be generated by Equations 6 and 7 described above.

When the orthogonal transformation matrix is generated, other values except for a predetermined number of upper values among the orthogonal transformation values constituting the orthogonal transformation matrix are replaced with "0" (S650).

For example, when there are L multipaths and N receive antennas, P is selected from the LN orthogonal transform values having the largest average channel power, and the remaining values are replaced with "0". For example, by using Equation 9, the orthogonal transform values corresponding to the background noise main region among the orthogonal transform values are replaced with "0".

In the channel estimation method according to an embodiment of the present invention, after performing the spatial domain orthogonal transformation as well as the frequency domain orthogonal transformation, the antenna correlation is considered by replacing the values corresponding to the background noise main region among the initial channel values with "0". In addition, channel estimation performance can be improved by removing background noise.

At this time, the number of orthogonal transform values replaced with "0", that is, the number of orthogonal transform values P corresponding to the main region of the channel value may be selected as an appropriate value in consideration of two aspects of channel distortion and background noise removal. This will be described with reference to FIG. 7.

FIG. 7 is a flowchart illustrating an embodiment of operation S650 of FIG. 6, in which an optimal number of orthogonal transform values P _opt corresponding to a channel value main region is calculated (S710).

In this case, the optimal P value may be calculated based on a pre-payment, mean square error (MSE) channel estimation performance, and may be calculated using, for example, Equation 13 described above.

Based on the optimum P value calculated in step S710, the remaining values except for the upper value corresponding to the optimal number of P among the orthogonal conversion values, that is, the channel average power values, are replaced with "0" (S720).

As such, by distinguishing the channel value main region and the background noise main region by using the optimal P value, channel estimation performance can be improved by properly considering channel distortion and background noise reduction.

Referring back to FIG. 6, when the orthogonal transform values corresponding to the background noise main region are replaced with "0", the final channel matrix is estimated by performing the spatial domain orthogonal inverse transform and the frequency domain orthogonal inverse transform on the replaced orthogonal transformation matrix. (S660, S670).

Here, the frequency domain orthogonal inverse transform may be performed by the FFT, and the final channel matrix may be estimated by Equations 10 and 11 described above.

In the above-described channel estimation method according to the embodiment of the present invention, the frequency domain and the spatial domain orthogonal transformation are sequentially performed, but the present invention is not limited thereto. Of course, when the spatial domain and the frequency domain orthogonal transformation are sequentially performed, it is obvious that the frequency domain and the spatial domain orthogonal inverse transformation are performed sequentially.

The channel estimation method according to an embodiment of the present invention performed through the above process can be applied not only to the SISO-OFDM environment but also to the MIMO-OFDM environment, thereby improving channel estimation performance in an environment using multiple reception antennas. Can be.

The apparatus and method for estimating a channel using frequency and spatial domain orthogonal transformation in a wireless communication system according to the present invention can be variously modified and applied within the scope of the technical idea of the present invention, and are not limited to the above embodiments. In addition, the embodiments and drawings are merely for the purpose of describing the contents of the invention in detail, not intended to limit the scope of the technical idea of the invention, the present invention described above is common knowledge in the technical field to which the present invention belongs As those skilled in the art can have various substitutions, modifications, and changes without departing from the spirit of the present invention, it is not limited to the embodiments and the accompanying drawings. And should be judged to include equality.

1 is a block diagram of a channel estimating apparatus according to an embodiment of the present invention.

2 is an exemplary diagram for a frequency domain orthogonal transformation according to an embodiment of the present invention.

3 is an exemplary diagram for a spatial domain orthogonal transformation according to an embodiment of the present invention.

4 is an exemplary diagram for "0" replacement according to an embodiment of the present invention.

5 is an exemplary diagram for a spatial domain and a frequency domain quadrature inverse transform according to an embodiment of the present invention.

6 is an operation flowchart of a channel estimation method according to an embodiment of the present invention.

FIG. 7 is a flowchart of an embodiment operation of step S650 illustrated in FIG. 6.

<Description of Symbols for Main Parts of Drawings>

110: initial channel estimator

120: orthogonal transform unit

130: replacement

140: final channel estimator

Claims (12)

A channel estimation method using frequency and spatial domain orthogonal transformation in an orthogonal frequency division multiplex (OFDM) based wireless communication system using multiple reception antennas, Estimating a subcarrier and an initial channel value for each of the multiple receive antennas based on the OFDM signal received by the multiple receive antennas; Generating an orthogonal transform value by orthogonally transforming the initial channel value into a frequency domain and a spatial domain; Replacing a predetermined number of lower values according to the magnitude of the generated orthogonal transformation values with "0"; And Estimating orthogonal inverse transform values including the predetermined number of zeros into a spatial domain and a frequency domain to estimate a final channel value for each of the subcarriers and the multiple receive antennas; Channel estimation method comprising a. The method of claim 1, Estimating the initial channel value And estimating the initial channel values for each of the subcarriers and the multiple receive antennas based on pilot signals included in each of the subcarriers. The method of claim 1, Estimating the initial channel value A channel estimation method for estimating the initial channel value using a least squares (LS) channel estimation method. The method of claim 1, Generating the orthogonal transformation value A channel estimation method generated by Equations 1 and 2 below. <Equation 1>

here,

Is a frequency domain orthogonal transformation matrix,

Is the initial channel estimation matrix,

Above

The unit matrix consisting of the eigenvectors of the frequency domain correlation matrix of () ^H denotes the Hermitian form of the matrix. <Equation 2>

here,

Is an orthogonal transformation matrix containing the orthogonal transformation value as a spatial domain orthogonal transformation matrix,

Denotes a unit matrix composed of eigenvectors of a spatial domain correlation matrix. A channel estimation method using frequency and spatial domain orthogonal transformation in an orthogonal frequency division multiplex (OFDM) based wireless communication system using multiple reception antennas, Estimating a subcarrier and an initial channel value for each of the multiple receive antennas based on the OFDM signal received by the multiple receive antennas; Generating an orthogonal transform value by orthogonally transforming the initial channel value into a frequency domain and a spatial domain; Calculating an optimal number of generated orthogonal transform values; Replacing an orthogonal transform value other than an upper value corresponding to the optimum number according to the magnitude of the value among the orthogonal transform values with "0"; And Estimating the orthogonal transform values including "0" by orthogonal inverse transform into a spatial domain and a frequency domain to estimate a final channel value for each of the subcarriers and the multiple receive antennas; Channel estimation method comprising a. The method of claim 5, Calculating the optimal number A channel estimation method in which the optimum number is calculated by Equation 3 below. <Equation 3>

Where P _opt is the optimal number, L is the number of multipath signals, N is the number of receive antennas, K is the number of subcarriers, SNR is the signal-to-noise ratio,

Is a value obtained by rearranging values from σ ₁ λ ₁ to σ _L λ _N from a large value, and the number of 1 to L,

Is a value obtained by rearranging the values from σ ₁ λ ₁ to σ _L λ _N from a large value, the number of 1 to N, σ is the eigenvalue of the correlation matrix for the initial channel estimation matrix in the frequency domain, and λ is It means the unique value of the correlation matrix for the initial channel estimation matrix in the spatial domain. A channel estimation apparatus using frequency and spatial domain orthogonal transformation in an orthogonal frequency division multiplexing wireless communication system using multiple reception antennas, An initial channel estimator for estimating a subcarrier and an initial channel value for each of the multiple reception antennas based on the OFDM signal received by the multiple reception antennas; An orthogonal transform unit which orthogonally transforms the initial channel value into a frequency domain and a spatial domain to generate an orthogonal transform value; A replacement unit for replacing a predetermined number of lower values according to the magnitude of the generated orthogonal transformation values with "0"; And A final channel estimator for estimating a final channel value for each of the subcarriers and the multiple receive antennas by performing orthogonal inverse transform on the orthogonal transform values including the predetermined number of zeros into a spatial domain and a frequency domain Channel estimation apparatus comprising a. The method of claim 7, wherein The initial channel estimator And an initial channel value for each of the subcarriers and the multiple receive antennas based on pilot signals included in each of the subcarriers. The method of claim 7, wherein The initial channel estimator And estimating the initial channel value using a least squares (LS) channel estimation method. The method of claim 7, wherein The orthogonal transform unit A channel estimating apparatus for generating the orthogonal transform value using Equations 1 and 2 below. <Equation 1>

here,

Is a frequency domain orthogonal transformation matrix,

Is the initial channel estimation matrix,

Above

The unit matrix consisting of the eigenvectors of the frequency domain correlation matrix of () ^H denotes the Hermitian form of the matrix. <Equation 2>

here,

Is an orthogonal transformation matrix containing the orthogonal transformation value as a spatial domain orthogonal transformation matrix,

Denotes a unit matrix composed of eigenvectors of a spatial domain correlation matrix. The method of claim 7, wherein The replacement part The optimal number of orthogonal transform values generated by the orthogonal transform unit is calculated, and the number of orthogonal transform values according to the magnitude of the value among the generated orthogonal transform values and the number corresponding to the calculated optimal number difference is increased. Channel estimation device for substituting a lower value of "0". The method of claim 11, The replacement part A channel estimating apparatus for calculating the optimum number by the following equation (3). <Equation 3>

Where P _opt is the optimal number, L is the number of multipath signals, N is the number of receive antennas, K is the number of subcarriers, SNR is the signal-to-noise ratio,

Is a value obtained by rearranging values from σ ₁ λ ₁ to σ _L λ _N from a large value, and the number of 1 to L,

Is a value obtained by rearranging the values from σ ₁ λ ₁ to σ _L λ _N from a large value, the number of 1 to N, σ is the eigenvalue of the correlation matrix for the initial channel estimation matrix in the frequency domain, and λ is It means the unique value of the correlation matrix for the initial channel estimation matrix in the spatial domain.

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