CN104904172A - Method for estimating and removing DC offset - Google Patents

Abstract

The present invention relates to a method in a direct conversion receiver for estimating and removing DC offset, said direct conversion receiver being arranged to receive radio communication signals in a wireless communication system, the method comprising the steps of: receiving and down sampling time domain signals, wherein said time domain signals comprise at least one first synchronisation signal; estimating a residual DC offset Delta d based on said at least one first synchronisation signal; computing a refined DC offset estimation d~ based on said estimated residual DC offset Delta d; and applying said refined DC offset estimation d~ on said time domain signals so as to remove DC offset from said time domain signals. Furthermore, the invention also relates to a receiver device, a computer program, and a computer program product thereof.

Description

The method of estimation and removal DC skew

Technical field

The present invention relates to the method for the DC skew of a kind of estimation and removal Direct Conversion Receiver.In addition, the invention still further relates to a kind of receiver device, computer program and computer program thereof.

Background technology

Direct current (DC) skew is the subject matter that Direct Conversion Receiver faces.Part local oscillator (LO) signal down-converts to baseband signal, this can cause unnecessary DC skew (see by Rainer Stuhlberger, R.Krueger, B.Adler, J.Kissing, " the descending performance of LTE when there is rf injury " that L.Maurer, G.Hueber and A.Springer etc. propose jointly, is loaded in the minutes the 189 to 192 page of the tenth the European Wireless technology conference held in October, 2007).

If DC migration processing is improper, Cell searching and data demodulates performance can be affected.Such as, in Long Term Evolution (LTE) system, Cell searching needs relativity of time domain, and unnecessary DC skew can destroy the correlation of Cell searching synchronizing signal.Although direct current subcarrier is also not used in the transfer of data of LTE system, channel condition information (CSI) estimation for DC component can be subject to the impact of DC skew, and DC skew directly affects the performance of LTE system.Therefore, before receiver side carries out data demodulates and decoding, estimation and the compensation of DC skew seem most important.

In LTE system, the compensation method of DC skew relates generally to two kinds of prior art modes, that is:

Notch filter or high pass filter mode-notch filter or high pass filter are a kind of digital filter circuits, provide the trap of the frequency corresponding with DC deviation frequency, thus can remove DC offset component from the signal received.

Mean value mode-the method for getting the sampling that time domain receives comprises the mean value got and receive sampling, to estimate that DC offsets.

Notch filter or high pass filter mode need the transition time grown very much, but also can make noise power spectral density distortion, thus increase the complexity of albefaction distortion noise.In LTE, DC offset units also needs to support different bandwidth configuration, makes the design of digital filter more complicated.

Apply the method for averaging as under the scene in low signal-to-noise ratio (SNR) region and decay, the DC offset estimation undertaken by getting sample mean is inaccurate, and significantly may reduce overall performance.

From the above, in LTE system and other associated communication systems, DC skew makes time domain receive sampling distortion, thus can reduce systematic function.Therefore, obtaining DC offset estimation accurately and carried out the DC skew of compensated receiver by DC offset estimation, is very important for keeping system performance.

Summary of the invention

The object of the present invention is to provide a solution, to alleviate or to solve defect and the problem of prior art.

Another object of the present invention is, provides the solution that more perfect, to solve the problem of estimation and alleviation DC skew.

According to a first aspect of the invention, described object is achieved by the method for the DC skew estimated and remove Direct Conversion Receiver, and described Direct Conversion Receiver, for receiving the wireless communication signals in wireless communication system, said method comprising the steps of:

Receive time-domain signal and lower down-sampled, described time-domain signal comprises at least one first synchronizing signal;

Based at least one first synchronizing signal estimation residue DC shifted by delta d described;

Based on the DC offset estimation value of the residue DC shifted by delta d calculation optimization of described estimation

The DC deviant of described optimization is estimated be applied to described time-domain signal, to remove DC skew from described time-domain signal.

The preferred embodiment of said method is loaded in the claim of enclosing.

The method can also perform with processing modes such as computers.Described method can be included in computer program.

According to a second aspect of the invention, above-mentioned purpose is achieved by Direct Conversion Receiver equipment, described Direct Conversion Receiver equipment for receiving the wireless communication signals in wireless communication system, described Direct Conversion Receiver equipment also for:

Receive time-domain signal and lower down-sampled, described time-domain signal comprises at least one first synchronizing signal;

Based at least one first synchronizing signal estimation residue DC shifted by delta d described;

Based on the DC offset estimation value of the residue DC shifted by delta d calculation optimization of described estimation

By the DC offset estimation value of described optimization be applied to described time-domain signal, to remove DC skew from described time-domain signal.

Described Direct Conversion Receiver equipment can improve, to make it all different embodiment being applicable to this method.

The invention provides a kind of method of DC skew of more perfect estimation Direct Conversion Receiver, improve the performance of receiver.The lifting of receiver performance realizes by utilizing the first synchronizing signal estimation residue DC skew, and remain DC skew then for the DC offset estimation value of calculation optimization, this estimated value has the accuracy higher than prior art.

Further, according to preferred embodiment, the inventive method carries out joint estimate to the time domain CSI of described first synchronizing signal with residue DC skew simultaneously.Therefore, the accuracy of the CSI estimation of described first synchronizing signal can improve.The present invention also can improve accuracy and descending (DL) data performance of cell search process.Therefore, the inventive method also avoid and uses complicated notch filter or high pass filter mode, and which needs the different mode supporting different band width configuration or multimode modulator-demodulator.

Below describe other application and advantages of the present invention in detail.

Accompanying drawing explanation

Shown accompanying drawing is intended to illustrate different embodiments of the invention, and described accompanying drawing comprises:

Fig. 1 shows a kind of structure of Direct Conversion Receiver.

Fig. 2 shows the DL SCH structure under LTE fdd mode.

Fig. 3 shows the LTE system small area search procedure of receiver side.

Fig. 4 shows a kind of receiver structure that the embodiment of the present invention provides.

Fig. 5 shows a kind of structure remaining DC offset estimation.

Fig. 6 shows the flow process of DC offset estimation that the embodiment of the present invention provides and compensation method.

The specific embodiment of the invention

In order to achieve the above object and other objects, the present invention relates to a kind of estimation and remove the method for DC skew of Direct Conversion Receiver.As mentioned above, by providing DC offset estimation accurately, significantly systematic function can be improved.

According to preferred embodiment, estimation and the removal of DC skew also can combine with cell search process, such as, determine frame head, community ID, Cyclic Prefix (CP) type etc.Therefore, the complexity of calculating can be reduced when determining DC offset estimation value.Further, accuracy and the downlink data performance of cell search process can also be improved.

To DL synchronizing process and the parameter of LTE system be described below, the invention provides foundation for describing in further detail.

In LTE system, the length of radio frames is 10ms, and radio frames comprises 10 subframes (being numbered 0 to 9), and each subframe can be divided into 2 time slots, and thus each radio frames comprises 20 time slots, is numbered 0 to 19.Further, each time slot comprises several OFDMs (OFDM) symbol, this depends on CP type and sub-carrier configuration (such as, when CP type is conventional CP type, subcarrier spacing is 15kHz, a time slot comprises 7 OFDM symbol).

In LTE, no matter band width configuration how, and DL synchronizing channel (SCH) is transmitted in 6 Resource Block (RB) of 5 subframes in center/centre.SCH comprises two parts, that is: master sync signal (PSS) and auxiliary synchronous signals (SSS).According to the structure of frame, i.e. frequency division multiplexing (FDD) or time division multiplexing (TDD) pattern, SCH transmits in the diverse location of Radio Resource.

In the fdd mode, PSS is mapped in time slot 0 and time slot 10 in last OFDM symbol, and SSS is mapped in the adjacent last OFDM symbol of the OFDM symbol that is mapped to PSS.The mapping of the descending SCH RB of typical FDD as shown in Figure 2.On the other hand, in tdd mode, PSS is mapped in the 3rd OFDM symbol in subframe 1 and subframe 6, and SSS to be mapped in time slot 1 and time slot 11 in last OFDM symbol.

In addition, in LTE, SSS sequence p (n) is generated by frequency domain Zadoff-Chu sequence according to following equation:

$p_u\left(n\right)=\left\{\begin{array}{cc}{e}^{-j\frac{\mathrm{\π}un(n+1)}{63}}& n=0,1,\mathrm{...},30\\ e^{-j\frac{\mathrm{\π}u(n+1)(n+2)}{63}}& n=31,32,\mathrm{...},61\end{array}\right.$ Equation (1)

Root u is by cell sector ID determine, cell sector ID can be three values: 0,1 and 2.Root u and cell sector ID between mapping relations as follows:

N to be the FTT of 128 can be by frequency domain length 62 PSS sequence be converted to the PSS sequence that time domain length is 128:

$PSS\left(n\right)=\underset{k=0}{\overset{N-1}{\Σ}}{\stackrel{\‾}{p}}_u\left(k\right)e^{-2j\mathrm{\π}kn/N}$ Equation (2)

Wherein, frequency domain PSS sequence for zero padding:

${\stackrel{\‾}{p}}_u\left(k\right)=\left\{\begin{array}{cc}0& k=0~32,64,96~127\\ p_u(k-33)& k=33~63\\ p_u(k-65)& k=65~95\end{array}\right.$ Equation (3)

And in LTE system, cell search process depends on SCH.First, PSS detects and is applied to lower down-sampled time-domain sampling (sample rate is 1.92Mbps), obtains time slot original position with basis with the shifted correlation result of all possible local PSS sequence.After acquisition time domain PSS position, carry out continuous print SSS detection at frequency domain, to detect frame head, community ID and CP type.It is based on the correlation between the SSS frequency domain sample data received and all possible local SSS sequence at receiving terminal that SSS detects.Before carrying out SSS detection, in order to eliminate channel effect from the SSS sampled data received, the CSI estimation of PSS is used in and utilizes FFT by before SSS sequence transitions to frequency domain, carries out conjugate multiplication with the SSS sequence extracted.Fig. 3 shows the structure of above-mentioned Cell searching.

This method for Direct Conversion Receiver comprises and to receive time-domain signal and lower down-sampled, and described time-domain signal receives from the transmitter of wireless communication system.Time-domain signal should comprise at least one for realizing receiving the first synchronizing signal of data syn-chronization.After this, based at least one first synchronizing signal estimation residue DC shifted by delta d described, based on the DC offset estimation value of the residue DC shifted by delta d calculation optimization of described estimation finally, the DC offset estimation value of optimization be applied in time-domain signal, to remove DC skew from time-domain signal.Therefore, by this method, systematic function is improved.

According to the embodiment of the present invention, described method is further comprising the steps of: estimate that original DC offsets based on described lower down-sampled time-domain signal the original DC skew of described estimation is deducted from described lower down-sampled time-domain signal and based on deducting the original DC skew of described estimation decline sample time domain input described in the first synchronizing signal.That is, be offset based on deducting original DC to the detection of the first synchronizing signal decline sample time domain signal carry out.Preferably, described first synchronizing signal is the PSS in LTE system, and this also means that the second synchronizing signal is the SSS in said system type.PSS and SSS is transmitted by SCH descending.

In addition, according to further embodiment of this invention, the method is further comprising the steps of: based on described the first synchronizing signal detected, to described residue DC shifted by delta d with describedly deducted original DC and offset decline sample time domain signal in CSI carry out joint estimate.The advantage of which is previously detailed description.

Conveniently understand the present invention better, also will set forth the Mathematical Modeling receiving wireless signal below.System parameters in this example is from LTE system, but those skilled in the art can understand, and these parameter values can be different according to the difference of the wireless communication system of embody rule the method.

At receiver side, the linear model of time-domain sampling can be:

$y\[n\]=\underset{l=0}{\overset{L-1}{\Σ}}h\[l,n\]x\[n-l\]+d+w\[n\]$ Equation (4)

Wherein, x [n] is the time-domain signal of transmission, h [l, n] (l=0,1 ..., L-1) and be channel tap when sampling time n, L (L >=1) is channel delay, and d is DC skew to be evaluated, and w [n] is thermal noise.

The time-domain sampling of lower down-sampled (1.92Mbps), after accumulation after a while, obtains the original estimated value of actual DC offset d.

$\begin{array}{c}\hat{d}=\frac{1}{M}\underset{k=0}{\overset{M-1}{\Σ}}y\[k\]=\frac{1}{M}\underset{k=0}{\overset{M-1}{\Σ}}\left(\underset{l=0}{\overset{L-1}{\Σ}}h\[l,k\]x\[k-l\]+d+w\[k\]\right)\\ =d+\frac{1}{M}\underset{k=0}{\overset{M-1}{\Σ}}\left(\underset{l=0}{\overset{L-1}{\Σ}}h\[l,k\]x\[k-l\]+w\[k\]\right)\≈d\end{array},$

Wherein, M offset for original DC in concrete average time total hits of estimation.Every 5ms, maximum M=1.92MHz × 5m,s=9 600 samplings may be used for the original estimation in LTE system.Therefore, originally initial DC offset estimation is estimated as.And when Received signal strength stands frequency selective fading common in wireless communication system or when SNR is low, original estimation may have very large estimation error, cause from after described Received signal strength removes original DC offset estimation, residue DC skew is still retained in described Received signal strength.

Described master sync signal according to the residue DC offset estimation based on PSS (the first synchronizing signal) of embodiment will be set forth below: from Received signal strength, deduct original estimated value by equation (4) afterwards, time domain PSS signal can be:

$\begin{array}{c}\hat{y}\[n\]=y\[n\]-\hat{d}=\underset{l=0}{\overset{L-1}{\Σ}}h\[l,n\]PSS\[n-k-l\]+(d-\hat{d})+w\[n\]\\ n=\stackrel{\‾}{k}+L-1,\stackrel{\‾}{k}+L,\stackrel{\‾}{k}+L+1,\mathrm{...},\stackrel{\‾}{k}+L+m-2\end{array}$ Equation (5)

Wherein, PSS [n] is time domain PSS signal, and h [l, n] is l the channel tap when sampling time n, and L is channel delay, and d is DC skew, and w [n] is thermal noise, and m is the PSS length for remaining DC offset estimation.Due to h [l, n] (l=0,1 ..., L-1) and the constant in an OFDM symbol in LTE system can be assumed to be, the n in h [l, n] ignores, then equation (5) also can be written as:

$\hat{y}\[n\]=\underset{l=0}{\overset{L-1}{\Σ}}h\[l\]PSS\[n-k-l\]+(d-\hat{d})+w\[n\].$

Further, be the original position index of sampling for the reception of DC offset estimation, k is the original position of the PSS detected, k _offsetbe the PSS in order to only use part receives and selected displacement.Such as, if all PSS samplings received (but abandon in original position the sampling being subject to multipath pass effect, and that is, index n=k+L-1, k+L ..., k+L+m-2) all for DC offset estimation, so, k _offset=0, m=128-(L-1) and m=128-(L-1); If only use 64 middle PSS signals received (index n=k+32, k+33 ..., k+95), so, k _offset=33-L and m=64.

Usually, use longer sequence to carry out residue DC offset estimation and will obtain better performance, but need larger memory to carry out coefficient storage, as follows:

$\mathrm{\Δ}d=d-\hat{d}$

$Y\[m\]={(\hat{y}\[\stackrel{\‾}{k}+L-1\],\hat{y}\[\stackrel{\‾}{k}+L\],\mathrm{...},\hat{y}\[\stackrel{\‾}{k}+L+m-2\])}^T$

$P\[m\]={\left(\begin{array}{ccccc}PSS\[k_{offset}+L-1\]& PSS\[k_{offset}+L-2\]& ...& PSS\[k_{offset}\]& 1\\ PSS\[k_{offset}+L\]& PSS\[k_{offset}+L-1\]& ...& PSS\[k_{offset}+1\]& 1\\ PSS\[k_{offset}+L+1\]& PSS\[k_{offset}+L\]& ...& PSS\[k_{offset}+2\]& 1\\ ...& ...& ...& ...& ...\\ PSS\[k_{offset}+L+m-2\]& PSS\[k_{offset}+L+m-3\]& ...& PSS\[k_{offset}+m-1\]& 1\end{array}\right)}_{m\×(L+1)}$

H[L]＝(h[0],h[1],...,h[L-1])

H[L,Δd]＝(h[0],h[1],...,h[L-1],Δd) ^T＝(H[L],Δd) ^T

$W\[m\]={(w\[\stackrel{\‾}{k}+L-1\],w\[\stackrel{\‾}{k}+L\],\mathrm{...},w\[\stackrel{\‾}{k}+L+m-2\])}^T.$

So, equation (5) can be write as with a matrix type:

Y [m]=P [m] H [L, Δ d]+W [m], equation (6)

Wherein, H [L, Δ d] is the column vector comprising CSI vector H [L] and residue DC shifted by delta d.Suppose that W [m] is additive white Gaussian noise (AWGN), then ML is carried out to H [L, Δ d] and estimate that obtaining LS separates, that is:

$\hat{H}\[L,\mathrm{\Δ}d\]={(P^H\[m\]P\[m\])}^{-1}{P}^H\[m\]Y\[m\]=C\[m\]Y\[m\]$ Equation (7)

Wherein,

C [m]=(P ^h[m] P [m]) ^-1p ^h[m], equation (8)

Due to known m × (L+1) matrix that P [m] is based on local time domain PSS sequence, wherein, as shown in equation (1) and equation (2), local time domain PSS sequence be use length be 128 FFT convert from local frequency domain PSS sequence, so, C [m] is (L+1) × m matrix, and this matrix can obtain from P [m] matrix according to equation (8).For the cell sector ID that correspondence is different all (possible) three PSS sequences, can precalculate and store different Matrix C [m].For residue DC offset estimation, according to cell sector ID time search of initial zone (or known cyclic cell search) testing result, select corresponding C [m] matrix.In addition, for shown in equation (7) pSS CSI and the joint estimate method of residue DC skew be only a kind of simple matrix multiplication, that the Y [m] that selected C [m] matrix and the time domain PSS of reception sampled is multiplied, wherein, time domain PSS sampling Y [m] of reception eliminates original estimated value according to equation (5) residue DC shifted by delta d is considered, joint estimate because CSI estimates in H [L] better PSS CSI can be obtained and estimate result.

Example

Suppose channel tap L=9 (EVA or the ETU channel defined in 3GPP LTE), and DC offset estimation is carried out in 64 PSS samplings received in the middle of using.In this case, k _offset=33-L=24 and m=64.For the different cell sector ID based on equation (2) and equation (3) local time domain PSS sequence PSS (n) can be generated, n=0,1 ..., 127, and P [m] is the matrix of a kind of 64 × 10, this matrix comprises the local PSS signal that index is 24 to 95:

$P\[m\]={\left(\begin{array}{ccccc}PSS\[32\]& PSS\[31\]& ...& PSS\[24\]& 1\\ PSS\[33\]& PSS\[32\]& ...& PSS\[25\]& 1\\ PSS\[34\]& PSS\[33\]& ...& PSS\[26\]& 1\\ ...& ...& ...& ...& ...\\ PSS\[95\]& PSS\[94\]& ...& PSS\[87\]& 1\end{array}\right)}_{64\×10}.$

Coefficient C [m] adopts the form of 10 × 64 matrixes, and this matrix can corresponding all cell sector ID carry out calculating and storing.

According to embodiment, the DC skew of optimization can by the original DC skew by estimation obtain with the residue DC shifted by delta d addition calculation of estimation, the skew namely optimized is by formula obtain.This point is very important, especially when SNR is low or channel is subject to frequency selective fading, when original DC offsets be obtain by getting the mean value receiving time-domain sampling, its estimation error can cause sizable residue DC to offset, thus can reduce performance.Therefore, offset relative to original DC the DC skew optimized better estimation result can be obtained.

As mentioned above, in LTE system, SCH is always interposed between in the RB of 6, centre/center and transmits between LTE/LTE-A descending is with 5ms, and subscriber equipment also periodically will perform cell search process.Therefore, PSS may be used for estimation DC skew, thus the method according to the embodiment of the present invention can realize according to following steps:

1. get the mean value of low pass (LP) filtering sampling, wherein low-pass filtering sampling carries out lower down-sampledly to obtain with the sample rate of 1.92Mbps to original time-domain signal received, thus obtain original DC and offset estimated value.

2. from LP filtering sampling, deduct the original DC skew obtained in step 1 estimated value, and carry out PSS detection.

3., after getting the position of PSS, the time domain PSS signal being 128 based on the length extracted carries out CSI and remains the joint estimate of DC offset estimation value Δ d.

4., before carrying out SSS (the second synchronizing signal) detection and other continuous print cell search process, from LP filtering sampling, deduct residue DC offset estimation value Δ d.

5. the original DC skew will obtained in step 1 estimated value be added with the residue DC offset estimation value Δ d obtained in step 3, to obtain the DC offset estimation value of the optimization for Received signal strength data demodulates.

6. adopt Alpha's filter to carry out noise reduction to the estimated value of the optimization obtained in step 5 further.

7., before data demodulates and decoding, by original time domain sampling, DC skew is compensated.

Also illustrate the receiver device structure shown in Fig. 4 and the flow chart shown in Fig. 6 in the present embodiment.As shown in Figure 4, the DC offset estimation equipment of Fig. 4 and cell search unit merge.Transmit in 6 RB in centre every 5ms, SCH, and, initiate cell search process based on carrying out lower down-sampled reception sampling y [k].First, take off the mean value of down-sampled signal, wherein, this signal carries out lower down-sampled with the frequency of 1.92Mbps in a certain duration of every 5ms (being 5ms to the maximum), thus obtain the estimated value of original DC skew, namely then, from lower down-sampled signal, deduct original DC to offset and start PSS detection, namely

During search of initial zone, need the shifted correlation result with all three possible local PSS sequences; During cyclic cell search, only need the shifted correlation result of the PSS sequence known with.After position PSS being detected and corresponding sequence, can also joint-detection residue DC shifted by delta d and PSS CSI.Next, before SSS detects and other cell search process are carried out, residue DC skew will be removed further from sampling also residue DC skew can be combined with original estimation, to obtain the estimated value of optimization before demodulation and decoding, the DC offset estimation value of optimization can be used to compensate DC skew, and before this, the DC offset estimation value of optimization first will pass through Alpha's filter.Alpha's filter will optimize the estimation of DC skew further, thus also improves performance.

Residue DC skew and CSI joint-detection unit will be described by composition graphs 5 hereinafter.Three possible filtering matrix C [m] carry out precomputation according to predefined filter length m and store in memory.Position and the cell sector ID of PSS detected afterwards (when cyclic cell search, known), first from lower down-sampled signal, extract the PSS sequence that length is 128, then select suitable filtering matrix C [m], and utilize equation (7) to obtain joint estimate value $\hat{H}\[L,\mathrm{\Δ}d\]:$ $\hat{H}\[L,\mathrm{\Δ}d\]={(X^H\[m\]X\[m\])}^{-1}{X}^H\[m\]Y\[m\]=C\[m\]Y\[m\].$

For cell search process, further from in deduct residue DC offset estimation value Δ d, and perform SSS and detect and further cell search process.The PSS CSI of estimation can be used as the initial CSI of SSS, thus eliminates channel effect before carrying out SSS detection.

In addition, it will be understood by those skilled in the art that any method of the present invention also can the mode by code in computer program realize.When this computer program runs in the mode of process, the step of described processing mode manner of execution can be made.Computer program is included in the computer readable medium of computer program.Computer readable medium can comprise any memory substantially, such as, ROM (read-only memory), PROM (programmable read only memory), EPROM (EPROM (Erasable Programmable Read Only Memory)), flash memory, EEPROM (EEPROM (Electrically Erasable Programmable Read Only Memo)) and disc driver.

In addition, the invention still further relates to the Direct Conversion Receiver equipment corresponding with the method for the embodiment of the present invention.Described receiver device comprises be necessary mode, and for performing the inventive method, that is, described equipment can comprise: processing mode, input pattern signal, mode signal output, sample mode, storage mode, communication mode, etc.The embodiment of the present invention is used for 3GPP wireless communication system, as LTE or LTE-A.Therefore, in this case, described receiver device is the part of subscriber equipment (UE), or comprises in a user device.

Finally, it should be understood that and the invention is not restricted to above-described embodiment, also relate to and comprise all embodiments in the right of enclosing.

Claims (12)

1. Patent claim:

   1. a method for the DC skew of estimation and removal Direct Conversion Receiver, it is characterized in that, described Direct Conversion Receiver, for receiving the wireless communication signals in wireless communication system, said method comprising the steps of:

   Receive time-domain signal and lower down-sampled, described time-domain signal comprises at least one first synchronizing signal;

   Based at least one first synchronizing signal estimation residue DC shifted by delta d described;

   Based on the DC offset estimation value of the residue DC shifted by delta d calculation optimization of described estimation and

   By the DC offset estimation value of described optimization be applied to described time-domain signal, to remove DC skew from described time-domain signal.
2. 2. method according to claim 1, is characterized in that, further comprising the steps of:

   Estimate that original DC offsets based on described lower down-sampled time-domain signal

   The original DC skew of described estimation is deducted from described lower down-sampled time-domain signal and

   Based on the described decline sample time domain signal having deducted the original DC skew of estimation, detect at least one first synchronizing signal described.
3. 3. method according to claim 2, is characterized in that, further comprising the steps of:

   Based on described at least one detecting first synchronizing signal, joint estimate is carried out to the channel condition information (CSI) in described residue DC shifted by delta d and the described decline sample time domain signal having deducted the original DC skew of estimation.
4. 4. method according to claim 3, is characterized in that, further comprising the steps of:

   The residue DC shifted by delta d deducting described estimation the decline sample time domain signal of the original DC skew of estimation has been deducted from described.
5. 5. method according to claim 2, is characterized in that, the DC skew of described optimization by the original DC skew by described estimation carry out with the residue DC shifted by delta d of described estimation that addition calculation obtains, namely
6. 6. method according to claim 5, is characterized in that, further comprising the steps of:

   Alpha's filter is used to the DC skew of described optimization, thus the DC of described optimization is offset carry out noise reduction.
7. 7. method according to claim 3, is characterized in that, described time-domain signal also comprises at least one second synchronizing signal, and described method is further comprising the steps of:

   Detect at least one second synchronizing signal described; And

   Based on described lower down-sampled time-domain signal, perform cell search process step further.
8. 8. method according to claim 7, is characterized in that, described wireless communication system is 3GPP cellular system, as LTE or LTE-A; At least one first synchronizing signal described is master sync signal (PSS), and at least one second synchronizing signal described is auxiliary synchronous signals (SSS).
9. 9. a computer program, is characterized in that, this program adopts the form of code, and when running in the mode of process, this program makes described processing mode enforcement of rights require the described method of 1-8.
10. 10. a computer program, comprise computer readable medium and computer program according to claim 9, it is characterized in that, described computer program is included in described computer readable medium, and it is one or more that computer program comprises in following combination: ROM (read-only memory), PROM (programmable read only memory), EPROM (EPROM (Erasable Programmable Read Only Memory)), flash memory, EEPROM (EEPROM (Electrically Erasable Programmable Read Only Memo)) and disc driver.
11. 11. 1 kinds of Direct Conversion Receiver equipment, for receiving the wireless communication signals in wireless communication system, is characterized in that, this Direct Conversion Receiver equipment also for:

    Receive time-domain signal and lower down-sampled, described time-domain signal comprises at least one first synchronizing signal;

    Based at least one first synchronizing signal estimation residue DC shifted by delta d described;

    Based on the DC offset estimation value of the residue DC shifted by delta d calculation optimization of described estimation and

    By the DC offset estimation value of described optimization be applied to described time-domain signal, to remove DC skew from described time-domain signal.
12. 12. Direct Conversion Receiver according to claim 11, is characterized in that, described wireless communication system is 3GPP cellular system, and as LTE or LTE-A, described Direct Conversion Receiver equipment is included in subscriber equipment (UE).