CN116545824A - Frequency offset estimation method, device and receiver - Google Patents

Frequency offset estimation method, device and receiver Download PDF

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Publication number
CN116545824A
CN116545824A CN202310630577.XA CN202310630577A CN116545824A CN 116545824 A CN116545824 A CN 116545824A CN 202310630577 A CN202310630577 A CN 202310630577A CN 116545824 A CN116545824 A CN 116545824A
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signal
frequency offset
value
spectral line
estimation
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谢世珺
张钰莅
王恒
熊锦添
张煜锋
梁豪
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National University of Defense Technology
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National University of Defense Technology
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H04L27/2655—Synchronisation arrangements
    • H04L27/2657—Carrier synchronisation
    • H04L27/2659—Coarse or integer frequency offset determination and synchronisation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H04L27/2649—Demodulators
    • H04L27/265—Fourier transform demodulators, e.g. fast Fourier transform [FFT] or discrete Fourier transform [DFT] demodulators
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H04L27/2655—Synchronisation arrangements
    • H04L27/2657—Carrier synchronisation
    • H04L27/266—Fine or fractional frequency offset determination and synchronisation
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Physics & Mathematics (AREA)
  • Discrete Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Mathematical Physics (AREA)
  • Measuring Frequencies, Analyzing Spectra (AREA)

Abstract

The application relates to the field of signal processing, and discloses a frequency offset estimation method, a device and a receiver, which comprise the following steps: carrying out multiple-time square removal on the signal to be detected to obtain a first signal; performing N-point FFT (fast Fourier transform) on the first signal with the length of N to obtain a second signal; acquiring a rough estimation value of a relative fractional frequency offset corresponding to the second signal, and sequentially correcting the first signal, carrying out N-point time domain zero padding and 2N-point FFT (fast Fourier transform) by utilizing the rough estimation value to acquire a third signal; obtaining a precise estimation value of the relative decimal frequency offset corresponding to the third signal; and obtaining a frequency offset estimation value according to the maximum spectral line index value, the coarse estimation value, the fine estimation value, the sampling frequency and the modulation order in the third signal frequency spectrum. According to the method, the accurate relative fractional frequency offset estimation value is obtained through two steps of coarse estimation and fine estimation, so that the accurate actual frequency offset estimation value can be obtained, and the frequency offset estimation performance is improved.

Description

Frequency offset estimation method, device and receiver
Technical Field
The present invention relates to the field of signal processing, and in particular, to a method, an apparatus, and a receiver for estimating frequency offset.
Background
The Doppler effect is caused by the existence of relative motion speeds at the receiving and transmitting ends in the communication system, so that Doppler frequency offset exists in a received signal, demodulation performance is affected, and the reliability of the system is poor. Therefore, the receiver needs to design a frequency offset estimator to compensate the frequency offset estimator to realize normal communication of the signal.
Existing frequency offset estimation algorithms are mainly divided into two categories: data assistance and non-data assistance. The data auxiliary scheme mainly removes modulation information through pilot signals and then carries out frequency offset estimation, and the method reduces link capacity due to the insertion of pilot data; the non-data auxiliary scheme mainly adopts a non-linear method to remove modulation information and then carries out frequency offset estimation.
In the traditional multiple frequency spectrum estimation frequency offset algorithm in the non-data auxiliary scheme, after the received multiple phase shift keying signals are subjected to de-modulation by adopting multiple times, the maximum peak value in the frequency spectrum is utilized for carrying out frequency offset estimation, and the algorithm has higher estimation precision when the frequency offset value is integer multiple of the frequency resolution, but in actual situations, the frequency offset value is not necessarily integer multiple of the frequency resolution, decimal frequency offset exists, and the estimation performance of the algorithm is deteriorated.
Disclosure of Invention
Accordingly, the present invention is directed to a method, an apparatus, and a receiver for estimating frequency offset, which can obtain an accurate relative fractional frequency offset estimation value and improve estimation performance. The specific scheme is as follows:
a method of frequency offset estimation, comprising:
carrying out multiple-time square removal on the signal to be detected to obtain a first signal;
performing N-point FFT (fast Fourier transform) on the first signal with the length of N to obtain a second signal; wherein N is a positive integer;
obtaining a rough estimation value of the relative fractional frequency offset corresponding to the second signal;
sequentially correcting the first signal by using the rough estimation value, carrying out N-point time domain zero padding and 2N-point FFT (fast Fourier transform) to obtain a third signal;
obtaining a precise estimation value of the relative decimal frequency offset corresponding to the third signal;
and obtaining an estimated value of the real frequency offset of the signal to be detected according to the maximum spectral line index value, the coarse estimated value, the fine estimated value, the sampling frequency and the modulation order in the third signal frequency spectrum.
Preferably, in the above method for estimating frequency offset provided by the embodiment of the present invention, obtaining a rough estimated value of a relative fractional frequency offset corresponding to the second signal includes:
searching a maximum spectral line index value in the second signal frequency spectrum;
calculating a DFT coefficient according to a maximum spectral line index value in the second signal spectrum and a first spectral line index value corresponding to the second signal real frequency offset; the first spectral line index value is the sum of the maximum spectral line index value and the corresponding relative fractional frequency offset in the second signal spectrum;
and obtaining a rough estimated value of the relative fractional frequency offset corresponding to the second signal according to the DFT coefficient.
Preferably, in the above method for estimating frequency offset provided by the embodiment of the present invention, obtaining a fine estimation value of a relative fractional frequency offset corresponding to the third signal includes:
searching a maximum spectral line index value in the third signal spectrum;
calculating the maximum amplitude value of the third signal spectrum according to the maximum spectral line index value in the third signal spectrum and the second spectral line index value corresponding to the third signal real frequency offset, and calculating spectral line amplitude values 1/2 of the maximum spectral line index value in the third signal spectrum by combining with DTFT; the second spectral line index value is the sum of the maximum spectral line index value and the corresponding relative fractional frequency offset in the third signal spectrum;
and obtaining a precise estimated value of the relative decimal frequency offset corresponding to the third signal according to the maximum amplitude value of the third signal frequency spectrum and the calculated spectral line amplitude value.
Preferably, in the above frequency offset estimation method provided by the embodiment of the present invention, the following formula is adopted to obtain the second signal:
x[n]＝z[n] M +w'[n]n＝0,1,...,N-1；
w'[n]＝w[n] M ；
g(n)＝e j2πi/M i＝0,1,...,M-1；
wherein X [ k ]]Is the second signal, f Δ Frequency offset f for local reference frequency and carrier frequency s For the sampling frequency to be the same,for the initial phase, w [ n ]]Mean value is zero, variance is sigma 2 G (n) is the signal to be received and k is X [ k ]]Sequence element subscripts of the sequence, M being the modulation order.
Preferably, in the above method for estimating frequency offset provided by the embodiment of the present invention, the following formula is adopted to obtain a rough estimated value of a relative fractional frequency offset corresponding to the second signal:
wherein, the liquid crystal display device comprises a liquid crystal display device,for roughly estimating the relative fractional frequency offset corresponding to the second signal, Y 0.5 For DFT coefficients of the spectral line 0.5 to the right of the maximum spectral line in the second signal frequency domain, Y -0.5 And DFT coefficients for spectral lines 0.5 to the left of the maximum spectral line in the second signal frequency domain.
Preferably, in the above frequency offset estimation method provided by the embodiment of the present invention, the following formula is adopted to perform 2N-point FFT on the signal after N-point time domain zero padding:
wherein X is 1 '[k]For the third signal, x 1 [n]Is the corrected signal; x is x 1 '[n]Is of the pair x 1 [n]And carrying out N-point time domain zero padding on the signal.
Preferably, in the above method for estimating frequency offset provided by the embodiment of the present invention, the following formula is adopted to obtain a fine estimation value of a relative fractional frequency offset corresponding to the third signal:
wherein, the liquid crystal display device comprises a liquid crystal display device,for the precise estimation value of the relative decimal frequency offset corresponding to the third signal, m' p For the maximum spectral line index value in the third signal spectrum, |X ',' 1 [m' p ]I is the maximum amplitude of the third signal spectrum, |X' 1 [m' p -0.5]I and X' 1 [m' p +0.5]And I is the spectral line amplitude of about 1/2 of the maximum spectral line index value in the third signal spectrum.
Preferably, in the above frequency offset estimation method provided by the embodiment of the present invention, the following formula is adopted to obtain an estimated value of the true frequency offset of the signal to be measured:
wherein, the liquid crystal display device comprises a liquid crystal display device,and the estimated value of the true frequency offset of the signal to be detected is obtained.
The embodiment of the invention also provides a frequency offset estimation device, which comprises:
the modulation information removing module is used for removing modulation information for a plurality of times on the signal to be detected to obtain a first signal;
the signal processing module is used for carrying out N-point FFT (fast Fourier transform) on the first signal with the length of N to obtain a second signal; wherein N is a positive integer;
the coarse estimation value acquisition module is used for acquiring a coarse estimation value of the relative decimal frequency offset corresponding to the second signal;
the signal processing module is further configured to sequentially perform correction, N-point time domain zero padding and 2N-point FFT on the first signal by using the rough estimation value, so as to obtain a third signal;
the fine estimation value acquisition module is used for acquiring a fine estimation value of the relative fractional frequency offset corresponding to the third signal;
and the frequency offset estimation value calculation module is used for obtaining an estimation value of the real frequency offset of the signal to be detected according to the maximum spectral line index value, the coarse estimation value, the fine estimation value, the sampling frequency and the modulation order in the third signal frequency spectrum.
The embodiment of the invention also provides a receiver, which comprises a processor and a memory, wherein the processor is connected with the memory;
the processor is used for carrying out square removal on modulation information on a signal to be detected for a plurality of times to obtain a first signal; performing N-point FFT (fast Fourier transform) on the first signal with the length of N to obtain a second signal; wherein N is a positive integer; obtaining a rough estimation value of the relative fractional frequency offset corresponding to the second signal; sequentially correcting the first signal by using the rough estimation value, carrying out N-point time domain zero padding and 2N-point FFT (fast Fourier transform) to obtain a third signal; obtaining a precise estimation value of the relative decimal frequency offset corresponding to the third signal; and obtaining an estimated value of the real frequency offset of the signal to be detected according to the maximum spectral line index value, the coarse estimated value, the fine estimated value, the sampling frequency and the modulation order in the third signal frequency spectrum.
From the above technical solution, the frequency offset estimation method provided by the present invention includes: carrying out multiple-time square removal on the signal to be detected to obtain a first signal; performing N-point FFT (fast Fourier transform) on the first signal with the length of N to obtain a second signal; wherein N is a positive integer; based on the maximum spectral line index value in the second signal spectrum, obtaining a rough estimation value of the relative decimal frequency offset corresponding to the second signal; sequentially correcting the first signal by using the coarse estimation value, carrying out N-point time domain zero padding and 2N-point FFT (fast Fourier transform) to obtain a third signal; obtaining a precise estimation value of the relative decimal frequency offset corresponding to the third signal; and obtaining an estimated value of the real frequency offset of the signal to be detected according to the maximum spectral line index value, the coarse estimated value, the fine estimated value, the sampling frequency and the modulation order in the third signal frequency spectrum.
According to the frequency offset estimation method provided by the invention, the accurate relative decimal frequency offset estimation value is obtained through two steps of coarse estimation and fine estimation, so that a more accurate actual frequency offset estimation value can be obtained, the problem that the frequency offset estimation is difficult in a multilevel phase shift keying modulation mode is solved, the frequency offset estimation performance is improved, and the performance of a communication system is further improved.
In addition, the invention also provides a corresponding device and a receiver for the frequency offset estimation method, so that the method has more practicability, and the device and the receiver have corresponding advantages.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the related art, the drawings that are required to be used in the embodiments or the related technical descriptions will be briefly described, and it is apparent that the drawings in the following description are only embodiments of the present invention, and other drawings may be obtained according to the provided drawings without inventive effort for those skilled in the art.
Fig. 1 is a flowchart of a frequency offset estimation method according to an embodiment of the present invention;
fig. 2 is a flowchart of an algorithm corresponding to a frequency offset estimation method according to an embodiment of the present invention;
fig. 3a is a constellation diagram before compensation according to an embodiment of the present invention;
fig. 3b is a compensated constellation diagram according to an embodiment of the present invention;
fig. 4 is a corresponding estimation performance diagram of the frequency offset estimation method provided by the embodiment of the present invention when the signal lengths are different;
fig. 5 is a diagram showing the comparison between the estimation performance of the frequency offset estimation method provided by the embodiment of the present invention and the estimation performance of the conventional algorithm in the theoretical frequency offset range;
FIG. 6 is a graph showing a comparison of normalized mean square error between a frequency offset estimation method and three other multi-time square spectrum estimation algorithms according to an embodiment of the present invention;
fig. 7 is a schematic structural diagram of a frequency offset estimation device according to an embodiment of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention provides a frequency offset estimation method, as shown in fig. 1, comprising the following steps:
s101, performing multiple-time square removal on modulation information on a signal to be detected to obtain a first signal.
It should be noted that, the signal to be measured may be a Multi-system phase shift keying (Multi-phase shift keying, MPSK) signal, or may be other signals, which is not limited herein.
Specifically, as shown in fig. 2, assuming that the signal to be measured is a MPSK signal, the signal to be measured after timing synchronization and sampling is expressed as:
where n=0, 1,.. Δ The frequency offset is the frequency offset between the local reference frequency and the carrier frequency, namely the residual frequency offset; f (f) s Is the sampling frequency;is the initial phase. w [ n ]]Mean value is zero, variance is sigma 2 Complex gaussian white noise of (a), noise power ratio snr=a 2 /2σ 2 . For MPSK modulation, g (n) may be expressed as:
g(n)＝e j2πi/M i＝0,1,...,M-1 (2)
where M is the modulation order.
Next, as shown in fig. 2, the M-th power of the modulation information is removed from the signal z [ n ] to be measured, to obtain a second signal x [ n ]:
x[n]＝z[n] M +w'[n] (3)
wherein w' [ n ]]＝w[n] M Depending on the statistical properties, a zero-mean gaussian distribution is still obeyed. At this time, the signal x [ n ]]Can be regarded as a single-frequency signal subjected to M frequency multiplication, and the frequency offset value is Mf Δ 。
S102, performing N-point FFT (fast Fourier transform) on a first signal with the length of N to obtain a second signal; wherein N is a positive integer.
Specifically, as shown in fig. 2, the first signal X [ N ] having a length of N is subjected to N-point FFT to obtain the second signal X [ k ]. It should be noted that, the second signal X [ k ] is obtained by performing FFT on the first signal X [ n ], the first signal X [ n ] is obtained by performing M-th power processing on the signal z [ n ] to be detected, and the frequency offsets are the same.
In a specific implementation, in the above frequency offset estimation method provided by the embodiment of the present invention, the following formula may be adopted to obtain the second signal:
where k is the subscript of the sequence element of X [ k ].
S103, obtaining a rough estimation value of the relative fractional frequency offset corresponding to the second signal;
specifically, as shown in FIG. 2, a second signal X [ k ] is obtained]After that, the second signal X [ k ] can be obtained]Corresponding relatively fractional frequency offset gamma 1 Rough estimate of (2)Υ 1 Can be understood as the second signal X k]The true frequency offset is a relatively fractional frequency offset of the frequency corresponding to the largest spectral line.
S104, correcting the first signal, carrying out N-point time domain zero padding and 2N-point FFT (fast Fourier transform) on the first signal by using the coarse estimation value to obtain a third signal;
specifically, as shown in FIG. 2, first, the resulting relatively fractional frequency offset gamma is utilized 1 Rough estimate of (2)For the first signal x [ n ]]When the correction is performed, the corrected signal is x 1 [n]；
Wherein Δζ is f s and/N, namely the interval between adjacent spectral lines.
Then, assume that the true frequency offset value at this time isFor the corrected signal x 1 [n]Obtaining a signal x subjected to N-point time domain zero padding after N-point time domain zero padding 1 '[n]Performing 2N-point FFT to obtain a third signal X' 1 [k]。
In a specific implementation, in the frequency offset estimation method provided by the embodiment of the present invention, the following formula may be adopted to perform 2N-point FFT on the signal after N-point time domain zero padding:
s105, obtaining a precise estimation value of the relative decimal frequency offset corresponding to the third signal;
specifically, when the third signal X 'is obtained' 1 [k]After that, a third signal X 'can be obtained' 1 [k]Corresponding relatively fractional frequency offset gamma 2 Fine estimates of (2)Υ 2 Can be understood as the third signal X' 1 [k]The true frequency offset of (2) is a relatively fractional frequency offset of the frequency corresponding to the largest spectral line.
S106, obtaining an estimated value of the real frequency offset of the signal to be detected according to the maximum spectral line index value, the coarse estimated value, the fine estimated value, the sampling frequency and the modulation order in the third signal frequency spectrum.
Specifically, according to the third signal X' 1 [k]Maximum spectral line index value m 'in spectrum' p Coarse estimation of relative fractional frequency offsetRefined estimate of the relative fractional frequency offset +.>Sampling frequency f s And modulating the order M to obtain a signal z [ n ] to be detected]Estimate of the true frequency offset of +.>
In the frequency offset estimation method provided by the embodiment of the invention, the accurate relative decimal frequency offset estimation value is obtained through two steps of coarse estimation and fine estimation, so that the more accurate actual frequency offset estimation value can be obtained, the problem that the frequency offset estimation is difficult in a multilevel phase shift keying modulation mode is solved, the frequency offset estimation performance is improved, and the performance of a communication system is further improved.
Further, in a specific implementation, in the above-mentioned frequency offset estimation method provided by the embodiment of the present invention, step S103 may specifically include the following steps of:
first, search for the second signal X [ k ]]Maximum spectral line index value m in spectrum p At this time, the second signal X [ k ]]First spectral line index value m corresponding to real frequency offset p +Υ 1 Then the true frequency offset assumed at this time may contain m p And gamma (gamma) 1 To express, the specific expression is:
f Δ ＝(m p +Υ 1 )Δξ/M (7)
wherein Δζ is f s and/N, namely the interval between adjacent spectral lines.
Substituting formula (7) into formula (3) to obtain a signal x [ n ]:
then, according to the second signal X [ k ]]Index value m of maximum value in frequency domain p And a second signal X [ k ]]First spectral line index value m corresponding to real frequency offset p +Υ 1 Calculating DFT coefficients:
substituting formula (8) into formula (9) for simplification to obtain:
finally, a second signal X [ k ] is calculated according to the DFT coefficient]Corresponding relatively fractional frequency offset gamma 1 Estimate of (2)
In a specific implementation, in the above frequency offset estimation method provided by the embodiment of the present invention, the figure is as follows2, the following formula can be adopted to obtain the corresponding relative decimal frequency offset gamma of the second signal 1 Rough estimate of (2)
In the method, in the process of the invention,corresponding to the second signal a relative decimal frequency offset y 1 Is a rough estimate of Y 0.5 DFT coefficients for the spectral line 0.5 to the right of the maximum spectral line in the second signal frequency domain, Y -0.5 DFT coefficients for the spectral line 0.5 to the left of the maximum spectral line in the second signal frequency domain.
Further, in a specific implementation, in the above-mentioned frequency offset estimation method provided by the embodiment of the present invention, step S105 may obtain a refined estimation value of a relative fractional frequency offset corresponding to the third signal, and specifically may include the following steps:
first, the third signal X 'is searched' 1 [k]Maximum spectral line index value m 'in spectrum' p At this time, the third signal X' 1 [k]The index value of the second spectral line corresponding to the real frequency offset is m' p +Υ 2 The method comprises the steps of carrying out a first treatment on the surface of the The true frequency offset value assumed at this time is calculated by the method containing m' p And gamma (gamma) 2 To express, the specific expression is:
f' Δ ＝(m' p +Υ 2 )Δξ'/M (12)
wherein Δζ' is f s and/2N, namely the interval between adjacent spectral lines.
Then, calculate the third signal X 1 '[k]Amplitude maximum of spectrum |X '' 1 [m' p ]I and calculate the distance to the third signal X 'in combination with DTFT' 1 [k]Spectral line amplitude |X 'at 1/2 around maximum spectral line index value in spectrum' 1 [m' p -0.5]I and X' 1 [m' p +0.5]I, its theoretical values are as follows:
from the formulas (13), (14) and (15):
thereafter, according to the third signal X' 1 [k]Amplitude maximum of spectrum |X '' 1 [m' p ]I and calculated line amplitude i X' 1 [m' p -0.5]I and X' 1 [m' p +0.5]I, obtain the third signal X' 1 [k]Corresponding relatively fractional frequency offset gamma 2 Fine estimates of (2)
In a specific implementation, in the above-mentioned frequency offset estimation method provided by the embodiment of the present invention, as shown in fig. 2, the following formula may be adopted to obtain the third signal X' 1 [k]Corresponding relatively fractional frequency offset gamma 2 Estimate of (2)
Wherein m' p For the third signal X' 1 [k]Maximum spectral line index value in spectrum, |X' 1 [m' p ]I is the third signal X' 1 [k]Amplitude maximum of spectrum, |X' 1 [m' p -0.5]I and X' 1 [m' p +0.5]I is the third signal X' 1 [k]Spectral line amplitude is about 1/2 of the maximum spectral line index value in the frequency spectrum.
In a specific implementation, in the above-mentioned frequency offset estimation method provided by the embodiment of the present invention, as shown in fig. 2, the following formula may be adopted to obtain a signal z [ n ] to be measured]Is the true frequency offset f of (2) Δ Estimate of (2)
Wherein, the liquid crystal display device comprises a liquid crystal display device,for signal z [ n ] to be measured]Is the true frequency offset f of (2) Δ Is used for the estimation of the estimated value of (a).
Assume that the original received signal length is N to be 2048, the sampling frequency is 1.024MHz, the signal-to-noise ratio is 10dB, and the frequency offset is 100.2kHz. Fig. 3a and 3b are respectively the modulation information constellations before and after compensation using the algorithm of the present invention.
In order to further illustrate the effects of the present invention, the following details of the above-described frequency offset estimation method provided by the embodiment of the present invention will be described in some specific examples.
For MPSK signals, where M takes 4, the modulated signal is a QPSK signal. The sampling frequency is 1.024MHz, as shown in FIG. 4, the signal lengths N are 512, 1024 and 2048, the normalized frequency offset is 20.48kHz/1.024 MHz=0.02, and as can be seen from FIG. 4, the larger the number of points N is, the better the estimation performance of the frequency offset estimation method provided by the invention under the condition of low signal-to-noise ratio is.
As shown in fig. 5, the signal length is N1024, and it can be seen that the frequency offset estimation method provided by the invention has better performance compared with the conventional multiple power spectrum estimation algorithm.
As shown in FIG. 6, the signal length N is 1024, the normalized frequency offset is-0.01, and it can be seen that the frequency offset estimation method provided by the invention has optimal estimation performance.
Based on the same inventive concept, the embodiment of the invention also provides a frequency offset estimation device, and because the principle of solving the problem of the device is similar to that of the frequency offset estimation method, the implementation of the device can refer to the implementation of the frequency offset estimation method, and the repetition is omitted.
In a specific implementation, as shown in fig. 7, the frequency offset estimation device provided by the embodiment of the present invention specifically includes:
the modulation information removing module 11 is configured to perform multiple-side removal of modulation information on a signal to be detected to obtain a first signal;
a signal processing module 12, configured to perform N-point FFT on the first signal with the length of N to obtain a second signal; wherein N is a positive integer;
a coarse estimation value obtaining module 13, configured to obtain a coarse estimation value of a relative fractional frequency offset corresponding to the second signal;
the signal processing module 12 is further configured to sequentially correct the first signal using the coarse estimation value, perform N-point time domain zero padding, and perform 2N-point FFT to obtain a third signal;
a fine estimation value obtaining module 14, configured to obtain a fine estimation value of the relative fractional frequency offset corresponding to the third signal;
the frequency offset estimation value calculation module 15 is configured to obtain an estimated value of a real frequency offset of the signal to be measured according to the maximum spectral line index value, the coarse estimation value, the fine estimation value, the sampling frequency and the modulation order in the third signal spectrum.
In the frequency offset estimation device provided by the embodiment of the invention, more accurate frequency offset value can be estimated through the interaction of the four modules, the problem that the frequency offset estimation of a multilevel phase shift keying modulation mode is difficult is solved, the frequency offset estimation performance is improved, and the performance of a communication system is further improved.
For more specific working procedures of the above modules, reference may be made to the corresponding contents disclosed in the foregoing embodiments, and no further description is given here.
Correspondingly, the embodiment of the invention also discloses a receiver, which comprises a processor and a memory; the processor is connected with the memory; the processor is used for removing modulation information for a plurality of times on the signal to be detected to obtain a first signal; performing N-point FFT (fast Fourier transform) on the first signal with the length of N to obtain a second signal; wherein N is a positive integer; obtaining a rough estimation value of the relative fractional frequency offset corresponding to the second signal; sequentially correcting the first signal by using the coarse estimation value, carrying out N-point time domain zero padding and 2N-point FFT (fast Fourier transform) to obtain a third signal; obtaining a precise estimation value of the relative decimal frequency offset corresponding to the third signal; and obtaining an estimated value of the real frequency offset of the signal to be detected according to the maximum spectral line index value, the coarse estimated value, the fine estimated value, the sampling frequency and the modulation order in the third signal frequency spectrum.
For more specific procedures regarding the functions of the above processor, reference may be made to the corresponding contents disclosed in the foregoing embodiments, and no further description is given here.
In this specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different point from other embodiments, so that the same or similar parts between the embodiments are referred to each other. For the apparatus and the receiver disclosed in the embodiments, since the apparatus and the receiver correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant points refer to the description of the method section.
Those of skill would further appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the various illustrative elements and steps are described above generally in terms of functionality in order to clearly illustrate the interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present application.
The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. The software modules may be disposed in Random Access Memory (RAM), memory, read Only Memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.
Finally, it is further noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
The method, the device and the receiver for estimating the frequency offset provided by the invention are described in detail, and specific examples are applied to the description of the principle and the implementation mode of the invention, and the description of the above examples is only used for helping to understand the method and the core idea of the invention; meanwhile, as those skilled in the art will have variations in the specific embodiments and application scope in accordance with the ideas of the present invention, the present description should not be construed as limiting the present invention in view of the above.

Claims (10)

1. A method for frequency offset estimation, comprising:
carrying out multiple-time square removal on the signal to be detected to obtain a first signal;
performing N-point FFT (fast Fourier transform) on the first signal with the length of N to obtain a second signal; wherein N is a positive integer;
obtaining a rough estimation value of the relative fractional frequency offset corresponding to the second signal;
sequentially correcting the first signal by using the rough estimation value, carrying out N-point time domain zero padding and 2N-point FFT (fast Fourier transform) to obtain a third signal;
obtaining a precise estimation value of the relative decimal frequency offset corresponding to the third signal;
and obtaining an estimated value of the real frequency offset of the signal to be detected according to the maximum spectral line index value, the coarse estimated value, the fine estimated value, the sampling frequency and the modulation order in the third signal frequency spectrum.
2. The method of frequency offset estimation according to claim 1, wherein obtaining a rough estimate of a relative fractional frequency offset corresponding to the second signal comprises:
searching a maximum spectral line index value in the second signal frequency spectrum;
calculating a DFT coefficient according to a maximum spectral line index value in the second signal spectrum and a first spectral line index value corresponding to the second signal real frequency offset; the first spectral line index value is the sum of the maximum spectral line index value and the corresponding relative fractional frequency offset in the second signal spectrum;
and obtaining a rough estimated value of the relative fractional frequency offset corresponding to the second signal according to the DFT coefficient.
3. The method of frequency offset estimation according to claim 2, wherein obtaining a refined estimate of the relative fractional frequency offset corresponding to the third signal comprises:
searching a maximum spectral line index value in the third signal spectrum;
calculating the maximum amplitude value of the third signal spectrum according to the maximum spectral line index value in the third signal spectrum and the second spectral line index value corresponding to the third signal real frequency offset, and calculating spectral line amplitude values 1/2 of the maximum spectral line index value in the third signal spectrum by combining with DTFT; the second spectral line index value is the sum of the maximum spectral line index value and the corresponding relative fractional frequency offset in the third signal spectrum;
and obtaining a precise estimated value of the relative decimal frequency offset corresponding to the third signal according to the maximum amplitude value of the third signal frequency spectrum and the calculated spectral line amplitude value.
4. The method of frequency offset estimation according to claim 3, wherein the second signal is obtained using the formula:
x[n]＝z[n] M +w'[n]n＝0,1,...,N-1；
w'[n]＝w[n] M ；
g(n)＝e j2π/iM i＝0,1,...,M-1；
wherein X [ k ]]Is the second signal, f Δ Frequency offset f for local reference frequency and carrier frequency s For the sampling frequency to be the same,for the initial phase, w [ n ]]Mean value is zero, variance is sigma 2 G (n) is the signal to be received and k is X [ k ]]Sequence element subscripts of the sequence, M being the modulation order.
5. The method of frequency offset estimation according to claim 4, wherein the following formula is adopted to obtain a rough estimate of the relative fractional frequency offset corresponding to the second signal:
wherein, the liquid crystal display device comprises a liquid crystal display device,for roughly estimating the relative fractional frequency offset corresponding to the second signal, Y 0.5 For DFT coefficients of the spectral line 0.5 to the right of the maximum spectral line in the second signal frequency domain, Y -0.5 And DFT coefficients for spectral lines 0.5 to the left of the maximum spectral line in the second signal frequency domain.
6. The method of frequency offset estimation according to claim 5, wherein the signal after N-point time domain zero padding is subjected to 2N-point FFT by using the following formula:
wherein X 'is' 1 [k]For the third signal, x 1 [n]Is the corrected signal; x is x 1 '[n]Is of the pair x 1 [n]And carrying out N-point time domain zero padding on the signal.
7. The method of frequency offset estimation according to claim 6, wherein the following formula is adopted to obtain a refined estimation value of the relative fractional frequency offset corresponding to the third signal:
wherein, the liquid crystal display device comprises a liquid crystal display device,for the precise estimation value of the relative decimal frequency offset corresponding to the third signal, m' p For the maximum spectral line index value in the third signal spectrum, |X ',' 1 [m' p ]I is the maximum amplitude of the third signal spectrum, |X' 1 [m' p -0.5]I and X' 1 [m' p +0.5]And I is the spectral line amplitude of about 1/2 of the maximum spectral line index value in the third signal spectrum.
8. The method of estimating frequency offset according to claim 7 wherein the estimated value of the true frequency offset of the signal to be measured is obtained by using the following formula:
wherein, the liquid crystal display device comprises a liquid crystal display device,and the estimated value of the true frequency offset of the signal to be detected is obtained.
9. A frequency offset estimation apparatus, comprising:
the modulation information removing module is used for removing modulation information for a plurality of times on the signal to be detected to obtain a first signal;
the signal processing module is used for carrying out N-point FFT (fast Fourier transform) on the first signal with the length of N to obtain a second signal; wherein N is a positive integer;
the coarse estimation value acquisition module is used for acquiring a coarse estimation value of the relative decimal frequency offset corresponding to the second signal;
the signal processing module is further configured to sequentially perform correction, N-point time domain zero padding and 2N-point FFT on the first signal by using the rough estimation value, so as to obtain a third signal;
the fine estimation value acquisition module is used for acquiring a fine estimation value of the relative fractional frequency offset corresponding to the third signal;
and the frequency offset estimation value calculation module is used for obtaining an estimation value of the real frequency offset of the signal to be detected according to the maximum spectral line index value, the coarse estimation value, the fine estimation value, the sampling frequency and the modulation order in the third signal frequency spectrum.
10. A receiver comprising a processor and a memory, the processor being coupled to the memory;
the processor is used for carrying out square removal on modulation information on a signal to be detected for a plurality of times to obtain a first signal; performing N-point FFT (fast Fourier transform) on the first signal with the length of N to obtain a second signal; wherein N is a positive integer; obtaining a rough estimation value of the relative fractional frequency offset corresponding to the second signal; sequentially correcting the first signal by using the rough estimation value, carrying out N-point time domain zero padding and 2N-point FFT (fast Fourier transform) to obtain a third signal; obtaining a precise estimation value of the relative decimal frequency offset corresponding to the third signal; and obtaining an estimated value of the real frequency offset of the signal to be detected according to the maximum spectral line index value, the coarse estimated value, the fine estimated value, the sampling frequency and the modulation order in the third signal frequency spectrum.
CN202310630577.XA 2023-05-31 2023-05-31 Frequency offset estimation method, device and receiver Pending CN116545824A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116962123A (en) * 2023-09-20 2023-10-27 大尧信息科技(湖南)有限公司 Raised cosine shaping filter bandwidth estimation method and system of software defined framework

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116962123A (en) * 2023-09-20 2023-10-27 大尧信息科技(湖南)有限公司 Raised cosine shaping filter bandwidth estimation method and system of software defined framework
CN116962123B (en) * 2023-09-20 2023-11-24 大尧信息科技(湖南)有限公司 Raised cosine shaping filter bandwidth estimation method and system of software defined framework

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