CN102244630A - Method and device for eliminating inter-subcarrier interference in OFDM (Orthogonal Frequency Division Multiplexing) system - Google Patents

Abstract

The invention provides a method for eliminating inter-subcarrier interfere caused by Doppler frequency shift in an OFDM (Orthogonal Frequency Division Multiplexing) system, which comprises following steps of extracting pilot carrier information in OFDM symbols according to received OFDM signals, and obtaining time domain channel shock response; generating a channel transmission matrix corresponding to the OFDM symbols by utilizing the time domain channel shock response of three adjacent OFDM symbols; and balancing a frequency domain of data subcarriers in the OFDM symbols according to the channel transmission matrix corresponding to the obtained OFDM symbols, and eliminating ICI (Inter-Carrier Interference) caused by the Doppler frequency shift. The interference eliminating method provided by the invention has the advantages that the algorithm is simple, and no large storage space is needed during computing, the channel transmission matrix is constructed by utilizing pilot frequency information, and the ICI is eliminated by frequency domain balance. According to the technical scheme disclosed by the embodiment of the invention, larger Doppler frequency shift can be resisted.

Description

The method of interference eliminated and device between the ofdm system sub-carriers

Technical field

The present invention relates to digital communicating field, particularly, the present invention relates to the method and the device of interference eliminated between a kind of ofdm system sub-carriers.

Background technology

Move the developing direction that becomes modern communication technology with the broadband, in many broadband wireless communication technique, OFDM (Orthogonal Frequency Division Multiplexing, OFDM) has one of technology of application prospect beyond doubt most.In the fading characteristic of channel, what the broadband wireless mobile service was had the greatest impact is multipath fading and Doppler frequency shift.And OFDM not only can be by inserting the method for Cyclic Prefix (CP), restrain the intersymbol interference that multipath brings effectively, can also be by reasonable estimation to the channel time-varying characteristics, the symbol lengths of design system alleviates the influence of channel time-varying characteristics to systematic function neatly.Because these technical characterstics of OFDM have avoided adopting complicated time-domain equalizer and adaptive tracing algorithm in receiver.And by using fast Fourier transform (FFT), can guarantee provides reliable, stable communication quality under simple relatively system hardware structure.Exactly because these advantages, OFDM technology are by the extensively employing of various wireless communication standard institute.OFDM multicarrier system has begun to obtain practical application in fields such as the terrestrial broadcast system of digital audio broadcasting, high definition TV HDTV and WIMAX communication systems.And people begin to concentrate the application of increasing energy exploitation OFDM technology in the high-speed mobile communications field, the most important candidate's standard of the present mobile communication technology that the OFDM technology has become.

Based in the digital communication system of OFDM because the relative motion between transmitting terminal and the receiving terminal produces Doppler frequency shift, Doppler frequency shift has destroyed the orthogonality between each subcarrier in the ofdm system, thereby brings the interference (ICI) between subcarrier.Though system configuration can be eliminated intersymbol interference, ofdm system still needs precise channels information to carry out channel equalization, thus the full remuneration multipath fading.The channel estimating of OFDM and balancing technique have decisive influence to the performance of whole system.One of advantage of OFDM maximum can be carried out simple frequency domain equalization exactly.Owing to introduced Cyclic Prefix, can realize channel equalization by simple division at receiving terminal.

The method that ICI eliminates can be divided into the method for equalization filtering on the whole and increase redundant method, wherein equalization filtering comprises time domain equalization and frequency domain equalization, the carrier-in-interference self elimination method is a kind of typical redundant method that increases, in fact these two kinds of methods can be unified each other, increased the redundant spectrum efficiency that reduced, the balanced estimation time varying channel that needs, need a large amount of pilot tones in the middle of the data symbol and follow the tracks of time varying channel, so also reduced the availability of frequency spectrum, but balanced can being operated under the pattern of iteration and decision-feedback so just saved the expense of a lot of pilot tones.In ofdm system, select the method for ICI interference eliminated need consider trading off between performance and the complexity.

Ofdm system is particularly responsive to ICI, and stronger ICI can produce damaging influence to the ofdm system performance, and the method and apparatus that therefore resists the ICI that is caused by Doppler frequency shift effectively is extremely important to ofdm system.

Summary of the invention

Purpose of the present invention is intended to solve at least one of above-mentioned technological deficiency, particularly solve based in the digital communication system of OFDM because the relative motion between transmitting terminal and the receiving terminal produces Doppler frequency shift, cause the problem disturbed between subcarrier, by utilizing pilot frequency information structure Channel Transmission matrix, utilize frequency domain equalization to eliminate ICI.

In order to realize the present invention's purpose, the embodiment of the invention has proposed the method for interference eliminated between a kind of ofdm system sub-carriers on the one hand, may further comprise the steps:

Pilot frequency information according in the ofdm signal extraction OFDM symbol that receives obtains time domain channel shock response; Utilize the time domain channel shock response of adjacent three OFDM symbols to generate the Channel Transmission matrix of this OFDM symbol correspondence

Channel Transmission matrix according to each the OFDM symbol correspondence that obtains Data subcarrier in the OFDM symbol is carried out frequency domain equalization, eliminate because the ICI that Doppler frequency shift causes.

The embodiment of the invention has also proposed the device of interference eliminated between a kind of ofdm system sub-carriers on the other hand, comprises receiver module, channel estimation module and balance module,

Described receiver module is used to receive ofdm signal;

Described channel estimation module, be used for extracting the pilot frequency information of OFDM symbol according to the ofdm signal that receives, obtain time domain channel shock response, and utilize the time domain channel shock response of adjacent three OFDM symbols to generate the Channel Transmission matrix of this OFDM symbol correspondence

Described balance module is used for the Channel Transmission matrix according to each the OFDM symbol correspondence that obtains

Data subcarrier in the OFDM symbol is carried out frequency domain equalization, eliminate because the ICI that Doppler frequency shift causes.

Technical scheme according to the embodiments of the invention proposition, solved because the relative motion between transmitting terminal and the receiving terminal produces Doppler frequency shift, cause the problem disturbed between subcarrier, the algorithm of the interference eliminated that embodiments of the invention propose is simple, do not need a large amount of memory spaces during calculating,, utilize frequency domain equalization to eliminate ICI by utilizing pilot frequency information structure Channel Transmission matrix, the technical scheme that embodiments of the invention propose can be resisted bigger Doppler frequency shift.The technical scheme that embodiments of the invention propose, rationally efficient using system resource, optimization system performance.In addition, the technical scheme that embodiments of the invention propose, very little to the change of existing system, can not influence the compatibility of system, and realize simple, efficient.

Aspect that the present invention adds and advantage part in the following description provide, and part will become obviously from the following description, or recognize by practice of the present invention.

Description of drawings

Above-mentioned and/or additional aspect of the present invention and advantage are from obviously and easily understanding becoming the description of embodiment below in conjunction with accompanying drawing, wherein:

Fig. 1 is the method flow diagram of interference eliminated between embodiment of the invention ofdm system sub-carriers;

Fig. 2 is an embodiment of the invention signal processing schematic diagram;

Fig. 3 is the structural representation of the device 100 of interference eliminated between embodiment of the invention ofdm system sub-carriers;

Fig. 4 is the structure of time slot figure of CMMB system;

Fig. 5 is the allocation plan pattern of pilot tone in the CMMB system;

Fig. 6 uses signal processing schematic diagram of the present invention in the embodiment of the invention CMMB system.

Embodiment

Describe embodiments of the invention below in detail, the example of described embodiment is shown in the drawings, and wherein identical from start to finish or similar label is represented identical or similar elements or the element with identical or similar functions.Below by the embodiment that is described with reference to the drawings is exemplary, only is used to explain the present invention, and can not be interpreted as limitation of the present invention.

In order to realize the present invention's purpose, the embodiment of the invention has proposed the method for interference eliminated between a kind of ofdm system sub-carriers, may further comprise the steps: the pilot frequency information according in the ofdm signal extraction OFDM symbol that receives, obtain time domain channel shock response; Utilize the time domain channel shock response of adjacent three OFDM symbols to generate the Channel Transmission matrix of this OFDM symbol correspondence

Channel Transmission matrix according to each the OFDM symbol correspondence that obtains

Data subcarrier in the OFDM symbol is carried out frequency domain equalization, eliminate because the ICI that Doppler frequency shift causes.

As shown in Figure 1, the method flow diagram for interference eliminated between embodiment of the invention ofdm system sub-carriers may further comprise the steps:

S101: obtain time domain channel shock response according to the pilot tone in the OFDM symbol.

In step S101, receiving terminal obtains time domain channel shock response according to the pilot frequency information in the ofdm signal extraction OFDM symbol that receives.

As shown in Figure 2, for embodiment of the invention signal processing schematic diagram,, embodiments of the invention are set forth below in conjunction with Fig. 2 for the ease of understanding the present invention.

The ground that is without loss of generality, the OFDM symbol lengths of establishing an ofdm system is N, its circulating prefix-length is G, G＜N, if channel latency length v≤G, in the medium arranged spaced L of frequency-domain OFDM symbol＞v pilot tone

l _i=(iN)/and L, 0≤i＜L.

After carrying out the FFT conversion to n time domain OFDM symbol, receiving terminal obtains its frequency-domain OFDM symbol

From Y ⁿThe middle pilot frequency locations place information of extracting

Then pilot frequency locations place channel response is

Right

The IFFT that does length and be L obtains time domain channel shock response

Right again

Carry out filtering, promptly set a threshold value, when

Less than this threshold value season ${\hat{h}}_{l_i}^n=\mathrm{0,0}\&le;i<L.$

S102: utilize the time domain channel shock response of adjacent three OFDM symbols to generate the Channel Transmission matrix of this OFDM symbol correspondence.

In step S102, suppose that it is linear change that channel directly gains at each OFDM intersymbol, then can utilize adjacent three OFDM symbols

With

Obtain the slope that each footpath of channel changes between adjacent-symbol.

Particularly, utilize adjacent three OFDM symbols With

Obtaining each slope that directly changes between adjacent-symbol of channel is

0≤k＜G (1)

To filtered

And

With

Be the FFT that length is N, obtain

${\hat{H}}_{\mathrm{mid}}=\mathrm{diag}\left\{\mathrm{FFT}\left(\right[{\hat{h}}_0^n,{\hat{h}}_1^n,...,{\hat{h}}_{G-1}^n,0,...,0\left]\right)\right\}---\left(2\right)$

${\hat{H}}_{\mathrm{<figure-callout\; id="1"\; label="slpoe\; r"\; filenames="HSA00000122313300022.png"\; state="\{\{state\}\}">slpoe</figure-callout>}}^{r_{}}=\mathrm{diag}\left\{\mathrm{FFT}\left(\right[{\widehat{\mathrm{\&alpha;}}}_0^{{\mathrm{<figure-callout\; id="1"\; label="r"\; filenames="HSA00000122313300022.png"\; state="\{\{state\}\}">r</figure-callout>}}_1},{\widehat{\mathrm{\&alpha;}}}_1^{{\mathrm{<figure-callout\; id="1"\; label="r"\; filenames="HSA00000122313300022.png"\; state="\{\{state\}\}">r</figure-callout>}}_1},...,{\widehat{\mathrm{\&alpha;}}}_{G-1}^{{\mathrm{<figure-callout\; id="1"\; label="r"\; filenames="HSA00000122313300022.png"\; state="\{\{state\}\}">\; <figure-callout\; id="0"\; label="r"\; filenames="HSA00000122313300021.png"\; state="\{\{state\}\}">r</figure-callout>\; </figure-callout>}}_1},0,...0\left]\right)\right\}---\left(3\right)$

${\hat{H}}_{\mathrm{<figure-callout\; id="2"\; label="slpoe\; r"\; filenames="HSA00000122313300023.png"\; state="\{\{state\}\}">slpoe</figure-callout>}}^{r_{}}=\mathrm{diag}\left\{\mathrm{FFT}\left(\right[{\widehat{\mathrm{\&alpha;}}}_0^{{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="HSA00000122313300023.png"\; state="\{\{state\}\}">r</figure-callout>}}_2},{\widehat{\mathrm{\&alpha;}}}_1^{{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="HSA00000122313300023.png"\; state="\{\{state\}\}">r</figure-callout>}}_2},...,{\widehat{\mathrm{\&alpha;}}}_{G-1}^{{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="HSA00000122313300023.png"\; state="\{\{state\}\}">\; <figure-callout\; id="0"\; label="r"\; filenames="HSA00000122313300021.png"\; state="\{\{state\}\}">r</figure-callout>\; </figure-callout>}}_2},0,...0\left]\right)\right\}---\left(4\right)$

Utilize the N * N coefficient matrix that generates in advance again

With Obtain the Channel Transmission matrix

$\hat{H}={\hat{H}}_{\mathrm{mid}}+({\mathrm{<figure-callout\; id="1"\; label="C\; r"\; filenames="HSA00000122313300022.png"\; state="\{\{state\}\}">C</figure-callout>}}^{r_{}}\&CenterDot;{\hat{H}}_{\mathrm{<figure-callout\; id="1"\; label="slope\; r"\; filenames="HSA00000122313300022.png"\; state="\{\{state\}\}">slope</figure-callout>}}^{r_{}}+{\mathrm{<figure-callout\; id="2"\; label="C\; r"\; filenames="HSA00000122313300023.png"\; state="\{\{state\}\}">C</figure-callout>}}^{r_{}}\&CenterDot;{\hat{H}}_{\mathrm{slope}}^{r_2})---\left(5\right)$

Coefficient matrix

With

Can generate in advance also in system and can calculate in real time, the element of the capable m row of its i is

$C^{r_1}(i,m)=T_s\&CenterDot;\left\{\begin{array}{cc}\frac{-0.5}{1-e^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HSA00000122313300023.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}(i-m)/N}}+\frac{1-{(-1)}^{i-m}}{N\&CenterDot;{(1-e^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HSA00000122313300023.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}(i-m)/N})}^2}& i\&NotEqual;\mathrm{<figure-callout\; id="1"\; label="m"\; filenames="HSA00000122313300022.png"\; state="\{\{state\}\}">m</figure-callout>}\\ \frac{1}{4}-\frac{N}{8}& i=m\end{array}\right.---\left(6\right)$

$C^{r_2}(i,m)=T_s\&CenterDot;\left\{\begin{array}{cc}\frac{-0.5}{1-e^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HSA00000122313300023.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}(i-m)/N}}-\frac{1-{(-1)}^{i-m}}{N\&CenterDot;{(1-e^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HSA00000122313300023.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}(i-m)/N})}^2}& i\&NotEqual;\mathrm{<figure-callout\; id="1"\; label="m"\; filenames="HSA00000122313300022.png"\; state="\{\{state\}\}">m</figure-callout>}\\ \frac{1}{4}+\frac{N}{8}& i=m\end{array}\right.---\left(7\right)$

S103: utilize the Channel Transmission matrix that the data subcarrier in the OFDM symbol is carried out frequency domain equalization.

In step S103, according to the Channel Transmission matrix of each the OFDM symbol correspondence that obtains

Data subcarrier in the OFDM symbol is carried out frequency domain equalization, eliminate because the ICI that Doppler frequency shift causes.

Particularly, for example, frequency domain equalization can adopt ' q-tap ' channel equalization.For m subcarrier, require to eliminate the ICI that its both sides adjacent tap subcarrier causes herein, q=2tap+1 then, common tap is less.The equalizer coefficients of m subcarrier is

${\stackrel{\&RightArrow;}{g}}_m={[g_{-q,m},g_{-q+1,m},...,{\mathrm{<figure-callout\; id="0"\; label="g"\; filenames="HSA00000122313300021.png"\; state="\{\{state\}\}">g</figure-callout>}}_{0,m},...,g_{q,m}]}^T,0\&le;m<N---\left(8\right)$

If m subcarrier data is Y in certain symbol that receives _m, then need to use these subcarrier data both sides adjacent q subcarrier data m subcarrier data carried out equalization operation by formula (9), obtain getting rid of the balanced dateout of most of ICI

${\hat{X}}_m={\left({\stackrel{\&RightArrow;}{g}}_m\right)}^H{\stackrel{\&RightArrow;}{Y}}_m---\left(9\right)$

${\stackrel{\&RightArrow;}{Y}}_m={[Y_{{(m-q)}_N},Y_{{(m-q+1)}_N},...,Y_{{\left(m\right)}_N},...,Y_{{(m+q)}_N}]}^T$

Channel Transmission matrix from acquired OFDM symbol

Can obtain and m the channel matrix that subcarrier is corresponding by formula (10)

Matrix

Middle element is the Channel Transmission matrix

Element, () herein _NBe reduced to ().

Then obtain equalizer coefficients, wherein according to (10) formula

Be the power of Gaussian noise, Average power for sub-carrier signal.

${\stackrel{\&RightArrow;}{g}}_m={({\hat{H}}_m{\left({\hat{H}}_m\right)}^H+\frac{{\mathrm{\&sigma;}}_w^2}{{\mathrm{\&sigma;}}_X^2}{I}_{q\&times;q})}^{-1}\&CenterDot;{\stackrel{\&RightArrow;}{v}}_m---\left(11\right)$

${\stackrel{\&RightArrow;}{v}}_m={[H_{{(m-\mathrm{tap})}_N,m},H_{{(m-\mathrm{tap}+1)}_N,m},...,H_{m,m},...,H_{{(m+\mathrm{tap})}_N,m}]}^T$

The method of interference eliminated between above-mentioned ofdm system sub-carriers can be applied to the CMMB system; frame of CMMB system comprises the time slot of 40 same structures; structure of time slot comprises that sender unit identification sequence (TXID), two length are the OFDM symbol that 2048 synchronizing sequence and 53 length are at 4096; the protection gap length of OFDM symbol is 512, and each OFDM symbol has 384 scattered pilots.For example, get N in the present embodiment _c=2 o'clock, used adjacent N when the CMMB system asks the Channel Transmission matrix of each symbol correspondence _cIndividual symbol, when asking the Channel Transmission matrix of n OFDM symbol correspondence:

When 1≤n≤51, the slope that utilizes n-1 and n+1 sign computation channel footpath gain linearity to change; Work as n=0, use second long synchronizing sequence LSYNC1 and the 1st slope that OFDM sign computation channel footpath gain linearity changes in the time slot; Work as n=52, use the 1st slope that long synchronizing sequence LSYNC0 calculating channel footpath gain linearity changes in the 51st OFDM symbol and next time slot.

The said method that the present invention proposes, solved because the relative motion between transmitting terminal and the receiving terminal produces Doppler frequency shift, cause the problem disturbed between subcarrier, the algorithm of the interference eliminated that embodiments of the invention propose is simple, do not need a large amount of memory spaces during calculating,, utilize frequency domain equalization to eliminate ICI by utilizing pilot frequency information structure Channel Transmission matrix, the technical scheme that embodiments of the invention propose can be resisted bigger Doppler frequency shift.The technical scheme that embodiments of the invention propose, rationally efficient using system resource, optimization system performance.In addition, the technical scheme that embodiments of the invention propose, very little to the change of existing system, can not influence the compatibility of system, and realize simple, efficient.

As shown in Figure 3, the structural representation for interference blanking unit 100 between the ofdm system sub-carriers comprises receiver module 110, channel estimation module 120 and balance module 130.

Wherein, receiver module 110 is used to receive ofdm signal.

Channel estimation module 120 is used for extracting according to the ofdm signal that receives the pilot frequency information of OFDM symbol, obtains time domain channel shock response, and utilizes the time domain channel shock response of adjacent three OFDM symbols to generate the Channel Transmission matrix of this OFDM symbol correspondence

Particularly, channel estimation module 120 obtains time domain channel shock response and comprises:

120 pairs of n time domain OFDM symbols of channel estimation module carry out obtaining its frequency-domain OFDM symbol after the FFT conversion

From Y ⁿThe middle pilot frequency locations place information of extracting

Obtaining pilot frequency locations place channel response is Wherein the OFDM symbol lengths is N, and circulating prefix-length is G, G＜N, and channel latency length v≤G is in the medium arranged spaced L of frequency-domain OFDM symbol＞v pilot tone

l _i=(iN)/and L, 0≤i＜L;

120 pairs of channel estimation modules

The IFFT that does length and be L obtains time domain channel shock response

120 pairs of channel estimation modules

Carry out filtering, when

During less than predetermined threshold, order ${\hat{h}}_{l_i}^n=\mathrm{0,0}\&le;i<L.$

Particularly, channel estimation module 120 utilizes the time domain channel shock response of adjacent three OFDM symbols to generate the Channel Transmission matrix of this OFDM symbol correspondence

May further comprise the steps:

Channel estimation module 120 utilizes adjacent three OFDM symbols

With

Obtain the slope that each footpath of channel changes between adjacent-symbol:

0≤k＜G wherein; 120 pairs of channel estimation modules are filtered

And

With

Be the FFT that length is N, obtain

${\hat{H}}_{\mathrm{mid}}=\mathrm{diag}\left\{\mathrm{FFT}\left(\right[{\hat{h}}_0^n,{\hat{h}}_1^n,...,{\hat{h}}_{G-1}^n,0,...,0\left]\right)\right\},$

${\hat{H}}_{\mathrm{slpoe}}^{{\mathrm{<figure-callout\; id="1"\; label="r"\; filenames="HSA00000122313300022.png"\; state="\{\{state\}\}">r</figure-callout>}}_1}=\mathrm{diag}\left\{\mathrm{FFT}\left(\right[{\widehat{\mathrm{\&alpha;}}}_0^{{\mathrm{<figure-callout\; id="1"\; label="r"\; filenames="HSA00000122313300022.png"\; state="\{\{state\}\}">r</figure-callout>}}_1},{\widehat{\mathrm{\&alpha;}}}_1^{{\mathrm{<figure-callout\; id="1"\; label="r"\; filenames="HSA00000122313300022.png"\; state="\{\{state\}\}">r</figure-callout>}}_1},...,{\widehat{\mathrm{\&alpha;}}}_{G-1}^{{\mathrm{<figure-callout\; id="1"\; label="r"\; filenames="HSA00000122313300022.png"\; state="\{\{state\}\}">\; <figure-callout\; id="0"\; label="r"\; filenames="HSA00000122313300021.png"\; state="\{\{state\}\}">r</figure-callout>\; </figure-callout>}}_1},0,...0\left]\right)\right\},$

${\hat{H}}_{\mathrm{slpoe}}^{{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="HSA00000122313300023.png"\; state="\{\{state\}\}">r</figure-callout>}}_2}=\mathrm{diag}\left\{\mathrm{FFT}\left(\right[{\widehat{\mathrm{\&alpha;}}}_0^{{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="HSA00000122313300023.png"\; state="\{\{state\}\}">r</figure-callout>}}_2},{\widehat{\mathrm{\&alpha;}}}_1^{{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="HSA00000122313300023.png"\; state="\{\{state\}\}">r</figure-callout>}}_2},...,{\widehat{\mathrm{\&alpha;}}}_{G-1}^{{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="HSA00000122313300023.png"\; state="\{\{state\}\}">\; <figure-callout\; id="0"\; label="r"\; filenames="HSA00000122313300021.png"\; state="\{\{state\}\}">r</figure-callout>\; </figure-callout>}}_2},0,...0\left]\right)\right\};$

Channel estimation module 120 is by N * N coefficient matrix

With

Obtain this OFDM symbol transmission matrix

Wherein, coefficient matrix

With

The element of the capable m row of i is

$C^{r_1}(i,m)=T_s\&CenterDot;\left\{\begin{array}{cc}\frac{-0.5}{1-e^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HSA00000122313300023.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}(i-m)/N}}+\frac{1-{(-1)}^{i-m}}{N\&CenterDot;{(1-e^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HSA00000122313300023.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}(i-m)/N})}^2}& i\&NotEqual;\mathrm{<figure-callout\; id="1"\; label="m"\; filenames="HSA00000122313300022.png"\; state="\{\{state\}\}">m</figure-callout>}\\ \frac{1}{4}-\frac{N}{8}& i=m\end{array}\right.,$

$C^{r_2}(i,m)=T_s\&CenterDot;\left\{\begin{array}{cc}\frac{-0.5}{1-e^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HSA00000122313300023.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}(i-m)/N}}-\frac{1-{(-1)}^{i-m}}{N\&CenterDot;{(1-e^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="HSA00000122313300023.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}(i-m)/N})}^2}& i\&NotEqual;\mathrm{<figure-callout\; id="1"\; label="m"\; filenames="HSA00000122313300022.png"\; state="\{\{state\}\}">m</figure-callout>}\\ \frac{1}{4}+\frac{N}{8}& i=m\end{array}\right..$

Balance module 130 is used for the Channel Transmission matrix according to each the OFDM symbol correspondence that obtains

Data subcarrier in the OFDM symbol is carried out frequency domain equalization, eliminate because the ICI that Doppler frequency shift causes.

Particularly, balance module 130 adopts frequency domain ' q-tap ' channel equalization, for m subcarrier, eliminates the ICI that its both sides adjacent tap subcarrier causes, and the equalizer coefficients of m subcarrier is

0≤m＜N, m subcarrier data is Y in a symbol that receives _m, q the subcarrier data adjacent with these subcarrier data both sides carries out equalization operation as follows to m subcarrier data, obtains getting rid of the balanced dateout of most of ICI

Wherein

${\stackrel{\&RightArrow;}{g}}_m={({\hat{H}}_m{\left({\hat{H}}_m\right)}^H+\frac{{\mathrm{\&sigma;}}_{\mathrm{<figure-callout\; id="2"\; label="w"\; filenames="HSA00000122313300023.png"\; state="\{\{state\}\}">w</figure-callout>}}^2}{{\mathrm{\&sigma;}}_X^2}{I}_{q\&times;q})}^{-1}\&CenterDot;{\stackrel{\&RightArrow;}{v}}_m,$ ${\stackrel{\&RightArrow;}{v}}_m={[H_{{(m-\mathrm{tap})}_N,m},H_{{(m-\mathrm{tap}+1)}_N,m},...,H_{m,m},...,H_{{(m+\mathrm{tap})}_N,m}]}^T,$ Channel Transmission matrix from acquired OFDM symbol

Obtain and m the channel matrix that subcarrier is corresponding

Matrix

Middle element is the Channel Transmission matrix

Element:

Be the power of Gaussian noise, Average power for sub-carrier signal.

The said apparatus that the present invention proposes, solved because the relative motion between transmitting terminal and the receiving terminal produces Doppler frequency shift, cause the problem disturbed between subcarrier, the algorithm of the interference eliminated that embodiments of the invention propose is simple, do not need a large amount of memory spaces during calculating,, utilize frequency domain equalization to eliminate ICI by utilizing pilot frequency information structure Channel Transmission matrix, the technical scheme that embodiments of the invention propose can be resisted bigger Doppler frequency shift.The technical scheme that embodiments of the invention propose, rationally efficient using system resource, optimization system performance.In addition, the technical scheme that embodiments of the invention propose, very little to the change of existing system, can not influence the compatibility of system, and realize simple, efficient.

For the ease of understanding the present invention,, technique scheme is further elaborated below in conjunction with the CMMB system.

Frame comprises the time slot of 40 same structures in the CMMB system; structure of time slot as shown in Figure 4; comprise that a length is that 256 sender unit identification sequence (TXID), two length are the OFDM symbol that 2048 synchronizing sequence (LSYNC) and 53 length are at 4096; the Cyclic Prefix of OFDM symbol (CP) length is 512; the Cyclic Prefix of TXID (CP_ID) length is 104, and protection (GD) length at interval is 24.Each OFDM symbol has 384 scattered pilots, the scattered pilot allocation plan as shown in Figure 5, in each time slot in n OFDM symbol effective subcarrier number m value rule of scattered pilot correspondence see formula (EXA-1).

$\mathrm{if}\mathrm{mod}(n,2)==0$

$m=\left\{\begin{array}{cc}8p+1,& p=\mathrm{0,1,2},...,191\\ 8p+3,& p=\mathrm{192,193,194},...,383\end{array}\right.---(\mathrm{EXA}-1)$

$\mathrm{if}\mathrm{mod}(n,2)==1$

$m=\left\{\begin{array}{cc}8p+5,& p=\mathrm{0,1,2},...,191\\ 8p+7,& p=\mathrm{192,193,194},...,383\end{array}\right.$

The present invention is applied to signal processing schematic diagram corresponding in the CMMB system as shown in Figure 6.

As embodiments of the invention, at first generate coefficient matrix

With

Generate coefficient matrix according to formula (6) and (7)

With

And storage, wherein N=4096.Obviously, also can in the subsequent calculations process, calculate in real time according to (6) and (7)

With

In element, and need not store in advance.

, need to scattered pilot extract, obtain time domain channel shock response, be specially thereafter:

For n OFDM symbol in each time slot,, press formula (EXA-1) at 384 scattered pilots of frequency domain extraction according to the parity of its sequence number

0≤i＜384.Centre position in the scattered pilot sequence is mended 128 0, is formed with the scattered pilot sequence of 512 elements

Scattered pilot sequence P to n OFDM symbol ⁿBe 512 IFFT, obtain 512 channel impulse response sequence

Obtain the channel impulse response sequence

After, carry out Filtering Processing, be specially: set threshold value λ＞0, make

The time,

0≤i＜512.

The sequence that after filtering, obtains

The centre position mends 0, makes Length reach 4096.To mending after 0

Be 4096 FFT, obtain

The domain channel response that utilization is tried to achieve is the linear slope that changes between adjacent OFDM symbol

Be specially:

Calculate the slope of adjacent 3 OFDM intersymbol frequency domain channel response linear variation according to formula (EXA-2).

${\widehat{\mathrm{\&Lambda;}}}_{\mathrm{<figure-callout\; id="1"\; label="k\; r"\; filenames="HSA00000122313300022.png"\; state="\{\{state\}\}">k</figure-callout>}}^{r_{}}=\frac{{\hat{H}}_k^n-{\hat{H}}_k^{n-1}}{4096+24+512},0\&le;k<4096---(\mathrm{EXA}-2)$

${\widehat{\mathrm{\&Lambda;}}}_{\mathrm{<figure-callout\; id="2"\; label="k\; r"\; filenames="HSA00000122313300023.png"\; state="\{\{state\}\}">k</figure-callout>}}^{r_{}}=\frac{{\hat{H}}_k^{n+1}-{\hat{H}}_k^n}{4096+24+512}$

Distinguishingly, when n=0, utilize the 2nd long synchronizing sequence (LSYNC1) in this time slot to obtain the slope of frequency domain channel response linear variation.Because the emission data of long synchronizing sequence are known, so (being 2048 FFT) can obtain 2048 domain channel response after obtaining frequency domain LSYNC.Again its domain channel response of 2048 is done the time domain channel response that 2048 IFFT obtains this position, and carry out filtering by the filtering method in the 5th step.The position is inserted 2048 0 therebetween afterwards, and carries out FFT and obtain 4096 domain channel response

(EXA-3) formula of pressing obtains the slope of the 2nd long synchronizing sequence and the 0th OFDM intersymbol frequency domain channel response linear variation of this time slot, this position

Calculate by (EXA-2) formula,

${\widehat{\mathrm{\&Lambda;}}}_{\mathrm{<figure-callout\; id="1"\; label="k\; r"\; filenames="HSA00000122313300022.png"\; state="\{\{state\}\}">k</figure-callout>}}^{r_{}}=\frac{{\hat{H}}_k^0-{\hat{H}}_{\mathrm{<figure-callout\; id="2"\; label="k\; lsync"\; filenames="HSA00000122313300023.png"\; state="\{\{state\}\}">k</figure-callout>}}^{\mathrm{lsync}}}{3608}---(\mathrm{EXA}-3)$

When n=52, utilize first long synchronizing sequence (LSYNC0) in next time slot to obtain the slope of frequency domain channel response linear variation, concrete grammar is identical with the channel response method of asking the LSYNC1 place, and (EXA-4) formula of pressing obtains the slope of the 1st long synchronizing sequence of next time slot and the 52nd OFDM intersymbol frequency domain channel response linear variation of this time slot, this position

Calculate by (EXA-2) formula,

${\widehat{\mathrm{\&Lambda;}}}_{\mathrm{<figure-callout\; id="2"\; label="k\; r"\; filenames="HSA00000122313300023.png"\; state="\{\{state\}\}">k</figure-callout>}}^{r_{}}=\frac{{\hat{H}}_k^{\mathrm{lsync}1}-{\hat{H}}_{\mathrm{<figure-callout\; id="52"\; label="k"\; filenames="HSA00000122313300021.png"\; state="\{\{state\}\}">k</figure-callout>}}^{52}}{3456}---(\mathrm{EXA}-4)$

In the foregoing description, the domain channel response of acquisition

Be exactly diagonal matrix H _MidIn element.

Further obtain diagonal matrix

With

Wherein, obtain in the foregoing description

With

Constitute diagonal matrix respectively With

Element.

Generate the Channel Transmission matrix of n OFDM symbol correspondence thereafter,

Promptly generate the Channel Transmission matrix of n OFDM symbol correspondence by formula (5)

As embodiments of the invention, in the CMMB system, use ' q_tap ' frequency-domain equalizer, at computation complexity and remove take all factors into consideration between the validity of ICI can select a suitable ' tap ' value (as tap=2,3 etc., so that the matrix inversion process is oversimplified), q=2tap+1.

If m subcarrier data in the OFDM symbol carried out equilibrium, need be from the Channel Transmission matrix of this symbol correspondence

Obtain corresponding element, obtain matrix

Suc as formula (EXA-5), () ₄₀₉₆Be reduced to ().

Again by Obtain equalizer coefficients according to formula (EXA-6) corresponding to current subcarrier

${\stackrel{\&RightArrow;}{g}}_m={({\hat{H}}_m{\left({\hat{H}}_m\right)}^H+\frac{{\mathrm{\&sigma;}}_{\mathrm{<figure-callout\; id="2"\; label="w"\; filenames="HSA00000122313300023.png"\; state="\{\{state\}\}">w</figure-callout>}}^2}{{\mathrm{\&sigma;}}_X^2}{I}_{q\&times;q})}^{-1}\&CenterDot;{\stackrel{\&RightArrow;}{v}}_m---(\mathrm{EXA}-6)$

${\stackrel{\&RightArrow;}{v}}_m={[H_{{(m-\mathrm{tap})}_N,m},H_{{(m-\mathrm{tap}+1)}_N,m},...,H_{m,m},...,H_{{(m+\mathrm{tap})}_N,m}]}^T$

After obtaining equalizer coefficients corresponding to m subcarrier

(EXA-7) carries out equilibrium treatment to m subcarrier according to formula, the subcarrier data behind the ICI that can be eliminated

${\stackrel{\&RightArrow;}{Y}}_m={[Y_{{(m-q)}_N},Y_{{(m-q+1)}_N},...,Y_{{\left(m\right)}_N},...,Y_{{(m+q)}_N}]}^T---(\mathrm{EXA}-7)$

${\hat{X}}_m={\left({\stackrel{\&RightArrow;}{g}}_m\right)}^H{\stackrel{\&RightArrow;}{Y}}_m$

One of ordinary skill in the art will appreciate that and realize that all or part of step that the foregoing description method is carried is to instruct relevant hardware to finish by program, described program can be stored in a kind of computer-readable recording medium, this program comprises one of step or its combination of method embodiment when carrying out.

In addition, each functional unit in each embodiment of the present invention can be integrated in the processing module, also can be that the independent physics in each unit exists, and also can be integrated in the module two or more unit.Above-mentioned integrated module both can adopt the form of hardware to realize, also can adopt the form of software function module to realize.If described integrated module realizes with the form of software function module and during as independently production marketing or use, also can be stored in the computer read/write memory medium.

The above-mentioned storage medium of mentioning can be a read-only memory, disk or CD etc.

The above only is a preferred implementation of the present invention; should be pointed out that for those skilled in the art, under the prerequisite that does not break away from the principle of the invention; can also make some improvements and modifications, these improvements and modifications also should be considered as protection scope of the present invention.

Claims (10)

1. the method for interference eliminated between an ofdm system sub-carriers is characterized in that, may further comprise the steps:

Pilot frequency information according in the ofdm signal extraction OFDM symbol that receives obtains time domain channel shock response;

Utilize the time domain channel shock response of adjacent three OFDM symbols to generate the Channel Transmission matrix of this OFDM symbol correspondence

Channel Transmission matrix according to each the OFDM symbol correspondence that obtains

Data subcarrier in the OFDM symbol is carried out frequency domain equalization, eliminate because the ICI that Doppler frequency shift causes.

2. the method for interference eliminated is characterized in that between ofdm system sub-carriers as claimed in claim 1, obtains time domain channel shock response and comprises:

N time domain OFDM symbol carried out obtaining its frequency-domain OFDM symbol after the FFT conversion

From Y ⁿThe middle pilot frequency locations place information of extracting

Obtaining pilot frequency locations place channel response is

Wherein the OFDM symbol lengths is N, and circulating prefix-length is G, G＜N, and channel latency length v≤G is in the medium arranged spaced L of frequency-domain OFDM symbol＞v pilot tone

l _i=(iN)/and L, 0≤i＜L;

Right

The IFFT that does length and be L obtains time domain channel shock response ${\hat{h}}_l^n=\{{\hat{h}}_{l_0}^n,{\hat{h}}_{l_1}^n,\&CenterDot;\&CenterDot;\&CenterDot;,{\hat{h}}_{l_{L-1}}^n\};$

Right

Carry out filtering, when

During less than predetermined threshold, order

3. the method for interference eliminated is characterized in that between ofdm system sub-carriers as claimed in claim 2, utilizes the time domain channel shock response of adjacent three OFDM symbols to generate the Channel Transmission matrix of this OFDM symbol correspondence

May further comprise the steps:

Utilize adjacent three OFDM symbols

With

Obtain the slope that each footpath of channel changes between adjacent-symbol:

0≤k＜G wherein;

To filtered

And

With

Be the FFT that length is N, obtain

${\hat{H}}_{\mathrm{mid}}=\mathrm{diag}\left\{\mathrm{FFT}\left(\right[{\hat{h}}_0^n,{\hat{h}}_1^n,\&CenterDot;\&CenterDot;\&CenterDot;,{\hat{h}}_{G-1}^n,0,\&CenterDot;\&CenterDot;\&CenterDot;,0\left]\right)\right\},$

${\hat{H}}_{\mathrm{slpoe}}^{r_1}=\mathrm{diag}\left\{\mathrm{FFT}\left(\right[{\widehat{\mathrm{\&alpha;}}}_0^{r_1},{\widehat{\mathrm{\&alpha;}}}_1^{r_1},\&CenterDot;\&CenterDot;\&CenterDot;,{\widehat{\mathrm{\&alpha;}}}_{G-1}^{r_1},0,\&CenterDot;\&CenterDot;\&CenterDot;0\left]\right)\right\},$

${\hat{H}}_{\mathrm{slpoe}}^{r_2}=\mathrm{diag}\left\{\mathrm{FFT}\left(\right[{\widehat{\mathrm{\&alpha;}}}_0^{r_2},{\widehat{\mathrm{\&alpha;}}}_1^{r_2},\&CenterDot;\&CenterDot;\&CenterDot;,{\widehat{\mathrm{\&alpha;}}}_{G-1}^{r_2},0,\&CenterDot;\&CenterDot;\&CenterDot;0\left]\right)\right\};$

By N * N coefficient matrix

With Obtain this OFDM symbol transmission matrix

Wherein, coefficient matrix

With

The element of the capable m row of i is

$C^{r_1}(i,m)=T_s\&CenterDot;\left\{\begin{array}{cc}\frac{-0.5}{1-e^{-j2\mathrm{\&pi;}(i-m)/N}}+\frac{1-{(-1)}^{i-m}}{N\&CenterDot;{(1-e^{-j2\mathrm{\&pi;}(i-m)/N})}^2}& i\&NotEqual;m\\ \frac{1}{4}-\frac{N}{8}& i=m\end{array}\right.,$

$C^{r_2}(i,m)=T_s\&CenterDot;\left\{\begin{array}{cc}\frac{-0.5}{1-e^{-j2\mathrm{\&pi;}(i-m)/N}}-\frac{1-{(-1)}^{i-m}}{N\&CenterDot;{(1-e^{-j2\mathrm{\&pi;}(i-m)/N})}^2}& i\&NotEqual;m\\ \frac{1}{4}+\frac{N}{8}& i=m\end{array}\right..$

4. the method for interference eliminated between ofdm system sub-carriers as claimed in claim 3, it is characterized in that described frequency domain equalization adopts ' q-tap ' channel equalization, for m subcarrier, eliminate the ICI that its both sides adjacent tap subcarrier causes, the equalizer coefficients of m subcarrier is

0≤m＜N, m subcarrier data is Y in a symbol that receives _m, q the subcarrier data adjacent with these subcarrier data both sides carries out equalization operation as follows to m subcarrier data, obtains getting rid of the balanced dateout of most of ICI Wherein

${\stackrel{\&RightArrow;}{g}}_m={({\hat{H}}_m{\left({\hat{H}}_m\right)}^H+\frac{{\mathrm{\&sigma;}}_w^2}{{\mathrm{\&sigma;}}_X^2}{I}_{q\&times;q})}^{-1}\&CenterDot;{\stackrel{\&RightArrow;}{v}}_m,$ ${\stackrel{\&RightArrow;}{v}}_m={[H_{{(m-\mathrm{tap})}_N,m},H_{{(m-\mathrm{tap}+1)}_N,m},\&CenterDot;\&CenterDot;\&CenterDot;,H_{m,m},\&CenterDot;\&CenterDot;\&CenterDot;,H_{{(m+\mathrm{tap})}_N,m}]}^T,$

Channel Transmission matrix from acquired OFDM symbol

Obtain and m the channel matrix that subcarrier is corresponding Matrix

Middle element is the Channel Transmission matrix Element:

,

Be the power of Gaussian noise, Average power for sub-carrier signal.

5. the method for interference eliminated between ofdm system sub-carriers as claimed in claim 4; it is characterized in that; the method of interference eliminated is applied to the CMMB system between described ofdm system sub-carriers; frame of described CMMB system comprises the time slot of 40 same structures; described structure of time slot comprises that sender unit identification sequence (TXID), two length are the OFDM symbol that 2048 synchronizing sequence and 53 length are at 4096; the protection gap length of described OFDM symbol is 512, and each OFDM symbol has 384 scattered pilots.

6. the method for interference eliminated is characterized in that between ofdm system sub-carriers as claimed in claim 5, described N _c=2, used adjacent N when described CMMB system asks the Channel Transmission matrix of each symbol correspondence _cIndividual symbol, when asking the Channel Transmission matrix of n OFDM symbol correspondence:

When 1≤n≤51, the slope that utilizes n-1 and n+1 sign computation channel footpath gain linearity to change;

Work as n=0, use second long synchronizing sequence LSYNC1 and the 1st slope that OFDM sign computation channel footpath gain linearity changes in the time slot;

Work as n=52, use the 1st slope that long synchronizing sequence LSYNC0 calculating channel footpath gain linearity changes in the 51st OFDM symbol and next time slot.

7. the device of interference eliminated between an ofdm system sub-carriers is characterized in that, comprises receiver module, channel estimation module and balance module,

Described receiver module is used to receive ofdm signal;

Described channel estimation module, be used for extracting the pilot frequency information of OFDM symbol according to the ofdm signal that receives, obtain time domain channel shock response, and utilize the time domain channel shock response of adjacent three OFDM symbols to generate the Channel Transmission matrix of this OFDM symbol correspondence

Described balance module is used for the Channel Transmission matrix according to each the OFDM symbol correspondence that obtains

Data subcarrier in the OFDM symbol is carried out frequency domain equalization, eliminate because the ICI that Doppler frequency shift causes.

8. the device of interference eliminated is characterized in that between ofdm system sub-carriers as claimed in claim 7, and described channel estimation module obtains time domain channel shock response and comprises:

Described channel estimation module carries out obtaining its frequency-domain OFDM symbol after the FFT conversion to n time domain OFDM symbol

From Y ⁿThe middle pilot frequency locations place information of extracting

Obtaining pilot frequency locations place channel response is

Wherein the OFDM symbol lengths is N, and circulating prefix-length is G, G＜N, and channel latency length v≤G is in the medium arranged spaced L of frequency-domain OFDM symbol＞v pilot tone

l _i=(iN)/and L, 0≤i＜L;

Described channel estimation module is right

The IFFT that does length and be L obtains time domain channel shock response

Described channel estimation module is right Carry out filtering, when During less than predetermined threshold, order ${\hat{h}}_{l_i}^n=\mathrm{0,0}\&le;i<L.$

9. the device of interference eliminated is characterized in that between ofdm system sub-carriers as claimed in claim 8, and described channel estimation module utilizes the time domain channel shock response of adjacent three OFDM symbols to generate the Channel Transmission matrix of this OFDM symbol correspondence

May further comprise the steps:

Described channel estimation module utilizes adjacent three OFDM symbols

With Obtain the slope that each footpath of channel changes between adjacent-symbol:

0≤k＜G wherein;

Described channel estimation module is to filtered

And With Be the FFT that length is N, obtain

${\hat{H}}_{\mathrm{mid}}=\mathrm{diag}\left\{\mathrm{FFT}\left(\right[{\hat{h}}_0^n,{\hat{h}}_1^n,\&CenterDot;\&CenterDot;\&CenterDot;,{\hat{h}}_{G-1}^n,0,\&CenterDot;\&CenterDot;\&CenterDot;,0\left]\right)\right\},$

${\hat{H}}_{\mathrm{slpoe}}^{r_1}=\mathrm{diag}\left\{\mathrm{FFT}\left(\right[{\widehat{\mathrm{\&alpha;}}}_0^{r_1},{\widehat{\mathrm{\&alpha;}}}_1^{r_1},\&CenterDot;\&CenterDot;\&CenterDot;,{\widehat{\mathrm{\&alpha;}}}_{G-1}^{r_1},0,\&CenterDot;\&CenterDot;\&CenterDot;0\left]\right)\right\},$

${\hat{H}}_{\mathrm{slpoe}}^{r_2}=\mathrm{diag}\left\{\mathrm{FFT}\left(\right[{\widehat{\mathrm{\&alpha;}}}_0^{r_2},{\widehat{\mathrm{\&alpha;}}}_1^{r_2},\&CenterDot;\&CenterDot;\&CenterDot;,{\widehat{\mathrm{\&alpha;}}}_{G-1}^{r_2},0,\&CenterDot;\&CenterDot;\&CenterDot;0\left]\right)\right\};$

Described channel estimation module is by N * N coefficient matrix

With

Obtain this OFDM symbol transmission matrix

Wherein, coefficient matrix

With

The element of the capable m row of i is

$C^{r_1}(i,m)=T_s\&CenterDot;\left\{\begin{array}{cc}\frac{-0.5}{1-e^{-j2\mathrm{\&pi;}(i-m)/N}}+\frac{1-{(-1)}^{i-m}}{N\&CenterDot;{(1-e^{-j2\mathrm{\&pi;}(i-m)/N})}^2}& i\&NotEqual;m\\ \frac{1}{4}-\frac{N}{8}& i=m\end{array}\right.,$

$C^{r_2}(i,m)=T_s\&CenterDot;\left\{\begin{array}{cc}\frac{-0.5}{1-e^{-j2\mathrm{\&pi;}(i-m)/N}}-\frac{1-{(-1)}^{i-m}}{N\&CenterDot;{(1-e^{-j2\mathrm{\&pi;}(i-m)/N})}^2}& i\&NotEqual;m\\ \frac{1}{4}+\frac{N}{8}& i=m\end{array}\right..$

10. the device of interference eliminated between ofdm system sub-carriers as claimed in claim 9, it is characterized in that described balance module adopts frequency domain ' q-tap ' channel equalization, for m subcarrier, eliminate the ICI that its both sides adjacent tap subcarrier causes, the equalizer coefficients of m subcarrier is

M subcarrier data is Y in a symbol that receives _m, q the subcarrier data adjacent with these subcarrier data both sides carries out equalization operation as follows to m subcarrier data, obtains getting rid of the balanced dateout of most of ICI

Wherein

${\stackrel{\&RightArrow;}{g}}_m={({\hat{H}}_m{\left({\hat{H}}_m\right)}^H+\frac{{\mathrm{\&sigma;}}_w^2}{{\mathrm{\&sigma;}}_X^2}{I}_{q\&times;q})}^{-1}\&CenterDot;{\stackrel{\&RightArrow;}{v}}_m,$ ${\stackrel{\&RightArrow;}{v}}_m={[H_{{(m-\mathrm{tap})}_N,m},H_{{(m-\mathrm{tap}+1)}_N,m},\&CenterDot;\&CenterDot;\&CenterDot;,H_{m,m},\&CenterDot;\&CenterDot;\&CenterDot;,H_{{(m+\mathrm{tap})}_N,m}]}^T,$

Channel Transmission matrix from acquired OFDM symbol

Obtain and m the channel matrix that subcarrier is corresponding

Matrix

Middle element is the Channel Transmission matrix

Element:

,

Be the power of Gaussian noise,

Average power for sub-carrier signal.

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