CN105471798A - SIG field and data field pilot weighting-based OFDM system phase tracking method - Google Patents

Abstract

The invention relates to an SIG field and data field pilot weighting-based OFDM system phase tracking method. According to the method, the frequency domain data of the strongest frequency point set of SIG field channels are utilized to calculate a residual phase deviation increase value in an OFDM symbol time interval; accumulated phase deviation is utilized to perform phase compensation on subsequent OFDM symbols; and the pilot phase deviation of compensated data fields is utilized to constantly correct the phase deviation increase value of the OFDM symbols. The method has high phase tracking accuracy, especially under a low signal-to-noise ratio condition; and the method cannot only be applied to 802.11n systems, but also MIMO-OFDM systems with SIG fields, and has a wide application range.

Description

Based on the ofdm system phase-tracking method of SIG field and data field pilot weighted

Technical field

The present invention relates to a kind of ofdm system phase-tracking method.

Background technology

For ofdm system, after carrier synchronization and compensate of frequency deviation, under certain signal to noise ratio condition, residual frequency departure is very little for subcarrier spacing, interference between the subcarrier now caused by frequency deviation is almost negligible, but, due to the existence of residual frequency departure, accumulation along with the time can cause the phase rotating of sub-carrier frequency domain signal, the duration of OFDM data frame is longer, the rotation of constellation point is more severe, after the rotatable phase of constellation point exceedes certain threshold value, the mistake in judgment of signal will be caused, especially the demodulation of high order modulation signal is affected, therefore must follow the tracks of the phase place of residual frequency departure and compensate, to eliminate this impact.

From the frame structure of 802.11n, in each OFDM symbol, there is pilot tone, under 20MHz bandwidth, pilot number is 4, and under 40MHz bandwidth, pilot number is 6.The modulation system of pilot tone is BPSK, and the signal of pilot tone is known.Traditional phase-tracking method adopts pilot signal to superpose in the same way then to ask the method for phase place to estimate that phase deviation carries out Phase Tracking.But under fading channel, some pilot point may meet with deep fade, and the signal to noise ratio at pilot point place is lower, and phase equivocation result is poor.And distribute the channel strength weighting estimating method of different confidence value to pilot point based on the power of channel strength, can improve the precision of phase estimation, but still be limited to the restriction of pilot point negligible amounts, the precision of Phase Tracking is improved limited.Therefore, need to find and be a kind ofly applicable to the method that ofdm system improves Phase Tracking precision under fading channel.

Summary of the invention

The object of this invention is to provide one and improve Phase Tracking precision under fading channel, thus improve the phase-tracking method of the global solution code performance of ofdm system.

For achieving the above object, the technical solution used in the present invention is:

A kind of ofdm system phase-tracking method based on SIG field and data field pilot weighted, the signal comprising several SIG fields and data field for receiving ofdm system receiver carries out phase equivocation and compensation, said method comprising the steps of:

Step (1): calculate the phase deviation that in the OFDM symbol time interval, residual frequency deviation produces according to first described SIG field, and it can be used as the phase deviation added value θ of first OFDM symbol of counting by first described SIG field _{rm_pers}, and then obtain the compensation accumulated phase θ of second OFDM symbol (1) _com(2), as follows 1. to 5. implementing:

Step is 1.: choose N _sindividually include described signal and the strongest subcarrier of channel, remember that its set is S _max;

Step is 2.: described S set in each described SIG field of hard decision respectively _maxin the polarity of frequency-region signal of subcarrier described in each, remember that its set is S _p;

Step is 3.: according to described S set _maxwith described S set _pcalculate described S set _maxin the frequency-region signal of subcarrier described in each superpose in the same way after phase deviation angle θ _sig(1);

Step is 4.: phase deviation angle θ described in initialization _sig(1) obtain the phase deviation that in the OFDM symbol time interval, residual frequency deviation produces, and it can be used as the phase deviation added value θ of first OFDM symbol of counting by first described SIG field _{rm_pers}(1);

Step is 5.: according to the phase deviation added value θ of described first OFDM symbol _{rm_pers}(1) the compensation accumulated phase θ of second OFDM symbol is obtained _com(2);

Step (2): successively residual phase deviation compensation carried out to follow-up i-th OFDM symbol of counting by first described SIG field and upgrade its phase deviation added value and calculate the compensation accumulated phase of its i-th+1 described OFDM symbol or directly calculate the compensation accumulated phase of its next described OFDM symbol, wherein i be greater than 1 integer, be divided into following three kinds of situations:

Situation a: when i-th OFDM symbol is SIG field, adopts it to compensate accumulated phase θ _comi () carries out the compensation of residual phase misalignment angle to this i-th OFDM symbol, according to the symbolic information after compensation, calculate the residual phase misalignment angle θ of this OFDM symbol _sig(i), and according to described residual phase misalignment angle θ _sigi () upgrades the phase deviation added value θ obtaining this i-th OFDM symbol _{rm_pers}(i); Again according to the phase deviation added value θ of this i-th OFDM symbol _{rm_pers}(i) and its compensation accumulated phase θ _comi () calculates the compensation accumulated phase θ of the i-th+1 described OFDM symbol _com(i+1);

Situation b: when i-th OFDM symbol is for training field, the phase deviation added value θ of this i-th OFDM symbol _{rm_pers}i () is relative to the phase deviation added value θ of the i-th-1 OFDM symbol _{rm_pers}(i-1) constant, directly according to the phase deviation added value θ of this i-th OFDM symbol _{rm_pers}the compensation accumulated phase θ of (i) and this i-th OFDM symbol _comi () calculates the compensation accumulated phase θ of its i-th+1 described OFDM symbol _com(i+1);

Situation c: when i-th OFDM symbol is data field, adopts it to compensate accumulated phase θ _comi () carries out the compensation of residual phase misalignment angle to this i-th OFDM symbol, according to the symbolic information after compensating and the pilot data of data field, calculate the residual phase misalignment angle θ of this i-th OFDM symbol _pilot(i), and according to the residual phase misalignment angle θ of described i-th OFDM symbol _piloti () upgrades the phase deviation added value θ obtaining this i-th OFDM symbol _{rm_pers}i (), if this i-th OFDM symbol is not data field described in last frame, then again according to the phase deviation added value θ of this i-th OFDM symbol _{rm_pers}the compensation accumulated phase θ of (i) and this i-th OFDM symbol _comi () calculates the compensation accumulated phase θ of its i-th+1 described OFDM symbol _com(i+1), if this i-th OFDM symbol is data field described in last frame, then the compensation accumulated phase of the i-th+1 described OFDM symbol is no longer calculated.

Step 1. in, judge the signal strength signal intensity of each subcarrier according to channel estimation results, more therefrom choose N _sindividually include described signal and the strongest subcarrier of channel.

Step 3. in, pass through

${\mathrm{\θ}}_{sig}\left(1\right)=angle\left(\underset{k\∈S_{max}}{\Σ}{Y}_k\right(1\left)S_k^{*}\right(1\left)\right)$

Calculate described phase deviation angle θ _sig(1), wherein, Y _k(1) be that described first SIG field is corresponding to described S set after channel equalization _maxan interior kth element, S _k(1) for described first SIG field is in described S set _maxthe polarity of the sub-carrier signal of an interior kth element, for S _k(1) conjugation, angle () is the computing of calculated complex angle.

Step 4. in, the phase deviation added value θ of first OFDM symbol _{rm_pers}(1)=δ θ _sig(1), wherein δ be less than 1 weight coefficient.

Step 5. in, the compensation accumulated phase θ of second OFDM symbol _com(2)=2 θ _{rm_pers}(1).

In situation a, pass through

${\mathrm{\θ}}_{sig}\left(i\right)=angle\left(\underset{k\∈S_{max}}{\Σ}{Y}_k^{com}\right(i\left)S_k^{*}\right(i\left)\right)$

Calculate the residual phase misalignment angle θ of this OFDM symbol _sig(i), wherein for described S set _maxthe pilot data of i-th OFDM symbol after channel equalization and described residual phase misalignment angle compensate of an interior kth element, S _ki () is for described i-th SIG field is in described S set _maxthe polarity of the sub-carrier signal of an interior kth element;

Pass through

θ _{rm_pers}(i)＝θ _{rm_pers}(i-1)+δ ₁θ _sig(i)

Upgrade the phase deviation added value θ obtaining this i-th OFDM symbol _{rm_pers}(i), wherein, δ ₁for being less than the weight coefficient of 1;

Pass through

θ _com(i+1)＝θ _com(i)+θ _{rm_pers}(i)

Calculate the compensation accumulated phase θ of the i-th+1 described OFDM symbol _com(i+1).

In situation b, the phase deviation added value θ of i-th OFDM symbol _{rm_pers}i () is relative to the phase deviation added value θ of the i-th-1 OFDM symbol _{rm_pers}(i-1) constant

θ _{rm_pers}(i)＝θ _{rm_pers}(i-1)，

Pass through

θ _com(i+1)＝θ _com(i)+θ _{rm_pers}(i)

Calculate the compensation accumulated phase θ of its i-th+1 described OFDM symbol _com(i+1).

In situation c, pass through

${\mathrm{\θ}}_{pilot}\left(i\right)=angle\left(\underset{k\∈C}{\Σ}weight\right(k\left)Y_k^{com}\right(i\left)P_k^{*}\right(i\left)\right)$

Calculate the residual phase misalignment angle θ of this i-th OFDM symbol _piloti (), wherein, weight (k) is described S set _maxthe credit weight of the pilot tone of an interior kth element, C is pilot point set, for described S set _maxin a kth element i-th OFDM symbol through channel equalization and and the compensation of described residual phase misalignment angle after pilot data, P _ki () is described S set _maxtransmitting in the pilot tone of an interior kth element;

Pass through

θ _{rm_pers}(i)＝θ _{rm_pers}(i-1)+δ ₂θ _pilot(i)

Upgrade the phase deviation added value θ obtaining this i-th OFDM symbol _{rm_pers}(i), wherein, δ ₂for being less than the feedback factor of 1;

Pass through

θ _com(i+1)＝θ _com(i)+θ _{rm_pers}(i)

Calculate the compensation accumulated phase θ of the i-th+1 described OFDM symbol _com(i+1).

Because technique scheme is used, the present invention compared with prior art has following advantages: phase-tracking method of the present invention, the frequency domain data that make use of the strongest frequency point sets scope of multiple SIG field channel calculates residual phase deviation added value, the pilot phase deviation of recycling following data fields constantly revises OFDM symbol phase deviation added value, has higher Phase Tracking precision.Especially when low signal-to-noise ratio, it not only can be applied to 802.11n system, and the MIMO-OFDM system for other the similar SIG of having fields all can use, and has very wide range of application.

Accompanying drawing explanation

Accompanying drawing 1 is three kinds of PPDU signal frame forms of 802.11n.

The phase error of conventional phase tracking under TGn_E fading channel model when accompanying drawing 2 is signal to noise ratio 20dB.

The phase error of phase-tracking method of the present invention under TGn_E fading channel model when accompanying drawing 3 is signal to noise ratio 20dB.

Accompanying drawing 4 is the receiving terminal Packet Error Ratio comparing result utilizing phase-tracking method of the present invention and conventional phase tracking under TGn_E fading channel model respectively.

Embodiment

Below in conjunction with embodiment shown in the drawings, the invention will be further described.

Embodiment one: a kind of signal comprising several SIG fields and data field for receiving ofdm system receiver carries out the ofdm system phase-tracking method based on SIG field and data field pilot weighted of phase equivocation and compensation, comprises the following steps:

Step (1): calculate the phase deviation that in the OFDM symbol time interval, residual frequency deviation produces according to first SIG field, and it can be used as the phase deviation added value θ of first OFDM symbol of counting by first SIG field _{rm_pers}, and then obtain the compensation accumulated phase θ of second OFDM symbol (1) _com(2).Especially by following steps 1. to 5. implementing.

Step is 1.: the signal strength signal intensity judging each subcarrier according to channel estimation results, more therefrom chooses N _sindividually include signal and the strongest subcarrier of channel, remember that its set is S _max.

Step is 2.: hard decision each SIG field upper set S respectively _maxin the polarity of frequency-region signal of each subcarrier, remember that its set is S _p.

Step is 3.: according to S set _maxand S set _pset of computations S _maxin the frequency-region signal of each subcarrier superpose in the same way after phase deviation angle θ _sig(1).Namely pass through

${\mathrm{\θ}}_{sig}\left(1\right)=angle\left(\underset{k\∈S_{max}}{\Σ}{Y}_k\right(1\left)S_k^{*}\right(1\left)\right)$

Calculate phase deviation angle θ _sig(1), wherein, Y _k(1) be that first SIG field is corresponding to S set after channel equalization _maxan interior kth element, S _k(1) be that first SIG field is in S set _maxthe polarity of the sub-carrier signal of an interior kth element, for S _k(1) conjugation, angle () is the computing of calculated complex angle.

Step is 4.: intialization phase misalignment angle θ _sig(1)

θ _{rm_pers}(1)＝δθ _sig(1)

Obtain the phase deviation that in the OFDM symbol time interval, residual frequency deviation produces, and it can be used as the phase deviation added value θ of first OFDM symbol of counting by first SIG field _{rm_pers}(1).Wherein δ be less than 1 weight coefficient.

Step is 5.: according to the phase deviation added value θ of first OFDM symbol _{rm_pers}(1) the compensation accumulated phase θ of second OFDM symbol is obtained _com(2)=2 θ _{rm_pers}(1).

Step (2): successively to follow-up i-th of counting by first SIG field (i be greater than 1 integer) OFDM symbol carries out residual phase deviation compensation and upgrades its phase deviation added value θ _{rm_pers}i () also calculates the compensation accumulated phase θ of the i-th+1 OFDM symbol _com(i+1) it or is directly calculated next, i.e. the compensation accumulated phase θ of the i-th+1 OFDM symbol _com(i+1).Now be divided into following three kinds of situations:

Situation a: when i-th OFDM symbol is SIG field, adopts it to compensate accumulated phase θ _comi () carries out the compensation of residual phase misalignment angle to this i-th OFDM symbol, according to the symbolic information after compensation, calculate the residual phase misalignment angle θ of this OFDM symbol _sig(i):

${\mathrm{\θ}}_{sig}\left(i\right)=angle\left(\underset{k\∈S_{max}}{\Σ}{Y}_k^{com}\right(i\left)S_k^{*}\right(i\left)\right),$

Wherein for S set _maxthe pilot data of i-th OFDM symbol after channel equalization and residual phase misalignment angle compensate of an interior kth element, S _ki () is that i-th SIG field is in S set _maxthe polarity of the sub-carrier signal of an interior kth element, for S _kthe conjugation of (i).

Again according to residual phase misalignment angle θ _sigi () upgrades the phase deviation added value θ obtaining this i-th OFDM symbol _{rm_pers}(i):

θ _{rm_pers}(i)＝θ _{rm_pers}(i-1)+δ ₁θ _sig(i)，

δ ₁for being less than the weight coefficient of 1.

Then, according to the phase deviation added value θ of this i-th OFDM symbol _{rm_pers}(i) and its compensation accumulated phase θ _comi () calculates the compensation accumulated phase θ of its i-th+1 OFDM symbol _com(i+1):

θ _com(i+1)＝θ _com(i)+θ _{rm_pers}(i)。

Situation b: when i-th OFDM symbol is for training field (HT_STF or HT_LTF field), phase tracking loop does not carry out phase deviation and compensates and residual phase estimation, the phase deviation added value θ of this i-th OFDM symbol _{rm_pers}i () is relative to the phase deviation added value θ of the i-th-1 OFDM symbol _{rm_pers}(i-1) constant:

θ _{rm_pers}(i)＝θ _{rm_pers}(i-1)，

The then direct phase deviation added value θ according to this i-th OFDM symbol _{rm_pers}(i) and its compensation accumulated phase θ _comi () calculates the compensation accumulated phase θ of its i-th+1 OFDM symbol _com(i+1):

θ _com(i+1)＝θ _com(i)+θ _{rm_pers}(i)。

Situation c: when i-th OFDM symbol is data field, adopts it to compensate accumulated phase θ _comi () carries out the compensation of residual phase misalignment angle to this i-th OFDM symbol, according to the symbolic information after compensating and the pilot data of data field, calculate the residual phase misalignment angle θ of this OFDM symbol _pilot(i):

${\mathrm{\θ}}_{pilot}\left(i\right)=angle\left(\underset{k\∈C}{\Σ}weight\right(k\left)Y_k^{com}\right(i\left)P_k^{*}\right(i\left)\right),$

Wherein, weight (k) is S set _maxthe credit weight of the pilot tone of an interior kth element, C is pilot point set, for S set _maxthe pilot data of i-th OFDM symbol after channel equalization and residual phase misalignment angle compensate of an interior kth element, P _ki () is S set _maxtransmitting in the pilot tone of an interior kth element;

Again according to residual phase misalignment angle θ _piloti () upgrades the phase deviation added value obtaining i-th OFDM symbol:

θ _{rm_pers}(i)＝θ _{rm_pers}(i-1)+δ ₂θ _pilot(i)，

δ ₂for being less than the feedback factor of 1.

If this i-th OFDM symbol is not last frame data field, then again according to the phase deviation added value θ of this i-th OFDM symbol _{rm_pers}the compensation accumulated phase θ of (i) and this i-th OFDM symbol _comi () calculates the compensation accumulated phase θ of its i-th+1 OFDM symbol _com(i+1):

θ _com(i+1)＝θ _com(i)+θ _{rm_pers}(i)，

If this i-th OFDM symbol is last frame data field, then no longer calculate the compensation accumulated phase of the i-th+1 OFDM symbol.

Three kinds of PPDU signal frame forms of 802.11n as shown in Figure 1, below for the HT_Mixed format signal frame of 802.11n, the SIG sequence of this HT_Mixed format signal frame comprises L_SIG, HT_SIG1 and HT_SIG2 totally 3 SIG fields, being m training field (m=N+1) altogether that HT_STF field and N number of HT_LTF field are formed after SIG sequence, is then data field.To receive this HT_Mixed format signal, the method that ofdm system frequency plot is followed the tracks of is described in detail below.

Phase-tracking method comprises the following steps:

1, calculate according to L_SIG field (i.e. first SIG field) phase deviation that in the OFDM symbol time interval, residual frequency deviation produces, it can be used as the phase deviation added value θ of first OFDM symbol _{rm_pers}, and then obtain the compensation accumulated phase θ of initial second OFDM symbol (HT_SIG1 field) (1) _com(2).Following (1)-(5) of concrete implementation step.

(1) judge the signal strength signal intensity of each subcarrier according to channel estimation results, therefrom choose N _sthe subcarrier that individual channel is the strongest, remembers that its set is for S _max.

(2) polarity of these sub-carrier frequency domain signals in hard decision L_SIG field, its set is designated as S _p.

(3) set of computations S _maxphase deviation angle after interior sub-carrier frequency domain signal superposes in the same way:

${\mathrm{\θ}}_{sig}\left(1\right)=angle\left(\underset{k\∈S_{max}}{\Σ}{Y}_k\right(1\left)S_k^{*}\right(1\left)\right).$

(4) digital baseband input signal of each OFDM symbol of initialization,

θ _{rm_pers}(1)＝δθ _sig(1)，

Wherein δ be less than 1 weight coefficient.

(5) compensation accumulated phase corresponding to (second OFDM symbol namely counted by first SIG field) initial HT_SIG1 field is:

θ _com(2)＝2θ _{rm_pers}(1)。

2, phase deviation angle θ is carried out to HT_SIG1 field (second OFDM symbol counted by first SIG field) _com(2) compensation, carry out residual phase estimation of deviation according to the information after compensating:

${\mathrm{\θ}}_{sig}\left(2\right)=angle\left(\underset{k\∈S_{max}}{\Σ}{Y}_k^{com}\right(2\left)S_k^{*}\right(2\left)\right)$

Then the phase deviation added value θ of HT_SIG1 field is upgraded _{rm_pers}(2):

θ _{rm_pers}(2)＝θ _{rm_pers}(1)+δ ₁θ _sig(2)

Calculate the compensation accumulated phase θ of HT_SI2 field (the 3rd OFDM symbol counted by first SIG field) _com(3):

θ _com(3)＝θ _com(2)+θ _{rm_pers}(2)。

3, phase deviation angle θ is carried out to HT_SIG2 field (the 3rd OFDM symbol counted by first SIG field) _com(3) compensation, carry out residual phase estimation of deviation according to the information after compensating:

${\mathrm{\θ}}_{sig}\left(3\right)=angle\left(\underset{k\∈S_{max}}{\Σ}{Y}_k^{com}\right(3\left)S_k^{*}\right(3\left)\right).$

Upgrade the phase deviation added value θ of HT_SIG2 field _{rm_pers}(3):

θ _{rm_pers}(3)＝θ _{rm_pers}(2)+δ ₁θ _sig(3)，

Calculate the compensation accumulated phase θ of HT_STF field (the 4th OFDM symbol counted by first SIG field) _com(4).

θ _com(4)＝θ _com(3)+θ _{rm_pers}(3)。

4, for HT_STF field and N number of HT_LTF field, phase tracking loop does not carry out phase deviation and compensates and residual phase estimation, only compensates the cumulative of phase place.Then

The phase deviation added value of i-th OFDM symbol remains unchanged,

θ _{rm_pers}(i)＝θ _{rm_pers}(i-1)，

Calculate the compensation accumulated phase of next OFDM symbol,

θ _com(i+1)＝θ _com(i)+θ _{rm_pers}(i)。

Then the compensation accumulated phase corresponding to (m+3+1 the OFDM symbol namely counted by first SIG field) first OFDM symbol of following data fields is:

θ _com(m+3+1)＝θ _com(m+3)+θ _{rm_pers}(m+3)＝θ _com(3)+(m+1)*θ _{rm_pers}(3)。

5, individual to the jth (j >=1) of data field, namely by first SIG field, i-th OFDM symbol of counting carries out the compensation of residual phase, estimates the residual phase deviation of this OFDM symbol according to the symbolic information after phase compensation,

${\mathrm{\θ}}_{pilot}\left(i\right)=angle\left(\underset{k\∈C}{\Σ}weight\right(k\left)Y_k^{com}\right(i\left)P_k^{*}\right(i\left)\right),$

Upgrade the phase deviation added value of i-th OFDM symbol:

θ _{rm_pers}(i)＝θ _{rm_pers}(i-1)+δ ₂θ _pilot(i)，

Calculate the compensation accumulated phase of the i-th+1 OFDM symbol again:

θ _com(i+1)＝θ _com(i)+θ _{rm_pers}(i)，

Until frame data terminate, Phase Tracking completes.

Phase-tracking method of the present invention and traditional pilot point weighted phases tracking are carried out simulation result contrast, simulated conditions is set to transmitting terminal and produces HT_Mixed format signal frame, MCS=7, signal emulates fading channel through TGn_E and enters receiving terminal, receiving terminal is after synchronous and compensate of frequency deviation, adopt different Phase Tracking modes respectively, the phase error result that signal to noise ratio is phase tracking loop during 20dB is respectively as shown in accompanying drawing 2 and accompanying drawing 3.

As can be seen from accompanying drawing 2 and accompanying drawing 3, after adopting method of the present invention, phase tracking error distribution is less than the error of the phase-tracking method of pilot weighted, and the precision of track loop is greatly improved, and the result of Phase Tracking can be stabilized in a less scope.

Emulation setting model same as above, under different signal to noise ratio snr, each emulation 1000 packets, adopt out of phase tracking, the Packet Error Ratio Comparative result of final receiving terminal as shown in Figure 3.

As can be seen from accompanying drawing 4, adopt phase-tracking method of the present invention, the Packet Error Ratio of system is lower than conventional pilot point weighted phases tracking, and the inventive method shows more superior performance.

Patent of the present invention provides a kind of method of carrying out Phase Tracking in an ofdm system, the frequency domain data of the heavy high frequency point sets scope of channel power in SIG field is utilized to carry out precise phase estimation of deviation, it can be used as the fixing initial value of the residual phase deviation of follow-up each OFDM symbol, recycling subsequent data symbols pilot point weighted phases deviation is revised, the precision of ofdm system receiving terminal Phase Tracking is improved, especially, when low signal-to-noise ratio, Phase Tracking precision has greatly improved.According to described disclosed embodiment, those skilled in the art can realize or use the present invention.The above embodiment is only preferred embodiment of the present invention, not in order to limit the present invention, within the spirit and principles in the present invention all, and any amendment done, equivalent replacement, improvement etc., all within protection scope of the present invention.

Claims (8)

1. the ofdm system phase-tracking method based on SIG field and data field pilot weighted, the signal comprising several SIG fields and data field for receiving ofdm system receiver carries out phase equivocation and compensation, it is characterized in that: said method comprising the steps of:

Step (1): calculate the phase deviation that in the OFDM symbol time interval, residual frequency deviation produces according to first described SIG field, and it can be used as the phase deviation added value θ of first OFDM symbol of counting by first described SIG field _{rm_pers}, and then obtain the compensation accumulated phase θ of second OFDM symbol (1) _com(2), as follows 1. to 5. implementing:

Step is 1.: choose N _sindividually include described signal and the strongest subcarrier of channel, remember that its set is S _max;

Step is 2.: described S set in each described SIG field of hard decision respectively _maxin the polarity of frequency-region signal of subcarrier described in each, remember that its set is S _p;

Step is 3.: according to described S set _maxwith described S set _pcalculate described S set _maxin the frequency-region signal of subcarrier described in each superpose in the same way after phase deviation angle θ _sig(1);

Step is 4.: phase deviation angle θ described in initialization _sig(1) obtain the phase deviation that in the OFDM symbol time interval, residual frequency deviation produces, and it can be used as the phase deviation added value θ of first OFDM symbol of counting by first described SIG field _{rm_pers}(1);

Step is 5.: according to the phase deviation added value θ of described first OFDM symbol _{rm_pers}(1) the compensation accumulated phase θ of second OFDM symbol is obtained _com(2);

Step (2): successively residual phase deviation compensation carried out to follow-up i-th OFDM symbol of counting by first described SIG field and upgrade its phase deviation added value and calculate the compensation accumulated phase of its i-th+1 described OFDM symbol or directly calculate the compensation accumulated phase of its next described OFDM symbol, wherein i be greater than 1 integer, be divided into following three kinds of situations:

Situation a: when i-th OFDM symbol is SIG field, adopts it to compensate accumulated phase θ _comi () carries out the compensation of residual phase misalignment angle to this i-th OFDM symbol, according to the symbolic information after compensation, calculate the residual phase misalignment angle θ of this OFDM symbol _sig(i), and according to described residual phase misalignment angle θ _sigi () upgrades the phase deviation added value θ obtaining this i-th OFDM symbol _{rm_pers}(i); Again according to the phase deviation added value θ of this i-th OFDM symbol _{rm_pers}(i) and its compensation accumulated phase θ _comi () calculates the compensation accumulated phase θ of the i-th+1 described OFDM symbol _com(i+1);

Situation b: when i-th OFDM symbol is for training field, the phase deviation added value θ of this i-th OFDM symbol _{rm_pers}i () is relative to the phase deviation added value θ of the i-th-1 OFDM symbol _{rm_pers}(i-1) constant, directly according to the phase deviation added value θ of this i-th OFDM symbol _{rm_pers}the compensation accumulated phase θ of (i) and this i-th OFDM symbol _comi () calculates the compensation accumulated phase θ of its i-th+1 described OFDM symbol _com(i+1);

Situation c: when i-th OFDM symbol is data field, adopts it to compensate accumulated phase θ _comi () carries out the compensation of residual phase misalignment angle to this i-th OFDM symbol, according to the symbolic information after compensating and the pilot data of data field, calculate the residual phase misalignment angle θ of this i-th OFDM symbol _pilot(i), and according to the residual phase misalignment angle θ of described i-th OFDM symbol _piloti () upgrades the phase deviation added value θ obtaining this i-th OFDM symbol _{rm_pers}i (), if this i-th OFDM symbol is not data field described in last frame, then again according to the phase deviation added value θ of this i-th OFDM symbol _{rm_pers}the compensation accumulated phase θ of (i) and this i-th OFDM symbol _comi () calculates the compensation accumulated phase θ of its i-th+1 described OFDM symbol _com(i+1), if this i-th OFDM symbol is data field described in last frame, then the compensation accumulated phase of the i-th+1 described OFDM symbol is no longer calculated.

2. the ofdm system phase-tracking method based on SIG field and data field pilot weighted according to claim 1, is characterized in that: step 1. in, judge the signal strength signal intensity of each subcarrier according to channel estimation results, more therefrom choose N _sindividually include described signal and the strongest subcarrier of channel.

3. the ofdm system phase-tracking method based on SIG field and data field pilot weighted according to claim 1, is characterized in that: step 3. in, pass through

${\mathrm{\θ}}_{sig}\left(1\right)=angle\left(\underset{k\∈S_{max}}{\Σ}{Y}_k\right(1)S_k^{*}\left(1\right))$

Calculate described phase deviation angle θ _sig(1), wherein, Y _k(1) be that described first SIG field is corresponding to described S set after channel equalization _maxan interior kth element, S _k(1) for described first SIG field is in described S set _maxthe polarity of the sub-carrier signal of an interior kth element, for S _k(1) conjugation, angle () is the computing of calculated complex angle.

4. the ofdm system phase-tracking method based on SIG field and data field pilot weighted according to claim 1, is characterized in that: step 4. in, the phase deviation added value θ of first OFDM symbol _{rm_pers}(1)=δ θ _sig(1), wherein δ be less than 1 weight coefficient.

5. the ofdm system phase-tracking method based on SIG field and data field pilot weighted according to claim 1, is characterized in that: step 5. in, the compensation accumulated phase θ of second OFDM symbol _com(2)=2 θ _{rm_pers}(1).

6. the ofdm system phase-tracking method based on SIG field and data field pilot weighted according to claim 1, is characterized in that: in situation a, passes through

${\mathrm{\θ}}_{sig}\left(i\right)=angle\left(\underset{k\∈S_{max}}{\Σ}{Y}_k^{com}\right(i)S_k^{*}\left(i\right))$

Calculate the residual phase misalignment angle θ of this OFDM symbol _sig(i), wherein for described S set _maxthe pilot data of i-th OFDM symbol after channel equalization and described residual phase misalignment angle compensate of an interior kth element, S _ki () is for described i-th SIG field is in described S set _maxthe polarity of the sub-carrier signal of an interior kth element;

Pass through

θ _{rm_pers}(i)＝θ _{rm_pers}(i-1)+δ ₁θ _sig(i)

Upgrade the phase deviation added value θ obtaining this i-th OFDM symbol _{rm_pers}(i), wherein, δ ₁for being less than the weight coefficient of 1;

Pass through

θ _com(i+1)＝θ _com(i)+θ _{rm_pers}(i)

Calculate the compensation accumulated phase θ of the i-th+1 described OFDM symbol _com(i+1).

7. the ofdm system phase-tracking method based on SIG field and data field pilot weighted according to claim 1, is characterized in that: in situation b, the phase deviation added value θ of i-th OFDM symbol _{rm_pers}i () is relative to the phase deviation added value θ of the i-th-1 OFDM symbol _{rm_pers}(i-1) constant

θ _{rm_pers}(i)＝θ _{rm_pers}(i-1)，

Pass through

θ _com(i+1)＝θ _com(i)+θ _{rm_pers}(i)

Calculate the compensation accumulated phase θ of its i-th+1 described OFDM symbol _com(i+1).

8. the ofdm system phase-tracking method based on SIG field and data field pilot weighted according to claim 1, is characterized in that: in situation c, passes through

${\mathrm{\θ}}_{pilot}\left(i\right)=angle\left(\underset{k\∈C}{\Σ}weight\right(k)Y_k^{com}\left(i\right)P_k^{*}\left(i\right))$

Calculate the residual phase misalignment angle θ of this i-th OFDM symbol _piloti (), wherein, weight (k) is described S set _maxthe credit weight of the pilot tone of an interior kth element, C is pilot point set, for described S set _maxin a kth element i-th OFDM symbol through channel equalization and and the compensation of described residual phase misalignment angle after pilot data, P _ki () is described S set _maxtransmitting in the pilot tone of an interior kth element;

Pass through

θ _{rm_pers}(i)＝θ _{rm_pers}(i-1)+δ ₂θ _pilot(i)

Upgrade the phase deviation added value θ obtaining this i-th OFDM symbol _{rm_pers}(i), wherein, δ ₂for being less than the feedback factor of 1;

Pass through

θ _com(i+1)＝θ _com(i)+θ _{rm_pers}(i)

Calculate the compensation accumulated phase θ of the i-th+1 described OFDM symbol _com(i+1).