WO2015196629A1

WO2015196629A1 - Method and device for estimating frequency offset of carriers

Info

Publication number: WO2015196629A1
Application number: PCT/CN2014/088426
Authority: WO
Inventors: 文武; 许秋平; 王凯
Original assignee: 中兴通讯股份有限公司
Priority date: 2014-06-27
Filing date: 2014-10-11
Publication date: 2015-12-30
Also published as: CN105282081A

Abstract

The present invention relates to the technical field of communications. Disclosed are a method and device for estimating a frequency offset of carriers. The method comprises: respectively performing zero insertion processing on frequency domain channel responses of all pilot sub-carriers of a first OFDM symbol and all pilot sub-carriers of a second OFDM symbol in received downlink baseband received signals, to obtain a first zero insertion frequency domain channel response and a second zero insertion frequency domain channel response; respectively performing inverse Fourier transformation on the first zero insertion frequency domain channel response and the second zero insertion frequency domain channel response to obtain a first time domain channel response and a second time domain channel response; and determining a frequency offset of the carriers according to the peak phase relationship in the obtained first time domain channel response and the obtained second time domain channel response. By means of the present invention, the frequency domain channel estimation of the pilot sub-carriers is transformed to the time domain, so signal energy is gathered at the peaks of the time domain channel responses, and the frequency offset estimation performance is improved. Meanwhile, the problem that the frequency offset estimation is limited to the same sub-carrier locations is avoided.

Description

Method and device for estimating carrier frequency offset

Technical field

The present invention relates to the field of communications technologies, and in particular, to a method and apparatus for carrier frequency offset estimation in an Orthogonal Frequency Division Multiplexing (OFDM) system.

Background technique

Among the common methods for estimating the carrier frequency offset, the CP correlation method and the conventional RS method are included.

The cyclic prefix (CP: Cyclic Prefix) correlation method uses the cyclic prefix CP of the OFDM symbol to perform frequency offset estimation. Since the CP and the OFDM symbol tail end transmit data are the same, the transmission data of the OFDM symbol tail end is multiplied by the corresponding CP segment. The conjugate of the data can obtain the phase difference caused by the carrier frequency offset, and then estimate the frequency offset. However, there will be problems with poor estimation accuracy.

The conventional reference signal (RS: Reference Signal) method performs frequency offset estimation by using the frequency domain channel response on the same pilot subcarrier of two OFDM symbols before and after, directly multiplies two frequency domain channel responses by conjugate, and then according to the conjugate The phase of the multiplied result determines the frequency offset. However, this method limits the pilots of two OFDM symbols to be at the same subcarrier position, otherwise the frequency offset estimation result will be seriously affected by multipath or time offset. Specifically, for example, in a Long Term Evolution (LTE) system, one subframe of a regular cyclic prefix (Normal CP) frame structure includes 14 OFDM symbols, symbols 0, and pilots of symbol 7, symbol 4, and symbol 11 The subcarriers have the same position, and the frequency offset can be estimated based on the conventional RS method, but the estimation range is small, only -/+1KHz; if the frequency offset estimation can be based on the symbol 4 and the symbol 7, the estimation range can reach -/+2.3KHz. However, their pilot subcarrier positions are staggered from each other, and the conventional RS method is not available in this case.

Summary of the invention

It is an object of the present invention to provide a method and apparatus for estimating carrier frequency offset, which can solve the problem that the estimation accuracy of the existing carrier frequency offset estimation method is poor and the applicable conditions are limited.

According to an embodiment of the present invention, a method for carrier frequency offset estimation is provided, including:

Performing zero-interpolation on the frequency domain channel responses of all pilot subcarriers of the first OFDM symbol and all pilot subcarriers of the second OFDM symbol in the received downlink baseband received signal, to obtain a first zero-crossing frequency domain channel Response and second interpolation frequency domain channel response;

Performing an inverse Fourier transform on the first zero-frequency frequency domain channel response and the second zero-cut frequency domain channel response, respectively, to obtain a first time domain channel response and a second time domain channel response;

A carrier frequency offset is determined based on the obtained peak phase relationship in the first time domain channel response and the second time domain channel response.

Preferably, the user terminal or the neighboring base station performs zero-interpolation on the frequency domain channel responses of all pilot subcarriers of the first OFDM symbol and all pilot subcarriers of the second OFDM symbol in the received downlink baseband received signal respectively. Obtaining a first zero-interpolation frequency domain channel response and a second zero-interpolation frequency domain channel response;

Preferably, the step of performing zero-interpolation processing on the frequency domain channel responses of all pilot subcarriers of the first OFDM symbol and all pilot subcarriers of the second OFDM symbol in the received downlink baseband received signal respectively includes: :

All frequency domain pilot channel responses of the first OFDM symbol are respectively placed on pilot subcarrier positions preset by the first OFDM symbol, and all non-pilot subcarriers are set to zero;

And, all frequency domain pilot channel responses of the second OFDM symbol are respectively placed on the pilot subcarrier positions preset by the second OFDM symbol, and all non-pilot subcarriers are set to zero.

Preferably, the step of determining a carrier frequency offset according to the peak phase relationship in the obtained first time domain channel response and the second time domain channel response comprises:

Determining, according to the first time domain channel response and the second time domain channel response, a peak phase difference between the first time domain channel response and the second time domain channel response;

A carrier frequency offset corresponding to the peak phase difference is determined according to a time interval preset by the first OFDM symbol and the second OFDM symbol.

Preferably, the step of determining a peak phase difference between the first time domain channel response and the second time domain channel response according to the first time domain channel response and the second time domain channel response comprises:

Determining, according to the first time domain channel response and the second time domain channel response, a time domain channel response of a peak position of the first time domain channel response and the second time domain channel response, respectively;

And determining a peak phase difference between the first time domain channel response and the second time domain channel response according to the time domain channel response of the first time domain channel response and the peak position of the second time domain channel response.

Preferably, selecting the peak position in the following manner comprises:

Determining, according to the first time domain channel response and the second time domain channel response, maximum peak values corresponding to the first time domain channel response and the second time domain channel response, respectively;

Comparing all peak positions of the OFDM symbol with the largest peak value as the first time domain channel response and the second time domain channel response by comparing the maximum time peaks of the first time domain channel response and the second time domain channel response The peak position.

Preferably, the step of determining a carrier frequency offset according to the peak phase relationship in the obtained first time domain channel response and the second time domain channel response further includes:

If the first OFDM symbol and the second OFDM symbol have an extra phase difference, determining the additional phase difference according to the pilot position offset and the time domain channel delay preset by the first OFDM symbol and the second OFDM symbol;

A carrier frequency offset is determined based on the additional phase difference and a peak phase relationship in the first time domain channel response and the second time domain channel response.

According to another embodiment of the present invention, an apparatus for estimating a carrier frequency offset includes:

a zero insertion module, configured to perform a zero-interpolation process on a frequency domain channel response of all pilot subcarriers of the first OFDM symbol and all pilot subcarriers of the second OFDM symbol in the received downlink baseband received signal, to obtain a first a zero-frequency domain channel response and a second zero-frequency frequency domain channel response;

The transforming module is configured to perform inverse Fourier transform on the first zero-frequency frequency domain channel response and the second zero-cut frequency domain channel response, respectively, to obtain a first time domain channel response and a second time domain channel response;

And a determining module configured to determine a carrier frequency offset according to the obtained peak phase relationship in the first time domain channel response and the second time domain channel response.

Preferably, the zero insertion module further comprises:

a first submodule, configured to place all frequency domain pilot channel responses of the first OFDM symbol on pilot subcarrier positions preset by the first OFDM symbol, and to zero all non-pilot subcarriers;

The second submodule is configured to place all frequency domain pilot channel responses of the second OFDM symbol on pilot subcarrier positions preset by the second OFDM symbol, and to zero all non-pilot subcarriers.

Preferably, the determining module further comprises:

And a difference submodule configured to determine a peak phase difference between the first time domain channel response and the second time domain channel response according to the first time domain channel response and the second time domain channel response;

And a frequency offset submodule configured to determine a carrier frequency offset corresponding to the peak phase difference according to a time interval preset by the first OFDM symbol and the second OFDM symbol.

Compared with the prior art, the present invention has the beneficial effects that the frequency domain channel estimation of the pilot subcarrier can be transformed into the time domain, and the peak of the time domain channel response is used to converge the signal energy, thereby effectively suppressing noise and increasing the frequency. Partial estimation performance, frequency offset estimation is more accurate. At the same time, the problem that the frequency offset estimation is limited to the same subcarrier position is avoided.

DRAWINGS

FIG. 1 is a schematic diagram of a method for estimating carrier frequency offset according to an embodiment of the present invention; FIG.

2 is a structural diagram of a device for estimating a carrier frequency offset according to an embodiment of the present invention;

3 is a LTE downlink reference signal RS mapping diagram of carrier frequency offset estimation according to an embodiment of the present invention;

4 is an additional phase difference diagram of an LTE 4, 7 symbol time domain channel response of a carrier frequency offset estimation according to an embodiment of the present invention;

FIG. 5 is an overall flowchart of carrier frequency offset estimation according to an embodiment of the present invention.

detailed description

The preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings.

FIG. 1 is a schematic diagram of a method for estimating a carrier frequency offset according to an embodiment of the present invention. As shown in FIG. 1 , the specific steps are as follows:

Step S1: performing zero-interpolation processing on the frequency domain channel responses of all pilot subcarriers of the first OFDM symbol and all pilot subcarriers of the second OFDM symbol in the received downlink baseband received signal, to obtain a first zero insertion Frequency domain channel response and second zero-frequency frequency domain channel response.

In step S1, the user terminal or the neighboring base station separately inserts frequency domain channel responses of all pilot subcarriers of the first OFDM symbol and all pilot subcarriers of the second OFDM symbol in the received downlink baseband received signal. Zero processing, obtaining a first zero-interpolation frequency domain channel response and a second zero-interpolation frequency domain channel response;

Further, all frequency domain pilot channel responses of the first OFDM symbol are respectively placed on pilot subcarrier positions preset by the first OFDM symbol, and all non-pilot subcarriers are set to zero;

And, all frequency domain pilot channel responses of the second OFDM symbol are respectively placed on pilot subcarrier positions preset by the first OFDM symbol, and all non-pilot subcarriers are set to zero.

Step S2: performing inverse Fourier transform on the first zero-interpolation frequency domain channel response and the second zero-interpolation frequency domain channel response, respectively, to obtain a first time domain channel response and a second time domain channel response.

Step S3: Determine a carrier frequency offset according to the obtained peak phase relationship in the first time domain channel response and the second time domain channel response.

In step S3, determining a peak phase difference between the first time domain channel response and the second time domain channel response according to the first time domain channel response and the second time domain channel response;

Further, the step of determining a peak phase difference between the first time domain channel response and the second time domain channel response according to the first time domain channel response and the second time domain channel response comprises:

Further, the step of selecting the peak position includes:

Further, the step of determining a carrier frequency offset according to the peak phase relationship in the obtained first time domain channel response and the second time domain channel response further includes:

2 is a structural diagram of a device for estimating a carrier frequency offset according to an embodiment of the present invention. As shown in FIG. 2, the method includes: a zero insertion module, a transformation module, and a determination module.

The zero insertion module is configured to perform a zero insertion process on a frequency domain channel response of all pilot subcarriers of the first OFDM symbol and all pilot subcarriers of the second OFDM symbol in the received downlink baseband received signal, respectively The first zero-interpolation frequency domain channel response and the second zero-crossing frequency domain channel response. The first submodule of the zero insertion module is configured to place all frequency domain pilot channel responses of the first OFDM symbol on the pilot subcarrier positions preset by the first OFDM symbol, and all non-pilots The subcarrier is set to zero. The second submodule of the zero insertion module is configured to place all frequency domain pilot channel responses of the second OFDM symbol on pilot subcarrier positions preset by the first OFDM symbol, and to all non-pilot subcarriers Zero.

The transform module is configured to perform inverse Fourier transform on the first zero-frequency frequency domain channel response and the second zero-cut frequency domain channel response, respectively, to obtain a first time domain channel response and a second time domain channel response.

The determining module is configured to determine a carrier frequency offset according to the obtained peak phase relationship in the first time domain channel response and the second time domain channel response. The difference submodule of the determining module is configured to determine the first time domain channel response and the second time domain channel response according to the first time domain channel response and the second time domain channel response. Peak phase difference between. The frequency offset submodule of the determining module is configured to determine a carrier frequency offset corresponding to the peak phase difference according to a time interval preset by the first OFDM symbol and the second OFDM symbol.

FIG. 3 is a schematic diagram of an LTE downlink reference signal RS mapping of a carrier frequency offset estimation according to an embodiment of the present invention. As shown in FIG. 3, after receiving a downlink baseband received signal from a base station, a user terminal or a neighboring base station receives a downlink baseband received signal. The frequency domain pilot channel response is placed in the original subcarrier position according to a preset resource mapping manner (ie, the mapping manner of the LTE downlink reference signal RS), and the non-pilot subcarrier is set to zero, thereby constructing a zero-frequency frequency domain channel. response.

It is assumed that two OFDM symbols in the downlink baseband received signal are respectively recorded as Sym1 and Sym2, and the time interval is Δt, each symbol has N subcarrier positions, the pilot position set of Sym1 is P1, and the pilot position of Sym2 is relative to Sym1. The pilot position offset v (takes a negative value if offset in a small direction), and sets the subcarrier spacing between pilots to be ΔK. To obtain the frequency domain channel responses H1(k) and H2(k) of the pilot positions of the two OFDM symbols respectively, first perform discrete Fourier transform (DFT) on Sym1 and Sym2,

Then using least squares (LS: Least-Square) to estimate the frequency domain channel response value,

Where k ranges from [0, N-1]; Pilot1(k) and Pilot2(k) are defined as the transmitted pilot symbols of Sym1 and Sym2, respectively. When k belongs to the pilot subcarrier position, they are each taken The corresponding frequency domain pilot channel response value.

The time domain channel response is obtained by performing an Inverse Discrete Fourier Transform (IDFT) on H1(k) and H2(k):

Where n has a value range of [0, N-1].

Then, the peak position is obtained from the time domain channel responses h1(n), h2(n). Since the subcarrier spacing is ΔK, there will be a peak of ΔK repetition in the time domain channel response h1(n), h2(n).

Finally, FIG. 4 is an additional phase difference diagram of the LTE 4 and 7 symbol time domain channel response according to the carrier frequency offset estimation provided by the embodiment of the present invention, as shown in FIG. 4, according to the time domain channel response h1(n), h2(n) Phase difference between peaks

Frequency offset

The relationship, using one or more peak estimation frequency offsets, the basic equation is as follows:

among them,

In fact, in the absence of frequency offset, there may still be a phase difference between the peaks of the time domain channel response, assuming that the time domain channel delay is m ₀ and the time domain channel response h(n)=δ(n ₁ -m ₀ ),then

It can be seen that there is an additional peak phase difference at the position of n≠m ₀ (that is, the position where the peak appears in the repeating segment).

In this way, the corresponding compensation needs to be made when determining the frequency offset. Therefore, the actually obtained phase difference caused by the frequency offset needs to eliminate the extra phase difference in the peak phase difference between the time domain channel responses to obtain the phase difference finally used for the frequency offset determination.

FIG. 5 is an overall flowchart of a carrier frequency offset estimation according to an embodiment of the present invention. As shown in FIG. 5, this embodiment is only a preferred embodiment of the present invention, and is not intended to limit the present invention. It will be apparent to those skilled in the art that various modifications and changes can be made in the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and scope of the present invention are intended to be included within the scope of the present invention.

The LTE bandwidth is 10M, the conventional CP is taken as an example, and the symbols 4 and 7 correspond to Sym1 and Sym2 (15.36MHz sampling rate). The specific implementation method is as follows:

(1) Construct a frequency domain channel response with zero insertion. The frequency domain pilot channel response is placed at the original subcarrier position, and the non-pilot subcarrier is set to zero.

(2) N is 1024, and the frequency domain pilot channel estimates H1(k) and H2(k) of symbols 4, 7 are determined. It is assumed that the time intervals of the two baseband OFDM symbols 4, 7 are Δt, each symbol has N subcarrier positions, the pilot position set of symbol 4 is P1, and the pilot position of symbol 7 is offset from the pilot position of symbol 4. Move v (take a negative value if offset in a small direction), and set the subcarrier spacing between pilots to ΔK. In order to obtain the frequency domain channel responses H1 and H2 of the symbols 4 and 7, respectively, the symbols 4 and 7 are DFT-transformed, and the fast Fourier transform (FFT) can also be used. Among them, FFT and DFT have the same effect, but have higher efficiency.

Then, using LS to estimate the frequency domain channel response value, we obtain:

Where k is in the range of [0, N-1]; Pilot1(k) and Pilot2(k) are defined as the transmitted pilot symbols of symbols 4 and 7, respectively, and when k belongs to the pilot subcarrier position, they are each Take the corresponding frequency domain pilot channel response value.

(3) The time domain channel response is obtained by IDFT transform for the frequency domain channel responses of symbols 4 and 7, and can also be used as an inverse fast Fourier transform (IFFT). Among them, IFFT and IDFT have the same effect, but only have higher efficiency.

The IDFT transform is performed on H1(k) and H2(k) to obtain the time domain channel response:

Where n has a value range of [0, N-1].

(4) Estimating the frequency offset based on the peak phase relationship in the time domain channel response of symbols 4 and 7. The peak position is obtained from the time domain channel responses h1(n), h2(n). Since the subcarrier spacing between the pilots is ΔK, there are ΔK shares in the time domain channel responses h1(n) and h2(n). Repeated peaks. Peak phase difference between h1(n) and h2(n) according to time domain channel response

Frequency offset

The relationship, using one or more peaks in combination, estimates the frequency offset.

The six peaks of the symbol 4, 7 time domain channel responses h1(n), h2(n) are approximately 6 different positions of n ₁ = n ₀ * 1024 / 6 (n ₀ =0, 1, ... 5) nearby.

The search for the peak position can be determined only based on the time domain channel response h1(n) or h2(n), or both can be searched and then the preferred peak position can be taken. The specific method is as follows:

N∈(n ₁ -cplength, n ₁ +cplength)

Cplength represents the CP length of the current symbol. If six peaks are found in each of the symbols 4 and 7, the magnitude of the maximum peak is compared, and the time domain channel response of the six peak positions of the symbol having the smallest maximum peak is acquired in accordance with the six peak positions of the symbol having the largest peak value.

In fact, in the absence of frequency offset, there may still be a phase difference between the peaks of the time domain channel response, assuming that the time domain channel delay is m ₀ and the time domain channel response h(n)=δ(n ₁ -m ₀ ), then the time domain channel response of symbols 4, 7 is determined as follows:

In this case, the peak position is n=n ₁ +m ₀ =m ₀ +n ₀ *1024/6, and the extra phase difference at the peak is

That is, the extra phase difference at the 1st, 3rd, and 5th peaks is 0, and the extra phase difference at the 2nd, 4th, and 6th peaks is π. Therefore, the actually obtained phase difference caused by the frequency offset needs to eliminate the extra phase difference in the peak phase difference between the time domain channel responses to obtain the phase difference finally used for the frequency offset determination.

The time domain channel responses defining the six peak positions of symbols 4, 7 are d4(n ₀ ), d7(n ₀ ), n ₀ =0, 1, ..., 5, and are separated by symbols 4, 7. The time between the points 4 and 7 obtained by dividing the number of points by the sampling rate is determined by determining the frequency offset as follows:

In summary, the present invention has the following technical effects: by transforming the frequency domain channel estimation of the pilot subcarrier into the time domain, the peak of the time domain channel response is concentrated to the signal energy, thereby effectively suppressing noise and improving the frequency offset estimation. performance. In addition, since the frequency domain channel response is placed at the atomic carrier position before the IFFT transform, the frequency offset estimation is more accurate, so that the problem that the pilot is not affected by the time shift is not present at the same carrier position.

Although the invention has been described in detail above, the invention is not limited thereto, and various modifications may be made by those skilled in the art in accordance with the principles of the invention. Therefore, modifications made in accordance with the principles of the invention are to be understood as falling within the scope of the invention.

Industrial applicability

According to the foregoing technical solution provided by the embodiment of the present invention, by transforming the frequency domain channel estimation of the pilot subcarrier into the time domain, the peak of the time domain channel response is used to converge the signal energy, thereby effectively suppressing noise and improving frequency offset estimation performance. The frequency offset estimation is more accurate. At the same time, the problem that the frequency offset estimation is limited to the same subcarrier position is avoided.

Claims

A method for estimating carrier frequency offset, comprising:

Performing zero-interpolation on the frequency domain channel responses of all pilot subcarriers of the first OFDM symbol and all pilot subcarriers of the second OFDM symbol in the received downlink baseband received signal, to obtain a first zero-crossing frequency domain channel Response and second interpolation frequency domain channel response;

Performing an inverse Fourier transform on the first zero-frequency frequency domain channel response and the second zero-cut frequency domain channel response, respectively, to obtain a first time domain channel response and a second time domain channel response;

A carrier frequency offset is determined based on the obtained peak phase relationship in the first time domain channel response and the second time domain channel response.
The method of claim 1 wherein

The user equipment or the neighboring base station performs a zero-interpolation process on the frequency domain channel responses of all the pilot subcarriers of the first OFDM symbol and all the pilot subcarriers of the second OFDM symbol in the received downlink baseband received signal, respectively a zero-frequency domain channel response and a second zero-frequency frequency domain channel response;

Performing an inverse Fourier transform on the first zero-frequency frequency domain channel response and the second zero-cut frequency domain channel response, respectively, to obtain a first time domain channel response and a second time domain channel response;

A carrier frequency offset is determined based on the obtained peak phase relationship in the first time domain channel response and the second time domain channel response.
The method according to claim 1, wherein said frequency domain channel response of all pilot subcarriers of a first OFDM symbol and all pilot subcarriers of a second OFDM symbol in a received downlink baseband received signal The steps of performing the interpolation processing separately include:

All frequency domain pilot channel responses of the first OFDM symbol are respectively placed on pilot subcarrier positions preset by the first OFDM symbol, and all non-pilot subcarriers are set to zero;

And, all frequency domain pilot channel responses of the second OFDM symbol are respectively placed on the pilot subcarrier positions preset by the second OFDM symbol, and all non-pilot subcarriers are set to zero.
The method of claim 1, wherein the step of determining a carrier frequency offset based on the obtained peak phase relationship in the first time domain channel response and the second time domain channel response comprises:

Determining, according to the first time domain channel response and the second time domain channel response, a peak phase difference between the first time domain channel response and the second time domain channel response;

A carrier frequency offset corresponding to the peak phase difference is determined according to a time interval preset by the first OFDM symbol and the second OFDM symbol.
The method of claim 4, wherein said determining between said first time domain channel response and said second time domain channel response is based on said first time domain channel response and said second time domain channel response The steps of the peak phase difference include:

Determining, according to the first time domain channel response and the second time domain channel response, a time domain channel response of a peak position of the first time domain channel response and the second time domain channel response, respectively;

And determining a peak phase difference between the first time domain channel response and the second time domain channel response according to the time domain channel response of the first time domain channel response and the peak position of the second time domain channel response.
The method of claim 5 wherein selecting the peak location in the following manner comprises:

Determining, according to the first time domain channel response and the second time domain channel response, maximum peak values corresponding to the first time domain channel response and the second time domain channel response, respectively;

Comparing all peak positions of the OFDM symbol with the largest peak value as the first time domain channel response and the second time domain channel response by comparing the maximum time peaks of the first time domain channel response and the second time domain channel response The peak position.
The method according to claim 1, wherein the step of determining a carrier frequency offset according to the peak phase relationship in the obtained first time domain channel response and the second time domain channel response further comprises:

If the first OFDM symbol and the second OFDM symbol have an extra phase difference, determining the additional phase difference according to the pilot position offset and the time domain channel delay preset by the first OFDM symbol and the second OFDM symbol;

A carrier frequency offset is determined based on the additional phase difference and a peak phase relationship in the first time domain channel response and the second time domain channel response.
A device for estimating a carrier frequency offset, comprising:

a zero insertion module, configured to perform a zero-interpolation process on a frequency domain channel response of all pilot subcarriers of the first OFDM symbol and all pilot subcarriers of the second OFDM symbol in the received downlink baseband received signal, to obtain a first a zero-frequency domain channel response and a second zero-frequency frequency domain channel response;

The transforming module is configured to perform inverse Fourier transform on the first zero-frequency frequency domain channel response and the second zero-cut frequency domain channel response, respectively, to obtain a first time domain channel response and a second time domain channel response;

And a determining module configured to determine a carrier frequency offset according to the obtained peak phase relationship in the first time domain channel response and the second time domain channel response.
The apparatus of claim 8 wherein said zero insertion module comprises:

a first submodule, configured to place all frequency domain pilot channel responses of the first OFDM symbol on pilot subcarrier positions preset by the first OFDM symbol, and to zero all non-pilot subcarriers;

The second submodule is configured to place all frequency domain pilot channel responses of the second OFDM symbol on pilot subcarrier positions preset by the second OFDM symbol, and to zero all non-pilot subcarriers.
The apparatus of claim 8 wherein said determining module comprises:

And a difference submodule configured to determine a peak phase difference between the first time domain channel response and the second time domain channel response according to the first time domain channel response and the second time domain channel response;

And a frequency offset submodule configured to determine a carrier frequency offset corresponding to the peak phase difference according to a time interval preset by the first OFDM symbol and the second OFDM symbol.