CN101645861A - Method and system for synchronously tracking received signal - Google Patents

Abstract

The invention discloses a method and a system for synchronously tracking a received signal. The method comprises the following steps: performing channel estimation on the received signal to obtain a channel estimation result; synchronously tracking the sample frequency offset of the received signal according to a main peak and a channel estimation value of a sampling point next to the main peak; and synchronously tracking the carrier frequency offset of the received signal according to the main peak. The method and the system for synchronously tracking the received signal can estimate and correct the sample frequency offset and the carrier frequency offset of the received signal in the period of tracking the received signal so as to ensure that the system works in a good condition all thetime.

Description

The method and system of following the tracks of synchronously to received signal

Technical field

The present invention relates to signal synchronizing method, relate more specifically to a kind of method and system of following the tracks of synchronously to received signal.

Background technology

Digital Television is since late nineteen eighties development in last century, and development is the existing vicennial time so far, and a lot of countries or company have all dropped into great effort and formulated the transmission standard of Digital Television and carry out industrialization.At present, there are four kinds of digital TV ground transmission standards:

1) (the Advanced Television SystemsCommittee of U.S.'s AS committee, abbreviation ATSC) eight level vestigial side bands of the lattice code of research and development (Trsllis-Coded 8-Level Vestigial Side-band is called for short 8-VSB) modulating system.

2) European digital video broadcast-terrestrial (Digital Video TerrestrialBroadcasting-Terrestrial, abbreviation DVB-T) Coded Orthogonal Frequency Division Multiplexing (COFDM) of standard employing (Coded Orthogonal Frequency Division Multiplexing is called for short COFDM) modulating system.

3) Japanese floor synthetic service digital broadcasting (Integrated Service DigitalBroadcasting-Terrestrial, abbreviation ISDB-T) frequency band segment transmissions (the Bandwidth Segmented Transmission that adopts, be called for short B ST) OFDM) (Orthogonal Frequency Division Multiplexing is called for short OFDM) modulating system.

4) single carrier and the multi-carrier OFDM modulation scheme of China Digital TV ground broadcast transfer system (Digital TelevisionTerrestrial Broadcasting is called for short DTTB) standard employing.

The DTTB of China uses broadcast spectrum, and the rate of information throughput of effective payload of each channel can be up to 33Mbps under the bandwidth of 8MHz.The core of system adopts m quadrature amplitude modulation/quadriphase PSK modulation techniques such as (Quadrature Amplitude Modulation are called for short QAM/QuadriPhase Shift Keying, is called for short QPSK), and its spectrum efficiency can be up to 4Bit/s/Hz.System uses more optimal forward error correction (Forward ErrorCorrection, be called for short FEC) to resist error burst, for example low-density checksum (LowDensity Parity Check is called for short LDPC) sign indicating number etc.

For realize quick and stable synchronously, the DTTB transmission system has adopted hierarchical frame structure.It has periodically, and can and Absolute Time Synchronization.Frame adopts four-layer structure.The elementary cell of frame structure is called signal frame, and signal frame is made up of frame head and frame two parts.Superframe is defined as one group of signal frame.Dividing frame definition is one group of superframe.The top layer of frame structure is called a day frame (Calendar Day Frame is called for short CDF).Signal structure is the cycle, and keeps synchronously with natural time.

The signal frame of DTTB transmission system uses the OFDM modulation of Domain Synchronous, and perhaps being called with the PN sequence is protection OFDM modulation at interval.A signal frame is made up of frame head and frame two parts, and they have identical baseband signalling speed 7.56MS/s.A signal frame can be used as an OFDM (OFDM) piece.An OFDM piece further is divided into a protection interval and an inverse discrete Fourier transform (InverseDiscrete Fourier Transform is called for short IDFT) piece.For the signal frame of DTTB system, frame synchronization sequence is as the protection interval of OFDM, and frame is as the IDFT piece.

The frame head part is made of the PN sequence, and frame head length has three kinds of options.Header signal adopts the 4QAM modulation identical with the Q road of I road.The PN sequence of frame head is except as the protection of OFDM piece at interval, can also be used for the purposes such as frame synchronization, carrier wave recovery and tracking, symbol clock recovery, channel estimating of signal frame at receiving terminal.

The bandwidth of each subcarrier of ofdm system is narrower, and each subcarrier need keep quadrature, thereby very responsive to the net synchronization capability of system.Owing to Doppler frequency shift, transmit and receive the influence of factors such as the crystal oscillator frequency of machine is inconsistent, the carrier frequency of system can be offset, and disturbs between subcarrier thereby cause, and influences demodulation performance.So precise synchronization is extremely important in ofdm system.

Present existing ofdm signal method for synchronous mainly is to carry out or carry out under the condition of no auxiliary data according to the known auxiliary data (being frame head PN sequence in the DTTB system) that provides.Synchronizing process generally is divided into two stages: catch and follow the tracks of.Through the synchronization acquistion stage,, still still there is the residual carrier frequency deviation because receiver is eliminated with the inconsistent carrier wave frequency deviation major part that causes of carrier of transmitter frequency; On the other hand, because receiver follows the inconsistent sampling clock frequency deviation that causes of sampling clock frequency of transmitter can cause certain sample-timing error.Need estimate and correct these two frequency deviations at tracking phase, always work in state preferably to guarantee system.

Summary of the invention

One or more problems in view of the above the invention provides a kind of method and system of following the tracks of synchronously to received signal.

The method of following the tracks of synchronously to received signal according to the embodiment of the invention comprises: carry out channel estimating to received signal, draw channel estimation results; According to the main footpath peak value in the channel estimation results, and main footpath peak value near the channel estimation value sampling frequency offset to received signal of sampled point follow the tracks of synchronously, and follow the tracks of synchronously according to main footpath peak value carrier wave frequency deviation to received signal.

Wherein, the process that sampling frequency offset is to received signal followed the tracks of synchronously comprises: according to main footpath peak value, and main footpath peak value before and the channel estimation value of afterwards n sampled point, draw the sampling deviation of the present frame of received signal, wherein, n for more than or equal to 1 and when carrying out over-sampling to received signal the integer of used over-sampling multiple; The sampling deviation of the former frame of the sampling deviation of the present frame of received signal and received signal is compared, draw comparative result, and draw the sampling time relative deviation of received signal according to comparative result; And according to the sampling time relative deviation of received signal, sampling frequency offset is to received signal adjusted.

Wherein, according to before the amplitude of main footpath peak value and the main footpath peak value and the amplitude of the channel estimation value of n sampled point afterwards draw the sampling deviation of the present frame of received signal, wherein, the sampling deviation of the present frame of received signal and $\mathrm{\α}=\frac{\left|\hat{h}(n_{\max }-n)\right|-\left|\hat{h}(n_{\max }+n)\right|}{\left|\hat{h}\left(n_{\max }\right)\right|}$ Be directly proportional,

Be main footpath peak value,

With

Be respectively to lead before the peak value of footpath and the channel estimation value of n sampled point afterwards.

In addition, also can according to before the power of main footpath peak value and the main footpath peak value and the average estimated channel power of n sampled point afterwards draw the sampling deviation of the present frame of received signal, wherein, the sampling deviation of the present frame of received signal and $\mathrm{\β}=\frac{{\left|\hat{h}(n_{\max }-n)\right|}^2-{\left|\hat{h}(n_{\max }+n)\right|}^2}{{\left|\hat{h}\left(n_{\max }\right)\right|}^2}$ Be directly proportional, Be main footpath peak value,

With Be respectively to lead before the peak value of footpath and the channel estimation value of n sampled point afterwards.

Wherein, after drawing the sampling time relative deviation of received signal, sampling frequency offset to received signal also comprises before adjusting: use digital phase-locked loop to lock the sampling time relative deviation of the received signal that draws.

Wherein, follow the tracks of synchronously according to the phase difference carrier wave frequency deviation to received signal between the main footpath peak value of the former frame of the main footpath peak value of the present frame of received signal and received signal.

The system that follows the tracks of synchronously to received signal according to the embodiment of the invention comprises: channel estimating unit, be used for carrying out to received signal channel estimating, and draw channel estimation results; Synchronous tracking cell, be used for according to channel estimation results main footpath peak value, and main footpath peak value near the channel estimation value sampling frequency offset to received signal of sampled point follow the tracks of synchronously, and follow the tracks of synchronously according to main footpath peak value carrier wave frequency deviation to received signal.

Wherein, tracking cell comprises synchronously: the sampling deviation acquiring unit, be used for according to main footpath peak value, and main footpath peak value before and the channel estimation value of afterwards n sampled point, draw the sampling deviation of the present frame of received signal, wherein, n for more than or equal to 1 and when carrying out over-sampling to received signal the integer of used over-sampling multiple; The relative deviation acquiring unit is used for the sampling deviation of the former frame of the sampling deviation of the present frame of received signal and received signal is compared, and draws comparative result, and draws the sampling time relative deviation of received signal according to comparative result; The sampling frequency offset adjustment unit is used for the sampling time relative deviation according to received signal, and sampling frequency offset is to received signal adjusted; And the carrier wave frequency deviation adjustment unit, be used for following the tracks of synchronously according to main footpath peak value carrier wave frequency deviation to received signal.

Wherein, before the sampling frequency offset acquiring unit is according to the amplitude of main footpath peak value and main footpath peak value and the amplitude of the channel estimation value of n sampled point afterwards draw under the situation of sampling deviation of present frame of received signal, the sampling deviation of the present frame of received signal and $\mathrm{\α}=\frac{\left|\hat{h}(n_{\max }-n)\right|-\left|\hat{h}(n_{\max }+n)\right|}{\left|\hat{h}\left(n_{\max }\right)\right|}$ Be directly proportional,

Be main footpath peak value,

With

Be respectively to lead before the peak value of footpath and the channel estimation value of n sampled point afterwards.Before the sampling frequency offset acquiring unit is according to the power of main footpath peak value and main footpath peak value and the average estimated channel power of n sampled point afterwards draw under the situation of sampling deviation of present frame of received signal, the sampling deviation of the present frame of received signal and $\mathrm{\β}=\frac{{\left|\hat{h}(n_{\max }-n)\right|}^2-{\left|\hat{h}(n_{\max }+n)\right|}^2}{{\left|\hat{h}\left(n_{\max }\right)\right|}^2}$ Be directly proportional,

Be main footpath peak value,

With

Be respectively to lead before the peak value of footpath and the channel estimation value of n sampled point afterwards.

The system that follows the tracks of synchronously to received signal according to the embodiment of the invention also comprises: phase locked-loop unit is used to lock the sampling time relative deviation of received signal.

By the present invention, can estimate the sampling frequency offset of this received signal and carrier wave frequency deviation and correct to received signal tracking phase, thereby can guarantee that system always works in state preferably.

Description of drawings

Accompanying drawing described herein is used to provide further understanding of the present invention, constitutes the application's a part, and illustrative examples of the present invention and explanation thereof are used to explain the present invention, do not constitute limitation of the invention.In the accompanying drawings:

Fig. 1 a to Fig. 1 c is the schematic diagram that illustrates as the structure of the signal frame of the elementary cell of DTTB data frame structure;

Fig. 2 a and Fig. 2 b are the schematic diagrames that illustrates according to the frame head structure of the pattern 1 of the embodiment of the invention and mode 3;

Fig. 3 is the method for following the tracks of synchronously to received signal that illustrates according to the embodiment of the invention;

Fig. 4 is the block diagram that illustrates according to the sampling frequency offset following principle of the embodiment of the invention;

Fig. 5 is the curve chart that illustrates according to the channel estimating sampled result of the embodiment of the invention;

Fig. 6 be illustrate according to the embodiment of the invention have sampling frequency offset the time two frames the curve chart of channel estimating sampled result; And

Fig. 7 is the block diagram that illustrates according to the carrier wave frequency deviation following principle of the embodiment of the invention.

Embodiment

Below with reference to accompanying drawing, describe the specific embodiment of the present invention in detail.

The elementary cell of DTTB data frame structure is a signal frame, and a signal frame is made up of frame head and frame two parts, and they have identical baseband signalling speed 7.56MS/s.Frame partly comprises the system information of 36 symbols and the data of 3744 symbols, totally 3780 symbols.The frame data have single carrier and two kinds of patterns of OFDM.The frame head part is made of the PN sequence, adopt the QPSK modulation identical of I road with the Q road, frame head length has 3 kinds of patterns: the pattern (mode 3) of the pattern (pattern 1) of 420 symbols (being 55.6us), the pattern (pattern 2) of 595 symbols (being 78.8us) and 945 symbols (being 125us), wherein, pattern 1 and 3 is used for the OFDM frame, pattern 2 is used for the single carrier frame, shown in Fig. 1 a to Fig. 1 c.What the present invention mainly considered is the OFDM frame, just pattern 1 and 3.

The frame head message length of frame head mode 1 is N=n _h+ n _Pn+ n _t=420 symbols are by n _hThe preamble of=82 symbols, n _PnThe PN sequence (PN255) and the n of=255 symbols _tThe back synchronous formation of=83 symbols, preamble and after be the cyclic extensions of PN255 synchronously, shown in Fig. 2 a.Per 255 signal frames are formed 1 superframe, and the frame head of each signal frame adopts the PN signal of out of phase in the superframe.

The frame head message length of frame head mode 3 is N=n _h+ n _Pn+ n _t=945 symbols are by n _hThe preamble of=217 symbols, n _PnThe PN sequence (PN511) and the n of=511 symbols _tThe back synchronous formation of=217 symbols, preamble and after be the cyclic extensions of PN511 synchronously, shown in Fig. 2 b.Per 200 signal frames are formed 1 superframe, and the frame head of each signal frame adopts the PN signal of out of phase in the superframe.

The PN sequence of frame head is except as the protection between the frame at interval, can also be used for the purposes such as frame synchronization, carrier wave recovery and tracking, symbol clock recovery, channel estimating of signal frame at receiving terminal.

Sampling frequency offset is owing to exist frequency departure to cause between the reception sampling clock of local receiver and the transmission sampling clock, causing receiving the sampling location is offset gradually, for ofdm system, can cause fast fourier transform (Fast Fourier Transform, be called for short FFT) window appearance skew, cause on current each subcarrier of OFDM symbol phase deviation to occur, and side-play amount is directly proportional with subcarrier number.Simultaneously, residual in the baseband signal that obtains after the down-conversion have a part carrier wave frequency deviation, at residual carrier wave frequency deviation hour, has been equivalent to cause on each subcarrier of current OFDM symbol roughly the same phase deviation occurs.In comprising the ofdm system of pilot signal, can utilize pilot tone to carry out frequency offset estimating according to the characteristics of the variation of the phase deviation substantially linear on each subcarrier.Do not have in the system of pilot tone signal at DTTB etc., need to adopt new method to carry out.Below we are example with frame head mode 1, the tracking of sampling frequency offset and carrier wave frequency deviation is described.

As shown in Figure 3, comprise according to the method for following the tracks of synchronously to received signal of the embodiment of the invention: S302, carry out channel estimating to received signal, draw channel estimation results; S304, according to the main footpath peak value in the channel estimation results, and main footpath peak value near the channel estimation value sampling frequency offset to received signal of sampled point follow the tracks of synchronously, and follow the tracks of synchronously according to main footpath peak value carrier wave frequency deviation to received signal.

Wherein, as shown in Figure 4, the process that sampling frequency offset is to received signal followed the tracks of synchronously comprises: according to main footpath peak value, and main footpath peak value before and the channel estimation value of afterwards n sampled point, draw the sampling deviation of the present frame of received signal, wherein, n for more than or equal to 1 and when carrying out over-sampling to received signal the integer of used over-sampling multiple; The sampling deviation of the former frame of the sampling deviation of the present frame of received signal and received signal is compared, draw comparative result, and draw the sampling time relative deviation of received signal according to comparative result; And according to the sampling time relative deviation of received signal, sampling frequency offset is to received signal adjusted.Wherein, can after drawing the sampling time relative deviation of received signal, before sampling frequency offset is to received signal adjusted, use digital phase-locked loop to lock the sampling time relative deviation of the received signal that draws.

Particularly, the Base-Band Processing when receiver adopts 2 times of over-samplings, just sample frequency f _s=15.12MHz is symbol rate R _sDuring 2 times of=7.56MS/s, corresponding sampling time interval is T _s=1/f _sThe frame head PN sequence that intercepting receives, the transmission PN sequence that employing and receiver are known carries out convolution or other method estimates channel time domain information h (n).Actual channel h (t) is continuous, and its amplitude is shown in the dotted line among Fig. 5, and the channel estimation results that desirable sampling obtains is the point that indicates black circles among Fig. 5, promptly $\tilde{h}\left(n\right)=h\left(n{T}_s\right),$ The channel estimation results that obtains according to actual samples then be wherein indicate "

" point, promptly $\hat{h}\left(n\right)=h(n(T_s+\mathrm{\Δ}{T}_s)+t_0).$ Find main footpath

The i.e. channel estimation results of amplitude maximum in all channel estimation results, according to it and about two points

Amplitude, can think the actual samples position with desirable sampling location departing from $\mathrm{\α}=\frac{\left|\hat{h}(n_{\max }-1)\right|-\left|\hat{h}(n_{\max }+1)\right|}{\left|\hat{h}\left(n_{\max }\right)\right|}$ Be directly proportional, when main footpath envelope is similar to the sinc function, can think that proportionality coefficient is 3/4, i.e. the sampling deviation of this frame When not having sampling frequency offset, the sampling deviation of this frame is caught up with frame

Be consistent; Inclined to one side Δ T when if the sampling interval is arranged _s, then passed through N between 2 frames _Ofdm=(3780+420) * 2=8400 sampling (passed through N for 3 of frame head modes _Ofdm=(3780+945) * 2=9450), sampling deviation can change, and as shown in Figure 6, changing value is

Can obtain the sampling time relative deviation thus

Can adjust sampling frequency offset according to this value.When sampling frequency offset is big, this frame master directly differs 1 or 2 sampling with last frame situation may take place, this part is also joined

In, can increase the working range that sampling frequency offset is followed the tracks of.

When estimating sampling deviation, also can utilize main footpath peak value and the power of two sampled points about it, think the actual samples position with desirable sampling location departing from $\mathrm{\β}=\frac{{\left|\hat{h}(n_{\max }-1)\right|}^2-|\hat{h}(n_{\max }+1){|}^2}{{\left|\hat{h}\left(n_{\max }\right)\right|}^2}$ Be directly proportional, when main footpath envelope is similar to the sinc function, can think that proportionality coefficient is 9/16, i.e. the sampling deviation of this frame

In addition, the over-sampling multiple that adopts in the Base-Band Processing of receiver is not 2 but during k (k can be integer or the mark greater than 1.5), the actual samples position with departing from of desirable sampling location can be similar to equally think with $\mathrm{\α}=\frac{\left|\hat{h}(n_{\max }-n)\right|-\left|\hat{h}(n_{\max }+n)\right|}{\left|\hat{h}\left(n_{\max }\right)\right|},$ $\mathrm{\β}=\frac{{\left|\hat{h}(n_{\max }-n)\right|}^2-{\left|\hat{h}(n_{\max }+n)\right|}^2}{{\left|\hat{h}\left(n_{\max }\right)\right|}^2}$ Be directly proportional, wherein n is an integer, and 1≤n＜k, and just proportionality coefficient need be adjusted accordingly.

Owing in the received signal noise is arranged, correct performance for the sampling time deviation of avoiding estimating with the effect of jitter sampling frequency offset of noise, can sampling frequency offset be locked with digital phase-locked loop DPLL.According to the sampling frequency offset of locking,, the sampled signal that received is afterwards carried out correcting frequency deviation then, again the sampled signal after correcting is sent into channel estimation module and demodulation module by methods such as resamplings.

After sampling frequency offset locking, also need to consider the tracking of residual carrier wave frequency deviation, as shown in Figure 7 according to the carrier wave frequency deviation tracking of the embodiment of the invention.Particularly, owing to pass through the synchronization acquistion stage therefore remaining carrier wave frequency deviation Δ f _cLess.The frame head PN sequence that same intercepting receives, the transmission PN sequence that employing and receiver are known carries out convolution or other method estimates channel time domain information h (n).When the carrierfree frequency deviation, become and The noise this frame master footpath h (n when ignoring channel _Max)=h (n _MaxT _s+ t ₀) identical with last frame master footpath, there is not the variation of phase place.At carrier wave frequency deviation is Δ f _cThe time, last frame master footpath ${\hat{h}}_{i-1}\left(n_{\max }\right)=h(n_{\max }{T}_s+t_0)e^{{\mathrm{\&phi;}}_0},$ This frame master footpath then is ${\hat{h}}_i\left(n_{\max }\right)=h(n_{\max }{T}_s+t_0)e^{{\mathrm{\&phi;}}_0+\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="A2008101180340021H2.png,A2008101180340022H1.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&pi;\&Delta;}{f}_c/f_s{N}_{\mathrm{ofdm}}},$ The phase place rotation has taken place, therefore as long as calculate $\mathrm{\&Delta;}{f}_c=\frac{\&angle;{\hat{h}}_i\left(n_{\max }\right)-\&angle;{\hat{h}}_{i-1}\left(n_{\max }\right)}{2\mathrm{\&pi;}{N}_{\mathrm{ofdm}}}{f}_s,$ Can estimate carrier wave frequency deviation.Because angle is to repeat in the cycle with 2 π, therefore carries out Nonlinear Transformation in Frequency Offset Estimation in this way, requires the synchronization module of front carrier wave frequency deviation to be corrected to

Within, promptly ± 900Hz within (for 3 requirements of frame head mode within ± 800Hz), estimate that as need bigger frequency deviation then should revise algorithm.

The same with sampling frequency offset, correct performance for the carrier wave frequency deviation of avoiding estimating with the effect of jitter carrier wave frequency deviation of noise, can carrier wave frequency deviation be locked with digital phase-locked loop DPLL.According to the carrier wave frequency deviation of locking, be multiplied by methods such as respective phase deflection then, the sampled signal that received is afterwards carried out correcting frequency deviation, again the sampled signal after correcting is sent into channel estimation module and demodulation module by giving each sampling.

Can know by the above, be used to realize that the system that follows the tracks of synchronously to received signal of the above method comprises: channel estimating unit, be used for carrying out to received signal channel estimating, draw channel estimation results; Synchronous tracking cell, be used for according to channel estimation results main footpath peak value, and main footpath peak value near the channel estimation value sampling frequency offset to received signal of sampled point follow the tracks of synchronously, and follow the tracks of synchronously according to main footpath peak value carrier wave frequency deviation to received signal.

Wherein, tracking cell comprises synchronously: the sampling deviation acquiring unit, be used for according to main footpath peak value, and main footpath peak value before and the channel estimation value of afterwards n sampled point, draw the sampling deviation of the present frame of received signal, wherein, n for more than or equal to 1 and when carrying out over-sampling to received signal the integer of used over-sampling multiple; The relative deviation acquiring unit is used for the sampling deviation of the former frame of the sampling deviation of the present frame of received signal and received signal is compared, and draws comparative result, and draws the sampling time relative deviation of received signal according to comparative result; The sampling frequency offset adjustment unit is used for the sampling time relative deviation according to received signal, and sampling frequency offset is to received signal adjusted; And the carrier wave frequency deviation adjustment unit, be used for following the tracks of synchronously according to main footpath peak value carrier wave frequency deviation to received signal.

Wherein, before the sampling frequency offset acquiring unit is according to the amplitude of main footpath peak value and main footpath peak value and the amplitude of the channel estimation value of n sampled point afterwards draw under the situation of sampling deviation of present frame of received signal, the sampling deviation of the present frame of received signal and $\mathrm{\&alpha;}=\frac{\left|\hat{h}(n_{\max }-n)\right|-\left|\hat{h}(n_{\max }+n)\right|}{\left|\hat{h}\left(n_{\max }\right)\right|}$ Be directly proportional, Be main footpath peak value,

With

Be respectively to lead before the peak value of footpath and the channel estimation value of n sampled point afterwards.Before the sampling frequency offset acquiring unit is according to the power of main footpath peak value and main footpath peak value and the average estimated channel power of n sampled point afterwards draw under the situation of sampling deviation of present frame of received signal, the sampling deviation of the present frame of received signal and $\mathrm{\&beta;}=\frac{{\left|\hat{h}(n_{\max }-n)\right|}^2-{\left|\hat{h}(n_{\max }+n)\right|}^2}{{\left|\hat{h}\left(n_{\max }\right)\right|}^2}$ Be directly proportional,

Be main footpath peak value,

With

Be respectively to lead before the peak value of footpath and the channel estimation value of n sampled point afterwards.

The system that follows the tracks of synchronously to received signal according to the embodiment of the invention also comprises: phase locked-loop unit is used to lock the sampling time relative deviation of received signal.

The above is embodiments of the invention only, is not limited to the present invention, and for a person skilled in the art, the present invention can have various changes and variation.Within the spirit and principles in the present invention all, any modification of being done, be equal to replacement, improvement etc., all should be included within the claim scope of the present invention.

Claims (11)

1. a method of following the tracks of synchronously to received signal is characterized in that, comprising:

Carry out channel estimating to received signal, draw channel estimation results;

According to the main footpath peak value in the described channel estimation results, and described main footpath peak value near the channel estimation value of sampled point the sampling frequency offset of described received signal is followed the tracks of synchronously, and the carrier wave frequency deviation of described received signal is followed the tracks of synchronously according to described main footpath peak value.

2. method of following the tracks of synchronously to received signal according to claim 1 is characterized in that, the process that the sampling frequency offset of described received signal is followed the tracks of synchronously comprises:

According to described main footpath peak value, and described main footpath peak value before and the channel estimation value of afterwards n sampled point, draw the sampling deviation of the present frame of described received signal, wherein, n for more than or equal to 1 and when described received signal is carried out over-sampling the integer of used over-sampling multiple;

The sampling deviation of the former frame of the sampling deviation of the present frame of described received signal and described received signal is compared, draw comparative result, and draw the sampling time relative deviation of described received signal according to described comparative result; And

According to the sampling time relative deviation of described received signal, the sampling frequency offset of described received signal is adjusted.

3. method of following the tracks of synchronously to received signal according to claim 2, it is characterized in that, according to before the amplitude of described main footpath peak value and the described main footpath peak value and the amplitude of the channel estimation value of n sampled point afterwards draw the sampling deviation of the present frame of described received signal, wherein, the sampling deviation of the present frame of described received signal with $\mathrm{\&alpha;}=\frac{\left|\hat{h}(n_{\max }-n)\right|-\left|\hat{h}(n_{\max }+n)\right|}{\left|\hat{h}\left(n_{\max }\right)\right|}$ Be directly proportional,

Be described main footpath peak value,

With

It is respectively before the peak value of described main footpath and the channel estimation value of n sampled point afterwards.

4. method of following the tracks of synchronously to received signal according to claim 2, it is characterized in that, according to before the power of described main footpath peak value and the described main footpath peak value and the average estimated channel power of n sampled point afterwards draw the sampling deviation of the present frame of described received signal, wherein, the sampling deviation of the present frame of described received signal with $\mathrm{\&beta;}=\frac{{\left|\hat{h}(n_{\max }-n)\right|}^2-{\left|\hat{h}(n_{\max }+n)\right|}^2}{{\left|\hat{h}\left(n_{\max }\right)\right|}^2}$ Be directly proportional,

Be described main footpath peak value, With

It is respectively before the peak value of described main footpath and the channel estimation value of n sampled point afterwards.

5. according to each described method of following the tracks of synchronously to received signal in the claim 2 to 4, it is characterized in that, after drawing the sampling time relative deviation of described received signal, before the sampling frequency offset of described received signal adjusted, also comprise:

Use digital phase-locked loop to lock the sampling time relative deviation of the described received signal that draws.

6. method of following the tracks of synchronously to received signal according to claim 5, it is characterized in that, the carrier wave frequency deviation of described received signal is followed the tracks of synchronously according to the phase difference between the main footpath peak value of the former frame of the main footpath peak value of the present frame of described received signal and described received signal.

7. a system that follows the tracks of synchronously to received signal is characterized in that, comprising:

Channel estimating unit is used for carrying out to received signal channel estimating, draws channel estimation results;

Synchronous tracking cell, be used for according to described channel estimation results main footpath peak value, and described main footpath peak value near the channel estimation value of sampled point the sampling frequency offset of described received signal is followed the tracks of synchronously, and the carrier wave frequency deviation of described received signal is followed the tracks of synchronously according to described main footpath peak value.

8. the system that follows the tracks of synchronously to received signal according to claim 7 is characterized in that, described synchronous tracking cell comprises:

The sampling deviation acquiring unit, be used for according to described main footpath peak value, and described main footpath peak value before and the channel estimation value of afterwards n sampled point, draw the sampling deviation of the present frame of described received signal, wherein, n for more than or equal to 1 and when described received signal is carried out over-sampling the integer of used over-sampling multiple;

The relative deviation acquiring unit, be used for the sampling deviation of the former frame of the sampling deviation of the present frame of described received signal and described received signal is compared, draw comparative result, and draw the sampling time relative deviation of described received signal according to described comparative result;

The sampling frequency offset adjustment unit is used for the sampling time relative deviation according to described received signal, and the sampling frequency offset of described received signal is adjusted; And

The carrier wave frequency deviation adjustment unit is used for according to described main footpath peak value the carrier wave frequency deviation of described received signal being followed the tracks of synchronously.

9. the system that follows the tracks of synchronously to received signal according to claim 8, it is characterized in that, before described sampling frequency offset acquiring unit is according to the amplitude of described main footpath peak value and described main footpath peak value and the amplitude of the channel estimation value of n sampled point afterwards draw under the situation of sampling deviation of present frame of described received signal, the sampling deviation of the present frame of described received signal and $\mathrm{\&alpha;}=\frac{\left|\hat{h}(n_{\max }-n)\right|-\left|\hat{h}(n_{\max }+n)\right|}{\left|\hat{h}\left(n_{\max }\right)\right|}$ Be directly proportional, Be described main footpath peak value, With It is respectively before the peak value of described main footpath and the channel estimation value of n sampled point afterwards.

10. the system that follows the tracks of synchronously to received signal according to claim 8, it is characterized in that, before described sampling frequency offset acquiring unit is according to the power of described main footpath peak value and described main footpath peak value and the average estimated channel power of n sampled point afterwards draw under the situation of sampling deviation of present frame of described received signal, the sampling deviation of the present frame of described received signal and $\mathrm{\&beta;}=\frac{{\left|\hat{h}(n_{\max }-n)\right|}^2-{\left|\hat{h}(n_{\max }+n)\right|}^2}{{\left|\hat{h}\left(n_{\max }\right)\right|}^2}$ Be directly proportional,

Be described main footpath peak value,

With

It is respectively before the peak value of described main footpath and the channel estimation value of n sampled point afterwards.

11. each described system that follows the tracks of synchronously to received signal in 10 is characterized in that according to Claim 8, also comprises:

Phase locked-loop unit is used to lock the sampling time relative deviation of described received signal.

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