CN100505597C - A novel OFDM frequency deviation evaluation and tracking scheme - Google Patents

Abstract

This invention relates to a new OFDM frequency-offset estimation and tracing scheme. The carrier frequency acquire stage in the scheme applies the insert of total '1' pilot frequency in the transmitting end time-domain signals and utilizes FFT module in the system at the receiving end to estimate the frequency offset to make the orthonormal one in the estimation sphere of (-N/2, N/2), the error bit rate of corrected OFDM system based on the offset estimate value is close to that without frequency offset. At the same time, the orthonormal frequency offset tracing sphere can reach to (-0.5,0.5) to the frequency offset of the tracing stage based on the circulation prefix meeting the tracing requirement very well. This invention uses the existing FFT module and a circulating prefix structure for related offset estimation to get an accurate computing result.

Description

A kind of OFDM frequency offset estimating and tracking scheme

Technical field

The present invention relates to communication technical field, relate in particular to a kind of OFDM of being applicable to (OFDM) system and contain FFT (fast fourier transform) module and the modulating system of band Cyclic Prefix in the frequency shift estimation method and the system thereof of carrier frequency acquisition phase and tracking phase.

Background technology

At present, in wireless communication technology field, OFDM (Orthogonal Frequency DivisionMultiplexing, OFDM) system is promoted gradually with its simple structure and good laser propagation effect and is used, ofdm system is to have parallel transmission data on the subcarrier of orthogonality at several, this system can reduce the adverse effect that frequency selective fading is brought than single-carrier system to a certain extent, and has simple in structure, advantages such as band efficiency is high, anti-multipath decline and impulsive noise than single-carrier system.The OFDM technology has caused the common concern of a plurality of industries that comprise telecommunications, radio and television, power communication, has especially obtained many application in the communications field.For example, European standard DAB (digital audio broadcasting), DVB (digital video broadcasting), ADSL (ADSL (Asymmetric Digital Subscriber Line)), IEEE802.11a and HlPERLAN II, or the like.

Now OFDM modulating system of the prior art is introduced in conjunction with Fig. 1, signal transmission in the system generally includes signal and sends processing, Channel Transmission and signal receive handles three parts, wherein signal transmission processing section is mainly used in signal is carried out the OFDM modulation, comprise signal is encoded, constellation mapping and IFFT processing such as (inverse Fourier transforms), also the conversion of signals that sends is become time-domain signal, carry out corresponding parallel serial conversion more successively, add Cyclic Prefix, digital-to-analogue conversion, send filtering and upconversion process, the transmission signal that will obtain at last by Channel Transmission to receiving terminal; The concrete processing procedure that signal Return Reception Dept. in the receiving terminal divides then is the inverse process that signal sends processing procedure.

Yet the symbol period that increases relatively in ofdm system can make it responsive more than carrier wave communication system to frequency shift (FS).Carrier wave frequency deviation will destroy the orthogonality between the OFDM symbol subcarrier, increase crosstalking between subchannel, thereby increase the error rate of ofdm system.Cause the reason of frequency shift (FS) to mainly contain unsteadiness of Doppler (Doppler) frequency displacement, transmitter and receiver crystal oscillator etc., these all cause the increase of the subcarrier interference and the error rate easily, therefore, accurately the frequency deviation of estimating OFDM system just becomes the key that influences the ofdm system performance.For carrier frequency synchronization in the wireless communication system or Frequency offset estimation, usually be divided into two stages, be carrier frequency synchronization or the frequency offset estimating and the correction of acquisition phase and tracking phase, thereby the frequency that guarantees receiving terminal and transmitting terminal is consistent, promptly guarantees the Frequency Synchronization of signal transmitting and receiving.

In the algorithm for estimating of in the past frequency shift (FS), no matter be based on the Frequency offset estimation of pilot tone, also be based on the Frequency offset estimation of Cyclic Prefix, all be the method that adopts related operation basically, make the frequency offset computations complexity increase greatly, cause difficulty increase in specific implementation process.

Summary of the invention

The purpose of this invention is to provide a kind of new OFDM frequency offset estimating and tracking scheme, promptly provide carrier frequency in a kind of wireless communication system to catch frequency deviation estimating method and system thereof with tracking phase, thereby it is comparatively simple to make that ofdm system and other contain catching with tracing process of whole frequency offset estimating in the modulating system of FFT module and band Cyclic Prefix, and can obtain frequency offset estimation result accurately.

The objective of the invention is to be achieved through the following technical solutions:

The invention provides the frequency deviation estimating method of carrier frequency acquisition phase in a kind of wireless communication system, comprising:

A, with the pilot signal of inserting in the time-domain signal that sends greater than 0, and each value that pilot signal comprises is all identical;

B, at receiving terminal the pilot tone in the signal that receives is analyzed, with integer frequency offset estimated value that obtains acquisition phase and the frequency offset estimating value of dividing several times.

Described steps A is:

The pilot signal of complete " 1 " will be inserted in OFDM (OFDM) system or the time-domain signal that contains the FFT module and adopt the system of Cyclic Prefix to send.

Described step B comprises:

Pilot signal after receiving terminal obtains sampling is removed Cyclic Prefix, and carries out FFT;

Determine the Frequency offset estimation value of integral multiple according to the position of the sample value correspondence of amplitude maximum after the conversion.

Described step B comprises:

Obtain front and back two parts of sampling back pilot signal at receiving terminal;

Respectively the two parts that obtain being carried out FFT handles;

To handle two-part 0 frequency values that obtains through FFT and be divided by, and calculate corresponding argument main value according to the described result who obtains of being divided by, and try to achieve the Frequency offset estimation value of branch several times.

Front and back two parts length of described pilot signal is identical, and can overlap, but can not be identical, and the sampled value of each several part continuously and do not have an interference of adjacent OFDM symbol.

Described step B also comprises:

With the Frequency offset estimation value of integral multiple and the Frequency offset estimation value of dividing the Frequency offset estimation value addition acquisition acquisition phase of several times.

The present invention also provides the frequency deviation estimating method of carrier frequency tracking phase in a kind of wireless communication system, comprising:

C, will receive the Cyclic Prefix in the OFDM symbol and be divided by one by one, and the result who obtains according to being divided by determines the Frequency offset estimation value of tracking phase with the data of its repeating part.

Described Cyclic Prefix is not subjected to the interference of adjacent OFDM symbol.

Described step C further comprises:

To receive the Cyclic Prefix of OFDM symbol and be divided by one by one respectively with the data of its repeating part, and calculate each and be divided by and obtain result's mean value, go out corresponding argument main value according to described mean value calculation, further determine the Frequency offset estimation value of tracking phase again.

Described step C further comprises:

To receive the Cyclic Prefix of OFDM symbol and be divided by one by one respectively with the data of its repeating part, calculate its corresponding argument main value respectively, and calculate the mean value that obtains the argument main value, according to described mean value, further determine the Frequency offset estimation value of tracking phase again.

By technical scheme that the invention described above provided as can be seen, the present invention inserts complete " 1 " pilot tone and utilizes the FFT module in the system that the frequency shift (FS) in the wireless communication system is estimated owing to having adopted in the time-domain signal of transmitting terminal, promptly complete " 1 " pilot tone of inserting in the acquisition phase utilization is carried out the estimation and the correction of frequency shift (FS), the normalized frequency offset estimation range is (N/2, N/2), and after the Frequency offset estimation value that obtains according to the present invention correction, the bit error rate of ofdm system approaches not have the bit error rate under the frequency shift (FS) condition basically.Simultaneously, among the present invention, for the Frequency offset estimation of tracking phase based on Cyclic Prefix, normalized frequency skew following range is (0.5,0.5), can satisfy the requirement of frequency-tracking well, and the bit error rate after proofreading and correct can approach not have the bit error rate under the frequency shift (FS) condition equally.

In a word, method of the present invention can make not only that whole calculating process is comparatively simple, arithmetic speed improves greatly, can also obtain frequency offset computations result accurately.

Description of drawings

Fig. 1 is the structural representation of ofdm system;

Fig. 2 is the pilot signal schematic diagram that inserts in the time domain;

Fig. 3 is a carrier frequency acquisition phase frequency offset estimating schematic diagram of the present invention;

Fig. 4 is a carrier frequency tracking phase frequency offset estimating schematic diagram of the present invention.

Embodiment

Before explanation the specific embodiment of the present invention, at first in conjunction with Fig. 1, prior OFDM system is done simple the introduction, and as shown in Figure 1, the data flow d in the ofdm system (k) is through forming the vector that a length is N (N is the quantity of subcarrier) after certain encoding process and the constellation mapping:

This vector produces the time domain data vector by serial to parallel conversion part 101 and IFFT (inverse Fourier transform) part 102, parallel serial conversion part 103:

And then add and obtain the time domain data vector after L the Cyclic Prefix by adding Cyclic Prefix part 104:

Carry out digital-to-analogue conversion through digital-to-analogue conversion part 105 again, be transferred to receiving terminal after send into Channel Transmission part 106 after transmission filtering and the up-conversion.At receiving terminal, received signal obtains containing the vector of Cyclic Prefix again after analog-to-digital conversion part 107 is carried out analog-to-digital conversion after the down-conversion and the processing that accepts filter:

Through remove Cyclic Prefix part 108 remove L Cyclic Prefix after remaining N sample value:

Handle last output vector accordingly by serial to parallel conversion part 109, FFT part 1010, parallel serial conversion part 1011 successively again

This vector handles laggard planet seat mapping through frequency domain equalization and certain decoding processing recovers initial data afterwards.

The core concept of the method for the invention is according to complete " 1 " pilot tone of inserting in the transmitting terminal time-domain signal, and carry out FFT at receiving terminal and handle, obtaining the Frequency offset estimation of carrier frequency acquisition phase, then be to determine the related offset estimated value according to the Cyclic Prefix that receives the OFDM symbol with the correlation of its repeating part for the Frequency offset estimation of carrier frequency tracking phase in the system.

Is example below in conjunction with accompanying drawing with the Frequency offset estimation of ofdm system, method of the present invention is carried out the description of principle, as shown in Figure 1, for the auxiliary frequency offset estimating of ofdm system carrier frequency acquisition phase pilot tone, in the transmitting terminal time domain, inserted complete " 1 " pilot signal.If under the situation that factors such as transmitting terminal corresponding transmission power allow, can also increase the pilot value of corresponding insertion certainly, and, along with the pilot value of inserting increases, can obtain frequency offset estimation result more accurately.

Among the present invention, the frequency offset estimating algorithm of ofdm system acquisition phase is based on the frequency-domain analysis of complete " 1 " pilot tone of time domain is carried out, as Fig. 2, can be used as pilot signal suc as formula (1) represented OFDM symbol with one in the time domain at transmitting terminal, described formula (1) is:

x(l)＝1，l＝0，1，2，ΛN+L-1 (1)

After the frequency shift (FS) that produces in the described pilot signal process transmission course, at the receiving terminal of channel, the base band discrete form of this pilot signal can be expressed as:

$\begin{array}{cc}r\left(l\right)=x\left(l\right){\mathrm{<figure-callout\; id="2"\; label="e\; j"\; filenames="C200310113313E00152.png"\; state="\{\{state\}\}">e</figure-callout>}}^j+n\left(l\right)={\mathrm{<figure-callout\; id="2"\; label="e\; j"\; filenames="C200310113313E00152.png"\; state="\{\{state\}\}">e</figure-callout>}}^j+n\left(l\right)& l=\mathrm{0,1},\mathrm{\&Lambda;\; N}+L-1\end{array}---\left(2\right)$

Wherein, N is a sub-carrier number, ε=f _d/ Δ f=Nf _d/ f _sBe normalized frequency deviant, f _dBe frequency shift (FS),

Being the transmission rate of data symbol s (), also is sampling rate, Δ f=f _s/ N is a subcarrier spacing, and n (|) average is 0 white complex gaussian noise.

As shown in Figure 1, generally include two parts for the estimation of the frequency shift (FS) of acquisition phase in the ofdm system, a part is the Frequency offset estimation of integral multiple; Another part is the Frequency offset estimation of branch several times.After obtaining the frequency shift (FS) result of corresponding integer-times frequency offset result and branch several times, two results added promptly can be obtained the Frequency offset estimation value of acquisition phase.

With reference to Fig. 3, at first the integer-times frequency offset of acquisition phase is estimated that if system's frequency of occurrences skew, the frequency spectrum that then receives pilot signal is equivalent to amplitude and is Delay pulse added white Gaussian noise, whole frequency pilot sign is after sampling and FFT conversion, the sampled value that will occur the amplitude maximum in the nearest sample value of delay pulse, the subcarrier ordinal number of the sampled value correspondence of this amplitude maximum is the Frequency offset estimation value of corresponding integral multiple just.The Frequency offset estimation value of described normalization integral multiple can be calculated by following formula:

${\widehat{\mathrm{\&epsiv;}}}_{\mathrm{int}}=\arg \left\{\underset{k}{\max }\left[\left|y\left(k\right)\right|\right]\right\}---\left(3\right)$

Still, again the mark overtones band skew of acquisition phase is estimated with reference to Fig. 3.At first the OFDM pilot signal of obtaining is proofreaied and correct with the Frequency offset estimation value of integral multiple, then two parts before and after it are carried out the FFT conversion respectively, the sampled value that M (M can get N/4, N/2,3N/4 or the like) point and back M are ordered is soon carried out the FFT processing respectively, and then two the 0 frequency translation values that will obtain in the frequency translation value are divided by.With M=N/2 is example, and two 0 frequency translation values that obtained are as follows respectively:

$y_1\left(0\right)=\sqrt{N/2}\{\frac{\sin \mathrm{\&pi;\&epsiv;}{e}^{-j[1-\frac{2(L+1)}{N}]\mathrm{\&pi;\&epsiv;}}}{\frac{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="C200310113313E00152.png"\; state="\{\{state\}\}">N</figure-callout>}}{2}\sin \frac{2\mathrm{\&pi;\&epsiv;}}{N}}+E\left[n\left(m\right)\right]\}\&ap;\frac{\sqrt{N/2}\sin \mathrm{\&pi;\&epsiv;}{e}^{-j[1-\frac{2L}{N}]\mathrm{\&pi;\&epsiv;}}}{\mathrm{\&pi;\&epsiv;}}---\left(4\right)$

$y_2\left(0\right)=\sqrt{N/2}\{\frac{\sin \mathrm{\&pi;\&epsiv;}{e}^{j\frac{2(L+1)}{N}\mathrm{\&pi;\&epsiv;}}}{\frac{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="C200310113313E00152.png"\; state="\{\{state\}\}">N</figure-callout>}}{2}\sin \frac{2\mathrm{\&pi;\&epsiv;}}{N}}+E\left[n\left(m\right)\right]\}\&ap;\frac{\sqrt{N/2}\sin \mathrm{\&pi;\&epsiv;}{e}^{j\frac{2L}{N}\mathrm{\&pi;\&epsiv;}}}{\mathrm{\&pi;\&epsiv;}}---\left(5\right)$

Wherein: 0＜| ε |＜0.5, and N/2 1, L〉〉 1, $E\left[n\left(m\right)\right]=\frac{2}{N}\underset{m=0}{\overset{N-1}{\mathrm{\&Sigma;}}}n\left(m\right),$ Then $\frac{y_2\left(0\right)}{y_1\left(0\right)}\&ap;e^{\mathrm{j\&pi;\&epsiv;}};$

In view of the above, calculate through corresponding argument main value again, and just can estimate corresponding normalization mark times frequency deviation value, be specially according to calculating the argument main value that obtains:

${\widehat{\mathrm{\&epsiv;}}}_{\mathrm{fra}}=\arg \left\{\frac{y_2\left(0\right)}{y_1\left(0\right)}\right\}/\mathrm{\&pi;}---\left(6\right)$

Because it is also insensitive behind complete " 1 " pilot signal of time domain (being all identical pilot signals of pilot signal value) adding Cyclic Prefix to multipath channel, so this algorithm goes for the Frequency offset estimation of multipath channel, and, the normalization frequency offset estimation range of acquisition be (N/2, N/2).

After having finished the Frequency offset estimation of acquisition phase; for the frequency of transmitting-receiving two-end in the assurance system keeps identical, promptly guarantee the carrier frequency synchronization of transmitting-receiving, the error rate in the minimizing system; usually also need the frequency shift (FS) in the system is followed the tracks of, so that proofread and correct the correspondent frequency skew in real time.Be frequency offset estimating based on Cyclic Prefix in the received signal for the frequency offset estimating of ofdm system tracking phase among the present invention, as shown in Figure 1, the frequency offset estimating of tracking phase is positioned to be removed before cyclic prefix portion divides.

Cyclic Prefix in the described received signal can be expressed as:

$\begin{array}{cc}{r}_L\left(p\right)=x_L\left(p\right){\mathrm{<figure-callout\; id="2"\; label="e\; j"\; filenames="C200310113313E00152.png"\; state="\{\{state\}\}">e</figure-callout>}}^j+n\left(p\right)& p=\mathrm{0,1},\mathrm{\&Lambda;\; L}-1\end{array}---\left(7\right)$

Back L data of the OFDM symbol that receives then are:

$\begin{array}{cc}{r}_N\left(q\right)=x_L(q-N)e^{\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="C200310113313E00152.png"\; state="\{\{state\}\}">j</figure-callout>}\frac{2\mathrm{\&pi;}}{N}\mathrm{q\&epsiv;}}+n\left(q\right)& q=N,N+1,\mathrm{\&Lambda;N}+L-1\end{array}---\left(8\right)$

Formula (8) can be simplified shown as:

$\begin{array}{cc}{r}_L\left(q\right)=x_L\left(q\right){\mathrm{<figure-callout\; id="2"\; label="e\; j"\; filenames="C200310113313E00152.png"\; state="\{\{state\}\}">e</figure-callout>}}^j+n\&prime;\left(q\right)& q=\mathrm{0,1},\mathrm{\&Lambda;\; L}-1\end{array}---\left(9\right)$

Wherein, n ' is the white Gaussian noise process that is different from n (q) (q), but their statistical natures are identical.

By formula (7) and formula (9) as can be seen, Cyclic Prefix and very strong correlation is arranged with its repeating part (being back L data of OFDM symbol), phase place deflection has taken place with respect to the useful signal of formula (7) in the useful signal that is formula (9), the phase difference of two groups of data contains stronger frequency offset information, therefore, can ask the estimated value of frequency shift (FS) according to this phase difference, Cyclic Prefix partly and with the part of its repetition is divided by one by one in the OFDM symbol that is about to receive, and calculate corresponding argument main value, determine to be specially the estimated value of frequency shift (FS) according to described argument main value:

$\widehat{\mathrm{\&epsiv;}}=\arg \left\{\frac{x\left(q\right){\mathrm{<figure-callout\; id="2"\; label="e\; j"\; filenames="C200310113313E00152.png"\; state="\{\{state\}\}">e</figure-callout>}}^j+n\&prime;\left(q\right)}{x\left(q\right){\mathrm{<figure-callout\; id="2"\; label="e\; j"\; filenames="C200310113313E00152.png"\; state="\{\{state\}\}">e</figure-callout>}}^j+n\left(q\right)}\right\}/2\mathrm{\&pi;}.---\left(10\right)$

And, being the evaluated error of the frequency shift (FS) that reduces tracking phase, can also on the basis of merchant or argument main value being got average, estimate again.

Generally, Cyclic Prefix will be set at the root mean square several times of multidiameter delay, so normally adopting the Cyclic Prefix that obtains among the present invention under multipath conditions is the latter half (about 50%) of received signal Cyclic Prefix, be not subjected to the interference of adjacent OFDM symbol with the Cyclic Prefix part that guarantees to obtain, concrete scope is by the multipath situation decision of channel.

Under multipath conditions, constellation mapping is if adopt BPSK (two-phase PSK), and the effect of frequency offset estimating is relatively poor, adopts multi-system PSK (phase shift keying), QAM (quadrature amplitude modulation) then will obtain frequency offset estimating effect preferably.Owing in estimation procedure, do not utilize the information of OFDM symbol mid portion, so the normalization frequency offset estimation range is (0.5,0.5).

The description of principle has been carried out comparatively meticulously to method of the present invention in the front, in conjunction with Fig. 3 and Fig. 4 the specific embodiment of the present invention is described further below again.

Referring to Fig. 3, in the frequency deviation capturing stage, the high-frequency signal that receiver receives obtains digital signal again after analog-to-digital conversion part 107 is carried out analog-to-digital conversion after the down-conversion and the processing that accepts filter:

This N+L sample value will be used for the Frequency offset estimation of branch several times on the one hand; After removing Cyclic Prefix part 108 to remove Cyclic Prefix, be left N useful sample value on the other hand:

This N sample value will be used for the Frequency offset estimation of integral multiple.In the frequency offset estimation process of integral multiple, at first 1010 FFT that carry out N point sample value handle N sample value through the FFT processing section, carry out the peaked search of corresponding amplitude, the normalization frequency offset estimating value that the pairing subcarrier ordinal number of the maximum amplitude that searches is exactly an integral multiple through search maximum part 301 then.And in the frequency offset estimation process of minute several times, at first to obtain digital signal to analog-to-digital conversion and carry out the correction of integer frequency offset through integer frequency offset correction portion 302 according to the integer frequency offset estimated value that obtains, two parts carry out the FFT processing of M point sample value respectively before and after obtaining the OFDM symbol then by FFT processing section 1010, specifically comprise FFT processing that preceding M is ordered and the FFT processing that back M is ordered, and the 0 frequency output valve that the FFT processing of two parts M being ordered by division processing module 303 obtains is divided by, the argument main value that obtains according to calculating argument main value part 304 calculates the normalization frequency offset estimating value of branch several times again, and promptly the argument main value just is described normalization frequency offset estimating value divided by π.The normalization frequency offset estimating value of branch several times and the normalization frequency offset estimating value of integral multiple just obtain the normalization frequency offset estimating value of acquisition phase through adder 305 additions, and be again that the normalization frequency offset estimating is on duty with subcarrier spacing, and then obtain the frequency offset estimating value.

Referring to Fig. 4, at the carrier frequency tracking phase, the signal that receiver receives obtains digital signal again after analog-to-digital conversion part 107 is carried out analog-to-digital conversion after the down-conversion and the processing that accepts filter:

Then the part through getting the Cyclic Prefix latter half 306, the part 307 of getting Cyclic Prefix latter half repeating part obtain the Cyclic Prefix latter half and with the part of its repetition, difference according to channel multi-path situation in the wireless communication system, can get received signal aft section 50%, 40%, 60% or the like, by division processing module 303 two groups of data are divided by respectively one by one.Get each result's of being divided by mean value through the part 308 of averaging again, at last will be as calculated the argument main value (can certainly calculate the argument main value earlier averages again) that obtains of argument main value part 304 divided by 2 π and multiply by subcarrier spacing, the gained result is the frequency offset estimating value of tracking phase.

The specific embodiment of the present invention that is provided by Fig. 3 and Fig. 4 as can be seen, the present invention has utilized existing FFT module in the ofdm system (being FFT part 1010) to carry out the estimation of the frequency offseting value of carrier frequency acquisition phase, therefore, can simplify the realization complexity of the frequency offseting value estimation of acquisition phase widely; And, among the present invention for the frequency offset estimating of tracking phase, be according to Cyclic Prefix and and the partial data of its repetition between the frequency offset information that contains of phase difference carry out the estimation of frequency shift (FS), implementation complexity can reduce equally greatly.

The present invention is except being adapted to above-mentioned ofdm system, and for having adopted Cyclic Prefix and the single-carrier system that contains the FFT module, the present invention is suitable equally.The described Cyclic Prefix that adopted is similar with its system works principle of single-carrier system and the ofdm system that contain the FFT module.

The above; only for the preferable embodiment of the present invention, but protection scope of the present invention is not limited thereto, and anyly is familiar with those skilled in the art in the technical scope that the present invention discloses; the variation that can expect easily or replacement all should be encompassed within protection scope of the present invention.Therefore, protection scope of the present invention should be as the criterion with the protection range of claims.

Claims (5)

1, a kind of OFDM frequency offset estimating and tracking scheme comprise that the frequency offset estimating of carrier frequency acquisition phase is handled, and the processing of the frequency offset estimating of carrier frequency tracking phase, it is characterized in that,

The frequency offset estimating of described carrier frequency acquisition phase is handled and is comprised:

A, the pilot signal of complete " 1 " will be inserted in orthogonal frequency division multiplex OFDM system or the time-domain signal that contains fast fourier transform FFT module and adopt the system of Cyclic Prefix to send;

B, the pilot tone in the signal that receives is analyzed at receiving terminal, with integer frequency offset estimated value that obtains acquisition phase and the frequency offset estimating value of dividing several times, the Frequency offset estimation value and the Frequency offset estimation value addition that divides several times of integral multiple obtained the Frequency offset estimation value of acquisition phase; Wherein, definite mode of the Frequency offset estimation value of described integral multiple comprises: the pilot signal after receiving terminal obtains sampling, and remove Cyclic Prefix, and carry out FFT; Determine the Frequency offset estimation value of integral multiple according to the position of the sample value correspondence of amplitude maximum after the conversion; Definite mode of the frequency offset estimating value of described minute several times comprises: the front and back two parts that obtain sampling back pilot signal at receiving terminal; Respectively the two parts that obtain being carried out FFT handles; To handle two-part 0 frequency values that obtains through FFT and be divided by, and calculate corresponding argument main value according to the described result who obtains of being divided by, and try to achieve the Frequency offset estimation value of branch several times;

The frequency offset estimating of described carrier frequency tracking phase is handled and is comprised:

C, will receive the Cyclic Prefix in the OFDM symbol and be divided by one by one, and the result who obtains according to being divided by determines the Frequency offset estimation value of tracking phase with the data of its repeating part.

2, a kind of OFDM frequency offset estimating according to claim 1 and tracking scheme, the front and back two parts length that it is characterized in that described pilot signal is identical, and can overlap, but can not be identical, the sampled value of each several part continuously and do not have an interference of adjacent OFDM symbol.

3, a kind of OFDM frequency offset estimating according to claim 1 and tracking scheme is characterized in that described Cyclic Prefix is not subjected to the interference of adjacent OFDM symbol.

4, a kind of OFDM frequency offset estimating according to claim 1 and tracking scheme is characterized in that described step C further comprises:

To receive the Cyclic Prefix of OFDM symbol and be divided by one by one respectively with the data of its repeating part, and calculate each and be divided by and obtain result's mean value, go out corresponding argument main value according to described mean value calculation, further determine the Frequency offset estimation value of tracking phase again.

5, according to claim 3 or 4 described a kind of OFDM frequency offset estimating and tracking schemes, it is characterized in that described step C further comprises:

To receive the Cyclic Prefix of OFDM symbol and be divided by one by one respectively with the data of its repeating part, calculate its corresponding argument main value respectively, and calculate the mean value that obtains the argument main value, according to described mean value, further determine the Frequency offset estimation value of tracking phase again.

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