CN110113276A - OFDM frequency deviation estimating method, system and device based on IEEE802.11 - Google Patents
OFDM frequency deviation estimating method, system and device based on IEEE802.11 Download PDFInfo
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- CN110113276A CN110113276A CN201810099899.5A CN201810099899A CN110113276A CN 110113276 A CN110113276 A CN 110113276A CN 201810099899 A CN201810099899 A CN 201810099899A CN 110113276 A CN110113276 A CN 110113276A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/0014—Carrier regulation
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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
- H04L27/2656—Frame synchronisation, e.g. packet synchronisation, time division duplex [TDD] switching point detection or subframe synchronisation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/0014—Carrier regulation
- H04L2027/0024—Carrier regulation at the receiver end
- H04L2027/0026—Correction of carrier offset
Abstract
The invention discloses a kind of OFDM frequency deviation estimating method, system and device based on IEEE802.11.Method obtains first carrier offset estimation value the following steps are included: autocorrelation operation before and after carrying out in the time domain to two identical long training sequences in the Preamble for receiving signal；The compensation of time domain carrier wave frequency deviation is carried out to Signal according to first carrier offset estimation value；Compensated Signal is converted into frequency-region signal from time-domain signal；The Signal of frequency domain is parsed, frequency domain reference signal is obtained；The Signal of frequency domain reference signal and frequency domain is subjected to locally associated property operation, obtains the second Nonlinear Transformation in Frequency Offset Estimation value；The compensation of time domain carrier wave frequency deviation is carried out to Payload according to first carrier offset estimation value and the second Nonlinear Transformation in Frequency Offset Estimation value.In conjunction with the time domain Nonlinear Transformation in Frequency Offset Estimation of Preamble and the frequency domain carriers offset estimation of Signal, more accurate time domain Nonlinear Transformation in Frequency Offset Estimation compensation finally can be obtained in Payload；The advantages of accuracy with higher, low complex degree and strong real-time.
Description
Technical field
The present invention relates to field of communication technology more particularly to a kind of OFDM frequency deviation estimating method based on IEEE802.11,
System and device.
Background technique
IEEE802.11 is a kind of communication protocol for being based on OFDM (orthogonal frequency division multiplexing) technology.This technology is by same
Time sends multiple subcarriers to promote throughput.Each subcarrier carries different information.Due to being between subcarrier
Orthogonal, so there is no interfere with each other.But OFDM technology is very sensitive to carrier wave frequency deviation (CFO), because carrier wave frequency deviation is not
Only sub-carrier information introduces phase rotation, and destroys the orthogonality between subcarrier, and subcarrier is allowed to interfere with each other (ICI).
So OFDM technology receiver will have effective Nonlinear Transformation in Frequency Offset Estimation and compensation.
For IEEE802.11 agreement, existing technology be substantially by the training sequence (STF or LTF) of Preamble into
Row Nonlinear Transformation in Frequency Offset Estimation, or tracking is iterated by some characteristics in DRP data reception process.But these methods are all
There is a problem of that accuracy is not high, complexity is high, real-time is poor.
A kind of ofdm communication system frequency deviation estimating method and device (application number: 201111049869.1), in Frequency Domain Solution
It analyses obtained feedback information to re-modulate and be transformed into time domain, does locally associated operation in time domain.It is done in time domain locally associated
The noise introduced can be interfered to avoid ICI, to there is higher accuracy, but introduce biggish complexity in this way.
It is a kind of suitable for MIMO-OFDM system carrier frequency bias estimation (application number: 201610147118.6), utilize
The auto-correlation of N number of STF (short training sequence) on Preamble carries out rough offset estimation, then with two LTF (long training sequence
Column) auto-correlation obtain accurate Nonlinear Transformation in Frequency Offset Estimation.Finally, compensation is arrived subsequent using this accurate Nonlinear Transformation in Frequency Offset Estimation value
The part Signal and Payload, guarantee the demodulation performance of these parts.But frequency deviation provided by the auto-correlation of two LTF
The accuracy of estimation is limited, therefore receptivity has certain loss.Some methods are some information using subsequent Payload
Be iterated estimation, during iteration, performance can passage at any time step up, but do not have real-time in this way,
Forward part cannot timely ensure in Payload.
Summary of the invention
The OFDM frequency deviation estimating method that in view of the deficiencies of the prior art, the invention proposes a kind of based on IEEE802.11,
System and device, this method, system or device complete locally associated operation in frequency domain, utilize the frequency domain local phase of the part Signal
The accuracy for promoting offset estimation is closed, solves that existing carrier frequency bias estimation accuracy is not high, complexity is big, real-time is poor
The problem of.
To achieve the goals above, technical solution of the present invention is as follows:
A kind of OFDM frequency deviation estimating method based on IEEE802.11, comprising the following steps: to reception signal
Two identical long training sequences in Preamble carry out front and back autocorrelation operation in the time domain, obtain first carrier frequency deviation
Estimated value；The compensation of time domain carrier wave frequency deviation is carried out to the Signal for receiving signal according to the first carrier offset estimation value；It will mend
Signal after repaying is converted to frequency-region signal from time-domain signal；The Signal of frequency domain is parsed, and to the information of parsing into
Row re-modulates, and obtains frequency domain reference signal；The Signal of the frequency domain reference signal and frequency domain is subjected to locally associated property fortune
It calculates, obtains the second Nonlinear Transformation in Frequency Offset Estimation value；According to the first carrier offset estimation value and the second Nonlinear Transformation in Frequency Offset Estimation value
The compensation of time domain carrier wave frequency deviation is carried out to the Payload for receiving signal.
Further, two identical long training sequences in the Preamble of described pair of reception signal carry out in the time domain
The formula of front and back autocorrelation operation are as follows:
Wherein, N is the length of long training sequence, yLTF1And yLTF2First long training sequence in respectively Preamble
With second long training sequence, ()*Indicate conjugation；
The first carrier offset estimation valueAre as follows:
Wherein, fsFor the sample rate for receiving signal.
Further, described that time domain carrier wave is carried out to the Signal for receiving signal according to the first carrier offset estimation value
The formula of frequency deviation compensation are as follows:
Wherein,For compensated time domain Signal,For compensated white Gaussian noise, foIt is actual
Carrier frequency bias.
Further, the formula that compensated Signal is converted to frequency-region signal from time-domain signal are as follows:
Wherein,It is the distance between OFDM symbol for the frequency domain Signal, L after conversion；fΔFor compensated carrier wave
Frequency deviation difference.
Further, the formula that the Signal of frequency domain reference signal and frequency domain is carried out to locally associated property operation are as follows:
Wherein,For conversion after frequency domain Signal,For the frequency domain reference signal；
The second Nonlinear Transformation in Frequency Offset Estimation value are as follows:
A kind of OFDM frequency deviation estimation system based on IEEE802.11, including the first frequency deviation estimating unit, Signal frequency deviation
Compensating unit, Fourier transformation unit, frequency domain reference signal acquiring unit, the second frequency deviation estimating unit, the compensation of Payload frequency deviation
Unit.
First frequency deviation estimating unit be used for receive signal Preamble in two identical long training sequences when
Front and back autocorrelation operation is carried out on domain, obtains first carrier offset estimation value.
Signal frequency offset compensation element be used for according to the first carrier offset estimation value to receive signal Signal into
The compensation of row time domain carrier wave frequency deviation.
Fourier transformation unit is used to compensated Signal being converted to frequency-region signal from time-domain signal.
Frequency domain reference signal acquiring unit carries out again for parsing to the Signal of frequency domain, and to the information of parsing
Modulation, obtains frequency domain reference signal.
Second frequency deviation estimating unit is used to the Signal of the frequency domain reference signal and frequency domain carrying out locally associated property fortune
It calculates, obtains the second Nonlinear Transformation in Frequency Offset Estimation value.
Payload frequency offset compensation element according to the first carrier offset estimation value and second carrier wave frequency deviation for estimating
Evaluation carries out the compensation of time domain carrier wave frequency deviation to the Payload for receiving signal.
Further, first frequency deviation estimating unit long training identical to two in the Preamble for receiving signal
Sequence carries out the formula of front and back autocorrelation operation in the time domain are as follows:
Wherein, N is the length of long training sequence, yLTF1And yLTF2First long training sequence in respectively Preamble
With second long training sequence, ()*Indicate conjugation.
The first carrier offset estimation valueAre as follows:
Wherein, fsFor the sample rate for receiving signal.
Further, the Signal frequency offset compensation element is according to the first carrier offset estimation value to reception signal
The formula of Signal progress time domain carrier wave frequency deviation compensation are as follows:
Wherein,For compensated time domain Signal,For compensated white Gaussian noise, foIt is actual
Carrier frequency bias.
Further, compensated Signal is converted to frequency-region signal from time-domain signal by the Fourier transformation unit
Formula are as follows:
Wherein,It is the distance between OFDM symbol for the frequency domain Signal, L after conversion；fΔFor compensated carrier wave
Frequency deviation difference.
The Signal of frequency domain reference signal and frequency domain is carried out locally associated property fortune by the frequency domain reference signal acquiring unit
The formula of calculation are as follows:
Wherein,For the frequency domain reference signal.
The second Nonlinear Transformation in Frequency Offset Estimation value are as follows:
A kind of OFDM frequency deviation estimation device based on IEEE802.11, including memory, processor and it is stored in described deposit
On reservoir and the computer program that can run on the processor；The computer program is realized when being executed by the processor
The step of above-mentioned any one method.
Beneficial effects of the present invention:
The present invention obtains an accurate carrier wave frequency deviation using the auto-correlation computation of two LTF of the part Preamble
Estimated value, and by it in time domain compensation to the subsequent part Signal；The Signal that time domain is compensated transforms to frequency domain progress
Demodulation parses information；Obtained information assume that as accurate information and re-modulates feedback, locally associated estimate in frequency domain
Meter, obtains more accurate carrier frequency bias；It is incorporated in the time domain Nonlinear Transformation in Frequency Offset Estimation of Preamble and the frequency domain in Signal
Nonlinear Transformation in Frequency Offset Estimation finally can obtain more accurate time domain Nonlinear Transformation in Frequency Offset Estimation compensation in the part Payload in time；With compared with
The advantages of high accuracy, low complex degree and strong real-time.
Detailed description of the invention
Fig. 1 is the physical layer Legacy frame format of IEEE802.11a/g agreement.
Fig. 2 is the physical layer HT-GF frame format of IEEE802.11n agreement.
Fig. 3 is the physical layer HT-MM frame format of IEEE802.11n agreement.
Fig. 4 is the flow diagram of the OFDM frequency deviation estimating method based on IEEE802.11 in the present invention.
Fig. 5 is Nonlinear Transformation in Frequency Offset Estimation simulation result diagram of the invention.
Specific embodiment
With reference to the accompanying drawings and examples, the present invention is further explained.
IEEE802.11 is the communication protocol of WLAN, sends and receives both sides and is effectively led under the protocol frame
Letter.Since protocol contents according to the present invention are physical layer communication frame format, thus first to its physical layer frame format into
The simple statement of row.
As shown in Figure 1-3, listing 3 kinds of physical layer frame formats of IEEE802.11a/g/n respectively, these frame formats are all
Based on OFDM modulation technique.Substantially, frame format is divided into three parts: Preamble (header), Signal (information),
Payload (payload).IEEE802.11a, IEEE802.11g, IEEE802.11n be respectively on the basis of IEEE802.11 into
3 kinds of standard agreements of one step development.
(1) Preamble: this part does not carry any information, and content is that agreement provides, and is used for frame synchronization, i.e. frame is examined
Survey, receive timing, power adjustment, carrier wave frequency deviation (CFO) estimation etc..
(2) characteristic information of frame, such as bandwidth, length, modulation format etc. Signal: are carried.These characteristic informations have
Very high robust and anti-noise ability are the prerequisites for being properly received information.So information is generally difficult to be disturbed to error.
(3) Payload: transferring content is carried.
Embodiment 1:
As shown in figure 4, a kind of OFDM frequency deviation estimating method based on IEEE802.11, comprising the following steps:
S1: front and back is carried out in the time domain to two identical long training sequences (LTF) in the Preamble for receiving signal
Autocorrelation operation obtains first carrier offset estimation value
S2: according to first carrier offset estimation valueThe compensation of time domain carrier wave frequency deviation is carried out to the Signal for receiving signal.
S3: compensated Signal is converted into frequency-region signal from time-domain signal.
S4: parsing the Signal of frequency domain, and re-modulates to the information of parsing, obtains frequency domain reference signal
S5: by frequency domain reference signalLocally associated property operation is carried out with the Signal of frequency domain, obtains the second carrier wave
Offset estimation value
S6: according to first carrier offset estimation valueWith the second Nonlinear Transformation in Frequency Offset Estimation valueTo the Payload for receiving signal
Carry out the compensation of time domain carrier wave frequency deviation.
The present invention obtains an accurate carrier wave frequency deviation using the auto-correlation computation of two LTF of the part Preamble
Estimated value, and by it in time domain compensation to the subsequent part Signal；The Signal that time domain is compensated transforms to frequency domain progress
Demodulation parses information；Obtained information assume that as accurate information and re-modulates feedback, locally associated estimate in frequency domain
Meter, obtains more accurate carrier frequency bias.It is incorporated in the time domain Nonlinear Transformation in Frequency Offset Estimation of Preamble and the frequency domain in Signal
Nonlinear Transformation in Frequency Offset Estimation finally can obtain more accurate time domain Nonlinear Transformation in Frequency Offset Estimation compensation in the part Payload in time.With compared with
The advantages of high accuracy, low complex degree and strong real-time.
Specifically, in step sl, the formula of front and back autocorrelation operation is carried out in the time domain are as follows:Wherein, N is the length of LTF, yLTF1And yLTF2Be respectively first LTF in Preamble and
Second LTF, ()*For conjugation.
Signal y (n) is received in addition to there are also carrier wave frequency deviations for noise, is indicated are as follows:
Wherein, x (n) is useful signal；Z (n) is white Gaussian noise, σ2For power；It is caused for Nonlinear Transformation in Frequency Offset Estimation
Phase rotation；foFor carrier frequency bias；fsIt is the sample rate for receiving signal.
So the front and back autocorrelation estimation of Preamble can indicate are as follows:
Wherein,For the white noise after auto-correlation, Gaussian distributed, power 2N | xLTF1|2σ2；xLTF1=xLTF2。
It is available by seeking angle, θ=angle (g) to gTherefore, first carrier offset estimation value is obtained
First carrier offset estimation valueIt is actual carrier frequency bias foEstimated value, due to that can not accurately obtain
Actual carrier frequency bias fo, so there is also a carrier wave frequency deviation residual values fΔ。
The general accuracy for measuring Nonlinear Transformation in Frequency Offset Estimation can indicate with the signal-to-noise ratio after auto-correlation, expression formula are as follows:
Specifically, in step s 2, the formula of time domain carrier wave frequency deviation compensation is carried out to Signal are as follows:
Wherein,For the part compensated time domain Signal；zsig(n) andFor the Gauss white noise of compensation front and back
Sound, power are all σ2；fΔFor compensated carrier wave frequency deviation residual values.
Using LTF time domain auto-correlation computation, first carrier offset estimation value is obtainedIn time domain compensation to reception signal
Signal can make Signal ignore the noise of ICI (inter-carrier interference) introducing when turning frequency domain from time domain substantially, promote Signal's
Demodulation performance.
Specifically, in step s3, Fast Fourier Transform (FFT) is carried out to compensated Signal, switched to from time domain
Frequency domain, this operation are to demodulate the steps necessary of OFDM.Formula is as follows:
Wherein,For FFT frequency point sequence；The frequency domain Signal by time domain compensation being expressed as；
Zsig(k) it is expressed as frequency domain white Gaussian noise, power is
Further,It can indicate are as follows:
Wherein,For white Gaussian noise (noise introduced comprising Frequency domain noise and ICI), power isL be with it is preceding
The distance (L >=N) of one OFDM symbol.
Specifically, in step s 4, to frequency domainIt is demodulated, parses information, obtain the part transmitting terminal Signal
Bit information, row information of going forward side by side feedback.Demodulation can choose hard decision or channel decoding.It is carried out after being decoded using channel
Feedback can be more accurate, because channel decoding has error correction, but needs certain delay；And hard decision feedback directly passes throughMost probable bit information is found, without considering delay.As obtained by experiment, two kinds of feedback performance differences are small.
Then, to using processing identical with transmitting terminal to re-modulate feedback information, frequency domain reference signal is obtainedFrequency domain reference signalAccording to receive signal estimate to obtain, not necessarily with the letter of receiving end actual modulated
Number Xsig(k) completely the same.
Specifically, in step s 5, by frequency domain reference signalWith the reception signal of frequency domainCarry out local phase
Close operation, formula are as follows:
Assuming that the frequency domain reference signal of estimationIt is completely correct, thenLocally associated result can
To indicate are as follows:
Finally, by carrying out seeking angle to GTherefore, the second Nonlinear Transformation in Frequency Offset Estimation value is obtained
The modulation format of Signal is the highest BPSK of robustness, and channel coding is also highest 1/2 code rate of robust, so
The demodulation performance of the demodulation performance ratio payload of Signal is much higher, is difficult to malfunction.So Signal information substantially can be with
It is assumed to be correctly, being fed back as Nonlinear Transformation in Frequency Offset Estimation is a kind of very reliable way.By Signal parsing information into
Row feedback modulation obtains modulationWith the reception signal of frequency domainCarry out it is locally associated, performance gain promotion want
It is higher than performance gain autocorrelative before and after time domain.
After locally associated, it is assumed that N=L, signal-to-noise ratio indicate are as follows:
In contrast, it can be seen that locally associated signal-to-noise ratio is the gain that 3dB is higher by than auto-correlation.
Specifically, in step s 6, it is to the final time domain carrier wave frequency deviation offset of Payload
As shown in figure 5, being Nonlinear Transformation in Frequency Offset Estimation simulation result diagram of the invention, offset estimation error is CDF, channel circumstance
For AWGN (SNR=1.5dB).Solid line be used alone front and back LTF autocorrelation estimation obtain as a result, 10% error is greater than
11KHz.Dotted line be added Signal frequency domain it is locally associated estimate obtain as a result, the error of offset estimation 10% of the invention is big
In 4KHz.Obviously, inventive can be very excellent.
Embodiment 2:
A kind of OFDM frequency deviation estimation system based on IEEE802.11, including the first frequency deviation estimating unit, Signal frequency deviation
Compensating unit, Fourier transformation unit, frequency domain reference signal acquiring unit, the second frequency deviation estimating unit, the compensation of Payload frequency deviation
Unit.
First frequency deviation estimating unit, for receive signal Preamble in two identical long training sequences when
Front and back autocorrelation operation is carried out on domain, obtains first carrier offset estimation value
Signal frequency offset compensation element, for according to first carrier offset estimation valueThe Signal for receiving signal is carried out
The compensation of time domain carrier wave frequency deviation.
Fourier transformation unit, for compensated Signal to be converted to frequency-region signal from time-domain signal.
Frequency domain reference signal acquiring unit is parsed for the Signal to frequency domain, and carries out weight to the information of parsing
New modulation, obtains frequency domain reference signal
Second frequency deviation estimating unit is used for frequency domain reference signalLocally associated property is carried out with the Signal of frequency domain
Operation obtains the second Nonlinear Transformation in Frequency Offset Estimation value
Payload frequency offset compensation element, for according to first carrier offset estimation valueWith the second Nonlinear Transformation in Frequency Offset Estimation valueThe compensation of time domain carrier wave frequency deviation is carried out to the Payload for receiving signal.
The present invention obtains an accurate Nonlinear Transformation in Frequency Offset Estimation using the auto-correlation computation of two LTF of Preamble
Value, and by it in time domain compensation to the subsequent part Signal；The Signal that time domain is compensated transforms to frequency domain and demodulates,
Parse information；Obtained information assume that as accurate information and re-modulate feedback, carries out locally associated estimation in frequency domain, obtains
To more accurate carrier frequency bias.It is incorporated in the time domain Nonlinear Transformation in Frequency Offset Estimation of Preamble and the frequency domain carriers frequency in Signal
Estimation partially finally can obtain more accurate time domain Nonlinear Transformation in Frequency Offset Estimation compensation in the part Payload in time.Standard with higher
The advantages of exactness, low complex degree and strong real-time.
Specifically, the first frequency deviation estimating unit carries out the formula of front and back autocorrelation operation in the time domain are as follows:Wherein, N is the length of LTF, yLTF1And yLTF2Be respectively first LTF in Preamble and
Second LTF, ()*For conjugation.
Signal y (n) is received in addition to there are also carrier wave frequency deviations for noise, is indicated are as follows:
Wherein, x (n) is useful signal；Z (n) is white Gaussian noise, σ2For power；It is caused for Nonlinear Transformation in Frequency Offset Estimation
Phase rotation；foFor carrier frequency bias；fsIt is the sample rate for receiving signal.
So the front and back autocorrelation estimation of Preamble can indicate are as follows:
Wherein,For the white noise after auto-correlation, Gaussian distributed, power 2N | xLTF1|2σ2；xLTF1=xLTF2。
It is available by seeking angle, θ=angle (g) to gTherefore, first carrier offset estimation value is obtained
First carrier offset estimation valueIt is actual carrier frequency bias foEstimated value, due to that can not accurately obtain
Actual carrier frequency bias fo, so there is also a carrier wave frequency deviation residual values fΔ。
The general accuracy for measuring Nonlinear Transformation in Frequency Offset Estimation can indicate with the signal-to-noise ratio after auto-correlation, expression formula are as follows:
Specifically, Signal frequency offset compensation element carries out the formula of time domain carrier wave frequency deviation compensation to Signal are as follows:
Wherein,For the part compensated time domain Signal；zsig(n) andFor the Gauss white noise of compensation front and back
Sound, power are all σ2；fΔFor compensated carrier wave frequency deviation residual values.
Using LTF time domain auto-correlation computation, first carrier offset estimation value is obtainedIn time domain compensation to reception signal
Signal can make Signal ignore the noise of ICI (inter-carrier interference) introducing when turning frequency domain from time domain substantially, promote Signal's
Demodulation performance.
Specifically, Fourier transformation unit carries out Fast Fourier Transform (FFT) to compensated Signal, turns from time domain
For frequency domain, this operation is to demodulate the steps necessary of OFDM.Formula is as follows:
Wherein,For FFT frequency point sequence；The frequency domain Signal by time domain compensation being expressed as；Zsig
(k) it is expressed as frequency domain white Gaussian noise, power is
Further,It can indicate are as follows:
Wherein,For white Gaussian noise (noise introduced comprising Frequency domain noise and ICI), power isL be with it is preceding
The distance (L >=N) of one OFDM symbol.
Specifically, frequency domain reference signal acquiring unit is to frequency domainIt is demodulated, parses information, obtain transmitting terminal
The bit information of the part Signal, row information of going forward side by side feedback.Demodulation can choose hard decision or channel decoding.Using channel
Feedback is carried out after decoding can be more accurate, because channel decoding has error correction, but needs certain delay；And hard decision is anti-
Feedback directly passes throughMost probable bit information is found, without considering delay.As obtained by experiment, two kinds of feedback performances are poor
It is different small.
Then, to using processing identical with transmitting terminal to re-modulate feedback information, frequency domain reference signal is obtainedFrequency domain reference signalAccording to receive signal estimate to obtain, not necessarily with the letter of receiving end actual modulated
Number Xsig(k) completely the same.
Specifically, the second frequency deviation estimating unit is by frequency domain reference signalWith the reception signal of frequency domainIt carries out
Locally associated operation, formula are as follows:
Assuming that the frequency domain reference signal of estimationIt is completely correct, thenLocally associated result can
To indicate are as follows:
Finally, by carrying out seeking angle to GTherefore, the second Nonlinear Transformation in Frequency Offset Estimation value is obtained
The modulation format of Signal is the highest BPSK of robustness, and channel coding is also highest 1/2 code rate of robust, so
The demodulation performance of the demodulation performance ratio payload of Signal is much higher, is difficult to malfunction.So Signal information substantially can be with
It is assumed to be correctly, being fed back as Nonlinear Transformation in Frequency Offset Estimation is a kind of very reliable way.By Signal parsing information into
Row feedback modulation obtains modulationWith the reception signal of frequency domainCarry out it is locally associated, performance gain promotion want
It is higher than performance gain autocorrelative before and after time domain.
After locally associated, it is assumed that N=L, signal-to-noise ratio indicate are as follows:
In contrast, it can be seen that locally associated signal-to-noise ratio is the gain that 3dB is higher by than auto-correlation.
Specifically, Payload frequency offset compensation element is to the final time domain carrier wave frequency deviation offset of Payload
Embodiment 3:
Present embodiments provide a kind of OFDM frequency deviation estimation device based on IEEE802.11, comprising: memory, processor
And the computer program that can be run on a memory and on a processor is stored, it is realized when computer program is executed by processor real
Apply the step S1-S6 of the method for example 1.
What has been described above is only a preferred embodiment of the present invention, and present invention is not limited to the above embodiments.It is appreciated that this
Other improvements and changes that field technical staff directly exports or associates without departing from the basic idea of the present invention
It is considered as being included within protection scope of the present invention.
Claims (10)
1. a kind of OFDM frequency deviation estimating method based on IEEE802.11, it is characterised in that:
The following steps are included:
Front and back autocorrelation operation is carried out in the time domain to two identical long training sequences in the Preamble for receiving signal,
Obtain first carrier offset estimation value；
The compensation of time domain carrier wave frequency deviation is carried out to the Signal for receiving signal according to the first carrier offset estimation value；
Compensated Signal is converted into frequency-region signal from time-domain signal；
The Signal of frequency domain is parsed, and the information of parsing is re-modulated, obtains frequency domain reference signal；
The Signal of the frequency domain reference signal and frequency domain is subjected to locally associated property operation, obtains the second Nonlinear Transformation in Frequency Offset Estimation
Value；
The Payload for receiving signal is carried out according to the first carrier offset estimation value and the second Nonlinear Transformation in Frequency Offset Estimation value
The compensation of time domain carrier wave frequency deviation.
2. the OFDM frequency deviation estimating method according to claim 1 based on IEEE802.11, it is characterised in that:
Two identical long training sequences in the Preamble of described pair of reception signal carry out front and back autocorrelation in the time domain
The formula of operation are as follows:
Wherein, N is the length of long training sequence, yLTF1And yLTF2First long training sequence in respectively Preamble and
Two long training sequences, ()*Indicate conjugation；
The first carrier offset estimation value are as follows:
Wherein, fsFor the sample rate for receiving signal.
3. the OFDM frequency deviation estimating method according to claim 2 based on IEEE802.11, it is characterised in that:
The public affairs for carrying out the compensation of time domain carrier wave frequency deviation to the Signal for receiving signal according to the first carrier offset estimation value
Formula are as follows:
Wherein,For compensated time domain Signal,For compensated white Gaussian noise, foFor actual carrier frequency
Bias.
4. the OFDM frequency deviation estimating method according to claim 1 based on IEEE802.11, it is characterised in that:
The formula that compensated Signal is converted to frequency-region signal from time-domain signal are as follows:
Wherein,It is the distance between OFDM symbol for the frequency domain Signal, L after conversion；fΔFor compensated carrier wave frequency deviation
Difference.
5. the OFDM frequency deviation estimating method according to claim 1 based on IEEE802.11, it is characterised in that:
The formula that the Signal of the frequency domain reference signal and frequency domain is carried out to locally associated property operation are as follows:
Wherein,For conversion after frequency domain Signal,For the frequency domain reference signal；
The second Nonlinear Transformation in Frequency Offset Estimation value are as follows:
6. a kind of OFDM frequency deviation estimation system based on IEEE802.11, it is characterised in that:
It is obtained including the first frequency deviation estimating unit, Signal frequency offset compensation element, Fourier transformation unit, frequency domain reference signal single
Member, the second frequency deviation estimating unit, Payload frequency offset compensation element；
First frequency deviation estimating unit is used for two identical long training sequences in the Preamble for receiving signal in the time domain
Front and back autocorrelation operation is carried out, first carrier offset estimation value is obtained；
When Signal frequency offset compensation element is used to carry out the Signal for receiving signal according to the first carrier offset estimation value
The compensation of domain carrier wave frequency deviation；
Fourier transformation unit is used to compensated Signal being converted to frequency-region signal from time-domain signal；
Frequency domain reference signal acquiring unit adjusts the information of parsing for parsing to the Signal of frequency domain again
System, obtains frequency domain reference signal；
Second frequency deviation estimating unit is used to the Signal of the frequency domain reference signal and frequency domain carrying out locally associated property operation, obtains
To the second Nonlinear Transformation in Frequency Offset Estimation value；
Payload frequency offset compensation element is used for according to the first carrier offset estimation value and the second Nonlinear Transformation in Frequency Offset Estimation value
The compensation of time domain carrier wave frequency deviation is carried out to the Payload for receiving signal.
7. the OFDM frequency deviation estimation system according to claim 6 based on IEEE802.11, it is characterised in that:
First frequency deviation estimating unit to receive signal Preamble in two identical long training sequences in the time domain
Carry out the formula of front and back autocorrelation operation are as follows:
Wherein, N is the length of long training sequence, yLTF1And yLTF2First long training sequence in respectively Preamble and
Two long training sequences, ()*Indicate conjugation；
The first carrier offset estimation valueAre as follows:
Wherein, fsFor the sample rate for receiving signal.
8. the OFDM frequency deviation estimation system according to claim 7 based on IEEE802.11, it is characterised in that:
When the Signal frequency offset compensation element carries out the Signal for receiving signal according to the first carrier offset estimation value
The formula of domain carrier wave frequency deviation compensation are as follows:
Wherein,For compensated time domain Signal,For compensated white Gaussian noise, foFor actual carrier frequency
Bias.
9. the OFDM frequency deviation estimation system according to claim 6 based on IEEE802.11, it is characterised in that:
Compensated Signal is converted to the formula of frequency-region signal by the Fourier transformation unit from time-domain signal are as follows:
Wherein,It is the distance between OFDM symbol for the frequency domain Signal, L after conversion；fΔFor compensated carrier wave frequency deviation
Difference；
The Signal of the frequency domain reference signal and frequency domain is carried out locally associated property fortune by the frequency domain reference signal acquiring unit
The formula of calculation are as follows:
Wherein,For the frequency domain reference signal；
The second Nonlinear Transformation in Frequency Offset Estimation value are as follows:
10. a kind of OFDM frequency deviation estimation device based on IEEE802.11, it is characterised in that:
Including memory, processor and it is stored in the computer program that can be run on the memory and on the processor；
The step of method as described in any one of claim 1 to 5 is realized when the computer program is executed by the processor.
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