CN102347924B - Frequency offset estimation and timing method and device - Google Patents
Frequency offset estimation and timing method and device Download PDFInfo
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Abstract
The invention discloses a frequency offset estimation and timing method and a frequency offset estimation and timing device. The method comprises the following steps of: performing rough timing on a received signal according to a rough timing scheme to obtain a rough timing result; performing decimal frequency offset estimation based on a repetitive structure of the received signal according to the rough timing result to obtain a decimal frequency offset estimation result; determining a searching window according to an error range of the rough timing result and the positions of ghost peaks produced by integral frequency offsets; and in the searching window, performing integral frequency offset detection on the received signal by utilizing the decimal frequency offset estimation result and at least one integral frequency offset, and obtaining an integral frequency offset estimation result and a precise timing result according to an integral frequency offset detection result. By the method and the device, the influence of the ghost peaks and noises on the frequency offset estimation results can be eliminated, the problem of over-high processing load caused by an irrational searching range in related technologies can be solved, and the frequency offset estimation and timing precision can be effectively improved; and the method and the device can be effectively adapted to scenes with high noises and frequency offsets.
Description
Technical field
The present invention relates to the communications field, relate in particular to a kind of frequency deviation and estimate and method and apparatus regularly.
Background technology
Multi-transceiver technology is a kind of Highspeed Data Transmission Technology, it is decomposed into data flow at a high speed the data flow of several low speed, each low rate data streams is parallel transmission on the subcarrier of quadrature, and than single-carrier system, multicarrier system has higher frequency efficiency.OFDM (Orthogonal Frequency Division Multiplexing, referred to as OFDM) be a kind of typical multicarrier system, it has introduced Cyclic Prefix (Cyclic Prefix, referred to as CP), can effectively overcome the intersymbol interference that multipath fading causes.OFDM is the core technology of Long Term Evolution (Long Term Evolution, referred to as LTE) system and the 4th Generation Mobile Communication System, and is adopted by a plurality of industrial standard.
It is a key factor that affects ofdm system performance that timing and frequency deviation are estimated, regularly refer to the original position of determining multicarrier frame or blocks of multicarrier symbols, to carry out anti-fast fourier transform (Inverse Fast Fourier Transform, IFFT) operation.Due to the carrier wave frequency deviation that the difference of Receiver And Transmitter crystal oscillator frequency produces, the orthogonality by destroying between subcarrier, will produce between serious subcarrier and disturb, and reduces the performance of system.So before IFFT operation, must carry out timing and frequency deviation and estimate and compensate.
The method that conventional ofdm system timing and frequency deviation are estimated has autocorrelation method and the cross-correlation method based on training sequence based on receiving signal repetitive structure.Typically the autocorrelation method based on receiving signal repetitive structure is timing and the frequency deviation combined estimation based on CP.The method has reasonable detector timing properties b under Gaussian channel.Because the autocorrelation peak that the method adopts is sharp-pointed not, under multipath channel, detector timing properties b obviously declines.The estimation range of the frequency deviation estimating method based on CP is less, only limits to subcarrier spacing half.At zero-frequency on the lower side, the cross-correlation method based on training sequence has good detector timing properties b, can produce sharp-pointed relevant peaks, but under non-zero frequency deviation, relevant peaks is subject to the impact of frequency deviation and the impact of the training sequence correlation that adopts.Zero correlation (Zero Correlation, referred to as ZC) sequence is a kind of conventional training sequence.At zero-frequency on the lower side, this sequence has good autocorrelation performance.But when there is large frequency deviation and even integer frequency offset, the correlation degradation of ZC sequence, can produce a lot of larger secondary lobes, adopt usual method cannot carry out timing and frequency deviation estimation.
Particularly, LTE system is the evolution of the third generation (3G) communication system, is that third generation partner program (3rd Generation Partnership Project, 3GPP) is in the global radio mobile communication standard of the 3.9G of proposition in 2004.LTE can improve and strengthen the air interface technologies of 3G system, adopts OFDM and multiple-input and multiple-output (Multiple-Input Multiple-Output, referred to as MIMO) as the sole criterion of its wireless network evolution.LTE system can provide the peak rate of descending 100Mbit/s and up 50Mbit/s under the system bandwidth of 20MHz.Meanwhile, LTE system can also be improved the performance of Cell Edge User, improves cell capacity, and can reduce system delay.
LTE system descending adopts OFDM (Orthogonal Frequency Division Multiple Access, OFDMA) access way, than single-carrier system, there is higher band efficiency, and can, by going here and there and changing the time that has greatly extended each symbol, can effectively resist the frequency selective fading that in mobile radio telecommunications, multidiameter delay causes; But the symbol period relatively increasing also causes LTE system more responsive than single-carrier system for carrier shift, makes LTE systematic function degradation.
The reason that causes carrier frequency shift (herein by frequency shift (FS) referred to as frequency deviation) is mainly that unsteadiness and the terminal high-speed of transmitter and receiver crystal oscillator moves the Doppler frequency shift causing.When there is frequency deviation between receiving and transmitting signal, be easy to cause the interference between each subcarrier, affect the correct demodulation of data, cause the increase of the error rate; When there is integer frequency offset, although there is no the interference between subcarrier, but the integral multiple skew due to subcarrier, make to lose correlation between data out of demodulation and the data of transmission, cause error rate of system to increase (in most cases the error rate can reach 50%), can not meet the basic demand of communication.
In LTE, existing frequency deviation estimation and timing method mainly contain following two kinds:
(method 1) adopts master sync signal (Primary Synchronization Signal, referred to as PSS) to carry out frequency deviation estimation and timing.For which, it is that in 3 candidate ZC sequences of 25,29,34 one represents that the master sync signal of LTE adopts radical exponent.This ZC sequence has good correlated performance on the lower side at zero-frequency, can reach higher frequency deviation and estimate and timing accuracy; But when there is frequency departure, while particularly there is large frequency deviation or even integer frequency offset, the correlation of ZC sequence can obviously reduce, and can produce more great secondary lobe, cannot effectively solve frequency deviation.
(method 2) adopts Cyclic Prefix (Cyclic Prefix, referred to as CP) to carry out frequency deviation estimation and timing.But, because this relevant peaks obtaining based on CP mode is regularly sharp-pointed not, easily be subject to the impact of noise, can reduce precision regularly, and when frequency deviation is greater than half subcarrier spacing, the accumulation of phase causing due to frequency deviation between two sampling points of difference can surpass one-period, cause carrying out correct Frequency Estimation, therefore, this method based on CP is only adapted at when low noise and frequency deviation are less than half subcarrier spacing applying, and has larger limitation.
Equally, at other, adopt in the communication system that comprises repeating part in multicarrier, signal structure, frequency deviation is estimated and regularly can be had Similar Problems equally.
Problem for the frequency deviation in correlation technique is estimated and timing accuracy is low and limitation is large, not yet proposes effective solution at present.
Summary of the invention
For the problem that the frequency deviation in correlation technique is estimated and timing accuracy is low and limitation is large, the present invention proposes a kind of frequency deviation and estimates and method and apparatus regularly, can effectively improve frequency deviation and estimate and precision regularly, and can be applicable to the scene of strong noise and large frequency deviation.
Technical scheme of the present invention is achieved in that
According to an aspect of the present invention, provide a kind of frequency deviation to estimate and method regularly.
According to frequency deviation of the present invention, estimate to comprise with method regularly: according to thick timing, carry out to received signal thick timing, obtain thick timing results; Repetitive structure based on described reception signal also carries out fractional part of frequency offset estimation according to described thick timing results, obtains fractional part of frequency offset estimated result; The location positioning search window at the false peak causing according to the error range of described thick timing results and integer frequency offset; In described search window, utilize described fractional part of frequency offset estimated result and at least one integer frequency offset to carry out integer frequency offset detection to described reception signal, and obtain integer frequency offset estimation result and accurate timing result according to integer frequency offset testing result.
Wherein, according to integer frequency offset testing result, obtain integer frequency offset estimation result and accurate timing result comprises: for each integer frequency offset that carries out integer frequency offset detection and adopt, utilize this integer frequency offset and described fractional part of frequency offset estimated result, described reception signal is carried out to compensate of frequency deviation, and in described search window, utilize the described reception signal after predetermined local signal and compensate of frequency deviation to carry out computing cross-correlation, using computing cross-correlation result as described testing result; Or
For each integer frequency offset that carries out integer frequency offset detection and adopt, utilize this integer frequency offset and described fractional part of frequency offset estimated result, predetermined local signal is carried out to compensate of frequency deviation, and in described search window, utilize described local signal and described reception signal after compensate of frequency deviation to carry out computing cross-correlation, using computing cross-correlation result as described testing result; Or
For each integer frequency offset that carries out integer frequency offset detection and adopt, utilize this integer frequency offset to carry out integer frequency offset compensation to predetermined local signal, and utilize described fractional part of frequency offset estimated result to carry out fractional part of frequency offset compensation to described reception signal, described reception signal after local signal after integer frequency offset compensation and fractional part of frequency offset compensation is carried out to computing cross-correlation, using computing cross-correlation result as described testing result; Or
For each integer frequency offset that carries out integer frequency offset detection and adopt, utilize this integer frequency offset to carry out integer frequency offset compensation to described reception signal, and utilize described fractional part of frequency offset estimated result to carry out fractional part of frequency offset compensation to predetermined local signal, local signal after reception signal after integer frequency offset compensation and fractional part of frequency offset compensation is carried out to computing cross-correlation, using computing cross-correlation result as described testing result.
In addition, according to integer frequency offset testing result, obtain integer frequency offset estimation result and accurate timing result comprises: the cross correlation value in the corresponding testing result of all integer frequency offsets is compared, using the corresponding integer frequency offset of the maximum cross-correlation value relatively obtaining as described integer frequency offset estimation result, and using the time location of described maximum cross-correlation value as described accurate timing result.
In addition, according to described thick timing, described reception signal is carried out to thick timing and comprise: the repetitive structure based on described reception signal, according to described thick timing, described reception signal is carried out to Autocorrelation Detection, obtain described thick timing results.
Preferably, the repetitive structure based on described reception signal according to described thick timing results, described reception signal is carried out to fractional part of frequency offset and estimate to comprise:
In the error range of described thick timing results, delete the sampled point in following sampled point set: { K, K+1 ..., K+N-1} and { K+L-N, K+L-N+1, ..., K+L-1}, wherein, K is the corresponding sampled point of described thick timing results, [N, N] is the error range of described thick timing results, and L is the sampling number of repeating part in the repetitive structure of described reception signal; Reception signal after sampled point being deleted based on auto-correlation scheme carries out fractional part of frequency offset estimation, obtains described decimal frequency bias estimated result.
In addition, the described search window of determining comprises described thick timing error scope, and does not comprise described false peak.
According to an aspect of the present invention, provide a kind of frequency deviation to estimate and device regularly.
According to frequency deviation of the present invention, estimate to comprise with device regularly: thick time block, for carrying out to received signal thick timing according to thick timing, obtains thick timing results; The first estimation module, carries out fractional part of frequency offset estimation for the repetitive structure based on described reception signal and according to described thick timing results, obtains fractional part of frequency offset estimated result; Determination module, for the location positioning search window at the false peak that causes according to the error range of described thick timing results and integer frequency offset; Detection module, in described search window, utilizes described fractional part of frequency offset estimated result and at least one integer frequency offset to carry out integer frequency offset detection to described reception signal; The second estimation module, for obtaining integer frequency offset estimation result and accurate timing result according to integer frequency offset testing result.
Wherein, described detection module each integer frequency offset for adopting carrying out integer frequency offset detection, utilize this integer frequency offset and described fractional part of frequency offset estimated result, described reception signal is carried out to compensate of frequency deviation, and in described search window, utilize the described reception signal after predetermined local signal and compensate of frequency deviation to carry out computing cross-correlation, using computing cross-correlation result as described testing result; Or
Described detection module each integer frequency offset for adopting carrying out integer frequency offset detection, utilize this integer frequency offset and described fractional part of frequency offset estimated result, predetermined local signal is carried out to compensate of frequency deviation, and in described search window, utilize described local signal and described reception signal after compensate of frequency deviation to carry out computing cross-correlation, using computing cross-correlation result as described testing result; Or
Described detection module each integer frequency offset for adopting carrying out integer frequency offset detection, utilize this integer frequency offset to carry out integer frequency offset compensation to predetermined local signal, and utilize described fractional part of frequency offset estimated result to carry out fractional part of frequency offset compensation to described reception signal, described reception signal after local signal after integer frequency offset compensation and fractional part of frequency offset compensation is carried out to computing cross-correlation, using computing cross-correlation result as described testing result; Or
Described detection module each integer frequency offset for adopting carrying out integer frequency offset detection, utilize this integer frequency offset to carry out integer frequency offset compensation to described reception signal, and utilize described fractional part of frequency offset estimated result to carry out fractional part of frequency offset compensation to predetermined local signal, local signal after reception signal after integer frequency offset compensation and fractional part of frequency offset compensation is carried out to computing cross-correlation, using computing cross-correlation result as described testing result.
In addition, described the second estimation module is for comparing the cross correlation value of the corresponding testing result of all integer frequency offsets, using the corresponding integer frequency offset of the maximum cross-correlation value relatively obtaining as described integer frequency offset estimation result, and using the time location of described maximum cross-correlation value as described accurate timing result.
In addition, described thick time block, specifically for the repetitive structure based on described reception signal, carries out Autocorrelation Detection according to described thick timing to described reception signal, obtains described thick timing results.
Alternatively, repetitive structure in described the first estimation module based on described reception signal also carries out fractional part of frequency offset while estimating according to described thick timing results to described reception signal, described the first estimation module for deleting the sampled point of following sampled point set in the error range of described thick timing results: { K, K+1, ..., K+N-1}, and { K+L-N, K+L-N+1, ..., K+L-1}, wherein, K is the corresponding sampled point of described thick timing results, [N, N] be the error range of described thick timing results, L is the sampling number of repeating part in the repetitive structure of described reception signal, and carry out fractional part of frequency offset estimation for the reception signal after sampled point being deleted based on auto-correlation scheme, obtain described decimal frequency bias estimated result.
In addition, the described search window of being determined by described determination module comprises described thick timing error scope, and does not comprise described false peak.
The present invention is by rational position and the size of the location positioning search window at the thick timing results of basis and false peak, and in definite search window, carry out integer frequency offset detection, obtain integer frequency offset estimation result and accurate timing result, can eliminate the impact on frequency offset estimation result of false peak and noise, and can avoid because hunting zone is unreasonable, causing in correlation technique the excessive problem for the treatment of capacity, effectively improve frequency deviation and estimate and accuracy regularly, can effectively adapt to the scene of strong noise, large frequency deviation.
Accompanying drawing explanation
Fig. 1 is according to the frequency deviation estimation of the embodiment of the present invention and the flow chart of method regularly;
Fig. 2 is according to the flow chart of the concrete processing example of the frequency deviation estimation of the embodiment of the present invention and method regularly;
Fig. 3 is according to determining the process chart of search window in the frequency deviation estimation of the embodiment of the present invention and method regularly;
Fig. 4 is according to the frequency deviation estimation of the embodiment of the present invention and the block diagram of device regularly.
Embodiment
For the problem that correlation technique frequency deviation is estimated and timing accuracy is low and limitation is large, the give chapter and verse rational search window of location positioning at thick timing results and false peak of the present invention, and in definite search window, carry out integer frequency offset detection, obtain integer frequency offset estimation result and accurate timing result, can avoid in correlation technique hunting zone unreasonable and cause the excessive problem for the treatment of capacity, and can eliminate the impact on frequency offset estimation result of false peak and noise, effectively improve frequency deviation and estimate and accuracy regularly.
Below in conjunction with accompanying drawing, describe embodiments of the invention in detail.
According to embodiments of the invention, provide a kind of frequency deviation to estimate and method regularly.
As shown in Figure 1, according to the frequency deviation of the embodiment of the present invention, estimate to comprise with method regularly:
Step S101, carries out thick timing to received signal according to thick timing, obtains thick timing results;
Step S103, the repetitive structure based on receiving signal is (for example,, in LTE system, repetitive structure is CP, and in 802.11a system, the part of repetition is short leader sequence and long preambles sequence) and carry out fractional part of frequency offset estimation according to thick timing results, obtain fractional part of frequency offset estimated result;
Step S105, the location positioning search window at the false peak causing according to the error range of thick timing results and integer frequency offset;
Step S107, in search window, utilize fractional part of frequency offset estimated result and at least one integer frequency offset to carry out to received signal integer frequency offset detection, and obtain integer frequency offset estimation result and accurate timing result according to integer frequency offset testing result, like this, according to the fractional part of frequency offset estimated result obtaining before and integer frequency offset estimation result, just can access final frequency offset estimation result.
By means of above-mentioned processing, by the location positioning rational position at the thick timing results of basis and false peak and the search window of suitable size, and in definite search window, carry out integer frequency offset detection, obtain integer frequency offset estimation result and accurate timing result, can eliminate the impact on frequency offset estimation result of false peak and noise, and can avoid because hunting zone is unreasonable, causing in correlation technique the excessive problem for the treatment of capacity, effectively improve frequency deviation and estimate and accuracy regularly, can effectively adapt to the scene of strong noise, large frequency deviation.
In above-mentioned processing, while obtaining integer frequency offset estimation result and accurate timing result according to integer frequency offset testing result, be mainly concerned with local signal and receive signal, and need to utilize fractional part of frequency offset estimated result and a plurality of integer frequency offset (for example, f
sc, 2f
scdeng, f wherein
scfor subcarrier spacing) carry out repeated detection, concrete detection can be divided into following 4 kinds of processing modes:
Processing mode one: for carrying out each integer frequency offset that integer frequency offset detection adopts (, when utilizing an integer frequency offset to carry out one-time detection), utilize this integer frequency offset and fractional part of frequency offset estimated result, carry out to received signal compensate of frequency deviation, and in search window, utilize predetermined local signal and the reception signal after compensate of frequency deviation to carry out computing cross-correlation, using computing cross-correlation result as testing result; Or
Processing mode two: for each integer frequency offset that carries out integer frequency offset detection and adopt, utilize this integer frequency offset and fractional part of frequency offset estimated result, predetermined local signal is carried out to compensate of frequency deviation, and in search window, utilize the local signal after compensate of frequency deviation to carry out computing cross-correlation with reception signal, using computing cross-correlation result as testing result; Or
Processing mode three: for each integer frequency offset that carries out integer frequency offset detection and adopt, utilize this integer frequency offset to carry out integer frequency offset compensation to predetermined local signal, and utilize fractional part of frequency offset estimated result to carry out to received signal fractional part of frequency offset compensation, reception signal after local signal after integer frequency offset compensation and fractional part of frequency offset compensation is carried out to computing cross-correlation, using computing cross-correlation result as testing result; Or
Processing mode four: for each integer frequency offset that carries out integer frequency offset detection and adopt, utilize this integer frequency offset to carry out to received signal integer frequency offset compensation, and utilize fractional part of frequency offset estimated result to carry out fractional part of frequency offset compensation to predetermined local signal, local signal after reception signal after integer frequency offset compensation and fractional part of frequency offset compensation is carried out to computing cross-correlation, using computing cross-correlation result as testing result.
When obtaining integer frequency offset estimation result and accurate timing result according to integer frequency offset testing result, can be by the corresponding testing result of all integer frequency offsets (, all testing results) cross correlation value in compares, using the corresponding integer frequency offset of the maximum cross-correlation value relatively obtaining as integer frequency offset estimation result, and using the time location of maximum cross-correlation value as accurate timing result.
For example, suppose after relatively, the maximum cross-correlation value obtaining is by f
scwhile detecting as integer frequency offset, obtain, now, by f
scas integer frequency offset estimation result, by f
scthe time location of corresponding this maximum cross-correlation value is as accurate timing result.
In addition, carrying out according to thick timing, thick process is regularly as follows: the repetitive structure based on receiving signal, according to thick timing, carry out to received signal Autocorrelation Detection, and obtain thick timing results.
In order to improve the accuracy of fractional part of frequency offset estimated result, when carrying out fractional part of frequency offset estimation, can in the error range of thick timing results, delete the sampled point in following sampled point set: { K, K+1 ..., K+N-1} and { K+L-N, K+L-N+1, ..., K+L-1}, wherein, K is the corresponding sampled point of thick timing results, [N, N] is the error range of thick timing results, and L is the sampling number of repeating part in the repetitive structure of reception signal; Reception signal after sampled point being deleted based on auto-correlation scheme carries out fractional part of frequency offset estimation, obtains decimal frequency bias estimated result.By deleting the sampled point in error range, can effectively improve the accuracy of fractional part of frequency offset estimated result, thereby contribute to further to improve the accuracy of integer frequency offset estimation.
In addition, definite search window should comprise thick timing error scope, thereby follow-up integer frequency offset is detected and can traverse all positions that correct timing may occur, in addition, search window should not comprise false peak, thus the harmful effect of avoiding false peak that frequency deviation is estimated and regularly brought.When determining search window, can be using the scope of thick timing results as minimum search window, using the peak-to-peak region of falseness, (error range of the thick timing results of this district inclusion) is as maximum search window (maximum search window does not comprise false peak), when practical operation, can detect with minimum search window or maximum search window, in addition, can also determine the actual search window adopting according to minimum search window and maximum search window, this definite window should comprise thick timing error scope, and does not comprise false peak.
LTE downlink system will take below as example, describe the present invention in detail and in LTE downlink system, carry out frequency deviation estimation and process regularly.Those skilled in the art are to be understood that, application process described below is only for setting forth the solution of the present invention, and be not used in restriction the present invention, the present invention goes for various employing multicarriers and signal has the wireless communication system of repetitive structure, and reaches the object of accurately carrying out frequency deviation estimation and timing.
As shown in Figure 2, in LTE downlink system, the method for the employing embodiment of the present invention is carried out frequency deviation and is estimated with process regularly as follows:
Step 21, carries out the thick timing of OFDM symbol according to formula (1) and formula (2).In this step, can carry out thick timing based on CP, CP Symbol Timing belongs to auto-correlation processing, can adapt to certain channel variation, although the relevant peaks is regularly sharp-pointed not, by some symbols cumulative, carry out thick timing offset statistics, can be by timing error Δ T
sbe controlled in tens sampling points.
Wherein, r
l(n) be l the descending ofdm signal of LTE receiving, N
cPbe circulating prefix-length, N is OFDM symbol lengths, and l is the sequence number of OFDM symbol, and, n ∈ { N
cP, N
cP+ 1 ..., N+N
cP.In order to fall low noise impact, after processing according to formula (1), can carry out M symbol according to formula (2) and add up, get maximum, the corresponding time location of this maximum is thick timing results K.
Step 22, completes fractional part of frequency offset according to formula (3) and estimates.In order to remove the impact of timing error in formula (1), when carrying out fractional part of frequency offset estimation, by formula (3), can remove the sampled point within the scope of timing error.
By means of formula (3), by the error sampled point in error range is removed, can effectively improve the precision that fractional part of frequency offset is estimated, and then can accurately estimate the frequency deviation result in the situation of decimal frequency bias.The impact causing when frequency deviation surpasses one-period, that is, between LTE OFDM receiving and transmitting signal, exist in the situation of integer frequency offset, only by fractional part of frequency offset, estimate to obtain correct estimated result, therefore need to continue to carry out subsequent step, that is, carry out integer frequency offset estimation.
Step 23, according to CP precision (that is, according to the error range of thick timing) regularly, determines the minimum search window W that frequency deviation is estimated
min.Minimum search window is wanted to travel through CP timing error, that is, and and minimum search window W
minsize can pass through formula (4) and represent:
W
min> Δ T
sformula (4)
That is to say, search window should comprise the whole error range of thick timing results.
Step 24, determines maximum search window according to the peak distance of integer frequency offset.Due in the situation that there is integer frequency offset, the IFFT conversion that forms the ZC sequence of LTE PSS is the ZC sequence of circulation Weighted Shifts, adds frequency deviation to be equivalent to it to carry out cyclic shift, now, the correlation of PSS is destroyed, produces secondary lobe, cannot distinguish different integer frequency offsets.But due under different integer frequency bias, the position at ZC Serial relation peak is different, so can adopt the position difference of relevant peaks to distinguish integer frequency offset.
Suppose when without integer frequency bias, relevant peaks is positioned at the original position of symbol, in the situation that there is integer frequency bias, the false relevant peaks distance nearest apart from symbol original position is D sample value, wherein, D is the relevant peaks that forms three ZC sequences of LTE PSS and adopt maximum likelihood method to detect when different integer frequency offset to obtain (, false peak) position, can be by advance by calculating and statistics obtains.
Maximum search window W
maxshould not surpass the position that false relevant peaks may occur, can pass through formula (5) and represent maximum search window:
W
max< D formula (5)
Step 25, according to definite before maximum search window and minimum search window, can determine the search window W of final employing
sear.Due to the maximum frequency deviation scope of needs traversal, therefore, can between minimum and maximum search window, select final search window, final definite search window can represent by formula (6):
W
min< W
sear< W
maxformula (6)
Step 26, the search window definite according to step 25, adopts the maximum likelihood method based on window search to carry out integer frequency offset detection (can utilize a plurality of integer frequency offsets to attempt), finally determines integer frequency offset f
iFO, can obtain accurate timing result K simultaneously
pric.
Particularly, take above-mentioned (processing mode one) be example, the decimal frequency bias obtaining by step 22 is f
fFO, carry out to the received signal decimal frequency bias compensation, the reception signal after being compensated, as shown in formula (7):
S (n)=r (n) exp (j2 π f
fFOnT
s) formula (7)
Local ZC sequence is L (n) after IFFT conversion, according to different integer frequency offset exp (j2 π mf for formula (8)
sckT
s) the reception signal after fractional part of frequency offset compensation is detected, that is:
Wherein, l is the sequence number of OFDM symbol, l ∈ 0 ..., N
symb-1}, N
symbfor the PSS of 5ms OFDM symbolic number in the cycle, m is the integer frequency offset of traversal, and K is the thick timing results of symbol that step 21 obtains, and N is the length of OFDM symbol, N
cPfor the length of Cyclic Prefix, f
scfor OFDM subcarrier spacing, T
sfor the sample time, L
*(n) be the conjugation of local sequence L (n), p is the sampling point sequence number of search in an OFMD symbol, and scope is as follows:
I in formula (8) is PSS 5ms cycle sequence number, by searching for a plurality of PSS cycle, then the search correlation of different cycles is added up, and can effectively suppress the impact of noise, improves accuracy of detection.Utilizing integer frequency offset to carry out after integer frequency offset detects, can determining integer frequency offset f by formula (9)
iFOwith accurate OFDM Symbol Timing P
pric.
Wherein, f
iFO=m
0, P
pric=p
0.
In above-mentioned processing, step 22 and step 23 can be carried out independently of one another to 25, that is, step 22 and step 23, to 25 being executed in parallel, can be also that sequencing is carried out.And step 24 can also be carried out before step 21.
Step 23,24 and 25 is to determine the step of search window, and Fig. 3 shows the detailed process of determining search window, as shown in Figure 3, determines that the mistake of search window is old as follows:
Step 31, carries out thick timing based on Cyclic Prefix;
Step 32, carries out thick timing offset statistics, obtains the error range of thick timing results;
Step 33, according to the error range of thick timing results, determines minimum search window (minimum search window should comprise error range);
Step 34, carries out integer frequency offset time domain peak distance and calculates, and, determines the position at false peak that is;
Step 35, according to the location positioning maximum search window at false peak;
Step 36, minimum search window and the definite maximum search window of step 35 according to step 33, determined are determined actual search window, this actual search window can comprise minimum search window, and is contained in maximum search window.
Wherein, step 31 can be carried out to 35 with step 34 independently of one another to 33, that is, step 31 to 33 with step 34 to 35 being executed in parallel, can be also that sequencing is carried out.
By means of above-mentioned processing, by the reasonable limits of the ofdm signal search window to through thick Symbol Timing and fractional part of frequency offset estimation, can on the basis of the thick timing of existing OFDM symbol, in conjunction with PSS, carry out frequency deviation estimation and accurate timing, the appearance of PSS secondary lobe while having avoided integer frequency offset, has eliminated the harmful effect that secondary lobe brings.And because search window is much smaller than the window adopting in correlation technique, treating capacity and Processing Test in the time of can effectively reducing each integer frequency offset and detect, reduce the complexity of system.Above-mentioned processing not only can be issued to good precision in little frequency deviation, low noise situation, in the situation that there is even integer frequency offset of strong noise, large frequency deviation, still can access accurate sending and receiving end frequency deviation and estimate and timing results.
According to embodiments of the invention, also provide a kind of frequency deviation to estimate and device regularly.
As shown in Figure 4, according to the frequency deviation of the embodiment of the present invention, estimate to comprise with device regularly:
Thick time block 41, for carrying out to received signal thick timing according to thick timing, obtains thick timing results;
The first estimation module 42, is connected to thick time block 41, for based on receiving the repetitive structure of signal and carrying out fractional part of frequency offset estimation according to thick timing results, obtains fractional part of frequency offset estimated result;
Determination module 43, thick time block 41, for the thick error range of timing results of basis and the location positioning search window at the false peak that integer frequency offset causes;
Detection module 44, is connected to determination module 43 and the first estimation module 42, in search window, utilizes fractional part of frequency offset estimated result and at least one integer frequency offset to carry out to received signal integer frequency offset detection;
The second estimation module 45, is connected to detection module 44, for obtain integer frequency offset estimation result and accurate timing result according to integer frequency offset testing result.
Detection module 44 can carry out integer frequency offset detection by mode in following 4:
Processing mode one: detection module 44 each integer frequency offset for adopting carrying out integer frequency offset detection, utilize this integer frequency offset and fractional part of frequency offset estimated result, carry out to received signal compensate of frequency deviation, and in search window, utilize predetermined local signal and the reception signal after compensate of frequency deviation to carry out computing cross-correlation, using computing cross-correlation result as testing result; Or
Processing mode two: detection module 44 each integer frequency offset for adopting carrying out integer frequency offset detection, utilize this integer frequency offset and fractional part of frequency offset estimated result, predetermined local signal is carried out to compensate of frequency deviation, and in search window, utilize the local signal after compensate of frequency deviation to carry out computing cross-correlation with reception signal, using computing cross-correlation result as testing result; Or
Processing mode three: detection module 44 each integer frequency offset for adopting carrying out integer frequency offset detection, utilize this integer frequency offset to carry out integer frequency offset compensation to predetermined local signal, and utilize fractional part of frequency offset estimated result to carry out to received signal fractional part of frequency offset compensation, reception signal after local signal after integer frequency offset compensation and fractional part of frequency offset compensation is carried out to computing cross-correlation, using computing cross-correlation result as testing result; Or
Processing mode four: detection module each integer frequency offset for adopting carrying out integer frequency offset detection, utilize this integer frequency offset to carry out to received signal integer frequency offset compensation, and utilize fractional part of frequency offset estimated result to carry out fractional part of frequency offset compensation to predetermined local signal, local signal after reception signal after integer frequency offset compensation and fractional part of frequency offset compensation is carried out to computing cross-correlation, using computing cross-correlation result as testing result.
The second estimation module 45 is specifically for comparing the cross correlation value in the corresponding testing result of all integer frequency offsets, using the corresponding integer frequency offset of the maximum cross-correlation value relatively obtaining as integer frequency offset estimation result, and using the time location of maximum cross-correlation value as accurate timing result.
Thick time block 41, specifically for the repetitive structure based on receiving signal, carries out Autocorrelation Detection to received signal according to thick timing, obtains thick timing results.
When the repetitive structure in the first estimation module 42 based on receiving signal also carries out fractional part of frequency offset estimation to received signal according to thick timing results, the first estimation module 42 is for deleting the sampled point of following sampled point set in the error range in thick timing results: { K, K+1, ..., K+N-1} and { K+L-N, K+L-N+1, ..., K+L-1}, wherein, K is the corresponding sampled point of thick timing results, [N, N] be the error range of thick timing results, L is the sampling number of repeating part in the repetitive structure of reception signal; And carry out fractional part of frequency offset estimation for the reception signal after sampled point being deleted based on auto-correlation scheme, obtain decimal frequency bias estimated result.In addition, the search window of being determined by determination module 43 comprises thick timing error scope, and does not comprise false peak.
Fig. 4 is the device corresponding with previous methods, the processing of this device shown in equally can execution graph 1 to 3, and its course of work and operation principle have been described in detail in method part, do not repeat them here.
It should be noted that, although frequency deviation is estimated to be described with process regularly with LTE system and according to OFDM symbol before, but the present invention is not limited to this, in other system, can reach based on above-mentioned processing procedure the object of frequency deviation estimation and accurate timing equally, for example, in 802.11a system, can carry out above-mentioned processing according to the short leader sequence and the long preambles sequence that repeat, and in other system, those skilled in the art know the repeating part of signal equally, therefore the detailed process in other system is similar with the process of describing before, no longer describe in detail herein.
In sum, by means of technique scheme of the present invention, by the thick Symbol Timing of process is carried out to error deletion, and search window is carried out to reasonable limits, can effectively improve frequency deviation and estimate and precision regularly, avoid false peak to estimate and impact regularly frequency deviation; And, in the situation that strong noise, large frequency deviation integer frequency offset even still can access accurate sending and receiving end frequency deviation and estimate and timing results; In addition,, because search window is much smaller than the window adopting in correlation technique, treating capacity and Processing Test in the time of can effectively reducing each integer frequency offset and detect, reduce the complexity of system.
The foregoing is only preferred embodiment of the present invention, in order to limit the present invention, within the spirit and principles in the present invention not all, any modification of doing, be equal to replacement, improvement etc., within all should being included in protection scope of the present invention.
Claims (12)
1. frequency deviation is estimated and a method regularly, it is characterized in that, described method comprises:
According to thick timing, carry out to received signal thick timing, obtain thick timing results;
Repetitive structure based on described reception signal also carries out fractional part of frequency offset estimation according to described thick timing results, obtains fractional part of frequency offset estimated result;
The location positioning search window at the false peak causing according to the error range of described thick timing results and integer frequency offset, comprise: in the situation that there is integer frequency offset, false peak separation is D sample value from the nearest distance of symbol original position, wherein, D adopts maximum likelihood method to detect the false peak position obtaining for forming three ZC sequences of LTE PSS when different integer frequency offset;
In described search window, utilize described fractional part of frequency offset estimated result and at least one integer frequency offset to carry out integer frequency offset detection to described reception signal, and obtain integer frequency offset estimation result and accurate timing result according to integer frequency offset testing result.
2. method according to claim 1, is characterized in that, according to integer frequency offset testing result, obtains integer frequency offset estimation result and accurate timing result comprises:
For each integer frequency offset that carries out integer frequency offset detection and adopt, utilize this integer frequency offset and described fractional part of frequency offset estimated result, described reception signal is carried out to compensate of frequency deviation, and in described search window, utilize the described reception signal after predetermined local signal and compensate of frequency deviation to carry out computing cross-correlation, using computing cross-correlation result as described testing result; Or
For each integer frequency offset that carries out integer frequency offset detection and adopt, utilize this integer frequency offset and described fractional part of frequency offset estimated result, predetermined local signal is carried out to compensate of frequency deviation, and in described search window, utilize described local signal and described reception signal after compensate of frequency deviation to carry out computing cross-correlation, using computing cross-correlation result as described testing result; Or
For each integer frequency offset that carries out integer frequency offset detection and adopt, utilize this integer frequency offset to carry out integer frequency offset compensation to predetermined local signal, and utilize described fractional part of frequency offset estimated result to carry out fractional part of frequency offset compensation to described reception signal, described reception signal after local signal after integer frequency offset compensation and fractional part of frequency offset compensation is carried out to computing cross-correlation, using computing cross-correlation result as described testing result; Or
For each integer frequency offset that carries out integer frequency offset detection and adopt, utilize this integer frequency offset to carry out integer frequency offset compensation to described reception signal, and utilize described fractional part of frequency offset estimated result to carry out fractional part of frequency offset compensation to predetermined local signal, local signal after reception signal after integer frequency offset compensation and fractional part of frequency offset compensation is carried out to computing cross-correlation, using computing cross-correlation result as described testing result.
3. method according to claim 1, is characterized in that, according to integer frequency offset testing result, obtains integer frequency offset estimation result and accurate timing result comprises:
Cross correlation value in the corresponding testing result of all integer frequency offsets is compared, using the corresponding integer frequency offset of the maximum cross-correlation value relatively obtaining as described integer frequency offset estimation result, and using the time location of described maximum cross-correlation value as described accurate timing result.
4. method according to claim 1, is characterized in that, according to described thick timing, described reception signal is carried out to thick timing and comprises:
Repetitive structure based on described reception signal, carries out Autocorrelation Detection according to described thick timing to described reception signal, obtains described thick timing results.
5. method according to claim 1, is characterized in that, the repetitive structure based on described reception signal also carries out fractional part of frequency offset according to described thick timing results to described reception signal and estimates to comprise:
In the error range of described thick timing results, delete the sampled point in following sampled point set: { K, K+1 ..., K+N-1} and { K+L-N, K+L-N+1, ..., K+L-1}, wherein, K is the corresponding sampled point of described thick timing results, [N, N] is the error range of described thick timing results, and L is the sampling number of repeating part in the repetitive structure of described reception signal;
Reception signal after sampled point being deleted based on auto-correlation scheme carries out fractional part of frequency offset estimation, obtains described decimal frequency bias estimated result.
6. according to the method described in any one in claim 1 to 5, it is characterized in that, the described search window of determining comprises described thick timing error scope, and does not comprise described false peak.
7. frequency deviation is estimated and a device regularly, it is characterized in that, described device comprises:
Thick time block, for carrying out to received signal thick timing according to thick timing, obtains thick timing results;
The first estimation module, carries out fractional part of frequency offset estimation for the repetitive structure based on described reception signal and according to described thick timing results, obtains fractional part of frequency offset estimated result;
Determination module, location positioning search window for the false peak that causes according to the error range of described thick timing results and integer frequency offset, comprise: in the situation that there is integer frequency offset, false peak separation is D sample value from the nearest distance of symbol original position, wherein, D adopts maximum likelihood method to detect the false peak position obtaining for forming three ZC sequences of LTE PSS when different integer frequency offset;
Detection module, in described search window, utilizes described fractional part of frequency offset estimated result and at least one integer frequency offset to carry out integer frequency offset detection to described reception signal;
The second estimation module, for obtaining integer frequency offset estimation result and accurate timing result according to integer frequency offset testing result.
8. device according to claim 7, is characterized in that,
Described detection module each integer frequency offset for adopting carrying out integer frequency offset detection, utilize this integer frequency offset and described fractional part of frequency offset estimated result, described reception signal is carried out to compensate of frequency deviation, and in described search window, utilize the described reception signal after predetermined local signal and compensate of frequency deviation to carry out computing cross-correlation, using computing cross-correlation result as described testing result; Or
Described detection module each integer frequency offset for adopting carrying out integer frequency offset detection, utilize this integer frequency offset and described fractional part of frequency offset estimated result, predetermined local signal is carried out to compensate of frequency deviation, and in described search window, utilize described local signal and described reception signal after compensate of frequency deviation to carry out computing cross-correlation, using computing cross-correlation result as described testing result; Or
Described detection module each integer frequency offset for adopting carrying out integer frequency offset detection, utilize this integer frequency offset to carry out integer frequency offset compensation to predetermined local signal, and utilize described fractional part of frequency offset estimated result to carry out fractional part of frequency offset compensation to described reception signal, described reception signal after local signal after integer frequency offset compensation and fractional part of frequency offset compensation is carried out to computing cross-correlation, using computing cross-correlation result as described testing result; Or
Described detection module each integer frequency offset for adopting carrying out integer frequency offset detection, utilize this integer frequency offset to carry out integer frequency offset compensation to described reception signal, and utilize described fractional part of frequency offset estimated result to carry out fractional part of frequency offset compensation to predetermined local signal, local signal after reception signal after integer frequency offset compensation and fractional part of frequency offset compensation is carried out to computing cross-correlation, using computing cross-correlation result as described testing result.
9. device according to claim 7, it is characterized in that, described the second estimation module is for comparing the cross correlation value of the corresponding testing result of all integer frequency offsets, using the corresponding integer frequency offset of the maximum cross-correlation value relatively obtaining as described integer frequency offset estimation result, and using the time location of described maximum cross-correlation value as described accurate timing result.
10. device according to claim 7, is characterized in that, described thick time block, specifically for the repetitive structure based on described reception signal, carries out Autocorrelation Detection according to described thick timing to described reception signal, obtains described thick timing results.
11. devices according to claim 7, it is characterized in that, repetitive structure in described the first estimation module based on described reception signal also carries out fractional part of frequency offset while estimating according to described thick timing results to described reception signal, described the first estimation module for deleting the sampled point of following sampled point set in the error range of described thick timing results: { K, K+1, ..., K+N-1}, and { K+L-N, K+L-N+1, ..., K+L-1}, wherein, K is the corresponding sampled point of described thick timing results, [N, N] be the error range of described thick timing results, L is the sampling number of repeating part in the repetitive structure of described reception signal, and carry out fractional part of frequency offset estimation for the reception signal after sampled point being deleted based on auto-correlation scheme, obtain described decimal frequency bias estimated result.
12. according to the device described in any one in claim 7 to 11, it is characterized in that, the described search window of being determined by described determination module comprises described thick timing error scope, and does not comprise described false peak.
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| CN103580732B (en) * | 2012-08-08 | 2017-06-06 | 华为技术有限公司 | A kind of frequency bias compensation method, apparatus and system |
| CN105187352B (en) * | 2015-08-07 | 2018-05-01 | 北京遥测技术研究所 | A kind of integer frequency bias method of estimation leading based on OFDM |
| US10531373B2 (en) * | 2015-10-23 | 2020-01-07 | Telefonaktiebolaget Lm Ericsson (Publ) | Apapratus and method for adaptive discovery signal measurement timing configuration |
| CN106375257B (en) * | 2016-08-29 | 2019-03-29 | 电子科技大学 | A kind of multistage frequency deviation estimating method based on FFT |
| CN108683482B (en) * | 2017-04-01 | 2021-03-09 | 电信科学技术研究院 | Method and device for estimating timing position |
| CN107018568B (en) * | 2017-05-08 | 2020-01-17 | 电子科技大学 | Pre-compensation method for random access Doppler frequency offset for air-to-ground communication |
| CN108989261B (en) * | 2018-09-30 | 2021-03-02 | 中国人民解放军国防科技大学 | Timing synchronization method, device and related equipment of communication system |
| CN110972253B (en) * | 2018-09-30 | 2021-11-09 | 北京小米松果电子有限公司 | Time-frequency offset estimation method, device, communication equipment and storage medium |
| CN110071888B (en) * | 2019-02-28 | 2020-06-12 | 成都坤恒顺维科技股份有限公司 | Fast time synchronization method in high-speed data transmission |
| CN110881012B (en) * | 2019-11-18 | 2022-05-31 | 展讯通信（上海）有限公司 | Time estimation method and device for OFDM modulation signal |
| CN111884958B (en) * | 2020-07-15 | 2023-05-12 | 芯象半导体科技(北京)有限公司 | Timing error compensation method, apparatus, device and computer readable storage medium |
| CN114079606B (en) * | 2020-08-17 | 2023-10-24 | 海能达通信股份有限公司 | Air interface time alignment method and device and electronic equipment |
| CN114257479B (en) * | 2020-09-23 | 2023-09-22 | 紫光展锐(重庆)科技有限公司 | Frequency offset estimation method and device, storage medium and terminal |
| CN112738000B (en) * | 2020-12-30 | 2022-04-22 | 东南大学 | PSS block cross-correlation detection method |
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| CN101223753A (en) * | 2005-07-20 | 2008-07-16 | Nxp股份有限公司 | Method and synchronizer for fine OFDM symbol synchronization and method/receiver for the reception of ofdm symbols |
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