A kind of frequency tracking method based on contiguous segmentation sliding window estimation frequency deviation
Technical field
The present invention relates to field of wireless communications systems, more particularly to a kind of frequency based on contiguous segmentation sliding window estimation frequency deviation
Rate tracking.
Background technique
In satellite mobile communication system, the baseband signal after demodulated down coversion is very easy to by environment, crystal oscillator not
Stable and Doppler shift influence, thus the carrier frequency shift containing dynamic change, this frequency shift (FS) can be led
It causes constellation point offset to make receiver that can not correctly demodulate source signal, therefore needs to carry out accurately carrier wave before demodulating
Frequency Synchronization simultaneously compensates.Usual carrier frequency synchronization is completed in two steps, i.e., carries out carrier wave initial acquisition and synchronous, benefit first
Repay most of frequency deviation;And then complete the capture and tracking of inherent spurious frequency deviation.Accuracy is captured in view of original frequency and frequency deviation is dynamic
The influence of state variation, accurately carrying out inherent spurious frequency deviation tracking just becomes particularly important.Unique code sign auxiliary is generallyd use now
Transmission technology, in the case where either statically or dynamically frequency deviation changes smaller situation, there are many unique code quenching frequency algorithm for estimating, such as kay to calculate
Method, fft algorithm etc., but Frequency Estimation performance of these algorithms under high dynamic frequency deviation changing environment is very unsatisfactory, is carrying out frequency
Rate can usually introduce biggish frequency error when compensating, so that frequency-tracking performance be made to decline.
Summary of the invention
It is an object of the invention to overcome the deficiencies of the prior art and provide one kind to be based on successive frame structure, auxiliary using carrier wave
It helps unique code symbol segmentation sliding window to estimate frequency deviation, and is segmented the method for progress frequency deviation compensation to realize smart Frequency Synchronization.
The purpose of the present invention is achieved through the following technical solutions: a kind of to estimate frequency deviation based on contiguous segmentation sliding window
Frequency tracking method, comprising the following steps:
S1: asking conjugation related locally known unique code sign to the unique code sign extracted from reception signal,
Remove modulation intelligence;
S2: to going unique code sign after modulation intelligence to be segmented by regular length;
S3: cumulative to every section of unique code grouping;
S4: every section of accumulated value is subjected to Frequency Estimation using frequency estimation algorithm, obtains the offset estimation value of each segmentation;
S5: successively being slided to the right with certain unique code window length, then successively calculates each point by fixed unique code length
The frequency estimation of section, thus obtains a series of continuous frequency estimations;
S6: a series of continuous frequency estimations obtained using step S5 are carried out segmentation frequency deviation to continuous data frame and mended
It repays.
The frequency estimation algorithm uses M&M algorithm, and M&M algorithm carries out the workflow of Frequency Estimation are as follows:
SS1:N unique code accumulated value seeks auto-correlation;
SS2: the phase increment of auto-correlation function is calculated;
SS3: phase increment is multiplied by smoothing factor;
Frequency estimation is calculated after SS4:M smooth phase angles are cumulative.
The offset estimation formula of the M&M algorithm are as follows:
In formula, TsFor symbol period, w (m) is smoothing factor, and R (m) is the auto-correlation function of definition, and arg { } is to seek angle
Function, unit are radian, are had:
Wherein M is algorithm design parameter, and value M=N/2, N are unique code accumulated value length, ZkExpression is gone modulated
Unique code cumulative signal.
The beneficial effects of the present invention are: being based on successive frame structure, estimated using photocarrier method unique code symbol segmentation sliding window
Frequency deviation, and the method for progress frequency deviation compensation is segmented to realize smart Frequency Synchronization.It solves existing algorithm to become in high dynamic frequency deviation
The Frequency Estimation performance changed under environment is very unsatisfactory, can usually introduce biggish frequency error when carrying out frequency compensation, thus
The problem of declining frequency-tracking performance.The present invention can reduce influence of the frequency deviation dynamic change to carrier track performance as far as possible,
Promote demodulation performance.
Detailed description of the invention
Fig. 1 is frequency-tracking flow chart of the present invention;
Fig. 2 is M&M Frequency Estimation flow chart;
Fig. 3 is that segmentation frequency deviation compensates schematic diagram.
Specific embodiment
Technical solution of the present invention is described in further detail with reference to the accompanying drawing, but protection scope of the present invention is not limited to
It is as described below.
The present invention is tired by going after modulation intelligence to be segmented unique code sign by regular length, then to every section of unique code grouping
Add, then by every section of accumulated value using M&M algorithm carry out Frequency Estimation, obtain the offset estimation value of each segmentation, and then with
Certain unique code window length is successively slided to the right, then the Frequency Estimation of each segmentation is successively calculated by fixed unique code length
Value, this makes it possible to obtain a series of continuous frequency estimations, finally using these continuous offset estimation values to continuous data frame into
Row segmentation frequency deviation compensation.
Satellite communication system usually presses frame transmission, and every frame data are by unique code (UW), data chunk at, it is assumed that every frame data
Unique code number is L, and the data symbol number between each unique code is R, and contiguous segmentation sliding window estimates the frequency of smart frequency deviation
Trace flow is as shown in Figure 1.
According to Fig. 1, unique code sign locally known first and the unique code sign extracted from reception signal
It asks conjugation related (i.e. conjugate multiplication), removes modulation intelligence;It is segmented later, if unique code regular length is 256, i.e. L=
256, according to the substantially variation range of frame dynamic frequency offset every in practical application, the unique code after conjugation can be segmented, such as will
256 UW points are 4 sections, and every section then includes 64 unique codes;The maximum of dynamic frequency offset range and M&M algorithm further according to data frame
Frequency Estimation range comprehensively considers, and every section of unique code can be divided into n group, and every group of m UW adds up, then M&M algorithm at this time
Maximum frequency estimation range be {-Fd/(2*m*R),Fd/ (2*m*R) }, wherein FdFor the character rate of channel frame, as long as guaranteeing
The maximum dynamic frequency offset one of data frame is scheduled within the scope of the Frequency Estimation of M&M algorithm;It is assumed that n=16, m=4, next
Every section of 16 groups of accumulated values are subjected to Frequency Estimation using M&M algorithm, obtain 4 frequency estimations, the workflow of M&M algorithm
As shown in Figure 2.
As shown in Fig. 2, M&M Frequency Estimation is by asking the auto-correlation function of accumulated value and the phase increment of the autocorrelation sequence
It realizes, offset estimation formula are as follows:
In formula, TsFor symbol period, w (m) is smoothing factor, and R (m) is the auto-correlation function of definition, and arg { } is to seek angle
Function (unit is radian), has:
Wherein M is algorithm design parameter, and optimal value is M=N/2, and N is unique code accumulated value length, ZkExpression goes to modulate
Unique code cumulative signal afterwards.
Next it using fixed unique code length as sliding window, successively slides R times to the right, then long by the fixation window of L=256
R*4 frequency estimation is successively calculated, wherein R and sliding window are long different with channel speed value according to different frame structures;Most
Segmentation frequency deviation is carried out to this frame data using * 4 frequency estimations of (R+1) acquired afterwards to compensate.Here with L=256, R
For=1, specific segmentation frequency deviation compensation schematic diagram is as shown in Figure 3.
It is 4 sections, every section of 64 UW by 256 UW points according to Fig. 3, can be calculated with fixing window long 256 first4
Offset estimation value, then sliding window can once calculate to the rightThus it may make up8
A continuous offset estimation value;As shown in figure 3, this frame data is segmented by dashed rectangle label again, the number of each label
Its corresponding offset estimation value is respectively adopted according to section to compensate, it can be seen thatCorresponding data segment crosses over two frames, i.e., next
The preceding 16*R data of frame data will carry out frequency deviation compensation, corresponding previous frequency using this last one calculated frequency deviation value
Last k frequency estimation is returned in trace flow figure to next secondary tracking, k is according to specific performance requirement, frame structure and channel
Rate is different and value is different, k=1 in this schematic diagram.It must further be noted that if present frame is first frame, it can be seen thatIt is corresponding
First data segment before there are also 16*R data, due to there is no return value when first frame calculates, this one piece of data
It can useCarry out frequency deviation compensation.
The above is only a preferred embodiment of the present invention, it should be understood that the present invention is not limited to described herein
Form should not be regarded as an exclusion of other examples, and can be used for other combinations, modifications, and environments, and can be at this
In the text contemplated scope, modifications can be made through the above teachings or related fields of technology or knowledge.And those skilled in the art institute into
Capable modifications and changes do not depart from the spirit and scope of the present invention, then all should be in the protection scope of appended claims of the present invention
It is interior.M&M algorithm of the present invention, other communication specialities personnel can be substituted with other frequency estimating methods, then all Ying Ben
In the protection scope of invention appended claims.