CN105471798B - Ofdm system phase-tracking method based on SIG field and data field pilot weighted - Google Patents
Ofdm system phase-tracking method based on SIG field and data field pilot weighted Download PDFInfo
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- CN105471798B CN105471798B CN201510834588.5A CN201510834588A CN105471798B CN 105471798 B CN105471798 B CN 105471798B CN 201510834588 A CN201510834588 A CN 201510834588A CN 105471798 B CN105471798 B CN 105471798B
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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
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2655—Synchronisation arrangements
- H04L27/2689—Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation
- H04L27/2695—Link with other circuits, i.e. special connections between synchronisation arrangements and other circuits for achieving synchronisation with channel estimation, e.g. determination of delay spread, derivative or peak tracking
Abstract
The present invention relates to a kind of ofdm system phase-tracking method based on SIG field and data field pilot weighted, it makes use of the frequency domain datas of the most strong frequency point sets range of SIG field channel to calculate residual phase deviation value added in an OFDM symbol time interval, phase compensation is carried out to consecutive OFDM-symbols using accumulated phase deviation, the pilot phase deviation of data field after compensating is recycled constantly to correct OFDM symbol phase deviation value added.This method Phase Tracking precision with higher can be applied not only to 802.11n system especially in the case where low signal-to-noise ratio, and the other similar MIMO-OFDM system with SIG field can be used, have very wide application range.
Description
Technical field
The present invention relates to a kind of ofdm system phase-tracking methods.
Background technique
For ofdm system, after carrier synchronization and frequency deviation compensation, under the conditions of certain signal-to-noise ratio, residual frequency departure phase
The very little for subcarrier spacing, the interference between the subcarrier as caused by frequency deviation almost can be ignored at this time,
But due to the presence of residual frequency departure, as the accumulation of time will cause the phase rotation of sub-carrier frequency domain signal, OFDM data
The duration of frame is longer, and the rotation of constellation point is more severe, after the rotatable phase of constellation point is more than certain threshold value, will lead
The mistake in judgment for the number of writing especially influences the demodulation of high order modulation signal, it is therefore necessary to track to the phase of residual frequency departure
And compensate, to eliminate this influence.
By the frame structure of 802.11n it is found that there are pilot tones in each OFDM symbol, under 20MHz bandwidth, pilot tone
Quantity is 4, under 40MHz bandwidth, pilot number 6.The modulation system of pilot tone is BPSK, and the signal of pilot tone is known
's.Traditional phase-tracking method be estimated using being superimposed and then asking in the same direction the method for phase for pilot signal phase deviation into
Row Phase Tracking.But under fading channel, certain pilot points may meet with deep fade, and the signal-to-noise ratio at pilot point compares
Low, phase equivocation result is poor.And the power based on channel strength distributes the channel of different confidence values to pilot point
Intensity weighted estimation method, can improve the precision of phase estimation, but still be limited to the restriction of pilot point negligible amounts, phase
The precision of tracking improves limited.It is, thus, sought for a kind of ofdm system that is suitable for improves Phase Tracking essence under fading channel
The method of degree.
Summary of the invention
The object of the present invention is to provide one kind to improve Phase Tracking precision under fading channel, to improve ofdm system
The phase-tracking method of whole decoding performance.
In order to achieve the above objectives, the technical solution adopted by the present invention is that:
A kind of ofdm system phase-tracking method based on SIG field and data field pilot weighted, for OFDM system
It unites the received signal progress phase equivocation comprising several SIG fields and data field of receiver institute and compensation, it is described
Method the following steps are included:
Step (1): calculate what residual frequency deviation in an OFDM symbol time interval generated according to first SIG field
Phase deviation, and increase as the phase deviation of first OFDM symbol started counting by first SIG field
Value θrm_pers(1), and then the compensation accumulated phase θ of second OFDM symbol is obtainedcom(2), as follows 1. to 5. real
It applies:
Step is 1.: choosing NsA includes the signal and the strongest subcarrier of channel, remembers that its collection is combined into Smax；
Step is 2.: the set S in each SIG field of hard decision respectivelymaxIn each subcarrier frequency domain letter
Number polarity, remember that its collection is combined into Sp；
Step is 3.: according to the set SmaxWith the set SpCalculate the set SmaxThe frequency of interior each subcarrier
Domain signal superimposed phase deviation angle, θ in the same directionsig(1)；
Step is 4.: initializing the phase deviation angle, θsig(1) residual frequency deviation in an OFDM symbol time interval is obtained
The phase deviation of generation, and it is inclined as the phase of first OFDM symbol started counting by first SIG field
Poor value added θrm_pers(1)；
Step is 5.: according to the phase deviation value added θ of first OFDM symbolrm_pers(1) second OFDM is obtained
The compensation accumulated phase θ of symbolcom(2)；
Step (2): successively subsequent i-th of the OFDM symbol started counting by first SIG field is carried out remaining
Phase deviation compensates and updates its phase deviation value added and the cumulative phase of compensation of its i+1 OFDM symbol is calculated
The compensation accumulated phase of its next OFDM symbol is directly calculated in position, and wherein i is the integer greater than 1, be divided into
Lower three kinds of situations:
Situation a: when i-th of OFDM symbol is SIG field, accumulated phase θ is compensated using itcom(i) to this i-th
OFDM symbol carries out the compensation of residual phase misalignment angle and calculates the last phase of the OFDM symbol according to compensated symbolic information
Position misalignment angle θsig(i), and according to the residual phase misalignment angle θsig(i) it updates and obtains the phase of i-th of OFDM symbol
Position deviation value added θrm_pers(i)；Further according to the phase deviation value added θ of i-th of OFDM symbolrm_pers(i) and its compensation is tired
Add phase thetacom(i) the compensation accumulated phase θ of the i+1 OFDM symbol is calculatedcom(i+1)；
Situation b: when i-th of OFDM symbol is training field, the phase deviation value added of i-th of OFDM symbol
θrm_pers(i) the phase deviation value added θ relative to (i-1)-th OFDM symbolrm_pers(i-1) constant, directly according to this i-th
The phase deviation value added θ of OFDM symbolrm_pers(i) and the compensation accumulated phase θ of i-th of OFDM symbolcom(i) it calculates
To the compensation accumulated phase θ of its i+1 OFDM symbolcom(i+1)；
Situation c: when i-th of OFDM symbol is data field, accumulated phase θ is compensated using itcom(i) to this i-th
OFDM symbol carries out the compensation of residual phase misalignment angle, according to the pilot data of compensated symbolic information and data field, meter
Calculate the residual phase misalignment angle θ of i-th of OFDM symbolpilot(i), and according to the residual phase of i-th of OFDM symbol
Misalignment angle θpilot(i) it updates and obtains the phase deviation value added θ of i-th of OFDM symbolrm_pers(i), if i-th of OFDM
Symbol is not data field described in last frame, then further according to the phase deviation value added θ of i-th of OFDM symbolrm_pers(i)
With the compensation accumulated phase θ of i-th of OFDM symbolcom(i) compensation that its i+1 OFDM symbol is calculated is cumulative
Phase thetacom(i+1), if i-th of OFDM symbol is data field described in last frame, no longer calculating i+1 is described
The compensation accumulated phase of OFDM symbol.
Step 1. in, the signal strength of each subcarrier is judged according to channel estimation results, then therefrom choose NsIt is a to include
The signal and the strongest subcarrier of channel.
Step 3. in, pass through
Calculate the phase deviation angle, θsig(1), wherein YkIt (1) is first SIG word after channel equalization
Section is corresponding in the set SmaxK-th interior of element, SkIt (1) is first SIG field in the set SmaxInterior k-th
The polarity of the sub-carrier signal of element,For Sk(1) conjugation, angle () are the operation of calculated complex angle.
Step 4. in, the phase deviation value added θ of first OFDM symbolrm_pers(1)=δ θsig(1), wherein δ be less than
1 weight coefficient.
Step 5. in, the compensation accumulated phase θ of second OFDM symbolcom(2)=2 θrm_pers(1)。
In situation a, pass through
Calculate the residual phase misalignment angle θ of the OFDM symbolsig(i), whereinFor the set SmaxInterior kth
I-th of OFDM symbol of a element passes through channel equalization and the compensated pilot data of residual phase misalignment angle, Sk(i)
It is i-th of SIG field in the set SmaxThe polarity of the sub-carrier signal of interior k-th of element；
Pass through
θrm_pers(i)=θrm_pers(i-1)+δ1θsig(i)
Update obtains the phase deviation value added θ of i-th of OFDM symbolrm_pers(i), wherein δ1For the weight less than 1
Coefficient；
Pass through
θcom(i+1)=θcom(i)+θrm_pers(i)
The compensation accumulated phase θ of the i+1 OFDM symbol is calculatedcom(i+1)。
In situation b, the phase deviation value added θ of i-th of OFDM symbolrm_pers(i) relative to (i-1)-th OFDM symbol
Phase deviation value added θrm_pers(i-1) constant
θrm_pers(i)=θrm_pers(i-1),
Pass through
θcom(i+1)=θcom(i)+θrm_pers(i)
The compensation accumulated phase θ of its i+1 OFDM symbol is calculatedcom(i+1)。
In situation c, pass through
Calculate the residual phase misalignment angle θ of i-th of OFDM symbolpilot(i), wherein weight (k) is the set
SmaxThe credit weight of the pilot tone of k-th interior of element, C are pilot tone point set,For the set SmaxInterior k-th yuan
Element i-th of OFDM symbol by channel equalization and with the compensated pilot data of residual phase misalignment angle, Pk(i) it is
The set SmaxTransmitting signal in the pilot tone of k-th interior of element；
Pass through
θrm_pers(i)=θrm_pers(i-1)+δ2θpilot(i)
Update obtains the phase deviation value added θ of i-th of OFDM symbolrm_pers(i), wherein δ2For the feedback less than 1
Coefficient；
Pass through
θcom(i+1)=θcom(i)+θrm_pers(i)
The compensation accumulated phase θ of the i+1 OFDM symbol is calculatedcom(i+1)。
Due to the above technical solutions, the present invention has the following advantages over the prior art: phase of the invention with
Track method, the frequency domain data that the most strong frequency point sets range of multiple SIG field channels is utilized calculate residual phase deviation value added,
The pilot phase deviation of following data fields is recycled constantly to correct OFDM symbol phase deviation value added, phase with higher
Tracking accuracy.Especially in the case where low signal-to-noise ratio, 802.11n system can be applied not only to, for other similar tool
Having the MIMO-OFDM system of SIG field can be used, and have very wide application range.
Detailed description of the invention
Attached drawing 1 is three kinds of PPDU signal frame formats of 802.11n.
Attached drawing 2 be signal-to-noise ratio 20dB when TGn_E fading channel model under conventional phase tracking phase error.
When attached drawing 3 is signal-to-noise ratio 20dB under TGn_E fading channel model phase-tracking method of the present invention phase error.
Attached drawing 4 is to be utilized respectively phase-tracking method of the present invention and conventional phase track side under TGn_E fading channel model
The receiving end Packet Error Ratio comparing result of method.
Specific embodiment
The invention will be further described for embodiment shown in reference to the accompanying drawing.
Embodiment one: one kind is for received comprising several SIG fields and data field to ofdm system receiver institute
Signal carry out phase equivocation and compensation the ofdm system Phase Tracking based on SIG field and data field pilot weighted
Method, comprising the following steps:
Step (1): the phase that residual frequency deviation generates in an OFDM symbol time interval is calculated according to first SIG field
Deviation, and as the phase deviation value added θ of first OFDM symbol started counting by first SIG fieldrm_pers
(1), and then the compensation accumulated phase θ of second OFDM symbol is obtainedcom(2).Especially by following steps 1. to 5. implementing.
Step is 1.: judging the signal strength of each subcarrier according to channel estimation results, then therefrom chooses NsA includes letter
Number and the strongest subcarrier of channel, remember that its collection is combined into Smax。
Step is 2.: each SIG field upper set S of hard decision respectivelymaxIn each subcarrier frequency-region signal polarity, note
Its collection is combined into Sp。
Step is 3.: according to set SmaxWith set SpSet of computations SmaxAfter the frequency-region signal of interior each subcarrier is superimposed in the same direction
Phase deviation angle, θsig(1).Pass through
Calculate phase deviation angle, θsig(1), wherein YkIt (1) is that first SIG field corresponds to after channel equalization
Set SmaxK-th interior of element, SkIt (1) is first SIG field in set SmaxThe pole of the sub-carrier signal of interior k-th of element
Property,For Sk(1) conjugation, angle () are the operation of calculated complex angle.
Step is 4.: intialization phase misalignment angle θsig(1)
θrm_pers(1)=δ θsig(1)
The phase deviation that residual frequency deviation generates in an OFDM symbol time interval is obtained, and as by first
The phase deviation value added θ for first OFDM symbol that SIG field starts countingrm_pers(1).Wherein δ is the weight system less than 1
Number.
Step is 5.: according to the phase deviation value added θ of first OFDM symbolrm_pers(1) second OFDM symbol is obtained
Compensation accumulated phase θcom(2)=2 θrm_pers(1)。
Step (2): successively to subsequent i-th (i is the integer greater than the 1) OFDM started counting by first SIG field
Symbol carries out residual phase deviation compensation and updates its phase deviation value added θrm_pers(i) and i+1 OFDM is calculated
The compensation accumulated phase θ of symbolcom(i+1) or directly it is next that its is calculated, i.e. the compensation of i+1 OFDM symbol is cumulative
Phase thetacom(i+1).It is divided into following three kinds of situations at this time:
Situation a: when i-th of OFDM symbol is SIG field, accumulated phase θ is compensated using itcom(i) to this i-th
OFDM symbol carries out the compensation of residual phase misalignment angle and calculates the last phase of the OFDM symbol according to compensated symbolic information
Position misalignment angle θsig(i):
WhereinFor set SmaxI-th of OFDM symbol of k-th interior of element passes through channel equalization and residual phase
The compensated pilot data of misalignment angle, SkIt (i) is i-th of SIG field in set SmaxThe sub-carrier signal of interior k-th of element
Polarity,For Sk(i) conjugation.
Further according to residual phase misalignment angle θsig(i) it updates and obtains the phase deviation value added of i-th of OFDM symbol
θrm_pers(i):
θrm_pers(i)=θrm_pers(i-1)+δ1θsig(i),
δ1For the weight coefficient less than 1.
Then, according to the phase deviation value added θ of i-th of OFDM symbolrm_pers(i) and it compensates accumulated phase θcom
(i) the compensation accumulated phase θ of its i+1 OFDM symbol is calculatedcom(i+1):
θcom(i+1)=θcom(i)+θrm_pers(i)。
Situation b: when i-th of OFDM symbol is training field (HT_STF HT_LTF field), phase tracking loop
Without phase deviation compensation and residual phase estimation, the phase deviation value added θ of i-th of OFDM symbolrm_pers(i) opposite
In the phase deviation value added θ of (i-1)-th OFDM symbolrm_pers(i-1) constant:
θrm_pers(i)=θrm_pers(i-1),
Then directly according to the phase deviation value added θ of i-th of OFDM symbolrm_pers(i) and it compensates accumulated phase θcom
(i) the compensation accumulated phase θ of its i+1 OFDM symbol is calculatedcom(i+1):
θcom(i+1)=θcom(i)+θrm_pers(i)。
Situation c: when i-th of OFDM symbol is data field, accumulated phase θ is compensated using itcom(i) to this i-th
OFDM symbol carries out the compensation of residual phase misalignment angle, according to the pilot data of compensated symbolic information and data field, meter
Calculate the residual phase misalignment angle θ of the OFDM symbolpilot(i):
Wherein, weight (k) is set SmaxThe credit weight of the pilot tone of k-th interior of element, C are pilot tone point set,For set SmaxI-th of OFDM symbol of k-th interior of element is compensated by channel equalization and residual phase misalignment angle
Pilot data afterwards, PkIt (i) is set SmaxTransmitting signal in the pilot tone of k-th interior of element；
Further according to residual phase misalignment angle θpilot(i) it updates and obtains the phase deviation value added of i-th of OFDM symbol:
θrm_pers(i)=θrm_pers(i-1)+δ2θpilot(i),
δ2For the feedback factor less than 1.
If i-th of OFDM symbol is not last frame data field, inclined further according to the phase of i-th of OFDM symbol
Poor value added θrm_pers(i) and the compensation accumulated phase θ of i-th of OFDM symbolcom(i) its i+1 OFDM symbol is calculated
Number compensation accumulated phase θcom(i+1):
θcom(i+1)=θcom(i)+θrm_pers(i),
If i-th of OFDM symbol is last frame data field, the compensation of no longer calculating i+1 OFDM symbol is tired
Add phase.
Three kinds of PPDU signal frame formats of 802.11n are as shown in Fig. 1, believed below with the HT_Mixed format of 802.11n
For number frame, the SIG sequence of the HT_Mixed format signal frame includes L_SIG, HT_SIG1 and HT_SIG2 totally 3 SIG words
Section, SIG sequence are total m training field (m=N+1) that HT_STF field and N number of HT_LTF field are constituted later, followed by
Data field.The method of ofdm system frequency plot tracking is carried out for receiving the HT_Mixed format signal below detailed
Explanation.
Phase-tracking method the following steps are included:
1, residual frequency deviation in an OFDM symbol time interval is calculated according to L_SIG field (i.e. first SIG field) to produce
Raw phase deviation, as the phase deviation value added θ of first OFDM symbolrm_pers(1), and then initial second is obtained
The compensation accumulated phase θ of a OFDM symbol (HT_SIG1 field)com(2).Specific implementation step is following (1)-(5).
(1) signal strength that each subcarrier is judged according to channel estimation results, therefrom chooses NsA strongest sub- load of channel
Wave remembers that its collection is combined into Smax。
(2) in hard decision L_SIG field these sub-carrier frequency domain signals polarity, set be denoted as Sp。
(3) set of computations SmaxInterior sub-carrier frequency domain signal superimposed phase deviation angle in the same direction:
(4) digital baseband input signal of each OFDM symbol is initialized,
θrm_pers(1)=δ θsig(1),
Wherein δ is the weight coefficient less than 1.
(5) the corresponding benefit of initial HT_SIG1 field (second OFDM symbol started counting by first SIG field)
Repay accumulated phase are as follows:
θcom(2)=2 θrm_pers(1)。
2, phase deviation is carried out to HT_SIG1 field (second OFDM symbol started counting by first SIG field)
Angle, θcom(2) compensation carries out residual phase estimation of deviation according to compensated information:
Then the phase deviation value added θ of HT_SIG1 field is updatedrm_pers(2):
θrm_pers(2)=θrm_pers(1)+δ1θsig(2)
Calculate the compensation accumulated phase of HT_SI2 field (the third OFDM symbol started counting by first SIG field)
θcom(3):
θcom(3)=θcom(2)+θrm_pers(2)。
3, phase deviation is carried out to HT_SIG2 field (the third OFDM symbol started counting by first SIG field)
Angle, θcom(3) compensation carries out residual phase estimation of deviation according to compensated information:
Update the phase deviation value added θ of HT_SIG2 fieldrm_pers(3):
θrm_pers(3)=θrm_pers(2)+δ1θsig(3),
Calculate the compensation accumulated phase of HT_STF field (the 4th OFDM symbol started counting by first SIG field)
θcom(4)。
θcom(4)=θcom(3)+θrm_pers(3)。
4, for HT_STF field and N number of HT_LTF field, phase tracking loop is compensated without phase deviation and remnants
Phase estimation only compensates the cumulative of phase.Then
The phase deviation value added of i-th of OFDM symbol remains unchanged,
θrm_pers(i)=θrm_pers(i-1),
The compensation accumulated phase of next OFDM symbol is calculated,
θcom(i+1)=θcom(i)+θrm_pers(i)。
Then first OFDM symbol (m+3+1 started counting by first SIG field of following data fields
OFDM symbol) corresponding compensation accumulated phase are as follows:
θcom(m+3+1)=θcom(m+3)+θrm_pers(m+3)=θcom(3)+(m+1)*θrm_pers(3)。
5, a to the jth of data field (j >=1), i.e., i-th of the OFDM symbol started counting by first SIG field into
The residual phase deviation of the OFDM symbol is estimated in the compensation of row residual phase according to the symbolic information after phase compensation,
Update the phase deviation value added of i-th of OFDM symbol:
θrm_pers(i)=θrm_pers(i-1)+δ2θpilot(i),
The compensation accumulated phase of i+1 OFDM symbol is calculated again:
θcom(i+1)=θcom(i)+θrm_pers(i),
Until a frame data terminate, Phase Tracking is completed.
Phase-tracking method of the invention and traditional pilot point weighted phases tracking are subjected to simulation result comparison,
Simulated conditions be set as transmitting terminal generate HT_Mixed format signal frame, MCS=7, signal by TGn_E emulate fading channel into
Entering receiving end, different Phase Tracking modes is respectively adopted after the compensation of synchronous and frequency deviation in receiving end, when signal-to-noise ratio is 20dB
The phase error result of phase tracking loop is respectively as shown in attached drawing 2 and attached drawing 3.
From being can be seen that in attached drawing 2 and attached drawing 3 using after method of the invention, phase tracking error distribution is less than pilot tone
The precision of the error of the phase-tracking method of weighting, track loop is greatly improved, and the result of Phase Tracking can be stablized
In one lesser range.
Emulation setting condition same as above respectively emulates 1000 data packets, using different phases under different Signal to Noise Ratio (SNR)
Position tracking, the Packet Error Ratio Comparative result of final receiving end are as shown in Fig. 3.
From attached drawing 4 as can be seen that using phase-tracking method of the invention, the Packet Error Ratio of system is lower than common pilot point
Weighted phases tracking, the method for the present invention show more superior performance.
The invention patent provides a kind of method for carrying out Phase Tracking in an ofdm system, utilizes channel in SIG field
The frequency domain data of the high frequency point sets range of power weight carries out precise phase estimation of deviation, as subsequent each OFDM symbol
Residual phase deviation fixation initial value, recycle subsequent data symbols pilot point weighted phases deviation be modified so that
The precision of ofdm system receiving end Phase Tracking is improved, and especially in the case where low signal-to-noise ratio, Phase Tracking precision has very
Big promotion.According to the disclosed embodiment, those skilled in the art can be realized or using the present invention.It is described above real
Applying example is only presently preferred embodiments of the present invention, is not intended to limit the invention, all within the spirits and principles of the present invention,
Any modification, equivalent replacement, improvement and so on, it is within the scope of the present invention.
Claims (8)
1. a kind of ofdm system phase-tracking method based on SIG field and data field pilot weighted, for ofdm system
Receiver the received signal comprising several SIG fields and data field carry out phase equivocation and compensation, feature
It is: the described method comprises the following steps:
Step (1): the phase that residual frequency deviation generates in an OFDM symbol time interval is calculated according to first SIG field
Deviation, and the phase deviation that residual frequency deviation in an OFDM symbol time interval is generated is as by first SIG field
The phase deviation value added θ of first OFDM symbol started countingrm_pers(1), and then the benefit of second OFDM symbol is obtained
Repay accumulated phase θcom(2), as follows 1. to 5. implementation:
Step is 1.: choosing NsA includes the signal and the strongest subcarrier of channel, remembers that the collection of the subcarrier of selection is combined into
Smax；
Step is 2.: the set S in each SIG field of hard decision respectivelymaxIn each subcarrier frequency-region signal
Polarity remembers that the polar collection of the frequency-region signal of the subcarrier is combined into Sp；
Step is 3.: according to the set SmaxWith the set SpCalculate the set SmaxThe frequency domain of interior each subcarrier is believed
Number in the same direction superimposed phase deviation angle, θsig(1)；
Step is 4.: initializing the phase deviation angle, θsig(1) residual frequency deviation in an OFDM symbol time interval is obtained to generate
Phase deviation, and using in one OFDM symbol time interval residual frequency deviation generate phase deviation as by first institute
State the phase deviation value added θ for first OFDM symbol that SIG field starts countingrm_pers(1)；
Step is 5.: according to the phase deviation value added θ of first OFDM symbolrm_pers(1) second OFDM symbol is obtained
Compensate accumulated phase θcom(2)；
Step (2): residual phase successively is carried out to subsequent i-th of the OFDM symbol started counting by first SIG field
Deviation compensation and update the phase deviation value added of i-th of OFDM symbol and the benefit of the i+1 OFDM symbol be calculated
It repays accumulated phase or the compensation accumulated phase of the i+1 OFDM symbol is directly calculated, wherein i is the integer greater than 1,
It is divided into following three kinds of situations:
Situation a: when i-th of OFDM symbol is SIG field, using the compensation accumulated phase θ of i-th of OFDM symbolcom(i) right
I-th of OFDM symbol carries out the compensation of residual phase misalignment angle and calculates the OFDM symbol according to compensated symbolic information
Residual phase misalignment angle θsig(i), and according to the residual phase misalignment angle θsig(i) it updates and obtains i-th of OFDM symbol
Number phase deviation value added θrm_pers(i)；Further according to the phase deviation value added θ of i-th of OFDM symbolrm_pers(i) and the
The compensation accumulated phase θ of i OFDM symbolcom(i) the compensation accumulated phase θ of the i+1 OFDM symbol is calculatedcom(i
+1)；
Situation b: when i-th of OFDM symbol is training field, the phase deviation value added θ of i-th of OFDM symbolrm_pers(i)
Phase deviation value added θ relative to (i-1)-th OFDM symbolrm_pers(i-1) constant, directly according to i-th of OFDM symbol
Phase deviation value added θrm_pers(i) and the compensation accumulated phase θ of i-th of OFDM symbolcom(i) i+1 is calculated
The compensation accumulated phase θ of the OFDM symbolcom(i+1)；
Situation c: when i-th of OFDM symbol is data field, using the compensation accumulated phase θ of i-th of OFDM symbolcom(i) right
I-th of OFDM symbol carries out the compensation of residual phase misalignment angle, according to the pilot tone of compensated symbolic information and data field
Data calculate the residual phase misalignment angle θ of i-th of OFDM symbolpilot(i), and according to the residual of i-th of OFDM symbol
Remaining phase deviation angle, θpilot(i) it updates and obtains the phase deviation value added θ of i-th of OFDM symbolrm_pers(i), if this i-th
A OFDM symbol is not data field described in last frame, then further according to the phase deviation value added of i-th of OFDM symbol
θrm_pers(i) and the compensation accumulated phase θ of i-th of OFDM symbolcom(i) benefit of the i+1 OFDM symbol is calculated
Repay accumulated phase θcom(i+1), if i-th of OFDM symbol is data field described in last frame, no longer calculating i+1 is a
The compensation accumulated phase of the OFDM symbol.
2. the ofdm system phase-tracking method according to claim 1 based on SIG field and data field pilot weighted,
It is characterized by: step 1. in, the signal strength of each subcarrier is judged according to channel estimation results, then therefrom choose NsIt is a to include
There are the signal and the strongest subcarrier of channel.
3. the ofdm system phase-tracking method according to claim 1 based on SIG field and data field pilot weighted,
It is characterized by: step 3. in, pass through
Calculate the phase deviation angle, θsig(1), wherein Yk(1) corresponding for first SIG field described after channel equalization
In the set SmaxK-th interior of element, SkIt (1) is first SIG field in the set SmaxInterior k-th of element
The polarity of sub-carrier signal,For Sk(1) conjugation, angle () are the operation of calculated complex angle.
4. the ofdm system phase-tracking method according to claim 1 based on SIG field and data field pilot weighted,
It is characterized by: step 4. in, the phase deviation value added θ of first OFDM symbolrm_pers(1)=δ θsig(1), wherein δ is
Weight coefficient less than 1.
5. the ofdm system phase-tracking method according to claim 1 based on SIG field and data field pilot weighted,
It is characterized by: step 5. in, the compensation accumulated phase θ of second OFDM symbolcom(2)=2 θrm_pers(1)。
6. the ofdm system phase-tracking method according to claim 1 based on SIG field and data field pilot weighted,
It is characterized by: passing through in situation a
Calculate the residual phase misalignment angle θ of the OFDM symbolsig(i), whereinFor the set SmaxInterior k-th yuan
I-th of OFDM symbol of element passes through channel equalization and the compensated pilot data of residual phase misalignment angle, Sk(i) for institute
I-th of SIG field is stated in the set SmaxThe polarity of the sub-carrier signal of interior k-th of element；
Pass through
θrm_pers(i)=θrm_pers(i-1)+δ1θsig(i)
Update obtains the phase deviation value added θ of i-th of OFDM symbolrm_pers(i), wherein δ1For the weight coefficient less than 1；
Pass through
θcom(i+1)=θcom(i)+θrm_pers(i)
The compensation accumulated phase θ of the i+1 OFDM symbol is calculatedcom(i+1)。
7. the ofdm system phase-tracking method according to claim 1 based on SIG field and data field pilot weighted,
It is characterized by: in situation b, the phase deviation value added θ of i-th of OFDM symbolrm_pers(i) it is accorded with relative to (i-1)-th OFDM
Number phase deviation value added θrm_pers(i-1) constant
θrm_pers(i)=θrm_pers(i-1),
Pass through
θcom(i+1)=θcom(i)+θrm_pers(i)
The compensation accumulated phase θ of the i+1 OFDM symbol is calculatedcom(i+1)。
8. the ofdm system phase-tracking method according to claim 1 based on SIG field and data field pilot weighted,
It is characterized by: passing through in situation c
Calculate the residual phase misalignment angle θ of i-th of OFDM symbolpilot(i), wherein weight (k) is the set Smax
The credit weight of the pilot tone of k-th interior of element, C are pilot tone point set,For the set SmaxK-th interior of element
I-th of OFDM symbol by channel equalization and with the compensated pilot data of residual phase misalignment angle, Pk(i) for institute
State set SmaxTransmitting signal in the pilot tone of k-th interior of element；
Pass through
θrm_pers(i)=θrm_pers(i-1)+δ2θpilot(i)
Update obtains the phase deviation value added θ of i-th of OFDM symbolrm_pers(i), wherein δ2For the feedback factor less than 1；
Pass through
θcom(i+1)=θcom(i)+θrm_pers(i)
The compensation accumulated phase θ of the i+1 OFDM symbol is calculatedcom(i+1)。
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