CN101552622B - Method and device to estimate the frequency deviation in TD-CDMA access system - Google Patents

Abstract

The present invention provides a method ad device to estimate the frequency deviation in TD-CDMA access system and pertains to the technical field of wireless communication. This method includes: step A: receive the data of the last 128 chips of Midamble code with frequency deviation, and calculate the first frequency deviation estimate result fM based on the data of the 128 chips and local basic Midamble code; step B: Do frequency deviation compensation calculation of the data demodulated through joint detection and the first frequency deviation estimation result fM to get the result of frequency deviation compensation; step C: Do frequency deviation estimate calculation of the result of frequency deviation compensation to get the second frequency deviation estimate result fD; step D: Do cumulative calculation of fM and fD to get the third frequency deviation estimate result fO. In this way, it may realize large-range and high accuracy frequency deviation estimate in TD-SCDMA system to meet the needs of some special circumstances.

Description

Frequency deviation estimating method in the TD-CDMA access system and device

Technical field

The invention belongs to wireless communication technology field, relate in particular to frequency deviation estimating method and device in a kind of TD-SCDMA (TimeDivision-Synchronous Code Division Multiple Access, TD SDMA inserts) system.

Background technology

At present; Most communication system (for example TD-SCDMA system) all is to adopt the method for coherent detection to carry out data demodulates, promptly require receiver be used for receiving wireless signal frequency should and the carrier frequency of wireless signal is in full accord or between the two error very little.Therefore, in order to guarantee that receiving function accurately follows the tracks of carrier frequency, the frequency offset estimating of receiver is just important, because have only the frequency departure that estimates the two exactly in time to correct to reach the purpose of accurate tracking.

A kind of frequency offset estimating algorithm comparatively commonly used is to utilize the demodulating data after joint-detection to carry out frequency offset estimating in the TD-SCDMA system; Yet the number of the employed data symbol near Midamble sign indicating number (training sequence) of this frequency offset estimating algorithm is few more; Frequency offset estimation range is big more, and the precision of frequency offset estimating is poor more; Otherwise the number of used data symbol is many more, and frequency offset estimation range is more little, but the precision of frequency offset estimating is high more.Emulation shows that the number of desired data symbol is no less than 4 when using the method to carry out frequency offset estimating.When SF (spreading factor)=16, this moment Midamble both sides the number N=704/16=44 of data symbol, if when only using 4 the data symbols in Midamble sign indicating number both sides, frequency offset estimating can reach 1176Hz; If when using all 22 data symbols of Midamble sign indicating number both sides, frequency offset estimating has only about 300Hz, but the former frequency offset estimating error will be much larger than the latter.As shown in Figure 1; Position view for 4 the data symbols in Midamble sign indicating number both sides in the TD-SCDMA system; A time slot is made up of 2 data parts (Data), 1 training sequence (Midamble sign indicating number) and 1 protection time slot (GP) in the TD-SCDMA system, and data division (Data) is distributed in the both sides of training sequence symmetrically.

In realizing process of the present invention; Find to exist at least in the prior art following problem: in most cases; Stable in order to follow the tracks of, use all 22 data symbols of Midamble sign indicating number both sides to carry out frequency offset tracking usually, promptly sacrifice frequency offset estimation range and exchange frequency offset estimation accuracy for.This moment, the frequency offset estimation range of 300Hz can satisfy the demands, but in some special scene, high-speed mobile scene for example, the frequency offset estimation range of 300Hz is just much of that far from.When translational speed reached 430km/h, Doppler frequency shift just can reach 800Hz, and if the sub-district takes place at this moment switches, frequency deviation can reach 1600Hz at most.At this moment, also be not enough even use minimum data symbol to calculate its data area of frequency deviation.

Summary of the invention

In order to address the above problem, the purpose of this invention is to provide frequency deviation estimating method and device in a kind of TD-SCDMA system, thereby can be implemented in the TD-SCDMA system on a large scale, high-precision frequency offset estimating, satisfied the needs of some special screne.

In order to achieve the above object, the present invention provides the frequency deviation estimating method in a kind of TD-CDMA access system, and said method comprises:

Steps A, reception have back 128 chip data of the training sequence Midamble sign indicating number of frequency deviation, calculate the first frequency offset estimation result f according to said 128 chip data and local basic Midamble yardage _M

Step B, the data and the said first frequency offset estimation result f that will demodulate through joint-detection _MCarry out compensate of frequency deviation and calculate, obtain the compensate of frequency deviation result;

Step C, said compensate of frequency deviation result is carried out frequency offset estimating calculate, obtain the second frequency offset estimation result f _D

Step D, to the said first frequency offset estimation result f _MWith the said second frequency offset estimation result f _DCarry out accumulation calculating, obtain the 3rd frequency offset estimation result f _O

Preferably, said steps A specifically comprises:

Steps A 1, pass through formula $\tilde{h}=\mathrm{IFFT}[\mathrm{FFT}\left(\tilde{M}\right)./\mathrm{FFT}\left(M\right)]$ Calculating original channel estimates

Wherein

Operator IFFT representes: fast adverse Fourier transform;

Operator FFT representes: FFT;

Operator ./expression: the contraposition of two sequences is divided by;

M representes: the basic Midamble sign indicating number in the TD-SCDMA system;

expression: back 128 the chip data that have frequency deviation Midamble sign indicating number that the TD-SCDMA system terminal receives;

Steps A 2,, said original channel carries out noise removing, the channel estimating behind the noise that is eliminated

to estimating

Steps A 3, utilize formula $\hat{M}=\mathrm{IFFT}[\mathrm{FFT}\left(M\right).\×\mathrm{FFT}\left(\hat{h}\right)]$ Right

Sequence is carried out reconstruction calculations, obtains not having the reception signal of frequency deviation

Operator wherein. * expression: the contraposition of two sequences is multiplied each other;

Steps A 4, at first utilize formula $X=\tilde{M}.\×{\hat{M}}^{*},$ Will

Sequence with The conjugate multiplication of sequence, wherein X=[X ₀, X ₁... x ₁₂₇], x is the sequence that comprises frequency deviation information; Pass through formula then $C_M=\underset{i=0}{\overset{i=63}{\mathrm{\Σ}}}{x}_i^{*}\×x_{i+64}$ Calculate the plural variable C that comprises frequency deviation information _M, wherein i is a natural number;

Steps A 5, utilize formula $f_M=\frac{1}{2\mathrm{\π}\×64T_c}\mathrm{Arctan}\left(\frac{\mathrm{Im}\left(C_M\right)}{\mathrm{Re}\left(C_M\right)}\right)$ Calculate the first frequency offset estimation result f _M, wherein

T _CExpression: spreading rate;

Im (C _M): represent plural variable C _MImaginary part;

Re (C _M): represent plural variable C _MReal part.

Preferably, after said steps A 5, said steps A also comprises:

Steps A 6, through formula f _M=sign (f _M) * min (f _M, F), to the said first frequency offset estimation result f _MBe optimized processing, wherein

Sign (x) function representation: the symbol of getting variable x;

(x, y) function representation: get one less in two real numbers of x and y, x, y are real number to min;

F representes: the maximum frequency deviation of foreseeing in the TD-SCDMA system.

Preferably, said step B specifically comprises:

Step B1, receive through the data sequence after the joint-detection demodulation

wherein

be i demodulating data symbols in the code channel after the joint-detection demodulation; Parameter i=0 wherein; 1; ...; N-1; N representes: the contained data symbol number of each code channel in the TD-SCDMA system; And N=704/SF, SF are the presently used spreading factor of TD-SCDMA system;

Step B2, whether judge parameter i less than N/2, if utilize formula ${{\tilde{d}}_i}^{\&prime;}={\tilde{d}}_i\&times;{\mathrm{<figure-callout\; id="2"\; label="e\; j"\; filenames="H2009100797338E00011.png"\; state="\{\{state\}\}">e</figure-callout>}}^j$ Calculate the compensate of frequency deviation result; Otherwise, utilize formula ${{\tilde{d}}_i}^{\&prime;}={\tilde{d}}_i\&times;e^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="H2009100797338E00011.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}{f}_M{T}_C[(i-N/2)\&times;\mathrm{SF}+72]}$ Calculate the compensate of frequency deviation result.

Preferably, be each N of Midamble sign indicating number both sides when the data symbol that uses _DIn the time of/2,2≤N wherein _D≤N, and N _DBe even number, N representes: the contained data symbol number of each code channel in the TD-SCDMA system, and N=704/SF, and SF is the presently used spreading factor of TD-SCDMA system, said step C specifically comprises:

Step C1, pass through formula ${\hat{d}}_i=\mathrm{HardJudge}\left({d^{\&prime;}}_i\right)$ Carry out the hard decision of data symbol, wherein, d ' _iBe the compensate of frequency deviation result who calculates among the step B2, i=0,1 ... N _D-1;

Step C2, at first according to formula $y_i={\hat{d}}_i\&times;{d_i}^{\&prime;*}$ Calculate d _i' with

The y as a result of conjugate multiplication _i, then according to formula $C_D=\underset{i=0}{\overset{i=N_D/2-1}{\mathrm{\&Sigma;}}}{y}_i\&times;y_{i+N_D/2}^{*}$ Calculate the plural variable C that comprises frequency deviation information _D, i=0 wherein, 1 ... N _D-1;

Step C3, utilize formula $f_D=\frac{1}{2\mathrm{\&pi;}{T}_C(N\&times;\mathrm{SF}+144)}\mathrm{Arctan}\left(\frac{\mathrm{Im}\left(C_D\right)}{\mathrm{Re}\left(C_D\right)}\right)$ Calculate the said second frequency offset estimation result f _D, wherein

Wherein, T _CExpression: spreading rate;

Im (C _D) expression: plural variable C _DImaginary part;

Re (C _D) expression: plural variable C _DReal part.

N representes: the data symbol number in the TD-SCDMA system in each code channel, and N=704/SF, SF are the presently used spreading factor of TD-SCDMA system.

Preferably, said step C is specially:

Step C4, employing cascade result's frequency offset estimating is to N1 _DIndividual data symbol carries out frequency offset estimating and calculates, and obtains the 4th frequency offset estimation result, wherein N1 _DBe even number;

Step C5, utilize said the 4th frequency offset estimation result all data symbols to be compensated the frequency offset estimation result after being compensated;

The frequency offset estimating of step C6, employing cascade structure is to the N2 in the frequency offset estimation result after the said compensation _DIndividual data symbol carries out frequency offset estimating, obtains the 5th frequency offset estimation result, wherein N2 _DBe even number, and N2 _DGreater than N1 _D

Step C7, said the 4th frequency offset estimation result and said the 5th frequency offset estimation result addition are obtained the said second frequency offset estimation result f _D

The present invention also provides the frequency deviation estimation device in a kind of TD-CDMA access system, and said device comprises:

Midamble data frequency offset estimator is used to receive back 128 chip data of the training sequence Midamble sign indicating number that has frequency deviation, calculates the first frequency offset estimation result f according to said 128 chip data and local basic Midamble yardage _M

The compensate of frequency deviation device is used for data that demodulate through joint-detection and the said first frequency offset estimation result f _MCarry out compensate of frequency deviation and calculate, obtain the compensate of frequency deviation result;

The demodulating data frequency offset estimator is used for that said compensate of frequency deviation result is carried out frequency offset estimating and calculates, and obtains the second frequency offset estimation result f _D

Accumulator is used for the said first frequency offset estimation result f _MWith the said second frequency offset estimation result f _DCarry out accumulation calculating, obtain the 3rd frequency offset estimation result f _O

At least one technical scheme in the technique scheme has following beneficial effect: through Midamble sign indicating number frequency offset estimating and demodulating data frequency offset estimating are combined; Realized in the TD-SCDMA system on a large scale, high-precision frequency offset estimating, make the TD network can satisfy the needs of some special screne.

Description of drawings

The position view that Fig. 1 meets for 4 data in Midamble sign indicating number both sides in the prior art;

Fig. 2 is a frequency deviation estimation approach flow chart in the embodiments of the invention;

Fig. 3 is the device block diagram of frequency offset estimating in the embodiments of the invention.

Embodiment

In an embodiment of the present invention, through Midamble sign indicating number (training sequence) frequency offset estimating and demodulating data frequency offset estimating are combined, realized in the TD-SCDMA system on a large scale, high-precision frequency offset estimating.

For the purpose, technical scheme and the advantage that make the embodiment of the invention is clearer,, the embodiment of the invention is done explanation in further detail below in conjunction with embodiment and accompanying drawing.At this, illustrative examples of the present invention and explanation are used to explain the present invention, but not as to qualification of the present invention.

Referring to Fig. 2, be frequency deviation estimation approach flow chart in the embodiments of the invention, concrete steps are following:

Step 21, reception have back 128 chip data of the Midamble sign indicating number of frequency deviation, calculate the first frequency offset estimation result f according to these 128 chip data and local basic Midamble yardage _M

In the present embodiment, can come execution in step 21 through the Midamble frequency offset estimator, and step 21 can comprise following concrete steps:

Original channel is estimated

for step 210, calculating

In the present embodiment, formula capable of using (1) calculates original channel estimation

$\tilde{h}=\mathrm{IFFT}[\mathrm{FFT}\left(\tilde{M}\right)./\mathrm{FFT}\left(M\right)]$ Formula (1)

Wherein, operator IFFT representes: fast adverse Fourier transform;

Operator FFT representes: FFT;

Operator ./expression: the contraposition of two sequences is divided by;

M representes: the basic Midamble sign indicating number in the TD-SCDMA system;

expression: back 128 the chip data that have frequency deviation Midamble sign indicating number that the TD-SCDMA system terminal receives;

Step 211, original channel is estimated that

carries out noise removing, the channel estimating behind the noise that is eliminated

This step can realize through noise eliminator of the prior art; Promptly eliminate original channel and estimate the noise item in

, from multipath channel, select the effective diameter channel.Application number for example: 200310116920.1 denominations of invention: a kind of patent documentation that is used for the denoising method of wireless communication system discloses the denoising method in a kind of wireless communication system; This method comprises: at first the signal in the channel is done initial option; Multipath channel in the selective channel; Utilize the relation of the signal to noise ratio of channel impulse response to calculate the Noise gate limit value then, compare through power and this Noise gate limit value at last, the noise remove in the channel with multipath channel.Certainly, the method for carrying out noise removing for channel estimating also can adopt other prior art means to realize, no longer applies at this and states.

Step 212,

sequence is carried out reconstruction calculations, obtain not having the reception signal

of frequency deviation

Can carry out the calculating that reconstruct does not have the reception signal of frequency deviation through formula (2) in the present embodiment.

$\hat{M}=\mathrm{IFFT}[\mathrm{FFT}\left(M\right).\&times;\mathrm{FFT}\left(\hat{h}\right)]$ Formula (2)

Wherein, operator. * expression: the contraposition of two sequences is multiplied each other;

Step 213, extraction frequency deviation information;

At first utilize formula (3); Conjugate multiplication with

sequence and

sequence obtains X as a result;

$X=\tilde{M}.\&times;{\hat{M}}^{*}$ Formula (3)

X=[x wherein ₀, x ₁... x ₁₂₈], wherein, x is a sequence that comprises frequency deviation information, thus can calculated complex variable C _M, also be appreciated that to be an intermediate variable

And then calculate the plural variable C that comprises frequency deviation information through formula (4) _M,

$C_M=\underset{i=0}{\overset{i=63}{\mathrm{\&Sigma;}}}{x}_i^{*}\&times;x_{i+64}$ (i is a natural number) formula (4)

Step 214, calculating frequency deviation;

Just adopt formula (5) to calculate the first frequency offset estimation result f _M,

$f_M=\frac{1}{2\mathrm{\&pi;}\&times;64T_c}\mathrm{Arctan}\left(\frac{\mathrm{Im}\left(C_M\right)}{\mathrm{Re}\left(C_M\right)}\right)$ Formula (5)

Wherein, T _CExpression: spreading rate, T in the TD-SCDMA system _C=1.28 million per second chips;

Im (C _M) expression: plural variable C _MImaginary part;

Re (C _M) expression: plural variable C _MReal part.

After execution of step 214, if the maximum frequency deviation F in the known TD-SCDMA system, so through formula (6) to f _MValue be optimized processing.

f _M=sign (f _M) * min (f _M, F) formula (6)

Wherein, sign (x) function representation: the symbol of getting variable x;

(x, y) function representation: get one less in two real numbers of x and y, x, y are real number to min;

Parameter F is represented: the maximum frequency deviation of foreseeing in the TD-SCDMA system also is not limited to this, certainly at the frequency acquisition of present embodiment in the stage; Maximum frequency deviation is generally 6kHz, if be used for the frequency-tracking stage, maximum frequency deviation generally can not surpass 300Hz; But some special screne for tracking phase; High-speed mobile scene for example, maximum frequency deviation can reach 1.6kHz (when translational speed is 430km/h), but in formula 6 this parameter F also the use experience value bring into and be optimized calculating.The set-up mode of this empirical value can for: can be made as 6kHz at this empirical value of acquisition phase, and this empirical value of tracking phase can be made as 1kHz.

Can obtain the first frequency offset estimation result f through step 210～step 214 _M, also can use additive method for Midamble sign indicating number frequency offset estimating certainly, for example the frequency offset estimating algorithm based on least square calculates the first frequency offset estimation result f _M

Step 22, the first frequency offset estimation result f that will in data that joint-detection demodulates and step 21, obtain _MCarry out compensate of frequency deviation and calculate, obtain the compensate of frequency deviation result;

In the present embodiment, can come execution in step 22 through the compensate of frequency deviation device, and step 22 can comprise following concrete steps:

Step 220, at first receive through the data sequence after the joint-detection demodulation wherein

be i demodulating data symbols in the code channel after the joint-detection demodulation; I=0 wherein; 1; ...; N-1; N representes: the data symbol number in the TD-SCDMA system in each code channel; And N=704/SF; SF is the presently used spreading factor of TD-SCDMA system, SF=1 in the TD-SCDMA system～16;

Whether the parameter i that step 221, judgement are chosen is less than N/2, if utilize formula (7) to calculate the compensate of frequency deviation result; Otherwise, utilize formula (8) to calculate the compensate of frequency deviation result.

${{\tilde{d}}_i}^{\&prime;}={\tilde{d}}_i\&times;{\mathrm{<figure-callout\; id="2"\; label="e\; j"\; filenames="H2009100797338E00011.png"\; state="\{\{state\}\}">e</figure-callout>}}^j$ Formula (7)

${{\tilde{d}}_i}^{\&prime;}={\tilde{d}}_i\&times;e^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="H2009100797338E00011.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}{f}_M{T}_C[(i-N/2)\&times;\mathrm{SF}+72]}$ Formula (8)

In the present embodiment, the user can use the compensate of frequency deviation device to come performing step 220 and step 221, can carry out compensate of frequency deviation through following program this moment and calculate.

for?i＝0:N-1

ifi＜N/2

${\tilde{d}}_i^{\&prime;}={\tilde{d}}_i\&times;{\mathrm{<figure-callout\; id="2"\; label="e\; j"\; filenames="H2009100797338E00011.png"\; state="\{\{state\}\}">e</figure-callout>}}^j$

else

${\tilde{d}}_i^{\&prime;}={\tilde{d}}_i\&times;e^{-\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="H2009100797338E00011.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;}{f}_M{T}_c[(i-N/2)\&times;\mathrm{SF}+72]}$

end

end

Though the first frequency offset estimation result f that obtains _MEstimation range can satisfy the requirement of high speed scene, but have the not high problem of estimated accuracy, therefore need further to improve estimated accuracy.Just execution in step 23.

Step 23, the compensate of frequency deviation result who obtains in the step 22 is carried out the demodulating data frequency offset estimating calculate, obtain the second frequency offset estimation result f _D

Suppose that at first employed data symbol is each N of Midamble both sides _D/ 2,2≤N wherein _D≤N, N _DBe even number, the N that is got this moment so _DIndividual symbol data does ${d_i}^{\&prime;}={{\tilde{d}}^{\&prime;}}_{i+(N-N_D)/2},$ I=0 wherein, 1 ..., N _D-1.Can accomplish by following three steps based on the demodulating data frequency offset estimating:

Step 231, symbol hard decision;

In the communication system, data symbol is owing to noise, decline, frequency deviation, reason such as synchronous, and the position of the planisphere that belongs to when making position and its transmission of receiving terminal data symbol in planisphere produces certain deviation.This step is exactly that what symbol adjudicates this symbol be at transmitting terminal according to receiving the position of data symbol in planisphere, uses here

Expression d _i' court verdict:

${\hat{d}}_i=\mathrm{HardJudge}\left({d^{\&prime;}}_i\right)$ (wherein, i=0,1 ... N _D-1) formula (9)

At application number: 200710119527.6 denominations of invention: introduced the hard decision method in a kind of TD-SCDMA system in the patent documentation of a kind of quadrature amplitude modulation demodulation method that is applied to communication system and device; Comprise the steps: step 1; Receiving terminal adopts planisphere that the symbol that receives is shone upon; Obtain the final symbol of said symbol, and to this final symbol operated in saturation; Step 2 is confirmed the predetermined thresholds at different levels of the soft bit demodulation of M unit quadrature amplitude modulation, goes out each bit of this final symbol according to the final sign computation after this predetermined threshold and the said operated in saturation.

Step 232, extraction frequency deviation information;

In step 232, at first utilize formula (10) to calculate d _i' with The y as a result of conjugate multiplication _i

$y_i={\hat{d}}_i\&times;{d_i}^{\&prime;*}$ (wherein, i=0,1 ... N _D-1) formula (10)

Then, utilize formula (11) to calculate to comprise the plural variable C of frequency deviation information _D

$C_D=\underset{i=0}{\overset{i=N_D/2-1}{\mathrm{\&Sigma;}}}{y}_i\&times;y_{i+N_D/2}^{*}$ (wherein, i=0,1 ... N _D-1) formula (11)

Step 233, calculating frequency deviation;

Just adopt formula (12) to calculate the second frequency offset estimation result f _D

$f_D=\frac{1}{2\mathrm{\&pi;}{T}_C(N\&times;\mathrm{SF}+144)}\mathrm{Arctan}\left(\frac{\mathrm{Im}\left(C_D\right)}{\mathrm{Re}\left(C_D\right)}\right)$ Formula (12)

Wherein, T _CExpression: spreading rate, T in the TD-SCDMA system _C=1.28 million per second chips;

Im (C _D) expression: plural variable C _DImaginary part;

Re (C _D) expression: plural variable C _DReal part.

N representes: the data symbol number in the TD-SCDMA system in each code channel, and N=704/SF, SF are the presently used spreading factor of TD-SCDMA system;

As a kind of preferred version,, can adopt the frequency offset estimating of cascade structure in the present embodiment for frequency offset estimating based on demodulating data.Promptly use N1 earlier _DIndividual data symbol carries out frequency offset estimating, utilizes this estimated result that all symbols are compensated then, re-uses the N2 among the result after the compensation _D(N2 _D＞N1 _D) individual data symbol carries out the frequency offset estimating second time, with twice estimated result addition as f _DCan effectively improve the precision of frequency offset estimating through execution in step 23.N1 _DAnd N2 _DBe even number, and N1 _DEven number between preferred 8～20;

Step 24, to the first frequency offset estimation result f _MWith the second frequency offset estimation result f _DCarry out accumulation calculating, obtain the 3rd frequency offset estimation result f _O

Promptly adopt the first frequency offset estimation result f of formula (13) with twice acquisition _MWith the second frequency offset estimation result f _DAdd up, and the result who obtains that will add up exports as last frequency offset estimation result.

f _O=f _M+ f _DFormula (13)

Can know by technique scheme, through Midamble sign indicating number frequency offset estimating and demodulating data frequency offset estimating are combined, realized in the TD-SCDMA system on a large scale, high-precision frequency offset estimating, make the TD network can satisfy the needs of some special screne.

In order to realize above-mentioned method embodiment, other embodiment of the present invention also provide frequency deviation estimating method and the device in a kind of TD-CDMA access system.What need at first explanation in addition is; Because following embodiment is for realizing aforesaid method embodiment; So this device all is to establish for each step that realizes preceding method; But the present invention is not limited to following embodiment, and any device of said method of realizing all should be contained in protection scope of the present invention.And in the following description, the content identical with preceding method omitted at this, to practice thrift length.

Referring to Fig. 2, be the device block diagram of the frequency offset estimating in the embodiments of the invention, by knowing that this device comprises among the figure:

Midamble data frequency offset estimator is used to receive back 128 chip data of the training sequence Midamble sign indicating number that has frequency deviation, calculates the first frequency offset estimation result f according to said 128 chip data and local basic Midamble yardage _M

The compensate of frequency deviation device is used for data that demodulate through joint-detection and the said first frequency offset estimation result f _MCarry out compensate of frequency deviation and calculate, obtain the compensate of frequency deviation result;

The demodulating data frequency offset estimator is used for that said compensate of frequency deviation result is carried out frequency offset estimating and calculates, and obtains the second frequency offset estimation result f _DAnd

Accumulator is used for the said first frequency offset estimation result f _MWith the said second frequency offset estimation result f _DCarry out accumulation calculating, obtain the 3rd frequency offset estimation result f _O

Wherein, above-mentioned Midamble data frequency offset estimator can execution in step 210～step 214, and this moment, this Midamble data frequency offset estimator comprised:

Channel estimation module is used for through formula $\tilde{h}=\mathrm{IFFT}[\mathrm{FFT}\left(\tilde{M}\right)./\mathrm{FFT}\left(M\right)]$ Calculating original channel estimates

Wherein

Operator IFFT representes: fast adverse Fourier transform;

Operator FFT representes: FFT;

Operator ./expression: the contraposition of two sequences is multiplied each other;

M representes: the basic Midamble sign indicating number in the TD-SCDMA system;

expression: back 128 the chip data that have frequency deviation Midamble sign indicating number that the TD-SCDMA system terminal receives;

Noise cancellation module; Be used for carrying out noise removing, the channel estimating behind the noise that is eliminated

to said original channel is estimated

Reconstructed module is used to utilize formula $\hat{M}=\mathrm{IFFT}[\mathrm{FFT}\left(M\right).\&times;\mathrm{FFT}\left(\hat{h}\right)]$ Right Sequence is carried out reconstruction calculations, obtains not having the reception signal of frequency deviation

Operator wherein. * expression: the contraposition of two sequences is multiplied each other;

First extracts the frequency deviation information module, is used at first utilizing formula $X=\tilde{M}.\&times;{\hat{M}}^{*},$ Will

Sequence with

The conjugate multiplication of sequence, wherein X=[x ₀, x ₁... x ₁₂₈], pass through formula then $C_M=\underset{i=0}{\overset{i=63}{\mathrm{\&Sigma;}}}{x}_i^{*}\&times;x_{i+64}$ Calculate the plural variable C that comprises frequency deviation information _M, wherein i is a natural number; And

First calculates the frequency deviation module, is used to utilize formula $f_M=\frac{1}{2\mathrm{\&pi;}\&times;64T_c}\mathrm{Arctan}\left(\frac{\mathrm{Im}\left(C_M\right)}{\mathrm{Re}\left(C_M\right)}\right)$ Calculate the first frequency offset estimation result f _M, wherein

T _CExpression: spreading rate;

Im (C _M): represent plural variable C _MImaginary part;

Re (C _M): represent plural variable C _MReal part.

In another embodiment of the present invention, this Midamble data frequency offset estimator also comprises the first frequency deviation result optimizing module, is used for through formula f _M=sign (f _M) * min (f _M, F), to the said first frequency offset estimation result f _MBe optimized processing, wherein

Sign (x) function representation: the symbol of getting variable x;

(x, y) function representation: get one less in two real numbers of x and y, x, y are real number to min;

F representes: the maximum frequency deviation of foreseeing in the TD-SCDMA system.

Above-mentioned demodulating data frequency offset estimator comprises:

Symbol hard decision module is used for through formula ${\hat{d}}_i=\mathrm{HardJudge}\left({d^{\&prime;}}_i\right)$ Carry out the hard decision of data symbol, i=0 wherein, 1 ... N _D-1;

Second extracts the frequency deviation information module, is used at first according to formula $y_i={\hat{d}}_i\&times;{d_i}^{\&prime;*}$ Calculate d _i' with

The y as a result of conjugate multiplication _i, then according to formula $C_D=\underset{i=0}{\overset{i=N_D/2-1}{\mathrm{\&Sigma;}}}{y}_i\&times;y_{i+N_D/2}^{*}$ Calculate the plural variable C that comprises frequency deviation information _D, i=0 wherein, 1 ... N _D-1; And

Second calculates the frequency deviation module, is used to utilize formula $f_D=\frac{1}{2\mathrm{\&pi;}{T}_C(N\&times;\mathrm{SF}+144)}\mathrm{Arctan}\left(\frac{\mathrm{Im}\left(C_D\right)}{\mathrm{Re}\left(C_D\right)}\right)$ Calculate the said second frequency offset estimation result f _D, wherein

Wherein, T _CExpression: spreading rate;

Im (C _D) expression: plural variable C _DImaginary part;

Re (C _D) expression: plural variable C _DReal part.

N representes: the data symbol number in the TD-SCDMA system in each code channel, and N=704/SF, SF are the presently used spreading factor of TD-SCDMA system;

Through Midamble sign indicating number frequency offset estimating and demodulating data frequency offset estimating are combined, realized in the TD-SCDMA system on a large scale, high-precision frequency offset estimating, make the TD network can satisfy the needs of some special screne.

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 improvement and retouching, these improvement and retouching also should be regarded as protection scope of the present invention.

Claims (7)

1. the frequency deviation estimating method in the TD-CDMA access system is characterized in that said method comprises:

Steps A, reception have back 128 chip data of the training sequence Midamble sign indicating number of frequency deviation, calculate the first frequency offset estimation result fM according to said 128 chip data and local basic Midamble yardage;

Step B, the data that will demodulate through joint-detection and the said first frequency offset estimation result fM carry out compensate of frequency deviation and calculate, and obtain the compensate of frequency deviation result;

Step C, said compensate of frequency deviation result is carried out frequency offset estimating calculate, obtain the second frequency offset estimation result f _D

Step D, to the said first frequency offset estimation result f _MWith the said second frequency offset estimation result f _DCarry out accumulation calculating, obtain the 3rd frequency offset estimation result f _O

2. method according to claim 1 is characterized in that, said steps A specifically comprises:

Step A1, by the formula

calculate the original channel estimation

where

Operator IFFT representes: fast adverse Fourier transform;

Operator FFT representes: FFT;

Operator ./expression: the contraposition of two sequences is divided by;

M representes: the basic Midamble sign indicating number in the TD-SCDMA system;

expression: back 128 the chip data that have frequency deviation Midamble sign indicating number that the TD-SCDMA system terminal receives;

Steps A 2,, said original channel carries out noise removing, the channel estimating behind the noise that is eliminated

to estimating

Steps A 3, utilize formula that

sequence is carried out reconstruction calculations, the reception signal

that obtains not having frequency deviation is operator wherein. and * expression: the contraposition of two sequences is multiplied each other;

Steps A 4, at first utilize formula Will Sequence with

The conjugate multiplication of sequence, wherein X=[x ₀, x ₁... x ₁₂₇], x is the sequence that comprises frequency deviation information; Pass through formula then Calculate the plural variable C that comprises frequency deviation information _M, wherein i is a natural number;

Steps A 5, utilize formula

Calculate the first frequency offset estimation result f _M, wherein

T _CExpression: spreading rate;

Im (C _M): represent plural variable C _MImaginary part;

Re (C _M): represent plural variable C _MReal part.

3. method according to claim 2 is characterized in that, after said steps A 5, said steps A also comprises:

Steps A 6, through formula f _M=sign (f _M) * min (f _M, F), to the said first frequency offset estimation result f _MBe optimized processing, wherein

Sign (x) function representation: the symbol of getting variable x;

(x, y) function representation: get one less in two real numbers of x and y, x, y are real number to min;

F representes: the maximum frequency deviation of foreseeing in the TD-SCDMA system.

4. method according to claim 1 is characterized in that, said step B specifically comprises:

Step B1, receive through the data sequence after the joint-detection demodulation

wherein

be i demodulating data symbols in the code channel after the joint-detection demodulation; Parameter i=0 wherein; 1; ...; N-1; N representes: the contained data symbol number of each code channel in the TD-SCDMA system; And N=704/SF, SF are the presently used spreading factor of TD-SCDMA system;

Step B2, judge that whether parameter i is less than N/2; If utilize formula

to calculate the compensate of frequency deviation result; Otherwise; Utilize formula

to calculate the compensate of frequency deviation result, Tc representes: spreading rate.

5. method according to claim 4 is characterized in that, when the data symbol that uses is each N of Midamble sign indicating number both sides _DIn the time of/2,2≤N wherein _D≤N, and N _DBe even number, N representes: the contained data symbol number of each code channel in the TD-SCDMA system, and N=704/SF, and SF is the presently used spreading factor of TD-SCDMA system, said step C specifically comprises:

Step C1, pass through formula

Carry out the hard decision of data symbol, wherein, d ' _iBe the compensate of frequency deviation result who calculates among the step B2, i=0,1 ... N _D-1;

Step C2, at first according to formula

Calculate With d _iThe y as a result of ' conjugate multiplication _i, then according to formula

Calculate the plural variable C that comprises frequency deviation information _D, i=0 wherein, 1 ... N _D-1;

Step C3, utilize formula $f_D=\frac{1}{2\mathrm{\&pi;}{T}_C(N\&times;\mathrm{SF}+144)}\mathrm{Arctan}\left(\frac{\mathrm{Im}\left(C_D\right)}{\mathrm{Re}\left(C_D\right)}\right)$ Calculate the said second frequency offset estimation result f _D, wherein

Wherein, T _CExpression: spreading rate;

Im (C _D) expression: plural variable C _DImaginary part;

Re (C _D) expression: plural variable C _DReal part.

N representes: the data symbol number in the TD-SCDMA system in each code channel, and N=704/SF, SF are the presently used spreading factor of TD-SCDMA system.

6. method according to claim 1 is characterized in that, said step C is specially:

The frequency offset estimating of step C4, employing cascade structure is to N1 _DIndividual data symbol carries out frequency offset estimating and calculates, and obtains the 4th frequency offset estimation result, wherein N1 _DBe even number;

Step C5, utilize said the 4th frequency offset estimation result all data symbols to be compensated the frequency offset estimation result after being compensated;

The frequency offset estimating of step C6, employing cascade structure is to the N2 in the frequency offset estimation result after the said compensation _DIndividual data symbol carries out frequency offset estimating, obtains the 5th frequency offset estimation result, wherein N2 _DBe even number, and N2 _DGreater than N1 _D

Step C7, said the 4th frequency offset estimation result and said the 5th frequency offset estimation result addition are obtained the said second frequency offset estimation result f _D

7. the frequency deviation estimation device in the TD-CDMA access system is characterized in that said device comprises:

Midamble data frequency offset estimator is used to receive back 128 chip data of the training sequence Midamble sign indicating number that has frequency deviation, calculates the first frequency offset estimation result f according to said 128 chip data and local basic Midamble yardage _M

The compensate of frequency deviation device is used for data that demodulate through joint-detection and the said first frequency offset estimation result f _MCarry out compensate of frequency deviation and calculate, obtain the compensate of frequency deviation result;

The demodulating data frequency offset estimator is used for that said compensate of frequency deviation result is carried out frequency offset estimating and calculates, and obtains the second frequency offset estimation result f _D

Accumulator is used for the said first frequency offset estimation result f _MWith the said second frequency offset estimation result f _DCarry out accumulation calculating, obtain the 3rd frequency offset estimation result f _O

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