CN106230762A - Doppler frequency offset estimation method and system - Google Patents
Doppler frequency offset estimation method and system Download PDFInfo
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- CN106230762A CN106230762A CN201610602159.XA CN201610602159A CN106230762A CN 106230762 A CN106230762 A CN 106230762A CN 201610602159 A CN201610602159 A CN 201610602159A CN 106230762 A CN106230762 A CN 106230762A
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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
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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
- H04L27/2626—Arrangements specific to the transmitter only
- H04L27/2627—Modulators
- H04L27/2628—Inverse Fourier transform modulators, e.g. inverse fast Fourier transform [IFFT] or inverse discrete Fourier transform [IDFT] modulators
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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
- H04L27/2649—Demodulators
- H04L27/265—Fourier transform demodulators, e.g. fast Fourier transform [FFT] or discrete Fourier transform [DFT] demodulators
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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
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Abstract
The present invention relates to a kind of Doppler frequency offset estimation method and system, first raw baseband signal is grouped, again each group of baseband signal group is carried out fast Fourier transform and the disposal of gentle filter respectively, obtain each first signal spectrum sequence, it is overlapped processing to the first signal spectrum sequence of preset group number, obtain secondary signal spectrum sequence, obtain the impact point of amplitude maximum in secondary signal spectrum sequence, the free transmission range of secondary signal spectrum sequence is determined according to impact point, and determine the amplitude central point in free transmission range, and then obtain the estimated value of the carrier frequency of raw baseband signal, actual value further according to the estimated value of carrier frequency of raw baseband signal and the carrier frequency of raw baseband signal obtains Doppler frequency deviation estimated value.Signal carrier frequency spectrum is mainly estimated by the present invention, unrelated with Modulation Types and character rate, thus is not limited by Modulation Types, applied range, but also is not limited by character rate, expands frequency offset estimation range.
Description
Technical field
The present invention relates to digital communication technology field, particularly relate to a kind of Doppler frequency offset estimation method and system.
Background technology
In current digital communication system, owing to degree of stability and the degree of accuracy of sending and receiving end system crystal oscillator can not complete phases
With, add the factors such as the Doppler frequency shift that transceiver terminal relative motion produces, all can cause receiving end signal and transmitting terminal signal
Carrier frequency can not identical, i.e. there is certain deviation.Thus for the receiving terminal of communication system, frequency deviation estimate with
Compensating module is very important ingredient.
In the most common digital communication system, estimate to estimate frequency deviation according to whether there is given data auxiliary to do frequency deviation
Algorithm is divided into data to assist (Data-Aided, DA) and the big class of unbound nucleus (Non-Data-Aided, NDA) two.At non-number
In frequency excursion algorithm according to auxiliary, data stream is often not inserted into given data section and utilizes, even for receiving terminal
Receiving terminal does not all know the relevant parameters such as the modulation type of channel receiving signal, the most just estimates to bring sizable being stranded to frequency deviation
Difficult.
For the communication system of low character rate, it is frequently encountered frequency deviation and exceedes the situation of character rate, as terminal is quick
The low character rate satellite communication system of movement, the Doppler frequency shift of system and Doppler frequency shift acceleration can in the short time drastically
Increase, cause system frequency deviation within a very short time to exceed the character rate of system, cause the performance of communication system drastically to deteriorate.
Summary of the invention
Based on this, it is necessary to for cannot determine receive signal modulation type time cannot accurately carry out frequency deviation estimate with
And the problem that frequency deviation is estimated to receive system symbol rate restriction, it is provided that a kind of Doppler frequency offset estimation method and system.
A kind of Doppler frequency offset estimation method, comprises the following steps:
Obtain the raw baseband signal in digital communication system channel, count to former according to default fast Fourier transform
Primordium band signal is grouped, it is thus achieved that each baseband signal group, and wherein, often the symbol numbers of the baseband signal of group baseband signal group is
The fast Fourier transform preset is counted；
Baseband signal in each group of baseband signal group is carried out fast Fourier transform respectively, it is thus achieved that each group baseband signal group
Corresponding each group discrete spectrum sequence；
Each group of discrete spectrum sequence is carried out the disposal of gentle filter respectively, it is thus achieved that answer each group of each group discrete spectrum sequence pair
First signal spectrum sequence；
The first signal spectrum sequence of preset group number is chosen, to preset group number in each group of the first signal spectrum sequence
One signal spectrum sequence carries out data investigation process, it is thus achieved that secondary signal spectrum sequence；
Obtain the impact point of amplitude maximum in secondary signal spectrum sequence, determine secondary signal spectrum sequence according to impact point
Free transmission range, and obtain the amplitude central point in free transmission range；
Obtain raw baseband signal symbol period, count according to amplitude central point, default fast Fourier transform and
Symbol period obtains the estimated value of the carrier frequency of raw baseband signal；
Obtain the actual value of the carrier frequency of raw baseband signal, according to the estimated value of the carrier frequency of raw baseband signal
Doppler frequency deviation estimated value is obtained with the actual value of the carrier frequency of raw baseband signal.
A kind of Doppler frequency deviation estimating system, including with lower unit:
Grouped element, for obtaining the raw baseband signal in digital communication system channel, according in default quick Fu
Leaf transformation is counted and is grouped raw baseband signal, it is thus achieved that each baseband signal group, wherein, and the often base band letter of group baseband signal group
Number symbol numbers be default fast Fourier transform count；
Spectrum processing unit, for the baseband signal in each group of baseband signal group is carried out fast Fourier transform respectively,
Obtain each group of each group discrete spectrum sequence corresponding to baseband signal group；
The disposal of gentle filter unit, for carrying out the disposal of gentle filter respectively to each group of discrete spectrum sequence, it is thus achieved that each group
Each group the first signal spectrum sequence that discrete spectrum sequence pair is answered；
Overlap-add procedure unit, for choosing the first signal spectrum sequence of preset group number in each group of the first signal spectrum sequence
Row, carry out data investigation process to the first signal spectrum sequence of preset group number, it is thus achieved that secondary signal spectrum sequence；
Passband processing unit, for obtaining the impact point of amplitude maximum in secondary signal spectrum sequence, true according to impact point
Determine the free transmission range of secondary signal spectrum sequence, and obtain the amplitude central point in free transmission range；
First estimation unit, for obtaining the symbol period of raw baseband signal, according to amplitude central point, default quick
Fourier transformation is counted and symbol period obtains the estimated value of carrier frequency of raw baseband signal；
Second estimation unit, for obtaining the actual value of the carrier frequency of raw baseband signal, according to raw baseband signal
The estimated value of carrier frequency and the actual value of carrier frequency of raw baseband signal obtain Doppler frequency deviation estimated value.
Doppler frequency offset estimation method according to the invention described above and system, it is first to carry out raw baseband signal point
Group, more each group of baseband signal group is carried out fast Fourier transform and the disposal of gentle filter respectively, it is thus achieved that each first signal spectrum
Sequence, is overlapped processing to the first signal spectrum sequence of preset group number, it is thus achieved that secondary signal spectrum sequence, obtains the second letter
In number spectrum sequence, the impact point of amplitude maximum, determines the free transmission range of secondary signal spectrum sequence, and determines according to impact point
Amplitude central point in free transmission range, and then obtain the estimated value of the carrier frequency of raw baseband signal, further according to original base band
The actual value of the estimated value of the carrier frequency of signal and the carrier frequency of raw baseband signal obtains Doppler frequency deviation estimated value.This
Signal carrier frequency spectrum is mainly estimated by the Doppler frequency offset estimation method of invention and system, with signal Modulation Types and be
System character rate is unrelated, thus is not limited by signal Modulation Types, applied range, but also not by system symbol rate
Limit, expand frequency offset estimation range.
Accompanying drawing explanation
Fig. 1 is the schematic flow sheet of the Doppler frequency offset estimation method of one of them embodiment；
Fig. 2 is the original signal spectrum schematic diagram of the baseband signal of one of them embodiment；
Fig. 3 is the first signal spectrum schematic diagram after smothing filtering of one of them embodiment；
Fig. 4 is the structural representation of the Doppler frequency deviation estimating system of one of them embodiment.
Detailed description of the invention
For making the purpose of the present invention, technical scheme and advantage clearer, below in conjunction with drawings and Examples, to this
Invention is described in further detail.Should be appreciated that detailed description of the invention described herein only in order to explain the present invention,
Do not limit protection scope of the present invention.
Shown in Figure 1, for the schematic flow sheet of Doppler frequency offset estimation method in one embodiment of the invention.This enforcement
Doppler frequency offset estimation method in example, comprises the following steps:
Step S101: obtain the raw baseband signal in digital communication system channel, becomes according to default fast Fourier
Changing counts is grouped raw baseband signal, it is thus achieved that each baseband signal group, wherein, often organizes the baseband signal of baseband signal group
The fast Fourier transform that symbol numbers is default is counted；
Raw baseband signal is mainly grouped by this step, carries out being grouped the character to raw baseband signal and does not produces
Impact, but also it is easy to follow-up processing procedure；
Step S102: the baseband signal in each group of baseband signal group is carried out fast Fourier transform respectively, it is thus achieved that each group
Each group discrete spectrum sequence that baseband signal group is corresponding；
In this step, it is that the baseband signal often organized in baseband signal group is carried out respectively fast Fourier transform, it is thus achieved that
The corresponding discrete spectrum sequence often organizing baseband signal group, this process completes baseband signal from time-domain signal to frequency-region signal
Conversion；
Step S103: each group of discrete spectrum sequence is carried out the disposal of gentle filter respectively, it is thus achieved that each group discrete spectrum sequence
Corresponding each group the first signal spectrum sequence；
Step S104: choose the first signal spectrum sequence of preset group number in each group of the first signal spectrum sequence, in advance
If the first signal spectrum sequence of group number carries out data investigation process, it is thus achieved that secondary signal spectrum sequence；
In this step, data investigation processes and the first signal spectrum sequence of preset group number is integrated into a secondary signal
Spectrum sequence；
Step S105: obtain the impact point of amplitude maximum in secondary signal spectrum sequence, determine the second letter according to impact point
The free transmission range of number spectrum sequence, and obtain the amplitude central point in free transmission range；
In this step, impact point and amplitude central point all include spectral magnitude and spectrum position information, spectral magnitude pair
Should be in the vertical coordinate of frequency spectrum, spectrum position is corresponding to the abscissa of frequency spectrum；
Step S106: obtain the symbol period of raw baseband signal, becomes according to amplitude central point, default fast Fourier
Change the estimated value of the carrier frequency obtaining raw baseband signal with symbol period of counting；
Step S107: obtain the actual value of the carrier frequency of raw baseband signal, according to the carrier frequency of raw baseband signal
The actual value of the estimated value of rate and the carrier frequency of raw baseband signal obtains Doppler frequency deviation estimated value.
In the present embodiment, first raw baseband signal is grouped, more each group of baseband signal group is carried out quickly respectively
Fourier transformation and the disposal of gentle filter, it is thus achieved that each first signal spectrum sequence, the first signal spectrum sequence to preset group number
It is overlapped processing, it is thus achieved that secondary signal spectrum sequence, obtains the impact point of amplitude maximum in secondary signal spectrum sequence, according to
Impact point determines the free transmission range of secondary signal spectrum sequence, and determines the amplitude central point in free transmission range, and then obtains former
The estimated value of the carrier frequency of primordium band signal, further according to the estimated value of carrier frequency and the original base band letter of raw baseband signal
Number carrier frequency actual value obtain Doppler frequency deviation estimated value.Doppler frequency offset estimation method and the system of the present invention are main
It is that signal carrier frequency spectrum is estimated, unrelated with signal Modulation Types and system symbol rate, thus do not modulated sample by signal
The restriction of formula, applied range, but also do not limited by system symbol rate, expand frequency offset estimation range.
Preferably, when raw baseband signal is grouped, when the symbol numbers of raw baseband signal is not in quick Fu
During the integral multiple that leaf transformation is counted, the afterbody in raw baseband signal deletes some symbols, makes the raw baseband signal after deleting
Symbol numbers be the integral multiple that fast Fourier transform is counted, owing to each baseband signal group can embody raw baseband signal
Frequency characteristic, therefore, delete that Doppler frequency deviation is estimated to produce impact by the tail portion symbol of raw baseband signal.
Wherein in an embodiment, the baseband signal in each group of baseband signal group is carried out fast Fourier transform respectively
Step comprise the following steps:
According toBaseband signal in each group of baseband signal group is carried out in quick Fu respectively
Leaf transformation；
In formula, R (i) represents discrete spectrum sequence, NfftRepresenting that the fast Fourier transform preset is counted, r (n) represents base
The time domain sequences of the baseband signal in band signal group, i represents fast Fourier transform point, and T represents the symbol of raw baseband signal
Cycle.
In the present embodiment, it is in default quick Fu due to the symbol numbers of the baseband signal in each group of baseband signal group
Leaf transformation is counted, and therefore, can be calculated discrete spectrum sequence easily according to above-mentioned fast Fourier transform formula.
Wherein in an embodiment, each group of discrete spectrum sequence is carried out respectively the step of the disposal of gentle filter include with
Lower step:
According toEach group of discrete spectrum sequence is carried out the disposal of gentle filter respectively；
In formula, R ' (k) represents the first signal spectrum sequence, and W represents the length of smothing filtering, and R (i) represents discrete spectrum sequence
Row, i represents fast Fourier transform point.
In the present embodiment, use the disposal of gentle filter that spectrum sequence can be made to become more fully apparent smooth, by using
Smoothing processing can improve the spectrogram of signal in the case of low signal-to-noise ratio well.
The effect of the disposal of gentle filter is described with instantiation below, it is assumed that signal is QPSK (Quadrature
Phase Shift Keyin, is called for short QPSK, QPSK) signal, signal to noise ratio is set for-6dB, the primary signal obtained
Frequency spectrum and smooth filtered signal spectrum are distinguished the most as shown in Figures 2 and 3, from figure it is apparent that after smothing filtering
Signal spectrum is high-visible, and the frequency spectrum of primary signal is then submerged in noise and is difficult to recognize.
Wherein in an embodiment, the first signal spectrum sequence of preset group number is carried out the step of data investigation process
Comprise the following steps:
According toFirst signal spectrum sequence of preset group number is carried out data investigation process；
In formula, RmK () represents secondary signal spectrum sequence, L represents preset group number, Rj' (k) expression jth group the first signal frequency
Spectral sequence.
In the present embodiment, although the docking collection of letters number is done the disposal of gentle filter and can be obviously improved the light slippage of signal spectrum
Degree, but owing to, under low signal-to-noise ratio, the fluctuation of noise amplitude is relatively big, thus uses one group of first signal spectrum sequence to do frequency deviation
Estimate often there be the biggest beating, carry out data investigation process by organizing the first signal spectrum sequence more, so can reduce noise
The fluctuation of amplitude, is effectively improved degree of stability and degree of accuracy that frequency deviation is estimated.The preset group number that L represents can regulate, and passes through
Regulation L can improve the precision that frequency deviation is estimated, the first signal spectrum sequence of preset group number is each group of the first signal spectrum sequence
In randomly select.
Wherein in an embodiment, obtain stable secondary signal spectrum sequence R clearlymAfter (k), obtain secondary signal
Maximum amplitude point in spectrum sequence, i.e. impact point, the spectrum position of this impact point is kmax, spectral magnitude is Rm(kmax), its
In,Can be with fast search to impact point according to formula.
Wherein in an embodiment, determine that according to impact point the step of the free transmission range of secondary signal spectrum sequence includes
Following steps:
According toDetermine the free transmission range of secondary signal spectrum sequence；
In formula, kmaxRepresent the spectrum position of impact point, Rm(kmax) represent the spectral magnitude of impact point, k1And k2Represent logical
The spectrum position of two end points with scope, k1≤k’≤k2, k ' represents each point spectrum position in free transmission range, Rm(k1) and Rm
(k2) represent the spectral magnitude of two end points of free transmission range, Rm(k ') represents the spectral magnitude of each point in free transmission range.
In the present embodiment, determining free transmission range according to above-mentioned formula, in frequency spectrum, the unit of spectrum amplitude is
DB, free transmission range is generally the spectral range between peak power and half peak power, be converted into spectral magnitude be exactly with
Within amplitude difference 3dB, therefore, may determine that two end points of free transmission range according to above-mentioned formula, so that it is determined that passband model
Enclose.
Wherein in an embodiment, the step obtaining the amplitude central point in free transmission range comprises the following steps:
According toThe spectrum position of the amplitude central point in acquisition free transmission range, in formula,Represent amplitude
The spectrum position of central point, k ' represents the spectrum position of each point in free transmission range, Rm(k ') represents each point in free transmission range
Spectral magnitude.
In the present embodiment, after determining free transmission range, according to the spectrum position of each point in free transmission range and spectral magnitude
May determine that the position of amplitude central point, the amplitude central point determined according to formula can reflect the character of spectral passband.
Wherein in an embodiment, count according to amplitude central point, fast Fourier transform and symbol period obtains former
The step of the estimated value of the carrier frequency of primordium band signal comprises the following steps:
According toObtain the estimated value of the carrier frequency of raw baseband signal, in formula,Represent original base band
The estimated value of the carrier frequency of signal,Representing the spectrum position of amplitude central point, T represents the symbol period of raw baseband signal,
NfftRepresent that the fast Fourier transform preset is counted.
In the present embodiment, the estimated value of the carrier frequency of raw baseband signal can be obtained according to formula, due to quickly
Fourier transformation is counted and the symbol period of raw baseband signal is typically all without there being deviation, therefore the estimated value of carrier frequency
Precision is relevant with the spectrum position of amplitude central point, and namely the positional precision of amplitude central point is relevant；Through smothing filtering and
Data investigation makes frequency spectrum more stable and accurate, and the positional precision of the amplitude central point obtained is high, and the position of amplitude central point
Put the precision that precision just determines the estimated value of carrier frequency, thus the precision of carrier frequency is the highest.
Wherein in an embodiment, according to the estimated value of the carrier frequency of raw baseband signal and raw baseband signal
The actual value of carrier frequency obtains the step of Doppler frequency deviation estimated value and comprises the following steps:
According toObtain Doppler frequency deviation estimated value, in formula,Represent Doppler frequency deviation estimated value,Represent
The estimated value of the carrier frequency of raw baseband signal, fcRepresent the actual value of the carrier frequency of raw baseband signal.
In the present embodiment, Doppler frequency deviation estimated value is exactly that the estimated value of carrier frequency of raw baseband signal is with original
Difference between the actual value of the carrier frequency of baseband signal, is obtaining the estimated value of carrier frequency of raw baseband signal and former
After the actual value of the carrier frequency of primordium band signal, both are subtracted each other and just can quickly obtain Doppler frequency deviation estimated value.
Wherein in an embodiment, digital communication system channel is additive white Gaussian noise channel, in baseband signal group
The expression formula of time domain sequences of baseband signal be:
In formula, r (n) represents the time domain sequences of the baseband signal in baseband signal group, aiRepresent the base in baseband signal group
Band signal mapping point, A represents the amplitude of the baseband signal in baseband signal group, and N represents the baseband signal in baseband signal group
Symbol numbers, T represents the symbol period of raw baseband signal, NsRepresent he number, TbRepresenting the width of code element, g represents pulse
Shaping function, pulse-shaping function duration length is Tb, fcRepresent the actual value of the carrier frequency of raw baseband signal,
feRepresent the actual value of the Doppler frequency deviation of raw baseband signal, θcRepresent the carrier wave initial phase of raw baseband signal, θeRepresent
The carrier phase deviation of raw baseband signal, w (n) represents additive white Gaussian noise signal.
In the present embodiment, the f in the expression formula of the time domain sequences of the baseband signal in baseband signal groupeRepresent real
Frequency departure, θeRepresent the carrier phase deviation of baseband signal, from expression formula it can be seen that w (n) is additive white Gaussian noise letter
Number, its spectrum curve is the straight line of a steady state value, and carrier frequency item has had more frequency departure fe, just it is embodied on discrete spectrum figure
The f that has been frequency spectrum overall offsete, utilize this information, it is only necessary to the overall frequency shift amount finding out reception signal spectrum is assured that
Carrier deviation f of sending and receiving ende, here it is the ultimate principle that Doppler frequency deviation of the present invention is estimated.
The Doppler frequency offset estimation method of the present invention can apply to the Doppler of low character rate system under low signal-to-noise ratio
Frequency deviation is estimated, wherein uses smothing filtering to make signal spectrum under low signal-to-noise ratio emerge out in noise, uses and organize number more
Make frequency spectrum more stable with accurately according to stacking method, then gone out the frequency deviation of system by steady and audible spectrum estimation.Due to
The process employs spectral smoothing filtering and multi-group data overlap-add procedure so that this method can under the lowest signal to noise ratio still
Normal work, thus there is no concern that the threshold effect of snr of received signal.Owing to the method is to carry out signal carrier frequency spectrum
Estimate, unrelated with signal Modulation Types and system symbol rate, thus this frequency deviation estimating method not by signal Modulation Types and is
The restriction of system character rate.It addition, the computation complexity of the method is moderate, thus the method can be widely used in Practical Project
In.
According to above-mentioned Doppler frequency offset estimation method, the present invention also provides for a kind of Doppler frequency deviation estimating system, the most just
The embodiment of the Doppler frequency deviation estimating system of the present invention is described in detail.
Shown in Figure 4, for the structural representation of Doppler frequency deviation estimating system in one embodiment of the invention.This enforcement
Doppler frequency deviation estimating system in example includes with lower unit:
Grouped element 210, for obtaining the raw baseband signal in digital communication system channel, according to default quick Fu
In leaf transformation count raw baseband signal be grouped, it is thus achieved that each baseband signal group, wherein, often organize the base band of baseband signal group
The fast Fourier transform that the symbol numbers of signal is default is counted；
Spectrum processing unit 220, for carrying out fast Fourier change respectively to the baseband signal in each group of baseband signal group
Change, it is thus achieved that each group discrete spectrum sequence that each group baseband signal group is corresponding；
The disposal of gentle filter unit 230, for carrying out the disposal of gentle filter respectively to each group of discrete spectrum sequence, it is thus achieved that each
Each group the first signal spectrum sequence that group discrete spectrum sequence pair is answered；
Overlap-add procedure unit 240, for choosing the first signal frequency of preset group number in each group of the first signal spectrum sequence
Spectral sequence, carries out data investigation process to the first signal spectrum sequence of preset group number, it is thus achieved that secondary signal spectrum sequence；
Passband processing unit 250, for obtaining the impact point of amplitude maximum in secondary signal spectrum sequence, according to impact point
Determine the free transmission range of secondary signal spectrum sequence, and obtain the amplitude central point in free transmission range；
First estimation unit 260, for obtaining the symbol period of raw baseband signal, according to amplitude central point, default
Fast Fourier transform is counted and symbol period obtains the estimated value of carrier frequency of raw baseband signal；
Second estimation unit 270, for obtaining the actual value of the carrier frequency of raw baseband signal, believes according to original base band
Number the estimated value of carrier frequency and the actual value of carrier frequency of raw baseband signal obtain Doppler frequency deviation estimated value.
Wherein in an embodiment, spectrum processing unit 220 basisTo each group of base band
Baseband signal in signal group carries out fast Fourier transform respectively；
In formula, R (i) represents discrete spectrum sequence, NfftRepresenting that the fast Fourier transform preset is counted, r (n) represents base
The time domain sequences of the baseband signal in band signal group, i represents fast Fourier transform point, and T represents the symbol of raw baseband signal
Cycle.
Wherein in an embodiment, the disposal of gentle filter unit 230 basisTo each group from
Scattered spectrum sequence carries out the disposal of gentle filter respectively；
In formula, R ' (k) represents the first signal spectrum sequence, and W represents the length of smothing filtering, and R (i) represents discrete spectrum sequence
Row, i represents fast Fourier transform point.
Wherein in an embodiment, overlap-add procedure unit 240 basisTo preset group number first
Signal spectrum sequence carries out data investigation process；
In formula, RmK () represents secondary signal spectrum sequence, L represents preset group number, Rj' (k) expression jth group the first signal frequency
Spectral sequence.
Wherein in an embodiment, passband processing unit 250 basis
Determine the free transmission range of secondary signal spectrum sequence；
In formula, kmaxRepresent the spectrum position of impact point, Rm(kmax) represent the spectral magnitude of impact point, k1And k2Represent logical
The spectrum position of two end points with scope, k1≤k’≤k2, k ' represents each point spectrum position in free transmission range, Rm(k1) and Rm
(k2) represent the spectral magnitude of two end points of free transmission range, Rm(k ') represents the spectral magnitude of each point in free transmission range.
Wherein in an embodiment, passband processing unit 250 basisObtain in free transmission range
The spectrum position of amplitude central point, in formula,Representing the spectrum position of amplitude central point, k ' represents each point in free transmission range
Spectrum position, Rm(k ') represents the spectral magnitude of each point in free transmission range.
Wherein in an embodiment, the first estimation unit 260 basisObtain the carrier wave of raw baseband signal
The estimated value of frequency, in formula,Represent the estimated value of the carrier frequency of raw baseband signal,Represent the frequency spectrum of amplitude central point
Position, T represents the symbol period of raw baseband signal, NfftRepresent that the fast Fourier transform preset is counted.
Wherein in an embodiment, the second estimation unit 270 basisObtain Doppler frequency deviation estimated value,
In formula,Represent Doppler frequency deviation estimated value,Represent the estimated value of the carrier frequency of raw baseband signal, fcRepresent original base
The actual value of the carrier frequency of band signal.
The Doppler frequency deviation estimating system of the present invention and the Doppler frequency offset estimation method one_to_one corresponding of the present invention, above-mentioned
Technical characteristic and beneficial effect thereof that the embodiment of Doppler frequency offset estimation method illustrates all are applicable to Doppler frequency deviation and estimate system
In the embodiment of system.
Each technical characteristic of embodiment described above can combine arbitrarily, for making description succinct, not to above-mentioned reality
The all possible combination of each technical characteristic executed in example is all described, but, as long as the combination of these technical characteristics is not deposited
In contradiction, all it is considered to be the scope that this specification is recorded.
Embodiment described above only have expressed the several embodiments of the present invention, and it describes more concrete and detailed, but also
Can not therefore be construed as limiting the scope of the patent.It should be pointed out that, come for those of ordinary skill in the art
Saying, without departing from the inventive concept of the premise, it is also possible to make some deformation and improvement, these broadly fall into the protection of the present invention
Scope.Therefore, the protection domain of patent of the present invention should be as the criterion with claims.
Claims (10)
1. a Doppler frequency offset estimation method, it is characterised in that comprise the following steps:
Obtain the raw baseband signal in digital communication system channel, count to described former according to default fast Fourier transform
Primordium band signal is grouped, it is thus achieved that each baseband signal group, and wherein, often the symbol numbers of the baseband signal of group baseband signal group is
Described default fast Fourier transform is counted；
Baseband signal in described each group of baseband signal group is carried out fast Fourier transform respectively, it is thus achieved that described each group of base band letter
Number each group discrete spectrum sequence that group is corresponding；
Described each group of discrete spectrum sequence is carried out the disposal of gentle filter respectively, it is thus achieved that described each group of discrete spectrum sequence pair is answered
Each group the first signal spectrum sequence；
The first signal spectrum sequence of preset group number is chosen, to described preset group number in described each group of the first signal spectrum sequence
The first signal spectrum sequence carry out data investigation process, it is thus achieved that secondary signal spectrum sequence；
Obtain the impact point of amplitude maximum in described secondary signal spectrum sequence, determine described secondary signal according to described impact point
The free transmission range of spectrum sequence, and obtain the amplitude central point in described free transmission range；
Obtain the symbol period of described raw baseband signal, become according to described amplitude central point, described default fast Fourier
Change the estimated value of the carrier frequency obtaining described raw baseband signal with described symbol period of counting；
Obtain the actual value of the carrier frequency of described raw baseband signal, according to estimating of the carrier frequency of described raw baseband signal
The actual value of the carrier frequency of evaluation and described raw baseband signal obtains Doppler frequency deviation estimated value.
Doppler frequency offset estimation method the most according to claim 1, it is characterised in that described to described each group of baseband signal
Baseband signal in group carries out the step of fast Fourier transform respectively and comprises the following steps:
According toBaseband signal in described each group of baseband signal group is carried out in quick Fu respectively
Leaf transformation；
In formula, R (i) represents described discrete spectrum sequence, NfftRepresent that described default fast Fourier transform is counted, r (n) table
Showing the time domain sequences of baseband signal in described baseband signal group, i represents fast Fourier transform point, and T represents described original base
The symbol period of band signal.
Doppler frequency offset estimation method the most according to claim 1, it is characterised in that described to described each group of discrete spectrum
Sequence carries out the step of the disposal of gentle filter respectively and comprises the following steps:
According toDescribed each group of discrete spectrum sequence is carried out the disposal of gentle filter respectively；
In formula, R ' (k) represents described first signal spectrum sequence, and W represents the length of smothing filtering, and R (i) represents described discrete frequency
Spectral sequence, i represents fast Fourier transform point.
Doppler frequency offset estimation method the most according to claim 1, it is characterised in that described to described preset group number
One signal spectrum sequence carries out the step of data investigation process and comprises the following steps:
According toFirst signal spectrum sequence of described preset group number is carried out data investigation process；
In formula, RmK () represents described secondary signal spectrum sequence, L represents described preset group number, Rj' (k) represent jth group first believe
Number spectrum sequence.
Doppler frequency offset estimation method the most according to claim 1, it is characterised in that described determine according to described impact point
The step of the free transmission range of described secondary signal spectrum sequence comprises the following steps:
According toDetermine the free transmission range of described secondary signal spectrum sequence；
In formula, kmaxRepresent the spectrum position of described impact point, Rm(kmax) represent the spectral magnitude of described impact point, k1And k2Table
Show the spectrum position of two end points of described free transmission range, k1≤k’≤k2, k ' represents each point frequency spectrum position in described free transmission range
Put, Rm(k1) and Rm(k2) represent the spectral magnitude of two end points of described free transmission range, RmIn (k ') represents described free transmission range
The spectral magnitude of each point.
Doppler frequency offset estimation method the most according to claim 1, it is characterised in that in the described free transmission range of described acquisition
The step of amplitude central point comprise the following steps:
According toObtain the spectrum position of amplitude central point in described free transmission range, in formula,Represent described
The spectrum position of amplitude central point, k ' represents the spectrum position of each point in described free transmission range, Rm(k ') represent described passband
In the range of the spectral magnitude of each point.
Doppler frequency offset estimation method the most according to claim 1, it is characterised in that described according to described amplitude center
Point, described fast Fourier transform are counted and described symbol period obtains the estimated value of carrier frequency of described raw baseband signal
Step comprise the following steps:
According toObtain the estimated value of the carrier frequency of described raw baseband signal, in formula,Represent described original base
The estimated value of the carrier frequency of band signal,Representing the spectrum position of described amplitude central point, T represents described raw baseband signal
Symbol period, NfftRepresent that described default fast Fourier transform is counted.
Doppler frequency offset estimation method the most according to claim 1, it is characterised in that described believe according to described original base band
Number the estimated value of carrier frequency and the actual value of carrier frequency of described raw baseband signal obtain Doppler frequency deviation estimated value
Step comprise the following steps:
According toObtain described Doppler frequency deviation estimated value, in formula,Represent described Doppler frequency deviation estimated value,
Represent the estimated value of the carrier frequency of described raw baseband signal, fcRepresent carrier frequency true of described raw baseband signal
Value.
Doppler frequency offset estimation method the most as claimed in any of claims 1 to 8, it is characterised in that described numeral
Communication system channel is additive white Gaussian noise channel, and the expression formula of the time domain sequences of the baseband signal in baseband signal group is:
In formula, r (n) represents the time domain sequences of the baseband signal in baseband signal group, aiRepresent the baseband signal in baseband signal group
Mapping point, A represents the amplitude of the baseband signal in baseband signal group, and N represents the symbol of the baseband signal in baseband signal group
Number, T represents the symbol period of raw baseband signal, NsRepresent he number, TbRepresenting the width of code element, g represents pulse-shaping letter
Number, pulse-shaping function duration length is Tb, fcRepresent the actual value of the carrier frequency of raw baseband signal, feRepresent
The actual value of the Doppler frequency deviation of raw baseband signal, θcRepresent the carrier wave initial phase of raw baseband signal, θeRepresent original base
The carrier phase deviation of band signal, w (n) represents additive white Gaussian noise signal.
10. a Doppler frequency deviation estimating system, it is characterised in that include with lower unit:
Grouped element, for obtaining the raw baseband signal in digital communication system channel, becomes according to default fast Fourier
Changing counts is grouped described raw baseband signal, it is thus achieved that each baseband signal group, wherein, and the often base band letter of group baseband signal group
Number symbol numbers be that described default fast Fourier transform is counted；
Spectrum processing unit, for the baseband signal in described each group of baseband signal group is carried out fast Fourier transform respectively,
Obtain each group discrete spectrum sequence that described each group of baseband signal group is corresponding；
The disposal of gentle filter unit, for carrying out the disposal of gentle filter respectively to described each group of discrete spectrum sequence, it is thus achieved that described
Each group the first signal spectrum sequence that each group discrete spectrum sequence pair is answered；
Overlap-add procedure unit, for choosing the first signal spectrum sequence of preset group number in described each group of the first signal spectrum sequence
Row, carry out data investigation process to the first signal spectrum sequence of described preset group number, it is thus achieved that secondary signal spectrum sequence；
Passband processing unit, for obtaining the impact point of amplitude maximum in described secondary signal spectrum sequence, according to described target
Point determines the free transmission range of described secondary signal spectrum sequence, and obtains the amplitude central point in described free transmission range；
First estimation unit, for obtaining the symbol period of described raw baseband signal, according to described amplitude central point, described pre-
If fast Fourier transform count and described symbol period obtains the estimated value of carrier frequency of described raw baseband signal；
Second estimation unit, for obtaining the actual value of the carrier frequency of described raw baseband signal, according to described original base band
The actual value of the estimated value of the carrier frequency of signal and the carrier frequency of described raw baseband signal obtains Doppler frequency deviation and estimates
Value.
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