KR20100071735A - Method for tracking sampling frequency offset and system for compensating sampling frequency offset using the same - Google Patents

Abstract

PURPOSE: A method for tracking sampling frequency offset and a system for compensating the sampling frequency offset using the same are provided to improve the efficiency of the compensation process by obtaining an tracked compensation order between a carrier frequency offset and a sampling frequency offset. CONSTITUTION: In relation with carrier frequency offset, fast Fourier transformation(FFT)(132) is performed. A baseband unit compensates coarse carrier frequency offset. A sampling frequency offset tracking unit(134) uses phase difference between different subcarrier pilot signals in a frequency region which is obtained by a first phase difference comparison equation. A sampling frequency offset tracing unit compares the phase difference with a second phase difference comparison equation. A sampling frequency offset estimation unit obtains an average of phase comparison values for all pilots. A sampling frequency offset compensation unit(136) compensates phase distortion using a final sampling frequency offset.

Description

Sampling frequency offset estimation method and sampling frequency offset compensation method using the same {Method for Tracking Sampling Frequency Offset and System for Compensating Sampling Frequency Offset Using the Same}

The present invention relates to a frequency offset estimation method, and more particularly, to a sampling frequency offset estimation method and orthogonal frequency division multiplexing (OFDM) system and a sampling frequency offset compensation method using the same.

Orthogonal Frequency Division Multiplexing (hereinafter, referred to as 'OFDM') systems degrade performance very sensitive to frequency offset due to overlapping subcarriers.

The frequency offset includes a sampling frequency offset generated by a difference between a carrier frequency between transmission and reception equipment and a carrier frequency offset generated by a Doppler effect generated during movement and a sampling frequency that transforms an analog signal into a digital signal.

Sampling frequency offset is a very fine value that was negligible for past communication systems. However, the OFDM system with high frequency efficiency is very sensitive to such fine frequency offset, which can degrade the performance of the system.

1 is a block diagram schematically illustrating an internal configuration of a mobile terminal generally used.

As shown in FIG. 1, a voltage controlled oscillator (VCO) 100 used as a frequency source is provided in a mobile terminal, and a radio frequency (RF) module for demodulating a signal is performed. 110, an A / D converter 120 in which sampling of a signal is performed, and a baseband unit 130 that estimates and compensates a frequency offset.

The VCO 100 used in the mobile terminal has a range of errors depending on temperature and environment because sophisticated products cannot be used due to price and volume constraints.

Therefore, there is a problem that the aforementioned carrier frequency offset and sampling frequency offset occur simultaneously due to such an error.

In order to solve such a problem, the present invention is to provide a sampling frequency offset estimation method and a sampling frequency offset compensation method using the same in an OFDM system.

According to another aspect of the present invention, there is provided a sampling frequency offset estimation method comprising: (a) extracting a pilot signal in an orthogonal frequency division multiple frame received from the transmitter in a frequency domain; (b) calculating a phase difference between pilot signals of different subcarriers over time based on the extracted pilot signal through a predetermined first phase difference comparison formula; (c) comparing a phase difference between different subcarriers along a frequency axis based on the calculated phase difference through a second preset phase difference comparison formula; And (d) estimating a final sampling frequency offset by obtaining an average after performing steps (b) and (c) for all pilots in the orthogonal frequency division multiple frame.

According to an aspect of the present invention, there is provided a sampling frequency offset estimation method comprising: (a) extracting a pilot signal from an orthogonal frequency division multiple frame received from the transmitter in a frequency domain; (b) calculating a phase difference between pilot signals of different subcarriers over time based on the extracted pilot signal through a predetermined first phase difference comparison formula; (c) a second phase difference comparison formula that sets a phase difference between different subcarriers along a frequency axis based on the calculated phase difference, wherein the second phase difference comparison formula is a subcarrier spacing between different subchannels and a spacing on a time axis between pilot signals; Reflecting any one or more of the intervals on the frequency axis between the pilot signals as parameters; And (d) estimating a final sampling frequency offset by obtaining an average after performing steps (b) and (c) when a predetermined subchannel in the orthogonal frequency division multiple frame is allocated.

According to an aspect of the present invention, a sampling frequency offset compensation method includes (a) performing a Fast Fourier Transform, extracting a pilot signal from an orthogonal frequency division multiple frame received from the transmitter, and performing different time-dependent operations. Calculating a phase difference between pilot signals of a subcarrier through a predetermined first phase difference comparison formula; (b) comparing a phase difference between different subcarriers according to a frequency axis based on the calculated phase difference, using a preset second phase difference comparison formula, in which the second phase difference comparison formula reflects the subcarrier spacing separated by a certain size as a parameter; Making; (c) estimating a final sampling frequency offset by performing an average after performing steps (a) and (b); And (d) compensating for phase distortion in the frequency domain using the estimated final sampling frequency offset.

With the above-described configuration, the present invention provides a method for estimating phase distortion generated in a signal due to a slight internal synchronization error in an OFDM system in various pilot arrangement environments.

According to the present invention, when the spectrum aggregation technique that logically bundles a frequency band physically separated due to lack of frequency is used, the present invention can easily estimate and compensate an offset using the estimation method proposed in the present invention.

The present invention provides an efficient frequency offset estimation compensation method by presenting the estimation compensation order in the relationship between the carrier frequency offset and the sampling frequency offset.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is said to "include" a certain component, it means that it can further include other components, without excluding other components unless specifically stated otherwise. In addition, the terms “… unit”, “… unit”, “module”, “block”, etc. described in the specification mean a unit that processes at least one function or operation, which is hardware or software or a combination of hardware and software. It can be implemented as.

First, before describing the frequency offset estimation technique, it is necessary to formulate the offset generated in the OFDM signal.

The OFDM signal transmitted from the transmitter is defined as in Equation 1 below.

s _i (t) is a time domain signal model used in a typical Orthogonal Frequency Division Multiplexing (OFDM) system. X _i (K) is a transmission signal (s _i (t)) in the time domain at the transmitter to sense the signal (hereinafter referred to Inverse Fast Fourier Transform, hereinafter 'IFFT') to a value inverse fast Fourier transform to transfer in the frequency domain Get

가 들어가 있는데 OFDM 프레임 전체를 모델링하기 위해 필요하다.But unlike the usual signal model, instead of t in the exponential term

Is needed to model the entire OFDM frame.

는 i번째 OFDM 심볼을 모델링 하기 위해 도입한 변수로 다음의 [수학식 2]와 같이 정의한다.k is the kth subcarrier, Ts is the sampling interval of the transmitter, N is the FFT size,

Is a variable introduced to model the i-th OFDM symbol, and is defined as in Equation 2 below.

G is a cyclic prefix (CP) size, and N is an FFT size.

For example, when N = 1024 and using 1/8 CP, one OFDM symbol has 1152 time samples in the time domain.

Therefore, if the total number of samples up to the third OFDM symbol in one frame is calculated

을 얻는다. 즉 3번째 OFDM 심볼까지의 총 샘플수는 3456개이다.

Get That is, the total number of samples up to the third OFDM symbol is 3456.

The OFDM signal of the transmitter defined in Equation 1 is transmitted to the receiver through a transmission channel. In general, such a transmission channel is represented by _Hi (k), which means a channel experienced by the k-th subcarrier of the i-th OFDM symbol. The signal r _i (t) received through such a channel is summarized by Equation 3 below.

을 지수에 포함한 Exponential Term은 신호에 가해지는 캐리어 주파수 오프셋(Carrier Frequency Offset: CFO)를 의미하고, w(t)는 백색 잡음을 의미한다.

Exponential Term, which is included in the exponent, denotes a carrier frequency offset (CFO) applied to a signal, and w (t) denotes white noise.

는 정규화된 캐리어 주파수 오프셋 값이다. 정규화된 캐리어 주파수 오프셋은 송수신단의 주파수 오차 및 도플러 주파수 오차를 포함하고 이 값을 부반송파 간격으로 나누어 정규화한 것이다.here,

Is the normalized carrier frequency offset value. The normalized carrier frequency offset includes the frequency error of the transceiver and the Doppler frequency error, and normalizes this value by dividing it by the subcarrier spacing.

Next, the receiver undergoes a sampling process via the A / D converter 120.

The sampled signal is X _i (n) as shown in Equation 4 below.

In Equation 4, the sampling timing at the receiving end is input instead of the time t in Equation 3.

Accordingly, Equation 4 is a formula for reflecting the sampling frequency offset desired in the present invention, and is a process of calculating the position of the n th sample at the receiver to find the n th sample time of the i th OFDM symbol.

에 송신단에서의 샘플 간격(Ts)을 곱해 i-1번째 심볼까지의 신호 길이(시간)을 계산한다.That is, [Equation 4] is the number of samples up to the i-1 th symbol to calculate the position of the sample included in the i th symbol

Multiply the sample interval (Ts) by the transmitter to calculate the signal length (time) up to the i-1th symbol.

Here, (i-1) t _d means a sampling interval accumulation error by the sampling frequency offset from the receiver to the i-1 th symbol.

t _d means an error value per one OFDM symbol that occurs due to a sampling frequency difference between a transmitter and a receiver. Ts 'means a sampling time interval at the receiving end, nTs' is a parameter for calculating the n-th sampling time in the i-th symbol.

The sampling time interval difference t _d in the OFDM symbol included in [Equation 4] is as shown in Equation 5 below.

Reflecting the sampling process described by [Equation 4] and [Equation 5] to the above-described received signal of [Equation 3] is defined as shown in [Equation 6].

Equation (7) above defines a sampling frequency offset in the present invention, where fs is an inverse of the sampling time interval Ts described above, fs 'is an inverse of Ts', and β is a sampling frequency offset to be estimated in the present invention. to be.

[Equation 8] is a sampling frequency offset is very small value as shown in the development process, so the equation development is simplified by approximating as above.

이다The signal in the time domain is now transformed into a signal in the frequency domain via the FFT 132. In other words, after passing through the FFT 132, the received signal in the frequency domain is expressed by Equation 9 below.

to be

는 원치 않는 간섭 성분(l번째 부반송파에 영향을 미치는 k번째 부반송파 성분)으로 수식 전개 과정에서 간략히 정리하기 위해 다음의 [수학식 10]과 같이 정의하여 별도로 분리하였다.

Is an unwanted interference component (k-th subcarrier component affecting the l-th subcarrier), which is separately defined by Equation 10 to simplify the equation development process.

이라 가정하고 [수학식 9]을 전개하면 아래와 같은 [수학식 11]을 얻는다.If k ≠ ｌ in Equation 10 (when subcarrier indices are different),

Suppose we develop Equation 9 and we get Equation 11 below.

R _i (l) is the received signal in the frequency domain excluding noise. Equation 11 reflects the influence of the carrier frequency offset and the sampling frequency offset, and can confirm the phase change caused by the sampling frequency offset β.

은

때문에 심볼 인덱스가 증가함에 따라 위상 변화가 이에 비례하여 누적되어 증가하는 것을 보여주며,

은 부반송파 인덱스(ㅣ)을 인수로 포함하여 부반송파 인덱스에 따라 위상 왜곡이 더 크게 발생함을 알 수 있다.

silver

Therefore, as the symbol index increases, the phase change accumulates and increases proportionally.

It can be seen that the phase distortion occurs more largely according to the subcarrier index by including the subcarrier index (ㅣ) as a factor.

Hereinafter, a sampling offset estimation technique according to an embodiment of the present invention will be described in detail.

The sampling offset estimation technique of the present invention estimates the phase of the signal based on the pilot signal. In order to estimate the above-described sampling offset, the present invention uses a continuous pilot signal.

The continuous pilot signal according to time in the frequency domain is defined as Equation 12 and Equation 13 below.

The pilot signal is a signal previously promised between the transmitting end and the receiving end. Equation 12 denotes a pilot signal carried on the l-th subcarrier of the received i-th OFDM symbol.

Similarly, the same pilot symbol carried on the l-th subcarrier of the i + 1 th symbol is defined by [Equation 13].

Since R _i (l) has already been defined in [Equation 11], the equation [13] is obtained by developing i + 1 in the symbol index instead of i.

The pilot signal thus defined is subjected to a process of comparing phases with each other as shown in Equation 14 below. As shown in [Equation 14], the complex conjugate operation of two signals is a calculation for a phase difference between two complex numbers.

From the phase difference calculation process, the right result of Equation 14 is obtained.

It can be seen that Equation 14 described above is arranged as a constant multiple of the carrier frequency offset ε in the absence of the sampling frequency offset β.

Basically, the phase difference between the calculation results of Equation 14 is obtained by using the feature that the same OFDM symbol has the same size carrier frequency offset.

In this case, since the carrier frequency offsets are the same, they are deleted from each other and only the sampling frequency offset items remain so that estimation is possible.

를 정의한다.New variables for these operations

Define.

는 [수학식 14]에서 수행한 동일한 부반송파에 실린 파일럿의 위상을 연속된 OFDM 심볼 간의 위상 비교하는 것에 해당한다.

Corresponds to a phase comparison between consecutive OFDM symbols with the phase of a pilot carried on the same subcarrier performed in Equation (14).

Here, the formula for calculating the phase difference in the frequency domain may be used as another term, a first phase difference comparison formula.

에 해당한다. As described above, in order to take advantage of the characteristic that the carrier frequency offsets of the same OFDM symbol are the same, a process of obtaining a phase difference of Equation 15 of different subcarriers is performed. This is shown in Equation 16 below.

Corresponds to

Here, the process of comparing the phase difference in the frequency domain may be used as another term called a second phase difference comparison formula.

This process is performed for all pilots in the frame, averaged, and summed up for the sampling frequency offset beta (Equation 16).

는 최종 샘플링 주파수 오프셋의 추정값이 된다. 그러나 [수학식 16]은 프레임 내 모든 Bin을 파일럿으로 채울 경우에 해당하므로 특정 패턴으로 삽입되는 실제 시스템으로 확장하는 과정을 수행해야 한다.therefore,

Is an estimate of the final sampling frequency offset. [Equation 16], however, corresponds to the case where all bins in a frame are filled with pilots. Therefore, it is necessary to extend the process to a real system inserted in a specific pattern.

Pilot deployments of various OFDM systems currently commercially available vary widely. As shown in FIG. 2, the pilot interval in the time domain is defined as K, the pilot interval in the frequency domain is defined as M, and the sampling frequency offset is estimated.

(1) A system that maintains the interval by K in the time domain (if frequency domain M = 1)

In this case, since the pilot interval is extended by K in the time domain, the continuous pilot definition equation of Equation 13 described above should be modified.

Likewise, if the above-described processes of [Equation 14], [Equation 15], and [Equation 16] are applied to the pilot situation, the following equation [17] is summarized.

(2) A system that maintains an interval as much as M in the frequency domain (in the case of the frequency domain K = 1). In the same manner as in [Equation 17], the following Equation 18 is obtained.

(3) in general (when K and M have a specific value other than 1)

In general, sampling frequency offset is a very small range (up to 40ppm for wireless LAN, 400Hz for 10MHz sampling frequency). Therefore, the phase shift caused by such a small value is difficult to distinguish in a real communication environment in which thermal noise exists, and thus there is a limit in applying the above methods as it is.

Therefore, as shown in FIG. 3, it is necessary to arrange the subcarriers separated by a certain size in a comparison manner.

Figure 3 compares the pilot phases at half intervals of the overall FFT size for robust robust estimation.

The sampling frequency offset estimation scheme is summarized as in Equation 20 below.

As described above, the phase comparison between adjacent pilots becomes insignificant due to noise as the sampling frequency offset is very small in a real system, so that the pilot signals separated by half of the total FFT size can be compared to obtain a more reliable estimation result. to be.

Hereinafter, the influence of the spectrum aggregation technique and the sampling offset will be described.

Spectrum aggregation technology supports logically large bandwidth by combining small bands that are separated from each other. Therefore, it is impossible to secure 40 (100) MHz bandwidth in one band, which is considered in IMT-Advanced. It is a technique to do.

Spectrum aggregation schemes that can be considered at present include subcarrier nulling techniques used in CR (Cognitive Radio).

When a sampling offset occurs in a system that nulls and transmits other subcarriers other than the used subcarrier, a signal that is shifted to one part is acquired and a phase distortion estimation and compensation method is required.

When spectrum aggregation (subcarrier nulling) is applied in the future, only a part of the entire FFT bandwidth of an OFDM system may be selectively used.

As shown in FIG. 4, even when subcarrier nulling is not used, subchannels that are separated from each other may be allocated to a user during downlink resource allocation.

Therefore, it is assumed that the bandwidth of each subchannel is W _N and the interval of subchannels is D, and the sampling frequency offset is estimated.

The sampling offset estimation when applying spectral aggregation is shown in Equation 21 below.

In a real OFDM system, not all OFDM frames are used for signal transmission, but a subchannel is allocated to one user.

[Equation 21] is an example of applying the aforementioned sampling frequency offset estimation technique (same as the equation developing process of [Equation 16]) from the receiver's point of view.

However, many variables are added because it is assumed that the pilot arrangement is a complicated case. The above-mentioned variables are summarized as follows.

N: FFT size, G: Cyclic Prefix size, D means subcarrier spacing between different subchannels, K: spacing on time axis (symbol) between pilot signals, M: spacing on frequency axis (subcarrier) between pilot signals .

The difference between [Equation 21] and [Equation 16] is summarized as follows.

The constants 1 / D and 1 / K are the parts that occur according to the pilot's frequency domain (subcarrier) spacing, and the argument Term above the Sigma symbol causes the two subchannels to be different in size so that the values change in order to perform calculations according to small values. It became.

The factors Mm and Mm + D in Theta reflect the pilot's frequency axis spacing M and subchannel spacing D.

5 is a block diagram schematically illustrating the internal configuration of the baseband unit 130 of the mobile terminal according to an embodiment of the present invention, Figure 6 is a residual carrier frequency offset according to an embodiment of the present invention to the sampling frequency offset estimation FIG. 7 is a diagram for explaining the influence of the residual sampling frequency offset on the carrier frequency offset estimation according to the embodiment of the present invention.

The baseband unit 130 according to an embodiment of the present invention will be described based on the part of estimating the sampling frequency offset, which is a feature of the present invention.

As mentioned above, the carrier frequency offset and the sampling frequency offset simultaneously affect the phase of the signal coordinates.

As shown in FIG. 6 and FIG. 7, it can be seen that the influence of the residual sampling frequency offset on the carrier frequency offset estimation is greater.

The baseband unit 130 estimates and compensates a coarse carrier frequency offset, estimates and compensates a sampling frequency offset, and finally estimates and compensates a fine carrier frequency offset.

In the case of the carrier frequency offset, various maximum likelihood (ML) techniques exist, so that the estimation of compensation is possible in the time domain and the frequency domain based on the FFT 132.

Accordingly, the estimation scheme proposed in the present invention estimates and compensates for the sampling frequency offset after passing through the FFT 132 in relation to the carrier frequency offset as described above, and estimates and compensates for the fine carrier frequency offset.

The baseband unit 130 according to the embodiment of the present invention includes a sampling frequency offset estimator 134 and a sampling frequency offset compensator 136.

The sampling frequency offset estimator 134 has a phase difference between pilot signals of different subcarriers in the frequency domain obtained through the preset first phase difference comparison formula, and calculates a phase difference between different subcarriers in the frequency domain. Use it to compare. Here, the first phase difference comparison formula is a series of procedures for estimating the sampling frequency offset, and means one or more algorithms of Equations 12, 13, 14, and 15.

The sampling frequency offset estimator 134 averages each phase comparison value for all pilots and then obtains a final sampling frequency offset. Here, the final sampling frequency offset means (16).

In addition, the sampling frequency offset estimator 134 maintains the pilot interval by K in the time domain in the OFDM frame and maintains the pilot interval by M in the frequency domain, and based on each phase comparison value, the final sampling frequency offset. Obtain

Here, the final sampling frequency offset refers to a formula of any one of Equation 17, Equation 18, Equation 19, and Equation 20.

In addition, the sampling frequency offset estimator 134 maintains the pilot interval by K in the time domain in the OFDM frame and maintains the pilot interval by M in the frequency domain, and based on each phase comparison value, the final sampling frequency offset. Obtain

Here, the final sampling frequency offset refers to a formula of any one of Equation 17, Equation 18, Equation 19, and Equation 20.

In addition, the sampling frequency offset estimator 134 calculates a final sampling frequency offset based on each phase comparison value in consideration of the case where a predetermined subchannel is allocated in the OFDM frame. Here, the final sampling frequency offset means (21).

The sampling frequency offset compensator 136 compensates for the phase distortion in the frequency domain by using the final sampling frequency offset.

The embodiments of the present invention described above are not implemented only by the apparatus and / or method, but may be implemented through a program for realizing functions corresponding to the configuration of the embodiment of the present invention, a recording medium on which the program is recorded And such an embodiment can be easily implemented by those skilled in the art from the description of the embodiments described above.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

1 is a block diagram schematically illustrating an internal configuration of a mobile terminal generally used.

2 is a diagram illustrating a general pilot deployment situation.

FIG. 3 is a diagram for explaining pilot phases at half intervals of the overall FFT size for robust estimation of noise according to an embodiment of the present invention.

FIG. 4 is a view for explaining a pilot deployment situation in which only part of the overall FFT bandwidth of an OFDM system is selectively used when spectrum aggregation (subcarrier nulling) according to an embodiment of the present invention is applied.

5 is a block diagram schematically illustrating an internal configuration of a baseband unit of a mobile terminal according to an embodiment of the present invention.

6 is a view for explaining the effect of the residual carrier frequency offset on the sampling frequency offset estimation according to an embodiment of the present invention.

7 is a view for explaining the influence of the residual sampling frequency offset on the carrier frequency offset estimation according to an embodiment of the present invention.

Claims (8)

A method of estimating sampling frequency offset of an orthogonal frequency division multiplexing (OFDM) frame received from a transmitting end of a multimedia transmission system, (a) extracting a pilot signal from an orthogonal frequency division multiplex frame received from the transmitter in a frequency domain; (b) calculating a phase difference between pilot signals of different subcarriers over time based on the extracted pilot signal through a predetermined first phase difference comparison formula; (c) comparing a phase difference between different subcarriers along a frequency axis based on the calculated phase difference through a second preset phase difference comparison formula; And (d) estimating the final sampling frequency offset by performing an average after performing steps (b) and (c) for all pilots in the orthogonal frequency division multiple frame; Sampling frequency offset estimation method comprising a. According to claim 1, In the step (d), In the pilot arrangement situation in which the pilot interval is maintained by K in the time domain in the orthogonal frequency division multiple frame and the pilot interval is maintained in M by the frequency domain, the average is obtained after performing steps (b) and (c). Obtaining the final sampling frequency offset by  Sampling frequency offset estimation method comprising a. According to claim 1, In the step (d), Obtaining a final sampling frequency offset by performing an average after performing steps (b) and (c) by comparing phases of subcarrier intervals separated by a predetermined size in the orthogonal frequency division multiplexing frame  Sampling frequency offset estimation method comprising a. A method of estimating sampling frequency offset of an orthogonal frequency division multiplexing (OFDM) frame received from a transmitting end of a multimedia transmission system, (a) extracting a pilot signal from an orthogonal frequency division multiplex frame received from the transmitter in a frequency domain; (b) calculating a phase difference between pilot signals of different subcarriers over time based on the extracted pilot signal through a predetermined first phase difference comparison formula; (c) a second phase difference comparison formula that sets a phase difference between different subcarriers along a frequency axis based on the calculated phase difference, wherein the second phase difference comparison formula is a subcarrier spacing between different subchannels and a spacing on a time axis between pilot signals; Reflecting any one or more of the intervals on the frequency axis between the pilot signals as parameters; And (d) estimating a final sampling frequency offset by obtaining an average after performing steps (b) and (c) when a predetermined subchannel is allocated in the orthogonal frequency division multiple frame; Sampling frequency offset estimation method comprising a. A sampling frequency offset compensation method for estimating and compensating for a sampling frequency offset of an orthogonal frequency division multiplexing (OFDM) frame received from a transmitting end of a multimedia transmission system, (a) After performing a Fast Fourier Transform, a pilot signal is extracted from an orthogonal frequency division multiplex frame received from the transmitter, and the first phase difference is a phase difference between pilot signals of different subcarriers over time. Calculating through a comparison formula; (b) comparing a phase difference between different subcarriers according to a frequency axis based on the calculated phase difference, using a preset second phase difference comparison formula, in which the second phase difference comparison formula reflects the subcarrier spacing separated by a certain size as a parameter; Making; (c) estimating a final sampling frequency offset by performing an average after performing steps (a) and (b); And (d) compensating for phase distortion in the frequency domain using the estimated final sampling frequency offset Sampling frequency offset compensation method comprising a. 6. The method of claim 5, After step (d), estimating and compensating a carrier frequency offset by using a maximum likelihood estimation technique (Maximun Likelihood) Sampling frequency offset compensation method further comprising. 6. The method of claim 5, And the second phase difference comparison formula compares pilot phases at half intervals of the total fast Fourier transform magnitudes. 6. The method of claim 5, And the second phase difference comparison formula compares pilot phases based on an interval in a time axis between pilot signals or an interval in a frequency axis between pilot signals.

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