KR20090132001A - Channel estimation device, ofdm receiving apparatus comprising the same estimation device and method of estimating channel - Google Patents

Abstract

PURPOSE: A channel estimating apparatus, an OFDM receiving device including the same, and a channel estimating method are provided to perform strong channel estimation by calculating a channel estimating value through an average of linear interpolation and lattice interpolation. CONSTITUTION: A delay unit(710) delays a signal in which FFT(Fast Fourier Transform) is performed as a fixed time. A complex interpolation part(780) performs linear and lattice complex interpolation through pilot symbols extracted from the signal. The linear and lattice complex interpolation is calculated by performing the linear interpolation and the lattice interpolation at the same time. An equalizer(760) compensates signal distortion by the channel estimation value extracted through the complex interpolation about the signal outputted from the delay unit. A CSI(Channel State Information) extracting part(770) extracts channel state information through an output signal from the complex interpolation part.

Description

Channel estimation apparatus, OFDM receiving apparatus comprising the apparatus and a channel estimation method

The present invention relates to an apparatus and method for receiving a symbol in an orthogonal frequency division multiplexing (OFDM) system, and more particularly to a channel estimating apparatus and method for improving channel estimation performance in an OFDM system.

In an OFDM system, the transmitted signals are affected by multi-paths with different amplitudes and delays. This multipath causes fading, which distorts the received signal received at the receiver. In addition, in order to ensure the mobility of the communication terminal, a means for compensating for distortion of the received signal caused by the above-described problem, estimating an accurate channel estimate, and equalizing the received signal according to the estimation. Is required.

In order to estimate a channel of a signal transmitted and received in an OFDM system, a predefined training symbol is required between a transmitter and a receiver. Especially for signals transmitted over an air channel, the scattered pilot symbols included in the signal are used to accurately decode the received signal in a noisy environment causing multi-echo. Channel estimation is performed.

Conventional methods for channel estimation using pilot include linear interpolation and cubic interpolation, and statistical characteristics of pilot values of previous symbols are used to improve channel estimation performance. .

The conventional channel estimation technique performs channel estimation after all of the distributed pilots are received. Since the interpolation technique of one method is used, channel estimation performance is greatly affected by fading.

1A and 1B are diagrams for describing channel estimation performance deteriorated due to fading.

FIG. 1A illustrates a case of accurately estimating a channel when there is no influence due to fading. FIG. 1B illustrates an error range generated when a pilot signal is distorted due to fading by multiple paths, and the channel is estimated by the distorted pilot. That is, since the channel is estimated within the error range indicated by the circle A, the exact channel cannot be estimated, and thus the reception performance of the signal is reduced by that amount.

An object of the present invention is to provide a channel estimating apparatus capable of robust channel estimation by minimizing the effects of fading due to multiple paths in an OFDM system, an OFDM receiver including the apparatus, and a channel estimating method.

In order to achieve the above object, the present invention is a delay for delaying the signal performed the FFT (Fast Fourier Transform) by a predetermined time; A complex interpolator for performing linear and lattice complex interpolation using pilot symbols extracted from the signal; And an equalizer (EQ) for compensating for the signal distortion by using the channel estimate extracted through the complex interpolation on the signal output from the delayer.

In the present invention, the complex interpolation unit includes a linear interpolation unit that performs linear interpolation on the time axis and the frequency axis; A lattice interpolation unit performing lattice interpolation with a lattice structure; And an average unit for averaging the linear interpolation unit and the lattice interpolation unit output. The average unit may include two averagers that halve the outputs of the linear interpolator and the lattice interpolator, and an adder that adds the outputs of the two averagers.

In the present invention, the linear interpolation is performed by weighting two pilot symbols on each of a time axis and a frequency axis, adding the weights, and dividing the result by a weighted sum. It is made by adding and dividing by the sum of the weights, the complex interpolation can be made by adding the output of the linear interpolation unit and the lattice interpolation unit by half using the average unit. That is, the complex interpolation can be achieved by performing linear interpolation and lattice interpolation together and taking the average.

Meanwhile, the channel estimating apparatus of the present invention may further include a CSI extractor for extracting channel state information (CSI) using the output signal from the complex interpolator.

In addition, the present invention, in order to achieve the above object, a delayer for delaying the signal subjected to the Fast Fourier Transform (FFT) by a predetermined time; A complex interpolator for performing linear and lattice complex interpolation using pilot symbols extracted from the signal; An equalizer (EQ) unit for compensating for signal distortion by using respective channel estimates extracted through linear interpolation and lattice interpolation of the complex interpolation unit with respect to the signal output from the delay unit; And an average unit for averaging the output of the equalizer unit.

In the present invention, the equalizer unit comprises: a first equalizer for compensating for signal distortion using the channel estimate extracted through the linear interpolation; And a second equalizer for compensating for signal distortion by using the channel estimate extracted through the lattice interpolation, wherein the average unit comprises: two averagers that half the output of each of the first and second equalizers; It may include an adder that sums the outputs of the two averagers.

Furthermore, the present invention, in order to achieve the above object, a CP remover for removing a CP (Cyclic Prefix) for an Orthogonal Frequency Division Multiplexing (OFDM) signal changed into a baseband digital signal through a receiver; An FFT unit which performs an FFT (Fast Fourier Transform) on the output signal of the CP removing unit; A pilot extractor for extracting a pilot symbol from the output signal of the FFT unit; A channel estimating apparatus for estimating a channel through linear and lattice interpolation using the pilot symbols for the output signal of the FFT unit; A demapper which demaps an output signal of the channel estimator; And a channel decoder for performing channel decoding on the output signal of the demapper.

In the present invention, the OFDM receiver includes a pre-FFT unit in front of the CP removing unit, and the pre-FFT unit includes mode detection, guard detection, and STO (Symbol) for the digital signal. Time Offset) and FCOR (Fractional Carrier Frequency Offset) estimation and Symbol Frequency Offset (SFO) estimation may be performed.

On the other hand, the present invention, to achieve the above object, the step of extracting a pilot symbol for the signal on which the FFT is performed; Extracting a channel estimate by performing linear and lattice complex interpolation using the pilot symbols; Compensating for the signal distortion using the channel estimate value for the signal; provides a channel estimation method comprising a.

In the present invention, extracting the channel estimate includes performing the linear interpolation and lattice interpolation; Halving the linear interpolation and lattice interpolation values; And adding the half-divided linear interpolation and lattice interpolation values. The method may further include delaying the signal by a predetermined time used to extract a channel estimate value. In the signal distortion compensation step, signal distortion may be compensated for by using the channel estimate value with respect to the delayed signal.

In order to achieve the above object, the present invention also comprises the steps of: extracting a pilot symbol for the signal on which the FFT is performed; Extracting respective channel estimates through linear interpolation and lattice interpolation using the pilot symbols; Compensating for each signal distortion for the signal using each of the channel estimates; And averaging the signals whose signal distortion is compensated for.

In the present invention, the averaging of the signals may include: dividing the signals whose signal distortion is compensated for; And adding the divided signals.

According to the present invention, an apparatus for estimating a channel, an OFDM receiver including the apparatus, and a channel estimating method perform complex interpolation by performing linear interpolation and lattice interpolation together and averaging in an OFDM system using a distributed pilot. Robust channel estimation can be achieved. As a result, a reception performance of about 3 dB in average gain can be obtained.

On the other hand, the complex interpolation used in the present invention can be performed through a simple S / W arithmetic operation. Accordingly, the channel estimating apparatus of the present invention, the OFDM receiver including the apparatus, and the channel estimating method have an advantage of easily improving channel estimation performance by adding relatively little hardware.

Hereinafter, with reference to the accompanying drawings will be described a preferred embodiment of the present invention; In the following description, when a component is described as being connected to another component, it may be directly connected to another component, but a third component may be interposed therebetween. In addition, in the drawings, the structure or size of each component is exaggerated for convenience and clarity of explanation, and parts irrelevant to the description are omitted. Like numbers refer to like elements in the figures. On the other hand, the terms used are used only for the purpose of illustrating the present invention and are not used to limit the scope of the invention described in the meaning or claims.

2 is a block diagram of an OFDM receiver according to an embodiment of the present invention.

Referring to FIG. 2, the OFDM receiver of the present embodiment includes an RF tuner 100 (RF Rx), an analog digital converter (200, ADC), a cyclic prefix remover (300), a pre-FFT unit ( 400, Pre-FFT Unit, FFT Unit 500, Pilot Extractor 600, Pilot Estimator, Channel Estimator 700, Demapper 800 and Channel Decoder 900, Channel Decoder ).

The RF tuner 100 converts the received signal into a baseband signal, and the ADC 200 converts the analog signal into a digital signal. The CP remover 300 removes the CP attached to the received signal, and the pre-FFT unit 400 obtains the synchronization for the symbol. That is, the pre-FFT unit 400 estimates mode detection, guard detection, symbol timing offset (STO) / fractional carrier frequency offset (FCFO), and symbol frequency offset (SFO).

The FFT unit 500 performs an FFT on the signals from which the CP has been removed, and the pilot extractor 600 extracts a distributed pilot with respect to the signals on which the FFT has been performed. Using the extracted pilot, the channel estimator 700 estimates a channel through complex interpolation. Details of the channel estimator 700 and complex interpolation will be described in more detail below with reference to FIG. 3.

After channel estimation, the demapper 800 performs demapping on the data through demodulation in response to the mapped modulation scheme. For example, when a transmission signal is mapped in BPSK (Binary Phase Shift Keying), DBPSK demodulation is performed. In the case where the transmission signal is mapped in QPSK (Quadrature Phase Shift Keying), DQPSK demodulation is performed.

After demapping, the channel decoder 900 performs final channel decoding based on the channel previously estimated by the channel estimating apparatus 700.

The OFDM receiver of the present embodiment employs a channel estimator using complex interpolation, thereby enabling robust channel estimation while minimizing the effects of fading.

3 and 4 are block diagrams illustrating structures that may be implemented as a channel estimator included in the OFDM receiver of FIG. 2.

Referring to FIG. 3, the channel estimator 700 of the present embodiment includes a delay unit 710, a complex interpolator 780, an equalizer 760, and a channel state information (CSI) extractor 770. It includes.

The delay unit 710 delays the signal on which the FFT is performed by the FFT unit 500 by a predetermined time used for complex interpolation, and the signal output through the delay unit 710 is a complex interpolator 780. The signal distortion is compensated for in the equalizer 760 by using the channel estimate extracted from the equalizer.

The complex interpolator 780 includes a linear interpolator 720, a lattice interpolator 730, two averagers 740a and 740b, and an adder 750. The linear interpolator 720 performs linear interpolation on the time axis and the frequency axis of the signal on which the FFT is performed using the pilot symbols extracted by the pilot extractor (not shown), and the lattice interpolator 730. Performs lattice interpolation in a lattice structure. Such linear interpolation and lattice interpolation are described in more detail in the description of FIGS. 5A and 5B. The two averagers 740a and 740b divide the outputs of the lattice interpolator 730 and the linear interpolator 720, respectively, and the adder 750 adds the outputs of the two averagers 740a and 740b. That is, the two averagers 740a and 740b and the adder 750 perform the function of averaging linear interpolation and lattice interpolation. Here, the averagers 740a and 740b may simply perform an output half function through a shift operation.

As a result, the complex interpolation method using the complex interpolation unit is a method of performing both linear interpolation and lattice interpolation and calculating the average to obtain a channel estimate. The complex interpolation of the present embodiment does not use one interpolation method such as linear or lattice, but performs interpolation using two interpolation methods together. Accordingly, the error generation range generated by one conventional interpolation method can be significantly reduced. Such complex interpolation can be easily performed using S / W (software) arithmetic. A more detailed description of complex interpolation will be given in FIGS. 6A and 6B.

The equalizer 760 compensates for the signal distortion by using the channel estimate extracted through the complex interpolation on the signal output from the delayer 710. Meanwhile, the CSI extractor 770 extracts channel state information by using the output signal from the complex interpolator.

The channel estimating apparatus 700 of the present embodiment extracts the channel estimation value using the complex interpolation unit 780, which uses only the average hardware and the adder for the average while using the existing hardware for linear and lattice interpolation. As they are added, they can be implemented with a relatively small increase in hardware. In addition, the functions of the averager and the adder for the average can be implemented through simple S / W arithmetic operation. On the other hand, since the number of pilot symbols used for complex interpolation is the same as the number of pilot symbols used for linear interpolation, it is not necessary to extract additional pilots. The channel estimator of the present embodiment performs linear and lattice interpolation together and calculates the average thereof, thereby enabling more accurate channel estimation, that is, robust channel estimation under the influence of fading.

Referring to FIG. 4, the channel estimating apparatus 700a of this embodiment is similar in principle to the channel estimating apparatus of FIG. The structure is different from that of the channel estimating apparatus of FIG. That is, the channel estimating apparatus 700a of the present embodiment includes only the linear interpolation unit 720 and the lattice interpolation unit 730 as the complex interpolation unit 780a. In addition, two equalizers that compensate for signal distortion for signals delayed in the delayer 710 using respective channel estimates extracted by the linear interpolator 720 and the lattice interpolator 730 instead of one equalizer. (760, 770). On the other hand, the outputs of the two equalizers 760 and 770 are divided in half through the averagers 740a and 740b of the average unit 790 and merged in the adder 750.

As a result, the channel estimator of FIG. 3 immediately averages the channel estimates extracted by the linear interpolator 720 and the lattice interpolator 730, and compensates for the signal distortion by using the averaged channel estimate. The apparatus uses the channel estimates of each of the linear interpolator 720 and the lattice interpolator 730 to compensate for the signal distortion for the delayed signals, respectively, and average the compensated signals. The results show almost similar channel estimation performance as can be seen in FIGS. 7A and 7B.

Whether to implement the structure of the channel estimating apparatus of FIG. 3 or the channel estimating apparatus of FIG. 4 may be selected by the user according to the structure of the receiving apparatus, the musk or the channel environment. On the other hand, considering the structure and cost, the channel estimator of FIG. 3, in which one equalizer is added, is advantageous in terms of cost and hardware reduction.

5A and 5B are structural diagrams of an OFDM symbol for explaining linear interpolation and lattice interpolation in channel estimation, respectively.

5A shows a process of performing linear interpolation. When estimating the channels of the symbols of A and B, channel estimation is performed through calculations such as Equations (1) and (2) below.

A = (P _{i -1, j} + P _{i + 3, j} ) / 2 ......................... Equation (1)

B = (A + P _{i + 1, j} ) / 2 ..................... Formula (2)

That is, in the case of the symbol of A, pilot symbols of the time axis are used, and in the case of the symbol of B, the pilot symbol of the frequency axis and the previously obtained A symbol are obtained. Such linear interpolation is generally calculated by weighting two symbols to be interpolated and dividing by the sum of the weights. That is, the general formula of linear interpolation is as follows.

Z = aX + bY ..................... (3)

Here, 0 <a <1, 0 <b <1, and a + b = 1 hold.

Previously, Equations (1) and (2) may be regarded as the case where the weights are each 1 in Equation (3).

Linear interpolation is performed two times on the time axis and the frequency axis. There are two methods of performing the time axis first and then the frequency axis, or the frequency axis first and then the time axis. But either way the result is the same.

5B shows a process for performing lattice interpolation. When estimating channels of symbols of C and D, channel estimation is performed through calculations such as Equations (4) and (5) below.

C = (2P _{i , j} + P _{i + 3, j} ) / 3 ................................. Formula (4)

D = (C + P _{i + 1, j} ) / 2 ... (5)

Lattice interpolation is similar in principle to linear interpolation. That is, the calculation can be deduced from equation (3). For example, equation (4) is the case where the weights are 2 and 1, and equation (5) is the case where the weights are 1, respectively. However, unlike linear interpolation in which the time axis and the frequency axis are sequentially performed, interpolation is simultaneously performed on the time axis and the frequency axis in an oblique direction forming the grating shown in FIG. 5B.

The Lattice interpolation method requires fewer pilot symbols than the linear interpolation method, and has a small H / W (hardware) for interpolation and a fast channel estimation time. It shows better channel estimation performance.

However, since only one interpolation method is used for both linear interpolation and lattice interpolation, there is a limit to accurate channel estimation when the pilot signal is severely distorted due to the effects of fading.

6A and 6B are structural diagrams of an OFDM symbol for explaining complex interpolation in the channel estimating apparatus of FIG.

6A and 6B, the complex interpolation method of the present invention is a method of estimating and averaging channels for symbols at the same position using a combination of conventional linear interpolation and lattice interpolation. When estimating the channel for the symbol of A by the complex interpolation method, the equation can be given as follows.

A = (P _{i + 1, j} + P _{i + 5, j} + P _{i +2} , j + P _{i + 4, j} ) / 4 ................. ... Equation (6)

Equation (6) can be analyzed by averaging linear interpolation and lattice interpolation at the same time. In other words, A _linear can be obtained by calculating A _linear = (P _{i + 1, j} + P _{i + 5, j} ) / 2 with _linear interpolation, and A _lattice = (P _{i +2} , j with _lattice interpolation You can find A _lattice by calculating + P _{i + 4, j} ) / 2. Therefore, when the two interpolation methods are added and divided by 2, the complex interpolation method of the present embodiment can be implemented. Here, the diagonal lines are indicated by lattice interpolation method, and the straight lines on the top, bottom, left and right sides are illustrated to explain the linear interpolation method.

On the other hand, equation (6) is a special equation that can be simply calculated for the symbol of A, and portions other than the position of A can be calculated by appropriately applying the following general equation.

Z = aX + bY + cS + dR ..................... (7)

Here, 0 <a <1, 0 <b <1, 0 <c <1, 0 <d <1, and a + b + c + d = 1 hold.

In other words, by applying weights to each symbol and dividing by the total weight, the channel of the symbol to be estimated can be estimated. In the case of equation (6), the weights of the four symbols are 1 each.

The complex interpolation method can easily estimate a channel through S / W arithmetic operation without adding H / W only if the pilot position is known. Of course, as shown in FIG. 3 or FIG. 4, it may be implemented by adding hardware such as an averager or an adder. If the conventional channel is estimated using two pilots, the complex interpolation method of the present invention applies the method using two pilots twice, that is, using two pilots of linear interpolation and two pilots of lattice interpolation and averaging the channel. Estimation can be done more accurately.

On the other hand, as can be seen in the channel estimator of Figure 3, such complex interpolation may be seen as a concept including a linear and lattice interpolation and an average, but as a concept including only linear and lattice interpolation as in the channel estimator of FIG. Of course, the averaging function can also be performed separately for the equalizer output.

In fact, as a result of applying such complex interpolation, it was found that the received signal performance, that is, the average gain, is improved by almost 3 dB or more, and thus the circle A of the error range in FIG. 1B can be significantly reduced. can confirm.

7A and 7B are graphs showing the channel estimation performance by the channel estimating apparatus of the present invention in comparison with the conventional channel estimating apparatus, wherein the x-axis shows EbN0 (bit energy to noise power) and the y-axis shows BER (Bit Error Rate). Indicates.

On the other hand, Figure 7a is an experiment at the Doppler frequency (Doppler Frequency) 270 Hz, Figure 7b is an experiment at the Doppler frequency 200 Hz. In addition, Method 1 uses the channel estimator of FIG. 3 and Method 2 uses the channel estimator of FIG.

As can be seen from 7a and 7b, by using the complex interpolation of the present invention, it can be seen that the average gain is improved by about 3 dB compared with the conventional linear interpolation. In addition, it can be seen that either Method 1 or Method 2 shows similar performance.

The channel estimating apparatus of the present embodiment employs a complex interpolation method, thereby reducing the effects of fading and performing robust channel estimation. In addition, such complex interpolation can be performed through relatively small hardware addition or simple S / W arithmetic. Therefore, the channel estimating apparatus of the present embodiment or the OFDM receiver including the channel estimating apparatus can easily improve the channel estimation performance through relatively little hardware addition.

8A and 8B are flowcharts illustrating channel estimation methods according to another exemplary embodiment. FIG. 8A illustrates the case of using the channel estimating apparatus of FIG. 3, and FIG. 8B illustrates the case of using the channel estimating apparatus of FIG. 4.

Referring to FIG. 8A, first, a pilot is extracted through a pilot extracting unit for signals on which an FFT is performed (S100). Next, the channel estimate is extracted through linear and lattice complex interpolation (S120). In this case, the channel estimate is a value obtained by averaging linear and lattice interpolation using an averager and an adder. After extracting the channel estimate value, the signal distortion is compensated for the signal delayed from the delayer using the channel estimate value (S140). Since complex interpolation has been described above with reference to FIGS. 6A and 6B, a detailed description thereof will be omitted herein.

Referring to FIG. 8B, first, a pilot is extracted through a pilot extracting unit for signals on which an FFT is performed (S200). Next, each channel estimate value is extracted through linear interpolation and lattice interpolation (S220). After extracting the channel estimate value, the signal distortion is compensated for each of the signals delayed from the delayer using the respective channel estimate value (S240). After signal distortion compensation, an average of the signals whose distortions are compensated using the averager and the adder is averaged (S260).

The channel estimating apparatus, the OFDM receiver including the apparatus, and the channel estimating method of the present invention described above can be applied to all wireless broadcasting systems using the OFDM scheme. For example, it can be applied to all DVB-x series of European broadcasting standards such as DVB-T and DVB-H, and also enables excellent channel estimation in terms of price and mobility performance.

So far, the present invention has been described with reference to the embodiments shown in the drawings, which are merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. . Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

1A and 1B are diagrams for describing channel estimation performance deteriorated due to fading.

2 is a block diagram of an OFDM receiver according to an embodiment of the present invention.

3 and 4 are block diagrams illustrating structures that may be implemented as a channel estimator included in the OFDM receiver of FIG. 2.

5A and 5B are structural diagrams of an OFDM symbol for explaining linear interpolation and lattice interpolation in channel estimation, respectively.

6A and 6B are structural diagrams of an OFDM symbol for explaining complex interpolation in the channel estimating apparatus of FIG.

7A and 7B are graphs showing the channel estimation performance by the channel estimating apparatus of the present invention in comparison with the conventional channel estimating apparatus.

8A and 8B are flowcharts illustrating channel estimation methods according to another embodiment of the present invention.

Claims (26)

A delayer for delaying the signal on which the Four Fourier Transform (FFT) is performed by a predetermined time; A complex interpolator for performing linear and lattice complex interpolation using pilot symbols extracted from the signal; And And an equalizer (EQ) for compensating for signal distortion by using the channel estimate extracted through the complex interpolation on the signal output from the delayer. According to claim 1, The complex interpolation unit A linear interpolator for performing linear interpolation on the time axis and the frequency axis; A lattice interpolation unit performing lattice interpolation with a lattice structure; And an average unit averaging the linear interpolation unit and the lattice interpolation unit output. The method of claim 2, And the averaging section includes two averaging devices that halve the outputs of the linear interpolation section and the lattice interpolation section, and an adder summing outputs of the two averaging sections. The method of claim 2, The linear interpolation is performed by weighting two pilot symbols on each of a time axis and a frequency axis, dividing by a weighted sum, The lattice interpolation is performed by adding weights to two pilot symbols forming a lattice structure and dividing by weight sum, And the complex interpolation is performed by adding half the outputs of the linear interpolation unit and the lattice interpolation unit by using the average unit. According to claim 1, The complex interpolation is performed by performing linear and lattice interpolation together and taking an average. According to claim 1, The complex interpolation is performed by adding weights to each of pilot symbols used for linear interpolation and pilot symbol positions used for lattice interpolation, and dividing by a weighted sum. The method of claim 6, The complex interpolation is performed by adding up the positions of two pilot symbols used for the linear interpolation and two pilot symbols used for the lattice interpolation and dividing by four. According to claim 1, And a CSI extractor for extracting channel state information (CSI) using the output signal from the complex interpolator. A delayer for delaying the signal on which the Four Fourier Transform (FFT) is performed by a predetermined time; A complex interpolator for performing linear and lattice complex interpolation using pilot symbols extracted from the signal; An equalizer (EQ) unit for compensating for signal distortion by using respective channel estimates extracted through linear interpolation and lattice interpolation of the complex interpolation unit with respect to the signal output from the delay unit; And And an average unit for averaging the output of the equalizer unit. The method of claim 9, The complex interpolation unit A linear interpolator for performing linear interpolation on the time axis and the frequency axis; And And a lattice interpolation unit performing lattice interpolation in a lattice structure. The method of claim 9, The equalizer unit, A first equalizer for compensating for signal distortion by using the channel estimate extracted through the linear interpolation; And And a second equalizer for compensating for signal distortion by using the channel estimation value extracted through the lattice interpolation. The method of claim 9, And the averaging section includes two averaging devices that halve the outputs of each of the first and second equalizers, and an adder that sums the outputs of the two averaging devices. A CP remover for removing a cyclic prefix (CP) with respect to an Orthogonal Frequency Division Multiplexing (OFDM) signal converted into a baseband digital signal through a receiver; An FFT unit which performs an FFT (Fast Fourier Transform) on the output signal of the CP removing unit; A pilot extractor for extracting a pilot symbol from the output signal of the FFT unit; A channel estimating apparatus for estimating a channel through linear and lattice interpolation using the pilot symbols for the output signal of the FFT unit; A demapper which demaps an output signal of the channel estimator; And And a channel decoder for performing channel decoding on the output signal of the demapper. The method of claim 13, The OFDM receiver is And a pre-FFT part in front of the CP removing part, The pre-FFT unit performs mode detection, guard detection, symbol time offset (STO), fractional carrier frequency offset (FCFO) estimation, and symbol frequency offset (SFO) estimation on the digital signal. Receiver. The method of claim 13, The channel estimating apparatus A delayer for delaying the signal on which the Four Fourier Transform (FFT) is performed by a predetermined time; A complex interpolator for performing linear and lattice complex interpolation using pilot symbols extracted from the signal; And And an equalizer (EQ) for compensating for the signal distortion by using the channel estimate extracted through the complex interpolation on the signal output from the delayer. The method of claim 15, The complex interpolation unit A linear interpolator for performing linear interpolation on the time axis and the frequency axis; A lattice interpolation unit performing lattice interpolation with a lattice structure; And an averager averaging the outputs of the linear interpolation unit and the lattice interpolation unit. The method of claim 16, And said averaging section includes two averaging devices that halve the outputs of each of the linear interpolation section and the lattice interpolation section, and an adder which sums the outputs of the two averaging sections. The method of claim 13, A delayer for delaying the signal on which the Four Fourier Transform (FFT) is performed by a predetermined time; A complex interpolator for performing linear and lattice complex interpolation using pilot symbols extracted from the signal; An equalizer (EQ) unit for compensating for signal distortion by using respective channel estimates extracted through linear interpolation and lattice interpolation of the complex interpolation unit with respect to the signal output from the delay unit; And And an average unit for averaging the output of the equalizer unit. The method of claim 18, The complex interpolation unit A linear interpolation unit performing linear interpolation on the time axis and a frequency axis, and a lattice interpolation unit performing lattice interpolation with a lattice structure, The equalizer unit, A first equalizer compensating for signal distortion using the channel estimate extracted through the linear interpolation, and a second equalizer compensating for signal distortion using the channel estimate extracted through the lattice interpolation, And said averaging section comprises two averaging devices that halve the outputs of each of said first and second equalizers and an adder which sums the outputs of said two averaging devices. Extracting a pilot symbol for the signal on which the FFT is performed; Extracting a channel estimate by performing linear and lattice complex interpolation using the pilot symbols; Compensating for signal distortion using the channel estimate value, for the signal. The method of claim 21, Extracting the channel estimate Performing the linear interpolation and lattice interpolation; Halving the linear interpolation and lattice interpolation results; And Adding the half-divided linear interpolation and lattice interpolation results. The method of claim 21, Delaying the signal by a predetermined time; And in the signal distortion compensating step, compensating for the signal distortion by using the channel estimate value with respect to the delayed signal. The method of claim 21, Extracting channel state information (CSI) using the channel estimate value. The method of claim 21, The complex interpolation is performed by performing linear interpolation and lattice interpolation together and taking an average. Extracting a pilot symbol for the signal on which the FFT is performed; Extracting respective channel estimates through linear interpolation and lattice interpolation using the pilot symbols; Compensating for each signal distortion for the signal using each of the channel estimates; And Averaging the signals whose signal distortion is compensated for. The method of claim 21, Averaging the signals Dividing the signals whose signal distortion is compensated for; And Adding the half-divided signals.

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