CN104052707B - High carrier number OFDM sample frequency fast synchronization methods - Google Patents
High carrier number OFDM sample frequency fast synchronization methods Download PDFInfo
- Publication number
- CN104052707B CN104052707B CN201410217150.8A CN201410217150A CN104052707B CN 104052707 B CN104052707 B CN 104052707B CN 201410217150 A CN201410217150 A CN 201410217150A CN 104052707 B CN104052707 B CN 104052707B
- Authority
- CN
- China
- Prior art keywords
- current sign
- capture
- value
- estimate
- tracking
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
- 238000000034 method Methods 0.000 title claims abstract description 76
- 238000005070 sampling Methods 0.000 claims abstract description 66
- 238000012937 correction Methods 0.000 claims abstract description 36
- 230000001186 cumulative effect Effects 0.000 claims abstract description 4
- 230000008569 process Effects 0.000 claims description 21
- 238000010606 normalization Methods 0.000 claims description 15
- 238000004458 analytical method Methods 0.000 claims description 6
- 238000012545 processing Methods 0.000 claims description 4
- 238000003780 insertion Methods 0.000 claims description 3
- 125000004122 cyclic group Chemical group 0.000 claims 1
- 238000005516 engineering process Methods 0.000 description 17
- 238000010586 diagram Methods 0.000 description 4
- 230000005540 biological transmission Effects 0.000 description 3
- 238000011156 evaluation Methods 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- 238000004088 simulation Methods 0.000 description 3
- 230000001360 synchronised effect Effects 0.000 description 3
- 239000013078 crystal Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000004422 calculation algorithm Methods 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000000739 chaotic effect Effects 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000037431 insertion Effects 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000006855 networking Effects 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 230000008054 signal transmission Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 230000009897 systematic effect Effects 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Landscapes
- Synchronisation In Digital Transmission Systems (AREA)
Abstract
The present invention relates to a kind of high carrier number OFDM sample frequency fast synchronization methods.It includes step：S1. frequency pilot sign is inserted in transmitting terminal；S2. sampling frequency offset precorrection is carried out to current sign using the capture estimate of previous symbol；S3. correspondence position pilot phase is obtained poor；S4. the sampling frequency offset capture value estimation of current sign is carried out using pilot phase difference, current sign capture value and previous symbol capture estimate are subjected to cumulative acquisition new estimation value；S6. when new capture value is more than the capture threshold value of setting, sampling frequency offset correction is carried out to current sign using the capture estimate of current sign based on frequency-domain correction method and exported；Pre-correction signal when new capture value is less than the capture threshold value of setting in output step S2；Next symbol is updated to current sign and continues executing with S2 S4.The present invention can carry out high-precision sampling frequency offset in real time to each OFDM symbol and correct.
Description
Technical field
The present invention relates to communication technical field, more particularly, to a kind of high carrier number OFDM sample frequency Fast synchronizations
Method.
Background technology
With the fast development of Internet technology, the clear Web TV of image height, massively multiplayer game and Online Video meeting etc.
Using slowly popularizing, but the network speed of China at this stage is also far from enough, it would be desirable to the more access skill of high speed
Art meets demand of the people for future bandwidth.Generation digital user line technology (NG-DSL, Next Generation
Digital Subscriber Line) technology will be following most important high-speed wired access technology, the band of this access technology
Width will exceed 100M, and transmission rate will exceed 1Gbps, and can be combined well with optical networking, significantly lift network speed
Degree.
On a physical layer, NG-DSL technologies use high-caliber OFDM (OFDM, Orthogonal
Frequency Division Multiplexing) technology.OFDM technology is a kind of high multi-carrier modulation of band efficiency
Technology, has a wide range of applications in wired and wireless access network.Different from traditional digital user line technology (DSL,
Digital Subscriber Line) technology, the OFDM modulation systems that NG-DSL technologies are used have high carrier number orthogonal with height
Modulation and Amplitude Modulation (QAM, Quadrature Amplitude Modulation) two major features, because this two major features causes NG-
DSL technologies have very high bandwidth and transmission rate, exactly because but also this two major features causes NG-DSL technologies for signal
Any access technology is all high than ever for synchronous requirement.Therefore, simultaneous techniques is particularly important in NG-DSL technologies.
In NG-DSL systems, we are become the OFDM baseband signals of generation in transmitting terminal using D/A converter
Analog signal is sampled into numeral by analog signal, the analog signal received by transmission in receiving terminal by A/D converter
Signal.Optimal situation is A/D, D/A equipment clock frequency Complete Synchronization in transmitting-receiving two-end, then samples out in receiving terminal
Signal be exactly unbiased signal, but the clock of two equipment can not possibly often accomplish identical, and clock crystal oscillator exists certain
Frequency drift phenomenon, it is inconsistent so to will result in transmitting-receiving two-end signal, inter-carrier interference is caused, so as to reduce the noise of system
Than.We are accomplished by estimating to greatest extent the deviation of transmitting-receiving two-end crystal oscillator frequency, and thus correct the signal of receiving terminal,
The output signal-to-noise ratio of lifting system.Among wired ofdm signal, influence the mainly sample frequency of the net synchronization capability of system same
Step (it is synchronous also to include timing synchronization, but this synchronization is easier to solve for systematic influence), particularly as NG-
This high carrier waves of DSL, the ofdm system of high-speed, the deviation that sampling frequency offset is produced to system are particularly important, it is impossible to estimate well
The high-speed transfer of meter sampling frequency offset system will not know where to begin.
The content of the invention
There is provided one kind raising sampling frequency offset to overcome at least one defect (deficiency) described in above-mentioned prior art by the present invention
The high carrier number OFDM sample frequency fast synchronization methods of the precision of estimate.
In order to solve the above technical problems, technical scheme is as follows：
A kind of high carrier number OFDM sample frequency fast synchronization methods, comprise the following steps：
S1. multidigit frequency pilot sign is inserted in transmitting terminal；
S2. sampling frequency offset precorrection is carried out to current sign using the capture estimate of previous symbol；
S3. the phase information of position pilot tone, position corresponding with transmitting terminal pilot phase letter are corresponded to after receiving terminal obtains precorrection
It is poor so as to obtain correspondence position pilot phase that breath seeks difference；
S4. the sampling frequency offset estimation for carrying out current sign using pilot phase difference obtains the capture value of current sign, ought
The capture value of preceding symbol carries out the cumulative capture estimate for obtaining current sign with the capture estimate of previous symbol；
S5. when the capture value of current sign is more than the capture threshold value of setting, current symbol is utilized based on frequency-domain correction method
Number capture estimate sampling frequency offset correction carried out to current sign export, and next symbol is updated to current sign and continues to hold
Row S2-S4；Pre-correction signal when the capture value of current sign is less than the capture threshold value of setting in output step S2, and it is next
Individual symbol is updated to current sign and continues executing with S2-S4.
In a kind of preferred scheme, in step S5, when the capture value of current sign is less than the capture threshold value of setting at present
One symbol does not perform S2-S4, and performs the tracking process of sampling frequency offset, specific as follows：
S6. next symbol is updated to current sign into tracking process, performs step S1-S3 again in tracking process and obtains
It is poor to pilot phase；
S7. the sampling frequency offset pursuit gain estimation for carrying out current sign using pilot phase difference obtains the pursuit gain of current sign
And the pursuit gain of current sign compares with tracking threshold value, will be current when the pursuit gain of current sign exceedes tracking threshold value
The tracking estimate that the tracking estimate of the pursuit gain of symbol and previous symbol is added up as current sign, and utilization ought
The tracking estimate of preceding symbol carries out frequency-domain correction output to current sign, previous when new pursuit gain is less than tracking threshold value
The tracking estimate of individual symbol exports precorrection letter when step S2 is performed in step S6 as the tracking estimate of current sign
Number；
S8. next semiology analysis tracks process.
New sampling frequency offset estimation is carried out in a kind of preferred scheme, in the step S4 using pilot phase difference to obtain
The capture value of current sign, be specially：
It is located at the pilot tone of transmitting terminal insertionLed in receiving terminal by corresponding
Frequency symbol demodulation is obtainedThe phase difference of pilot tone for then drawing correspondence position is：
WhereinPilot tone for correspondence position is divided by：
In formula (1) and (2), N is OFDM symbol data bit length, and Δ f represents to normalize sampling frequency offset, and L is circulation
Prefix length, m represents m-th of OFDM symbol, m=1, and 2,3 ..., k represents k-th of subcarrier, k=0,1,2,3 ... N-1, j generations
Table plural number, Xm,sWhat is represented is the data of transmitting terminal, and s is identical with k implications, represents the sequence number of carrier number；
Section 2 in formula (2) is inter-carrier interference, when number of sub carrier wave is larger, the phase of inter-carrier interference
The approximate average of obeying of value is 0 Gaussian Profile, therefore drawsValue be：
The value of m and k in formula (3) and observeCarry out the normalization sampling frequency offset Δ f of estimating system,
The as capture value of current sign.
In a kind of preferred scheme, carry out current sign capture value obtain when also use using pilot frequency carrier wave sequence number k as
The weighted mean method of weighted factor carries out data processing, is specially：
Wherein AmFor offset estimation constant term, i.e.,：
The value of m, k, N, L in formula (4) and (5) and observeCarry out the normalization sampling of estimating system
Frequency deviation Δ f, as current sign capture value.
In a kind of preferred scheme, obtained Δ f is calculated as current using formula (4) and formula (5) in step S7
The pursuit gain of symbol.
In a kind of preferred scheme, the formula that the step S2 carries out precorrection is：
WhereinFor the estimate of previous symbol.
6. high carrier number OFDM sample frequency fast synchronization methods according to claim 5, it is characterised in that step
Tracking threshold value in S7 is set according to priori：
Wherein Δ is tracking estimate, and m is symbolic number, and ρ is tracking threshold coefficient,For tracking threshold value.
In a kind of preferred scheme, the pilot signal inserted in the step S1 is 8.
Compared with prior art, the beneficial effect of technical solution of the present invention is：
(1) present invention calculates the pilot tone of transmitting terminal position corresponding with receiving terminal by inserting pilot tone in OFDM symbol
Phase difference, estimates sampling frequency offset, and the capture estimate of previous symbol is used to enter the corresponding position pilot tone of current sign
Row precorrection, the capture value of current sign is added with the capture estimate of previous symbol capture estimate is updated,
The precorrection of latter symbol repeats the operation of current sign, until new capture capture value more than the capture threshold value set as
Only.Experimental results demonstrate typically only need to the estimation no more than three symbols and can be obtained by the higher normalization of precision
Sampling frequency offset capture value.By the substantial amounts of simulation analysis for NG-DSL systems, sum up and meet NG-DSL output signal-to-noise ratios
Under the conditions of, the approximation relation of normalization sampling frequency offset and symbolic number, m Δs f≤10-7.Therefore, even if first of acquisition procedure is estimated
Meter has certain inaccurate, but can't produce king-sized influence to system signal noise ratio in the case that symbolic number is less,
And evaluated error first can be limited in m Δs f≤10 using the method for the present invention-7Within the scope of, therefore the present invention can
Corrected with carrying out high-precision sampling frequency offset in real time to each OFDM symbol.
(2) present invention utilizes the method for iteration capture estimate is rapidly converged near exact value, met
The required precision of system.And it make use of the data processing scheme of optimization so that the computation complexity reduction of this programme.
(3) present invention adds tracking process after acquisition procedure, sets tracking threshold value to cause the technical program multiple
Miscellaneous degree in precision with having reached compromise so that the present invention possesses relatively low complexity and higher precision, suitable for Practical Project system
System.
Brief description of the drawings
Fig. 1 is a kind of flow chart of high carrier number OFDM sample frequencys fast synchronization method specific embodiment of the present invention.
Fig. 2 produces schematic diagram for ofdm system sampling frequency offset in the present invention.
Fig. 3 is frequency-domain correction Method And Principle schematic diagram of the present invention.
Fig. 4 is normalization sampling frequency offset estimation curve of the invention under different tracking threshold values.
Fig. 5 for the present invention estimate MSE and two kinds of accurate conventional estimated method estimate MSE curve ratios compared with
Figure.
Fig. 6 is the present invention and two kinds of accurate conventional method estimating speeds and the comparison figure of MSE precision.
Fig. 7 is in NG-DSL systems, an OFDM symbol is compared using the planisphere before and after present invention correction.
Fig. 8 be NG-DSL systems in, an OFDM symbol by be originally inputted under sampling frequency offset disturbed condition signal to noise ratio with
The comparison figure for the output signal-to-noise ratio being interfered.
Fig. 9 is in NG-DSL systems, an OFDM symbol compares figure by the signal to noise ratio before and after present invention correction.
Embodiment
Accompanying drawing being given for example only property explanation, it is impossible to be interpreted as the limitation to this patent；
In order to more preferably illustrate the present embodiment, some parts of accompanying drawing have omission, zoomed in or out, and do not represent actual product
Size；
To those skilled in the art, it is to be appreciated that some known features and its explanation, which may be omitted, in accompanying drawing
's.
In the description of the invention, it is to be understood that term " first ", " second " are only used for describing purpose, and can not
It is interpreted as indicating or implies relative importance or imply the quantity of indicated technical characteristic.Thus, " first " of restriction, "
One or more this feature can be expressed or be implicitly included to two " feature.In the description of the invention, unless otherwise saying
Bright, " multiple " are meant that two or more.
In the description of the invention, it is necessary to illustrate, unless otherwise clearly defined and limited, term " installation ", " company
Connect " it should be interpreted broadly, for example, it may be being fixedly connected or being detachably connected, or it is integrally connected；It can be machine
Tool is connected or electrically connected；It can be joined directly together or be indirectly connected with by intermediary, it may be said that two
The connection of element internal.For the ordinary skill in the art, with concrete condition above-mentioned term can be understood in the present invention
Concrete meaning.
Technical scheme is described further with reference to the accompanying drawings and examples.
Embodiment 1
As shown in figure 1, being a kind of stream of high carrier number OFDM sample frequencys fast synchronization method specific embodiment of the present invention
Cheng Tu.Fig. 1 is participated in, a kind of high carrier number OFDM sample frequency fast synchronization methods of this specific embodiment specifically include following step
Suddenly：
S101. multidigit frequency pilot sign is inserted in transmitting terminal；Usually, the feedback according to channel estimation for channel status exists
Transmitting terminal insertion multidigit frequency pilot sign is used for the estimation of sampling frequency offset, is preferably inserted into 8 frequency pilot signs.Inserted in transmitting terminal
Pilot toneThen corresponding frequency pilot sign can be demodulated to come in receiving terminal：
Wherein, m represents m-th of OFDM symbol, m=1, and 2,3 ..., k represents k-th of subcarrier, k=0,1,2,3 ... N-1；
S102. sampling frequency offset precorrection is carried out to current sign using the capture estimate of previous symbol；Specifically, it is right
In current sign, precorrection process is carried out to correspondence position pilot tone first with the capture estimate of previous symbol, precorrection is public
Formula is：
Wherein, whereinFor the capture estimate of previous symbol.
S103. the phase information of position pilot tone, position corresponding with transmitting terminal pilot phase are corresponded to after receiving terminal obtains precorrection
It is poor so as to obtain correspondence position pilot phase that information seeks difference；Specifically, according to the frequency pilot sign and receiving terminal pair that are inserted in transmitting terminal
Answer the pilot tone of position to obtain the phase difference of pilot tone of correspondence position to be：
WhereinPilot tone for correspondence position is divided by：
In formula (1) and (2), N is OFDM symbol data bit length, and Δ f represents to normalize sampling frequency offset, such as Fig. 2 institutes
Show；L is circulating prefix-length, and m represents m-th of OFDM symbol, m=1, and 2,3 ..., k represents k-th of subcarrier, k=0,1,2,
3 ... N-1, j represent plural number, XM, sWhat is represented is the data of transmitting terminal, and s is identical with k implications, represents the sequence number of carrier number；
Section 2 in formula (2) is inter-carrier interference, when number of sub carrier wave is larger, the phase of inter-carrier interference
Value is approximate to obey the Gaussian Profile that average is 0.Therefore, formula (2) is being carried out to take angle computing, i.e. formula (1), now only had
Imaginary bit can be just obtained in phase angle, i.e. formula (2)
With, due in formula (2)
Section 2, that is, the phase for the item that adds up obeys average and is 0 normal distribution, so taking angle for previous itemTherefore drawValue be：
S104. the capture value that new sampling frequency offset capture value estimation obtains current sign is carried out using pilot phase difference, will
The capture value of current sign carries out the cumulative capture estimate for obtaining current sign with the capture estimate of previous symbol；
Formula (3) is symbolic number m, carrier number k, normalization sampling frequency offset Δ f and phase differenceBetween relation, due to
Using pilot tone, therefore when the value for knowing m and k in formula (3), utilize what is observedCarry out the normalization sampling of estimating system
Frequency deviation Δ f, as current sign capture value.
Because the present invention is used in the higher NG-DSL systems of input signal-to-noise ratio, interchannel noise is smaller, so using
Weighted mean method using pilot frequency carrier wave sequence number k as weighted factor carries out data processing, is specially：
Wherein AmFor offset estimation constant term, i.e.,：
The value of m, k, N, L in formula (4) and (5) and observeCarry out the normalization sampling of estimating system
Frequency deviation Δ f, as current sign capture value.
In actual applications, one OFDM symbol can just be carried out using formula (4) and (5) using 8 frequency pilot signs
Fitting estimation, completes the estimation of first symbol, because first symbol is without its previous symbol, therefore first symbol
Capture value is also its estimate, so as to obtain the estimate Δ f of first symbol1, but the estimate of first symbol often deposits
In certain deviation, it is therefore desirable to proceed the correction of estimate, now first meets and becomes previous symbol, second
Symbol becomes current sign；
For second symbol as current sign, correspondence position is led first with the capture estimate of first symbol
Frequency carries out precorrection process, and precorrection formula is the precorrection formula in S102, and the precorrection to second symbol obtains pilot tone
Information R 'm,k, by the pilot frequency information R ' obtained after precorrectionm,kRepeat the estimation procedure of first symbol, obtain one it is new
Normalize sampling frequency offset capture value Δ f '2, i.e., it is poor to obtain in S103 pilot phase using pilot frequency information, according to new in S104
Pilot phase difference combine formula (4) and (5) and can be carried out new sampling frequency offset capture value estimation, and then obtained one newly
Normalization sampling frequency offset capture value Δ f '2, the capture value of as second symbol, it is seen then that obtain pilot tone letter in step S102
Cease R 'm,kRepeatedly the estimation procedure of first symbol can be obtained by the estimation of the sampling frequency offset capture value of second symbol afterwards.
In step S104, after the completion of the estimation of second symbol, the estimate Δ f of first symbol is utilized1With second symbol
Capture value Δ f '2As a result estimate is updated, that is, obtains the capture estimate of second symbol：
Δ f=Δs f1+Δf′2 (7)。
S105. when the capture value of current sign is more than the capture threshold value of setting, based on frequency-domain correction method using currently
The capture estimate of symbol carries out sampling frequency offset correction to current sign and exported, and next symbol is updated to current sign continuation
Perform S102-S104；Precorrection letter when the capture value of current sign is less than the capture threshold value of setting in output step S102
Number, and next symbol is updated to current sign and continues executing with S102-S104.
In above-mentioned steps, the capture estimate Δ f ' of current sign2Than the capture estimate Δ f of previous symbol1It is small
A lot, it is that correction of the estimate to exact value direction is captured to previous symbol, latter symbol repeats the operation of current sign,
Capture estimate is further updated.Experimental results demonstrate typically only needing to the estimation no more than three symbols can just obtain
Sampling frequency offset capture value is accurately normalized to one.The estimation procedure of first three symbol usually is referred to as into normalization to adopt
The acquisition procedure of sample frequency deviation.By the substantial amounts of simulation analysis for NG-DSL systems, summary is met NG-DSL output letters
Make an uproar than under the conditions of, the approximation relation of normalization sampling frequency offset and symbolic number.
mΔf≤10-7 (8)
Therefore, even if first of acquisition procedure estimation have it is certain inaccurate, but in the case that symbolic number is less
King-sized influence can't be produced on system signal noise ratio, and will can first estimate mistake using the formula (3) in the present invention
Difference is limited within the scope of formula (8), therefore the present invention can carry out real-time sampling frequency offset correction to each OFDM symbol.
Complete acquisition procedure after, in order to further improve precision and reduction calculate complexity, invention introduces with
Track process, i.e., in step S105, when the capture value of current sign is less than the capture threshold value of setting by step S102 pre- school
Positive signal carries out the output of current sign, and now next symbol does not perform step S102-S104, but carries out sampling frequency offset
Tracking process, it is specific as follows：
S106. next symbol is updated to current sign into tracking process, according to channel estimation pair during tracking
Inserting multidigit frequency pilot sign in transmitting terminal in the feedback of channel status is used for the estimation of sampling frequency offset, utilizes previous sign estimation
Sampling frequency offset out carries out sampling frequency offset precorrection to current sign, the phase of correspondence position pilot tone after receiving terminal obtains precorrection
Position information, it is poor so as to obtain correspondence position pilot phase that position corresponding with transmitting terminal PilotPhase information seeks difference；Herein namely again
It is poor that execution step S101-S103 obtains pilot phase；
S107. the sampling frequency offset pursuit gain estimation for carrying out current sign using pilot phase difference obtains the tracking of current sign
Value, and the pursuit gain of current sign is compared with tracking threshold value, when the tracking estimate of current sign exceedes tracking threshold value
When, the tracking estimate of the tracking estimate of current sign and previous symbol is added up and estimated as the tracking of current sign
Evaluation, and using current sign tracking estimate to current sign carry out frequency-domain correction output, when new pursuit gain be less than with
During track threshold value, the tracking estimate of previous symbol exports in step S106 as the tracking estimate of current sign and performs step
Pre-correction signal during rapid S102；
In specific implementation process, the capture of the acquisition methods of the pursuit gain of current sign and current sign in step S107
Value-acquiring method is identical, i.e., same to be calculated using formula (4) and formula (5), the difference is that the Δ f now obtained not as
The capture value of current sign, but it is used as the pursuit gain of current sign in step S107.
Tracking process can be judged the pursuit gain of current sign, when the pursuit gain of current sign exceedes tracking threshold value
The tracking estimate of current sign is added up with the tracking estimate of previous symbol, and estimate is tracked using accumulated value
Renewal and using update after tracking estimate carry out frequency-domain correction, when new tracking estimate less than tracking threshold value when, it is right
Estimate, which is not done, to be updated operation and is worked without carrying out new frequency-domain correction, it is only necessary to is utilized and is performed again after step S102
Precorrection frequency-region signal can meet the requirement of system as output signal.
The present invention is after acquisition procedure is completed, into tracking process, and each symbol will also repeat to capture during tracking
The estimation of process and renewal process, but the difference is that during tracking, can judge to be according to the size of tracking value of feedback
The no renewal that sampling frequency offset estimate is normalized.Main two tasks of tracking process：First be with new estimate come pair
The deviation previously estimated is finely adjusted；Second is to detect whether that new larger deviation occurs, and can be produced if there is if,
The process of recapture will be carried out.Because the sampling frequency offset pursuit gain estimated during tracking is often smaller, carry out every time
The speed of service of system can be influenceed if the adjustment of small value, and this small change does not have significantly for signal to noise ratio
Improve, therefore we can ignore the estimate less than certain threshold value in Practical Project.So the computing in order to reduce system
Complexity, the analysis according to formula (8) to NG-DSL system synchronization parameters sets a tracking threshold value：
Wherein Δ is tracking estimate, and m is symbolic number, and ρ is tracking threshold coefficient,For tracking threshold value.
, when pursuit gain exceedes tracking threshold value, the frequency domain symbol of system is being carried out using new estimate during tracking
Correct；When pursuit gain is less than tracking threshold value, the frequency-region signal of current sign is corrected without using new estimate, is only needed
Will just can be with using the result in pre-correction stage.What the tracking threshold coefficient in formula (9) was together decided on by precision and complexity,
I.e. when ρ takes higher value, estimated accuracy and complexity of the invention is higher；When ρ takes smaller value, estimated accuracy of the invention and
Complexity is relatively low.In order to obtain the sampling frequency offset estimation method of lower complexity and degree of precision, in actual applications according to reality
Border situation, the selection of a compromise is carried out to estimated accuracy and complexity, so as to reach the optimized parameter suitable for real system
Selection.
, it is necessary to be utilized in time using the method for frequency-domain correction to output frequency-region signal after the completion of each sign estimation
Estimate is corrected, and the fundamental diagram of frequency-domain correction is as shown in Figure 3.
The present invention has carried out performance evaluation and emulation to the above method, specific as follows：
In a line length in 50m NG-DSL systems, each OFDM data bit length is 8192 (FFT/IFFT length),
Normalization sampling frequency offset is 3ppm, and pilot frequency carrier wave sequence number is followed successively by：{ 505507509511513515517519 }, tracking threshold value system
Number is respectively 4,8, the emulation of new sampling frequency synchronization under 20 3 kind of different situations.And carried out with two kinds of traditional methods
Compare, method one is document " Estimation and compensation of frequency offset in DAC/ADC
The sampling frequency synchronization method proposed in clocks in OFDM systems ", method two is document " under high-order QAM modulation
OFDM carrier wave combines correction with sampling frequency offset " propose sampling frequency synchronization method.
As shown in figure 4, being the estimate curve using the different tracking threshold condition down-sampling frequency deviations of present invention emulation.Can be with
It was found that in figureCurve is to track estimation curve when threshold value ρ is 4, it can be found that now having many flat estimates, explanation
Under this threshold coefficient value condition, the present invention and the correction that too many estimate need not be carried out, it is only necessary to estimate several times
Evaluation estimated in the case of producing relatively large deviation and frequency-region signal corrected, but simultaneously it has also been discovered that this
The deviation of estimate is maximum in the case of kind, is the equal of the reduction that the present invention exchanges complexity for using the loss in precision.
In figureCurve is to track estimation curve when threshold value ρ is 8, it can be found that curve now does not haveCurve is so put down
It is smooth, but ratio of precisionCurve is higher, is a kind of compromise situation.In figureCurve is to track estimation when threshold value ρ is 20
Curve, this curve substantially needs that each symbol is reevaluated and corrected, in this case estimated accuracy highest,
But complexity is also highest.Therefore by above-mentioned analysis, tracking threshold coefficient value can be taken as 8, precision can be reached
With the compromise of complexity.
As shown in figure 5, being the MSE curves of the inventive method and two kinds of accurate methods described above, MSE curves are
Judge a whether accurate major criterion of estimation, usually defining MSE is：
By Fig. 5 it can be found that the MSE values of the inventive method are very low, and tracking estimate can be with input signal-to-noise ratio
Increase and more accurately, there is very accurate estimation in 40dB~60dB intervals, disclosure satisfy that the precision of NG-DSL systems will
Ask.And the estimating speed of the present invention also can be very fast, i.e., the most accurately estimation is carried out using minimum symbolic number, this is also
The present invention uses the effect produced by iterative calculation method.Fig. 6 is the normalization sampling frequency offset obtained by different estimate symbol numbers
Estimate, to embody the estimating speed characteristic of synchronous invention.
It will be appreciated from fig. 6 that the present invention soon can converge to tracking estimate near exact value, same estimate symbol number
The MSE of gained is also smaller than above two method.Because simulated environment is that sampling deviation is 0.3ppm, upper figure shows that MSE is
1e-17~1e-18 orders of magnitude, it is possible thereby to calculate jitter value on the 1e-9 orders of magnitude, we recognize in actual offset estimation
Required precision of the system for sampling frequency offset is met for the deviation of this magnitude.The display present invention can be accorded with using less estimation
Number reach higher estimated accuracy.
Complete estimation when, it is necessary to using estimate to signal carry out frequency-domain correction, using formula (6) updating formula and
It is corrected according to Fig. 3 frequency-domain correction schematic diagram, the frequency domain planisphere after being corrected can be to the star before and after correction
Seat figure is compared to judge calibration result, as shown in Figure 7.It can be found that not calibrated planisphere is very chaotic, system without
Method is correctly demodulated, and can produce very big error code.
During Fig. 8 is NG-DSL systems, an OFDM symbol by be originally inputted under sampling frequency offset disturbed condition signal to noise ratio with
The output signal-to-noise ratio being interfered.It can be seen that the effect of sampling frequency offset so that the signal to noise ratio of signal is substantially reduced, seriously
It has impact on the transmission of signal.During Fig. 9 is NG-DSL systems, an OFDM symbol compares by the signal to noise ratio before and after present invention correction
Figure.As can be seen that after the correction by inventive algorithm, the signal to noise ratio of signal has larger lifting.Compare Fig. 8 and figure
9 signal to noise ratio that can be seen that after correction are basically identical with input signal-to-noise ratio in low-frequency range, can be poorer than input signal-to-noise ratio in high band
2dB or so, this is due to that frequency-domain correction method is difficult to ICI is completely eliminated.But in NG-DSL systems, the adjustment water of high band
Flat relatively low, the requirement to signal to noise ratio is not as low-frequency range harshness, so can carry out no error code demodulation in simulations.
The same or analogous part of same or analogous label correspondence；
Position relationship is used for being given for example only property explanation described in accompanying drawing, it is impossible to be interpreted as the limitation to this patent；
Obviously, the above embodiment of the present invention is only intended to clearly illustrate example of the present invention, and is not pair
The restriction of embodiments of the present invention.For those of ordinary skill in the field, may be used also on the basis of the above description
To make other changes in different forms.There is no necessity and possibility to exhaust all the enbodiments.It is all this
Any modifications, equivalent substitutions and improvements made within the spirit and principle of invention etc., should be included in the claims in the present invention
Protection domain within.
Claims (8)
1. a kind of high carrier number OFDM sample frequency fast synchronization methods, it is characterised in that comprise the following steps：
S1. multidigit frequency pilot sign is inserted in transmitting terminal；
S2. sampling frequency offset precorrection is carried out to current sign using the capture estimate of previous symbol；
S3. the phase information of position pilot tone is corresponded to after receiving terminal obtains precorrection, position corresponding with transmitting terminal PilotPhase information is asked
Difference is poor so as to obtain correspondence position pilot phase；
S4. the sampling frequency offset estimation for carrying out current sign using pilot phase difference obtains the capture value of current sign, will currently accord with
Number the capture estimate of capture value and previous symbol carry out the capture estimate of cumulative acquisition current sign；
S5. when the capture value of current sign is more than the capture threshold value of setting, current sign is utilized based on frequency-domain correction method
Capture estimate and sampling frequency offset correction output is carried out to current sign, and next symbol is updated to current sign and continued executing with
S2-S4；Pre-correction signal when the capture value of current sign is less than the capture threshold value of setting in output step S2, and it is next
Symbol is updated to current sign and continues executing with S2-S4.
2. high carrier number OFDM sample frequency fast synchronization methods according to claim 1, it is characterised in that step S5
In, when the capture value of current sign is less than the capture threshold value of setting, next symbol does not perform S2-S4, and performs sampling frequency offset
Tracking process, it is specific as follows：
S6. next symbol is updated to current sign into tracking process, performs step S1-S3 again in tracking process and is led
Frequency phase difference；
S7. the sampling frequency offset pursuit gain estimation for carrying out current sign using pilot phase difference obtains the pursuit gain of current sign and will
The pursuit gain of current sign is compared with tracking threshold value, when the pursuit gain of current sign exceedes tracking threshold value, by current sign
Pursuit gain and previous symbol the tracking estimate that add up as current sign of tracking estimate, and utilization currently accords with
Number tracking estimate to current sign carry out frequency-domain correction output, when new pursuit gain less than tracking threshold value when, previous symbol
Number tracking estimate as the tracking estimate of current sign, pre-correction signal during step S2 is performed in output step S6；
S8. next semiology analysis tracks process.
3. high carrier number OFDM sample frequency fast synchronization methods according to claim 2, it is characterised in that the step
The capture value that new sampling frequency offset estimation obtains current sign is carried out using pilot phase difference in S4, is specially：
It is located at the pilot tone of transmitting terminal insertionIn receiving terminal by corresponding frequency pilot sign
Demodulation is obtainedThe phase difference of pilot tone for then drawing correspondence position is：
WhereinPilot tone for correspondence position is divided by：
In formula (1) and (2), N is OFDM symbol data bit length, and Δ f represents to normalize sampling frequency offset, and L is cyclic prefix
Length, m represents m-th of OFDM symbol, m=1, and 2,3 ..., k represents k-th of subcarrier, and k=0,1,2,3 ... N-1, j is represented again
Number, Xm,sWhat is represented is the data of transmitting terminal, and s is identical with k implications, represents the sequence number of carrier number；
Section 2 in formula (2) is inter-carrier interference, when number of sub carrier wave is larger, and the phase value of inter-carrier interference is near
It is 0 Gaussian Profile like average is obeyed, therefore drawsValue be：
The value of m and k in formula (3) and observeCarry out the normalization sampling frequency offset Δ f of estimating system, be
The capture value of current sign.
4. high carrier number OFDM sample frequency fast synchronization methods according to claim 3, it is characterised in that entering the trade
Preceding symbol capture value also uses the weighted mean method using pilot frequency carrier wave sequence number k as weighted factor to carry out data processing when obtaining,
Specially：
Wherein AmFor offset estimation constant term, i.e.,：
The value of m, k, N, L in formula (4) and (5) and observeCarry out the normalization sampling frequency offset of estimating system
Δ f, as current sign capture value.
5. high carrier number OFDM sample frequency fast synchronization methods according to claim 4, it is characterised in that in step S7
Obtained Δ f is calculated using formula (4) and formula (5) as the pursuit gain of current sign.
6. high carrier number OFDM sample frequency fast synchronization methods according to claim 5, it is characterised in that the step
S2 carry out precorrection formula be：
WhereinFor the estimate of previous symbol.
7. high carrier number OFDM sample frequency fast synchronization methods according to claim 6, it is characterised in that in step S7
Tracking threshold value set according to priori：
Wherein Δ is tracking estimate, and m is symbolic number, and ρ is tracking threshold coefficient,For tracking threshold value.
8. the high carrier number OFDM sample frequency fast synchronization methods according to claim any one of 1-7, it is characterised in that
The pilot signal inserted in the step S1 is 8.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201410217150.8A CN104052707B (en) | 2014-05-21 | 2014-05-21 | High carrier number OFDM sample frequency fast synchronization methods |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201410217150.8A CN104052707B (en) | 2014-05-21 | 2014-05-21 | High carrier number OFDM sample frequency fast synchronization methods |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN104052707A CN104052707A (en) | 2014-09-17 |
| CN104052707B true CN104052707B (en) | 2017-07-28 |
Family
ID=51505083
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201410217150.8A Active CN104052707B (en) | 2014-05-21 | 2014-05-21 | High carrier number OFDM sample frequency fast synchronization methods |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN104052707B (en) |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105141564B (en) * | 2015-07-28 | 2018-10-12 | 广东顺德中山大学卡内基梅隆大学国际联合研究院 | A kind of horizontal OFDM sampling frequency synchronization methods of high sub-carrier number high order modulation |
| CN105680924B (en) * | 2016-01-28 | 2019-04-16 | 西南交通大学 | Based on the MIMO-OFDM system frequency deviation estimating method of frequency domain differential demodulation phase under superelevation mobile condition |
| CN106453187B (en) * | 2016-09-26 | 2019-06-11 | 珠海全志科技股份有限公司 | A kind of ofdm system method for synchronized and device |
| CN106789786A (en) * | 2016-12-07 | 2017-05-31 | 信阳师范学院 | A kind of novel sampling frequency synchronization algorithm |
| CN107612857B (en) * | 2017-09-14 | 2020-10-02 | 中山大学 | Sampling frequency offset estimation method based on pilot frequency |
| CN107948111B (en) * | 2017-12-13 | 2020-08-14 | 北京智芯微电子科技有限公司 | Sampling frequency offset correction method of OFDM system |
| CN108761487B (en) * | 2018-07-13 | 2024-02-23 | 中国电子科技集团公司第二十六研究所 | Large-bandwidth laser wind-finding radar system |
| CN109802906B (en) * | 2019-01-21 | 2021-12-07 | 北京中科晶上科技股份有限公司 | Frequency offset estimation method of modulation signal |
| CN110602018B (en) * | 2019-09-19 | 2022-02-22 | 中国电子科技集团公司第五十四研究所 | Digital frequency correcting device of compatible ultra-low speed scattering communication system |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1520669A (en) * | 2001-06-22 | 2004-08-11 | ��ķɭ��ɹ�˾ | Method and system for compensation of carrier frequency offset in OFDM receiver |
| CN102075485A (en) * | 2011-01-20 | 2011-05-25 | 深圳市阿派斯实业有限公司 | Sampling clock synchronization method for orthogonal frequency division multiplexing (OFDM) system |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| TW200924458A (en) * | 2007-11-28 | 2009-06-01 | Alcor Micro Corp | Apparatus and method for estimating and compensating sampling frequency offset |
-
2014
- 2014-05-21 CN CN201410217150.8A patent/CN104052707B/en active Active
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1520669A (en) * | 2001-06-22 | 2004-08-11 | ��ķɭ��ɹ�˾ | Method and system for compensation of carrier frequency offset in OFDM receiver |
| CN102075485A (en) * | 2011-01-20 | 2011-05-25 | 深圳市阿派斯实业有限公司 | Sampling clock synchronization method for orthogonal frequency division multiplexing (OFDM) system |
Non-Patent Citations (3)
| Title |
|---|
| "Estimation and Compensation of Frequency Offset in ADC/ACD clocks in OFDM systems";H. Shafiee, B. Nourani, M. Khoshgard;《IEEE Communications Society》;20041231;第4卷;2397-2401 * |
| "基于导频的OFDM时钟采样频偏估计";刘元，彭端，陈楚;《通信技术》;20080521;第41卷(第2期);20-24 * |
| "高阶QAM调制下OFDM的载波与采样频偏联合纠正";刘田，杨琳等;《电子学报》;20130331;第41卷(第3期);481-487 * |
Also Published As
| Publication number | Publication date |
|---|---|
| CN104052707A (en) | 2014-09-17 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN104052707B (en) | High carrier number OFDM sample frequency fast synchronization methods | |
| CN104811974B (en) | Data processing method based on IEEE802.11n standards in WiFi comprehensive test instruments | |
| CN103095615B (en) | The method and device that a kind of phase noise is estimated, compensated | |
| CN108199994A (en) | A kind of wireless comprehensive test instrument ofdm signal frequency deviation estimating method and system | |
| CN102404268B (en) | Method for estimating and compensating doppler frequency offset in Rician channels in high-speed mobile environment | |
| CN102307175A (en) | Multicarrier system soft-decision method | |
| CN103023831B (en) | A kind of carrier frequency bias estimation being applicable to burst waveform | |
| CN101374134A (en) | Method for estimating accurate frequency bias for time-domain synchronization OFDM receiver | |
| CN113037663B (en) | Improved code element rate estimation method suitable for non-constant envelope signal | |
| CN102333370B (en) | In ofdm system based on extracting/the sampling clock synchronous method of compensation mechanism | |
| CN106888178A (en) | A kind of OFDM/OQAM system channel estimation methods | |
| CN107454032A (en) | OFDM frequency offset estimation method based on amplitude product between subcarriers | |
| CN108881080B (en) | OFDM anti-ICI detection method based on sliding window and deep learning | |
| CN100486238C (en) | Method of low-complexity frequency deviation estimation based on adjustable time frequency training sequence | |
| CN102185820A (en) | Unscented-Kalman-transformation-based orthogonal frequency division multiplexing (OFDM) frequency offset estimation method | |
| CN105072071A (en) | Sampling frequency offset compensation method based on NG-DSL system | |
| CN106375257B (en) | A kind of multistage frequency deviation estimating method based on FFT | |
| CN103338166B (en) | A kind of channel estimation methods of improvement | |
| CN107426128A (en) | OFDM receiver carrier phase offset method of estimation based on training sequence | |
| CN115426224B (en) | Channel estimation method and system based on OTFS (optical transport plane) signal | |
| CN103986683A (en) | OFDM symbol timing synchronization method based on high carrier number | |
| CN113794661B (en) | Method and system for optimizing receiving performance based on phase noise | |
| CN101141428B (en) | Pilot encoding method and device for orthogonal frequency division multiplexing system | |
| CN103501284B (en) | A kind of method of fine timing synchronization in DVB-T2 system | |
| CN101286958B (en) | Terrestrial broadcasting channel estimating method for digital television and device thereof |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C06 | Publication | ||
| PB01 | Publication | ||
| C10 | Entry into substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |