CN1992700A - Time-frequency synchronization method for multi-antenna OFDM communication system - Google Patents

Abstract

The invention relates to a time-frequency synchronous method of multi-antenna orthogonal frequency-division complex communication system, wherein said method comprises that: at the sender, inserting lead sequence into the frame data of each emission antenna, while the lead sequence comprises two short PN sequences and two long PN sequences; at the receiver, receiving the data frame of each receiving antenna; based on said lead sequence, checking out frame reach time, evaluating the sample mark time shift and frequency shift of data frame, to adjust the time and frequency of data frame, to realize time-frequency synchronization.

Description

Time-frequency synchronization method in the multi-antenna OFDM communication system

Technical field

The present invention relates to the time-frequency synchronization method in a kind of multi-antenna OFDM communication system, can realize that according to time-frequency synchronization method of the present invention higher frame arrives the accuracy of parameter Estimation such as detection, symbol time skew, frequency shift (FS), still can use in the time and frequency-offset scope than broad, necessary system resource is fewer.

Background technology

Duplicating multi-antenna orthogonal frequency division (MIMO-OFDM) system is the hot issue that current industrial circle and academia pay close attention to, there have been many wireless communication systems to be based on MIMO-OFDM's, as IEEE 802.16e, IEEE802.11n etc., and MIMO-OFDM dominate in next generation mobile communication system very likely.

Adopt the main cause of MIMO-OFDM to be that the MIMO-OFDM system can provide the ability of broadband wireless access, and in broadband access, design effectively and the few targeting sequencing of resource requirement be very challenging problem.

Time-frequency synchronization appears at list of references 1 (J.Beek in the classical ofdm system, M.Sandel and P.O.Borjesson, " ML estimation of time and frequencyoffset in OFDM systems; " IEEE Trans.Signal Processing, vol.45, no.7, pp.1800-1805, July, 1997), list of references 2 (P.Moose, " Atechnique for orthogonal frequency division multiplexingfrequency offset correction; " IEEE Trans.Communications, vol.42, no.10, pp.2908-2914, Oct., 1994) and list of references 3 (F.Tufvesson, O.Edfors, and M.Faulkner, " Time and frequency synchronizationfor OFDM using PN-sequence preambles; " Pro.IEEE VTC-Fall, pp.2203-2207,1999) in.

Being summarized as follows of these synchronized algorithms: targeting sequencing generally is divided into short sequence part and long sequence part, use short sequence part, can estimate time and frequency shift scope than broad, obtain on time and the frequency thick synchronously, use long sequence part then, precise synchronization is carried out in the time and frequency shift to remnants, and this is called synchronously thin.

At list of references 4 (US 2002/0041635 A1, " Preamble design formultiple input-multiple output (MIMO); orthogonal frequencydivision multiplexing (OFDM) system) and list of references 5 (US2002/0122382 A1; " Synchronization in a multiple-input/multiple-output (MIMO) orthogonal frequency divisionmultiplexing (OFDM) system for wireless applications ") in; a kind of targeting sequencing method for designing has been proposed; briefly be described below: after frame arrives; at first to obtain symbol time synchronous by the pseudo noise sequence on the time domain (PN) is mated, obtain integral multiple subcarrier spacing frequency deviation (abbreviation integer frequency bias) estimation by mating then, carry out the estimation of decimal gall nut carrier spacing frequency deviation (abbreviation decimal frequency bias) at last with the pseudo noise sequence on the frequency domain.

It should be noted that time, frequency deviation range, the accuracy of Time and Frequency Synchronization and necessary targeting sequencing length are to need emphasis to consider in the MIMO-OFDM Communication System Design.

For the time-frequency synchronization method in the list of references 1,2,3, time and frequency-offset scope and accuracy are a pair of contradiction, promptly the deviation range that will allow to correct is enough big, then accuracy is just lower, and to make the accuracy height, then the scope that can correct is just smaller, solve this contradiction, must use two groups of targeting sequencings: short sequence and long sequence, this must expend more system resource.

List of references 4,5 improves this contradiction, can use one group of targeting sequencing under the big situation of time migration, just can obtain than higher accuracy, but when if frequency shift (FS) simultaneously is big simultaneously, the performance of whole synchronized algorithm will rapid deterioration.

Summary of the invention

In order to overcome above-mentioned defective the present invention has been proposed, therefore the purpose of this invention is to provide the time-frequency synchronization method in a kind of multi-antenna OFDM communication system, can realize that according to time-frequency synchronization method of the present invention higher frame arrives the accuracy of parameter Estimation such as detection, symbol time skew, frequency shift (FS), still can use in the time and frequency-offset scope than broad, necessary system resource is fewer.According to the present invention, under all bigger situation of time migration, frequency shift (FS), can carry out the combined synchronization of time-frequency, using under the less system resource prerequisite, can access higher accuracy.

To achieve these goals, according to the present invention, time-frequency synchronization method in a kind of multi-antenna OFDM communication system has been proposed, said method comprising the steps of: at transmitting terminal, insert targeting sequencing in the one-tenth frame data at each transmitting antenna, described targeting sequencing comprises two short PN sequences and two long PN sequences; At receiving terminal, reception is from the Frame on each reception antenna, according to described targeting sequencing included in the Frame, detect frame time of advent, estimate the sampling symbol time migration and the frequency shift (FS) of Frame, and the Frame that receives is carried out adjustment on time and the frequency, thereby realize Time and Frequency Synchronization according to the sampling symbol time migration that estimates and frequency shift (FS).

Preferably, described one-tenth frame data are the binary bit stream of input to be carried out Space Time Coding, OFDM modulation and framing handle the data that the back is obtained.

Preferably, the step of inserting targeting sequencing at the one-tenth frame data of each transmitting antenna comprises: targeting sequencing is inserted into the original position of each frame, is inserted in the data division then.

Preferably, described framing data comprise superframe, and each superframe comprises several OFDM frames, and each OFDM frame comprises the OFDM symbol of described targeting sequencing and several carrying data.

Preferably, described two short PN sequences are identical, and two long PN sequences also are identical, and short PN sequence is to take from the afterbody of long PN sequence.

Preferably, lacking the length of PN sequence and the length of long PN sequence selects according to system complexity and the compromise of accuracy synchronously.

Preferably, be identical at the targeting sequencing structure of each transmitting antenna, all be tactic two short PN sequences and two long PN sequences, and the PN sequence have nothing in common with each other.

Preferably, described frame time of advent, the sampling symbol time migration that estimates Frame and the step of frequency shift (FS) of detecting comprises: the time of advent that roughly estimates frame, unite then and estimate sampling symbol time migration and integer frequency deviation, estimate the decimal frequency shift (FS) at last.

Preferably, the described step that roughly estimates the time of advent of frame comprises: in such a way, and according to judgment variables m _j(k) estimate time of advent of frame:

(1) judges m _j(k)＞0 whether all reception antennas are all satisfied, if, execution in step (2) then;

$\left(2\right)---\mathrm{mk}=\mathrm{median}\left\{\begin{array}{cccc}{m}_1\left(k\right)& m_2\left(k\right)& \·\·\·& m_{N_r}\left(k\right)\end{array}\right\};$

Wherein median{} is the operation of getting median, and the pairing k value of m (k) is the frame time of advent of all reception antennas,

Wherein, at time k place, for reception antenna j, judgment variables m _j(k) be expressed as:

m _j(k)＝|G _j(k)|-TH×P _j(k)

Wherein, TH is that the frame of setting arrives threshold value,

$G_j\left(k\right)=\underset{l=0}{\overset{L-1}{\mathrm{\Σ}}}(x_j(k-l)\×x_j^{*}(k-l-L)),$

$P_j\left(k\right)=\underset{l=0}{\overset{L-1}{\mathrm{\Σ}}}(x_j(k-l)\×x_j^{*}(k-l)),$

x _j(k) be received signal,

L is the length of short PN sequence.

Preferably, the described step that estimates sampling symbol time migration and integer frequency deviation of uniting comprises:

If the received signal after the definition frame zero-time is r _j(k), corresponding reception antenna j and transmitting antenna i then are used for the judgment variables Λ of estimate symbol time migration and integer frequency deviation _{I, j}(k, m) as follows:

${\mathrm{\Λ}}_{i,j}(k,m)=\underset{l=0}{\overset{D-1}{\mathrm{\Σ}}}(r_j(k-l)\×{\mathrm{pn}}_i^{*}\left(l\right))+\underset{l=0}{\overset{D-1}{\mathrm{\Σ}}}(R_j(m-n)\×{\mathrm{PN}}_i^{*}\left(n\right))$

Wherein, corresponding to Λ _{I, j}(k, k when m) maximum, symbol time skew and integer frequency deviation that m corresponds respectively to that reception antenna j estimates from the signal of transmitting antenna i, each k of corresponding all transmitting antennas is got minimum value obtain reception antenna j and go up the symbol time skew that received signal should be corrected, each m of all transmitting antennas is got median obtain integer frequency deviation.

Preferably, the described step that estimates the decimal frequency shift (FS) comprises: if the received signal after define symbol time synchronized and integer frequency deviation are corrected is s _j(k), at reception antenna j, be used to estimate the judgment variables λ of decimal frequency shift (FS) _j(f) as follows:

${\mathrm{\λ}}_j\left(f\right)={\tan }^{-1}\left(\underset{l=0}{\overset{D-1}{\mathrm{\Σ}}}{s}_j(k-l)s_j^{*}(k-l-D)\right).$

According to the present invention, method for synchronous in the novel MIMO-OFDM system of one cover is provided, this method has the following advantages simultaneously: higher frame arrives the accuracy of parameter Estimation such as detection, symbol time skew, frequency shift (FS), still can use in the time and frequency-offset scope than broad, necessary system resource is fewer.

The present invention can be used as the Time and Frequency Synchronization Module Design scheme in the MIMO-OFDM system, because its performance and the advantage that takies aspects such as resource is few, the present invention has very high patent and is worth in the broadband wireless communications field.

Description of drawings

Below in conjunction with the detailed description of preferred embodiment of accompanying drawing to being adopted, above-mentioned purpose of the present invention, advantage and feature will become apparent by reference, wherein:

Fig. 1 shows the block diagram of the transmitter of MIMO-OFDM system;

Fig. 2 shows the block diagram of the receiver of MIMO-OFDM system;

Fig. 3 shows the schematic block diagram according to time-frequency synchronization method of the present invention;

Fig. 4 shows the schematic diagram according to targeting sequencing structure of the present invention;

Fig. 5 shows the algorithm block diagram that arrives detector according to frame of the present invention;

Fig. 6 shows the algorithm block diagram of and integer frequency bias estimator synchronous according to union of symbol of the present invention;

Fig. 7 shows the algorithm block diagram according to decimal frequency bias estimator of the present invention;

Fig. 8 shows each reception antenna frame schematic graph of the time of advent;

Fig. 9 shows with integer frequency bias and estimates the independently schematic graph of the detected signal of sign synchronization algorithm; And

Figure 10 shows the schematic graph of the detected signal of the sign synchronization algorithm of uniting with the integer frequency bias estimation.

Embodiment

Fig. 1 shows the block diagram of the transmitter of MIMO-OFDM system.As shown in Figure 1, binary bit stream at first sends into encoder and interleaver 101 carries out chnnel coding and Bit Interleave, send into digital modulator 103 then and carry out the mapping of bit to the constellation map symbol, then send into Space Time Coding device 105 and carry out Space Time Coding, the form of Space Time Coding device can be a spatial reuse, it also can be space-time block code or space-time grid coding, next be that data are modulated by OFDM modulator 107-109 respectively, need at last data are carried out binding and layout, this realizes by data framing device 113-115, at this moment, data framing device 113-115 need be inserted into the different targeting sequencing that targeting sequencing insert module 111 produces the original position of each frame, be data division then, the new frame structure that the present invention proposes has detailed introduction below.

The receiver scheme of MIMO-OFDM system as shown in Figure 2.Send into Time and Frequency Synchronization estimator 205 and time-frequency corrector 201-203 simultaneously from the digital signal on each reception antenna, Time and Frequency Synchronization estimator 205 detects frame time of advent, estimate sampling symbol time migration and frequency shift (FS), send into time-frequency corrector 201-203, time-frequency corrector 201-203 carries out adjustment on time and the frequency according to these parameters to the data that receive, data after the Time and Frequency Synchronization are at first sent into ofdm demodulator 207-209 and are carried out data demodulates, decoding or detect when decoder 211 carries out data empty when sending into sky then, the data of last decoder output when empty are carried out symbol by digital demodulator 213 successively and are operated to the mapping of bit and by deinterleaving and channel decoding that deinterleaver decoder 215 carries out bit.

In order to obtain the accuracy of parameter Estimation such as the higher frame time of advent, symbol time skew, frequency shift (FS), proposed according to Time and Frequency Synchronization estimator 205 of the present invention, as shown in Figure 3.Fig. 3 shows the schematic block diagram according to time-frequency synchronization method of the present invention.

Particularly, digital signal at first enters frame and arrives detector 301, roughly estimates the time of advent of frame, sends into time migration estimation-integer frequency bias estimator 303 then, and here, we are expressed as frequency shift (FS)

Δf＝Nf _c+δf _c (1)

Wherein, f _cThe subcarrier spacing of expression OFDM, N is an integer, can on the occasion of, also can be negative value, δ be one greater than-0.5 and smaller or equal to+0.5 decimal.Time migration estimation-integer frequency bias estimator 303 can estimate sampling symbol time migration and parameter N simultaneously, estimates parameter δ by decimal frequency bias estimator 305 at last.

Corresponding to the time-frequency synchronization of the present invention's proposition, and, the present invention proposes a kind of novel targeting sequencing structure, as shown in Figure 4 in order to reduce essential system resource occupancy.

The data of whole transmission (being called superframe) comprise several OFDM frames 401, each OFDM frame 401 is made up of one or more targeting sequencing 403 and several OFDM symbols 405 that carry data that are used for Time and Frequency Synchronization, and targeting sequencing 403 comprises two short PN sequences 407 and two long PN sequences 409.Targeting sequencing structure corresponding to each transmitting antenna is identical, but the PN sequence all is different, the length of short PN sequence and the length of long PN sequence are selected according to system complexity and the compromise of accuracy synchronously, two short PN sequences are identical, two long PN sequences also are identical, and short PN sequence is to take from the afterbody of long PN sequence.According to the present invention, be identical at the targeting sequencing structure of each transmitting antenna, all be tactic two short PN sequences and two long PN sequences, and the PN sequence have nothing in common with each other.

Fig. 5 shows the algorithm block diagram that arrives detector according to frame of the present invention.

As shown in Figure 5.Each reception antenna at first calculates judgment variables, calculates judgment variables m for reception antenna j at time k _j(k), m _j(k) the formula that is calculated as follows:

m _j(k)＝|G _j(k)|-TH×P _j(k) (2)

Wherein, TH is a preset threshold, if the definition received signal is x _j(k), then $G_j\left(k\right)=\underset{l=0}{\overset{L-1}{\mathrm{\Σ}}}(x_j(k-l)\×x_j^{*}(k-l-L)),$ $P_j\left(k\right)=\underset{l=0}{\overset{L-1}{\mathrm{\Σ}}}(x_j(k-l)\×x_j^{*}(k-l)).$ The judgment variables m that each reception antenna calculates _j(k) all send into greater than zero judgement median value (521), judge that greater than zero median value (521) execution following two goes on foot operation:

(1) judges m _j(k)＞0 whether all antennas are all satisfied, carry out next step in this way;

$\left(2\right)---m\left(k\right)=\mathrm{median}\left\{\begin{array}{cccc}{m}_1\left(k\right)& m_2\left(k\right)& \·\·\·& m_{N_r}\left(k\right)\end{array}\right\}.$

Wherein median{} is the operation of getting median, and handling like this is that frame for the redundancy of utilizing a plurality of reception antennas improves under a plurality of transmit antenna case detects the time of advent.The pairing k value of m (k) is the frame time of advent of all reception antennas.

Fig. 6 shows the algorithm block diagram of and integer frequency bias estimator synchronous according to union of symbol of the present invention.

Sampling symbol time synchronized and the frequency shift (FS) of integral multiple subcarrier spacing are united and are estimated, as shown in Figure 6.If the received signal after the definition frame zero-time is r _j(k), corresponding reception antenna j-transmitting antenna i, calculate judgment variables:

${\mathrm{\Λ}}_{i,j}(k,m)=\underset{l=0}{\overset{D-1}{\mathrm{\Σ}}}\left(r_j(k-l){\×\mathrm{pn}}_i^{*}\left(l\right)\right)+\underset{l=0}{\overset{D-1}{\mathrm{\Σ}}}(R_j(m-n)\×{\mathrm{PN}}_i^{*}\left(n\right))$

(3)

Corresponding to Λ _{I, j}(k, k when m) maximum, symbol time skew and integer frequency deviation that m corresponds respectively to that reception antenna j estimates from the signal of transmitting antenna i, each k of corresponding all transmitting antennas is sent into k get minimum value (627) and obtain reception antenna j and go up the symbol time skew that received signal should be corrected, each m of all transmitting antennas is sent into m get median (629) and obtain integer frequency deviation.

Fig. 7 shows the algorithm block diagram according to decimal frequency bias estimator of the present invention.

The decimal frequency bias estimator that the present invention proposes as shown in Figure 7.If the received signal after define symbol time synchronized and integer frequency bias are corrected is s _j(k), then reception antenna j obtains decimal frequency bias by the judgment variables that is calculated as follows:

${\mathrm{\λ}}_j\left(f\right)={\mathrm{tam}}^{-1}\left(\underset{l=0}{\overset{D-1}{\mathrm{\Σ}}}{s}_j(k-l)s_j^{*}(k-l-D)\right)---\left(4\right)$

Wherein the CORDIC among Fig. 7 is the processing unit of a special use, carries out tan ^-1Angle value is promptly taken out in () operation.

The example that to enumerate the method according to this invention below describes in detail.

Wireless communications environment at a distributed multi-antenna, suppose that transmitting terminal has four adjacent antennas, the signal of four transmit antennas all can arrive receiving terminal, receiving terminal has eight antennas, wherein four adjacent (being called group one), other four adjacent (being called group two),, the position difference of this two group of received antenna is bigger, and eight road signal demands that receiving terminal receives carry out distributed focusing on.Have 1024 subcarriers among the OFDM, the length of Cyclic Prefix is 256.

It is the interleaver of 40000 bits that transmitting terminal adopts Turbo coding and length, through sending into the space division multiplexing module after the QPSK modulation, obtain four channel parallel datas, then through the OFDM modulation, the length of the short-and-medium PN sequence of targeting sequencing is 128, and the length of long PN sequence is 256.Send simultaneously by four antennas at last.

Channel model is as follows, four transmit antennas and time migration and the frequency shift (FS) difference organized on 16 channels between four reception antennas of one are less, four transmit antennas and time migration and the frequency shift (FS) difference organized on 16 channels between four reception antennas of two are also less, and all be evenly to distribute at random, and time migration between the two group of received antennas and frequency shift (FS) difference are bigger, four transmit antennas and organize channel between four reception antennas of one for adding up independently COST207 model, four transmit antennas and organize channel between four reception antennas of two for adding up independently ITU VA 60 models.

The schematic diagram of frame time of advent of each reception antenna as shown in Figure 8.Each reception antenna all obtains frame time of advent by calculating formula (2) and judgement formula (2) greater than zero, and then the judgment variables that each reception antenna calculates is got median estimates frame time of advent.Can be as can be seen from Figure 8, the detected frame of each reception antenna is all different the time of advent, and what have may be far away the time of advent apart from correct frame, the present invention has adopted the method for getting median, obtains the frame time of advent that an energy is accepted by all reception antennas.

The sampling symbol time synchronized all carried out by each reception antenna and estimation is united in the frequency shift (FS) of integral multiple subcarrier spacing, calculates formula (3) respectively, obtains received signal should be corrected on each reception antenna symbol time skew and integer frequency deviation.In order to contrast independent estimations and associating estimation performance difference, provided the judgment variables conversion curve in time of sampling symbol time synchronized, as Fig. 9 and shown in Figure 10.From these two figure as can be seen, the independent estimations of sampling symbol time synchronized and the frequency shift (FS) of integral multiple subcarrier spacing, when having integer frequency bias, can not estimate the uniting estimation and then can estimate of sampling symbol time synchronized and the frequency shift (FS) of integral multiple subcarrier spacing.

The final step of Time and Frequency Synchronization is the estimation of decimal frequency bias, can obtain decimal frequency bias by the judgment variables that calculating formula (4) provides, and the method that provides is here done in time domain, in like manner, also can do at frequency domain.Decimal frequency bias estimates and the estimation of uniting of sampling symbol time synchronized, the frequency shift (FS) of integral multiple subcarrier spacing uses all that long PN sequence does.

Afterwards, the data of carrying out obtaining after the adjustment on time and the frequency respectively from the digital signal on each reception antenna are at first sent into ofdm demodulator and are carried out data demodulates, send into ZF BLAST detector then and carry out the detection of data, the data of last detector output are carried out symbol to operations such as the mapping of bit, deinterleaving that the deinterleaver decoder carries out bit and channel decodings by digital demodulator successively.

According to the present invention, method for synchronous in the novel MIMO-OFDM system of one cover is provided, this method has the following advantages simultaneously: higher frame arrives the accuracy of parameter Estimation such as detection, symbol time skew, frequency shift (FS), still can use in the time and frequency-offset scope than broad, necessary system resource is fewer.

The present invention can be used as the Time and Frequency Synchronization Module Design scheme in the MIMO-OFDM system, because its performance and the advantage that takies aspects such as resource is few, the present invention has very high patent and is worth in the broadband wireless communications field.

Although below show the present invention in conjunction with the preferred embodiments of the present invention, one skilled in the art will appreciate that under the situation that does not break away from the spirit and scope of the present invention, can carry out various modifications, replacement and change to the present invention.Therefore, the present invention should not limited by the foregoing description, and should be limited by claims and equivalent thereof.

Claims (11)

1, the time-frequency synchronization method in a kind of multi-antenna OFDM communication system said method comprising the steps of:

At transmitting terminal, in one-tenth frame data, insert targeting sequencing at each transmitting antenna, described targeting sequencing comprises two short PN sequences and two long PN sequences.

At receiving terminal, reception is from the Frame on each reception antenna, according to described targeting sequencing included in the Frame, detect frame time of advent, estimate the sampling symbol time migration and the frequency shift (FS) of Frame, and the Frame that receives is carried out adjustment on time and the frequency, thereby realize Time and Frequency Synchronization according to the sampling symbol time migration that estimates and frequency shift (FS).

2, method according to claim 1 is characterized in that described one-tenth frame data are the binary bit stream of input to be carried out Space Time Coding, OFDM modulation and framing handle the data that the back is obtained.

3, method according to claim 1 is characterized in that at the one-tenth frame data of each transmitting antenna the step of inserting targeting sequencing comprises: targeting sequencing is inserted into the original position of each frame, is inserted in the data division then.

4, method according to claim 1 is characterized in that described framing data comprise superframe, and each superframe comprises several OFDM frames, and each OFDM frame comprises the OFDM symbol of described targeting sequencing and several carrying data.

5, method according to claim 1 is characterized in that: described two short PN sequences are identical, and two long PN sequences also are identical, and short PN sequence is to take from the afterbody of long PN sequence.

6, method according to claim 1 is characterized in that: the length of short PN sequence and the length of long PN sequence are selected according to system complexity and the compromise of accuracy synchronously.

7, method according to claim 1 is characterized in that: the targeting sequencing structure at each transmitting antenna is identical, all be tactic two short PN sequences and two long PN sequences, and the PN sequence has nothing in common with each other.

8. method according to claim 1, it is characterized in that: described frame time of advent, the sampling symbol time migration that estimates Frame and the step of frequency shift (FS) of detecting comprises: the time of advent that roughly estimates frame, unite then and estimate sampling symbol time migration and integer frequency deviation, estimate the decimal frequency shift (FS) at last.

9. method according to claim 8 is characterized in that: the described step that roughly estimates the time of advent of frame comprises: in such a way, and according to judgment variables m _j(k) estimate time of advent of frame:

(1) judges m _j(k)＞0 whether all reception antennas are all satisfied, if, execution in step (2) then;

$\left(2\right)---m\left(k\right)=\mathrm{median}\left\{\begin{array}{cccc}{m}_1\left(k\right)& m_2\left(k\right)& \·\·\·& m_{N_r}\left(k\right)\end{array}\right\};$

Wherein median{} is the operation of getting median, and the pairing k value of m (k) is the frame time of advent of all reception antennas,

Wherein, at time k place, for reception antenna j, judgment variables m _j(k) be expressed as:

m _j(k)＝|G _j(k)|-TH×P _j(k)

Wherein, TH is that the frame of setting arrives threshold value,

$G_j\left(k\right)=\underset{l=0}{\overset{L-1}{\mathrm{\Σ}}}(x_j(k-l)\×x_j^{*}(k-l-L)),$

$P_j\left(k\right)=\underset{l=0}{\overset{L-1}{\mathrm{\Σ}}}(x_j(k-l)\×x_j^{*}(k-l)),$

x _j(K) be received signal,

L is the length of short PN sequence.

10, method according to claim 8 is characterized in that: the described step that estimates sampling symbol time migration and integer frequency deviation of uniting comprises:

If the received signal after the definition frame zero-time is r _j(k), corresponding reception antenna j and transmitting antenna i then are used for the judgment variables Λ of estimate symbol time migration and integer frequency deviation _{I, j}(k, m) as follows:

${\mathrm{\Λ}}_{i,j}(k,m)=\underset{l=0}{\overset{D-1}{\mathrm{\Σ}}}(r_j(k-l)\×p{n}_i^{*}\left(l\right))+\underset{l=0}{\overset{D-1}{\mathrm{\Σ}}}(R_j(m-n)\×P{N}_i^{*}\left(n\right))$

Wherein, corresponding to Λ _{I, j}(k, k when m) maximum, symbol time skew and integer frequency deviation that m corresponds respectively to that reception antenna j estimates from the signal of transmitting antenna i, each k of corresponding all transmitting antennas is got minimum value obtain reception antenna j and go up the symbol time skew that received signal should be corrected, each m of all transmitting antennas is got median obtain integer frequency deviation.

11, method according to claim 8 is characterized in that: the described step that estimates the decimal frequency shift (FS) comprises: if the received signal after define symbol time synchronized and integer frequency deviation are corrected is s _j(k), at reception antenna j, be used to estimate the judgment variables λ of decimal frequency shift (FS) _j(f) as follows:

${\mathrm{\λ}}_j\left(f\right)={\tan }^{-1}\left(\underset{l=0}{\overset{D-1}{\mathrm{\Σ}}}{s}_j(k-l)s_j^{*}(k-l-D)\right).$

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