CN1214437C - Synchronizing pulse generating method and method of receiving OFDM signal - Google Patents
Synchronizing pulse generating method and method of receiving OFDM signal Download PDFInfo
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- CN1214437C CN1214437C CNB008024278A CN00802427A CN1214437C CN 1214437 C CN1214437 C CN 1214437C CN B008024278 A CNB008024278 A CN B008024278A CN 00802427 A CN00802427 A CN 00802427A CN 1214437 C CN1214437 C CN 1214437C
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2655—Synchronisation arrangements
- H04L27/2662—Symbol synchronisation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2655—Synchronisation arrangements
- H04L27/2668—Details of algorithms
- H04L27/2673—Details of algorithms characterised by synchronisation parameters
- H04L27/2676—Blind, i.e. without using known symbols
- H04L27/2678—Blind, i.e. without using known symbols using cyclostationarities, e.g. cyclic prefix or postfix
Abstract
An OFDM receiver generates a synchronizing pulse for specifying a fast Fourier transform window by examining an output from a correlator, in order to find out a mostly-correlated sub-intervals between samples of symbol separated depending on the length of an effective part of a symbol. A synchronizing pulse is generated between these sub-intervals (102). Only when the current error is significant and sustainable, a synchronizing pulse timing is adjusted. A signal expressing an adjustment amount is used to determine a phase rotation applied to an output from an FFT circuit.
Description
Technical field
The present invention relates to the OFDM modulation, relate in particular to the generation of the lock-out pulse of the OFDM character boundary of representing that for example Fourier transform demodulation is used.
Background technology
Ofdm system is known.The OFDM receiver synchronously in the various technology of use.In these technology some all must transmit special synchronizing signal.Other technologies depend on whole symbol by live part and the standard OFDM signal of protecting the interval to constitute, and protection often is called at interval protects interval, cycle to expand or cycle joint language.
Protection is located at interval at the front of live part of symbol, comprises the repetition of data of the end of live part.(this with comprising that the Data Protection identical with the data at the top of live part is identical after being placed on live part at interval).
The synchronization technology that depends on the repeating data in the protection at interval compound sampling of the length by using the live part that only separates symbol usually is relative to each other and moves.Thus, produce the commutator pulse of the Fourier transform that is used for received signal.The timing of pulse is that fourier transform windows only comprises the timing from the data of monadic symbols.
When regularly improper, produce intersymbol interference (ISI).But,, allow also when avoiding ISI that the timing of pulse has a certain amount of variation by using protection at interval.Protection at interval must be longer than the width of the long delay of being predicted between the signal that receives through different paths.Protection is compared relative little at interval with the live part of signal, protection comprises Nu/32, Nu/16, Nu/8 or Nu/4 sampling at interval usually, here, and the number of samples in the live part of Nu is-symbol.
Have from the various technology of the derivation lock-out pulse that is relative to each other.Can suitably move under the general condition of acceptance but do not wishing regularly and producing during pulse and bring the environment of ISI though these have.
When not having noise or multichannel to disturb, the device that is relative to each other has in protection sampling at interval and sampling to produce beyond the interval of MD and is equivalent to that mean value is set to 0 output in as the live part of the symbol of equivalence.The device that is relative to each other in this interval produces high level output.This high level output finishes with the terminal of 1 symbol and the top of next signal.One of device originally detects the peak of resultant signal after the output of integration correlator, with the terminal generation commutator pulse of each symbol.
Under difference postponed situation that received multichannel disturbs, for avoiding ISI, lock-out pulse must occur on the repeating part between the protection at interval of 2 signals that receive to have in the window of equal wide at same signal.But the device that is relative to each other produces the output of having a mind to by the interval of being handled the sampling of protection sampling at interval one or both of by the device that is relative to each other.According to environment, the result provides commutator pulse in the optimal window outside, and then brings ISI.
European patent application EP 0772332 has been put down in writing the other technologies that produce lock-out pulse.One of its disclosed technology is that the output dependence of correlator is in the transmission to phase-locked loop (PLL).Even like this, also appear under the situation that the noise of having a mind to or multichannel disturb and produce the such result of lock-out pulse in the optimal window outside.And, the last symbol period that quite a lot of number of the locking of realizing must be arranged of PLL, therefore, acquisition time is quite long.
The other problems that device originally produces for example results from, and when adjusting lock-out pulse as the result of variations of signal condition, the degree that the stowed value in the frequency bin (bin) of FFT output causes the phase place rotation changes.The channel-estimator of back and gatherer can be handled these variations, thereby acquisition time is further elongated the sizable processing power of needs.
Therefore, be desirable to provide the technology of avoiding or alleviating the lock-out pulse of the problems referred to above at least that produces.
Summary of the invention
Situation of the present invention is documented in the scope of additional claim.
According to an aspect of the present invention; provide a kind of character boundary that produces the ofdm signal that expression comprises the significant character cycle that is spaced apart by protection the method for lock-out pulse; comprise step: a part of corresponding the data in the data in each protection at interval and each effective period; the signal of expression by the degree of correlation between the sampling of the received signal of separating corresponding to the cycle of the live part of symbol is provided; thus; signal provides expression to confirm as the output at relevant interval intentionally in each symbol; but also comprise and determine the degree of correlation that in described interval, changes, thereby detecting the maximal correlation degree wherein appears and son at interval with this son at interval in the step of supply lock-out pulse.
In another kind of situation, produce lock-out pulse by supplying with expression by the signal of the degree of correlation between the sampling of the received signal of separating corresponding to the cycle of the live part of symbol, this signal supply schedule is shown in the output at the relevant interval of having confirmed to have a mind to therebetween then, the lock-out pulse production method comprise son that the maximal correlation degree wherein appears in judgement at interval with this son at interval in the step of supply lock-out pulse.
Under the situation that multichannel is disturbed, it is maximum by all after dates corresponding to protection repetition at interval that the degree of correlation is judged as width.This is the optimal cycle of lock-out pulse that produces, even its reason is to follow different the delay and when receiving same-sign, can guarantee that also each fourier transform windows only comprises the sampling from monadic symbols.Utilize technology of the present invention, check the output of the device that is relative to each other, judge the time that the above-mentioned the most suitable cycle occurs.
In the most preferred embodiment, the output of the device that is relative to each other is compared with threshold value, and regulation should produce the best son in the cycle of lock-out pulse and be represented by the cycle that the output of the device that is relative to each other exceeds described threshold value at interval.Better, be more preferably maximum level defined threshold based on correlator output corresponding to the output change threshold value of the device that is relative to each other.
As independently aspect of the present invention, can see the utilization of threshold value.In this aspect, consideration applies the output of expression by the correlator of the degree of correlation between the sampling of the received signal of the sampling interval separation of defined amount to level detector, and only the signal section of (preferably variable) level of overshoot is assigned to the time that other unit should produce lock-out pulse.
Random time in the window of hope expression maximal correlation, for example this window middle part also can produce commutator pulse.During signal conditions change, this moment point also moves, and this moment, lock-out pulse was in response to this variation.But in the most preferred embodiment, the timing of lock-out pulse only just changes when satisfying certain condition.When for example, only confirming that current timing only has the error of stated number object time and/or only just change regularly during error current overshoot amount.As independently invention situation, by this technology, with to each variation and different angles produces the phase place rotation of each carrier wave of the output of FFT, thereby avoided on original channel-estimator, producing the too much variation of timing of the Fourier transform action of the homework burden that repeats.
Under another kind of situation of the present invention, the device that each sampling of FFT output is applied different phase place rotations is configured in the output of FFT, this device puts on the signal of the amount of movement of lock-out pulse corresponding to the indicating impulse generator, the amount of the phase place rotation that other unit applies.Therefore, can be according to circumstances or the moment utmost point timing that promptly compensates lock-out pulse change.Apply the phase place rotation by the circuit that disposes between FFT and channel-estimator and gatherer, perhaps channel-estimator and gatherer apply the phase place rotation.Better form the timing variation (according to above-mentioned state) that produces lock-out pulse with less frequency, be more preferably, only produce ormal weight usually.Thus, promote in FFT output, to apply determining of suitable phase place rotation.These phase place rotations can be calculated corresponding to the signal of the actual of the timing of representing lock-out pulse or the degree of predicting.Based on such signal, can derive from the search list of address appointment.
Under the situation of described prior art, the output of correlator is for example used the sliding window summation averaging device from up-to-date Ng the addition of sampling of the device that is relative to each other is come filtering.But this filtering technique changes the shape of the output of correlator, and therefore in most preferred embodiment of the present invention, the sampling by the up-to-date L1 of addition is to the output filtering of the device that is relative to each other, but L1 is more much smaller than Ng.
The signal that the output of taking-up sliding window summation averaging device handles, provides frequency to do to revise slightly is a kind of known technology.This technology is preferably also used in device according to the present invention.But, calculate for realizing more accurate frequency, in the most preferred embodiment of the present invention, in the output of first filter, add second filter, produce expression and do the average output of addition with the number of samples more much more than L1.For example, output can be to be equivalent to the output that should obtain from the single filter of Ng up-to-date sampling of addition.
According to a further aspect in the invention, a kind of lock-out pulse generating means is provided, the method that is used for above-mentioned generation lock-out pulse produces lock-out pulse, this lock-out pulse generating means comprises: be used to provide the device of expression by the signal of the degree of correlation between the sampling that separates received signal corresponding to the cycle of symbol live part, thereby this signal provides expression to confirm as the output at relevant interval intentionally in each symbol; Be used to determine the degree of correlation that in described interval, changes, thus detect the maximal correlation degree wherein appears and son at interval with this son at interval in the device of supply lock-out pulse.
According to a further aspect in the invention, also provide a kind of method of the ofdm signal of decoding, the method comprising the steps of: receive ofdm signal; Use the method for above-mentioned generation lock-out pulse to produce a lock-out pulse; Use described lock-out pulse that a fast fourier transform is applied to from the device of the compound sampling of ofdm signal derivation.
According to a further aspect in the invention, also provide a kind of OFDM receiver, it comprises: the device that is used to receive ofdm signal; A kind of lock-out pulse generating means, be used for producing lock-out pulse according to the method for above-mentioned generation lock-out pulse, this lock-out pulse generating means comprises: be used to provide the device of expression by the signal of the degree of correlation between the sampling that separates received signal corresponding to the cycle of symbol live part, thereby this signal provides expression to confirm as the output at relevant interval intentionally in each symbol; Be used to determine the degree of correlation that in described interval, changes, thus detect the maximal correlation degree wherein appears and son at interval with this son at interval in the device of supply lock-out pulse; Be used to use described lock-out pulse that a fast fourier transform is applied to from the device of the compound sampling of ofdm signal derivation.
Accompanying drawing summary explanation
Fig. 1 is the block diagram according to OFDM receiver of the present invention;
Fig. 2 is a key diagram of simply representing ofdm signal;
Fig. 3 is the block diagram that is used to produce the existing device of lock-out pulse;
Fig. 4 simply is illustrated in the key diagram that applies the effect of multichannel interference in the output that is relative to each other;
Fig. 5 is the block diagram of synchronous circuit of the present invention;
Fig. 6 is the block diagram of timing recovery circuit that forms the part of synchronous circuit;
Fig. 7 is the key diagram of expression from the part of the reference waveform of the output derivation of being correlated with, and this part occupies the son interval of the lock-out pulse of portion's most probable generation within it;
Fig. 8 is the figure of variation of 3 values of expression Ns, L1, L2.
Embodiment
With reference to figure 1, OFDM receiver 2 disposes received signals, sends the antenna 4 of described signal to the low-converter 6 that is the IF signal to RF signal transformation.Then it is transformed to baseband signal by IF base band frequency converter 8.This frequency converter produces the compound sampling of each OFDM symbol that sends in its output.These compound samplings are sent to fast Fourier transform (FFT) circuit 14 by 10 digitlizations of modulus (A/D) transducer through frequency tuning circuit 12.Fft circuit 14 becomes frequency domain to sampling from time domain, and the symbol data of output is sent to phase rotation device 15, channel-estimator and gatherer 16 and decoder 17.
According to technology of the present invention,, promote to realize not relying on the positive feedback system of feedback or phase-locked loop for adjusting local oscillator frequency.But, in other structures, wish the aforesaid feedback of configuration, synchronous circuit 18 can be in response to for example from the compound sampling of modulus (A/D) transducer 10 and/or from the signal of channel-estimator and gatherer 16.
Compound sampling is delivered to Symbol Synchronization Circuit 20, and this circuit produces the frequency offset signal of frequency tuning circuit 12 and the lock-out pulse that is used by fast Fourier transform (FFT) circuit 14.On the fft circuit 14 lock-out pulse must be arranged, so that each conversion action is consistent with the starting position of OFDM symbol.
Above-mentioned circuit all is that prior art is known except that phase rotation device 15.The present invention is relevant with the technology novel, invention that Symbol Synchronization Circuit 20 is used especially.
With reference to figure 2 (a), set the OFDM symbol and constitute by Nu+Ng sampling with Nu sampling in the live part U of the expression signal headed by Ng the sampling in the G of protection interval.Protection at interval Ng the sampling (each symbol is all represented with hacures) in the G comprises last Ng identical data of sampling with the live part U of symbol.
With reference to figure 3, in the synchronous circuit of prior art, supply with first-in first-out (FIFO) register 30 of the device 28 that is relative to each other continuously from the compound sampling of IF base band frequency converter 8.This register brings Nu corresponding sampling delay owing to comprise Nu part.The output of register 30 is sent to the complex conjugate circuit 32 of each unscented transformation for the correlator 28 of its complex conjugate.Then, with the multiplier 34 of correlator 28 each complex conjugate is multiplied by the sampling (or complex conjugate circuit 32 being inserted in the other path of multiplier 34) that postpones of not having from modulus (A/D) transducer 10.
Protection at interval the delay in the G the complex conjugate of sampling whenever be multiplied by the sampling of the equal value that derives from the terminal of the follow-up live part U of symbol, the output of correlator is located in high level.At other constantly, random value is used in the output of correlator.The output of Fig. 2 (b) expression correlator.In fact addition on average the stage after more carry out, be better understanding, the suitableeest output after a plurality of symbol additions of Fig. 2 (b) expression are average.
FFT is with Nu sampling action of the live part of signal.From Fig. 2; any time in can sampling last Ng of symbol (promptly; just be in the situation of high level at the waveform of Fig. 2 (b)) supply synchronizing signal t; and; because outfit protection G at interval means that Nu sampling of front is the sampling from same signal, ISI judges avoidance.
Fig. 4 represents the possibility of one of effect that multichannel is disturbed.The same signal that Fig. 4 (a) and Fig. 4 (b) expression different time receive, the signal that Fig. 4 (a) expression is more weak than the signal that receives at first in this case.
The output that the correlator of Fig. 3 was supplied with when there be not the signal of Fig. 4 (a) in the output that the correlator of Fig. 3 was supplied with when there was not the signal of Fig. 4 (b) in Fig. 4 (c) expression, Fig. 4 (d) expression.When two signals all existed, correlator produced the output of Fig. 4 (e) expression.(Fig. 4 this moment (c) is illustrated in to Fig. 4 (e) and carries out the average correlator output of addition on a plurality of symbols).
The waveform of Fig. 4 (e) has 3 parts 101,102 and 103.These parts represent that by the relevant set of having a mind between the value of being separated by the sampling of the Nu in one or two signal the output of correlator is in the interval of high level.Be careful part 102 from last Ng sampling of the symbol of signal 4 (a) as with last Ng the unique part of the waveform of appearance simultaneously of sampling of the symbol of signal 4 (b).Therefore, son interval 102 is to avoid ISI can supply with unique interval of timing signal simultaneously.
But the output of correlator is during by the existing circuit integration of Fig. 3, and output becomes the output shown in Fig. 4 (f).The peak value of this output occurs in the terminal of part 103, and the meaning is at the latest in this position.Especially, mean that FFT14 only handles the sampling from the symbol i of the signal of Fig. 4 (b), additional treatments is from the sampling of the symbol i+1 of the signal of Fig. 4 (a).
With reference to figure 5, the synchronous circuit 20 of embodiments of the invention is same with the existing device of Fig. 3, is equipped with the correlator 28 that is formed by shift register 30, complex conjugate circuit 32 and multiplier 34.Summation averaging device 46 is delivered in the output of correlator 28, and it can be the fifo register identical with the existing device of Fig. 3, but this moment, the part number equals the L1 than Ng much less.Symbol summation averaging device 48 is delivered in the output of FIFO46, and it is for corresponding to carrying out addition from the sampling of Ns symbol before each sampling of FIFO 46.Therefore, the output of symbol addition averager equals the sample output of the correlator make summation averaging with L1 sampling and Ns.Under the multichannel disturbed condition shown in Figure 4, output is level and smooth slightly because of the summation averaging of L1, but similar with the waveform shown in Fig. 4 (e).
Then timing recovery circuit 50 is delivered in output.This supplies with FFT14 with synchronizing signal.
Simply represent by the block diagram of Fig. 6 by the function that timing recovery circuit 50 is carried out.Deliver to absolute value circuit 52 from the sampling of signal summation averaging device 48 outputs.Absolute value circuit 52 calculates the absolute value of each sampling, i.e. (x
2+ y
2)
1/2These are checked (wherein x and y are the homophases of sampling and refer to the quadrature phase composition) by the peak detector 54 of judging peaked sampling.Window produces circuit 56 in response to judging the most close sampling of conduct less than the peak value both sides of 0.75 times the threshold value that is equal to peak value from the sampling of absolute value circuit 52 with by the peak value that circuit 54 detects.Thus, window produces circuit 56 and detects the n of the highest degree of correlation that expression comes the signal of autocorrelator
MinTo n
MaxSample range.Fig. 7 illustrates the reference waveform from the sampling of symbol summation averaging device 48 of expression in this cycle.From n
MinTo n
MaxThe timing signal that produces of cycle may be applicable to and avoid ISI.
The comparator 60 relatively time and the window of this timing signal for generating produces the n that circuit 56 is judged
MinTo n
MaxThe sampled value scope.When big difference is arranged very, the value of change storage on counter circuit 62.When one of several values of storage reaches defined threshold on counter circuit 62, being used for the scope n that depends on 56 calculating of window generation circuit is only adjusted in the timing of synchronizing signal
MinTo n
MaxThe signal of amount deliver to signal generator 58.Device is constituted as: at sampling n
MinAnd n
MaxBetween roughly in the middle of the place produce timing signal, but only have with current timing signal continuous and/or adjust during sizable error.
Among this embodiment, comparator 60 as shown in Figure 7, for increasing number of samples, n
MinTo n
MaxScope be divided into 4 quadrant, i.e. q1, q2, q3 and q4.Comparator 60 judges that initial " early " register in the counter 62 only increased by 1 when the current timing of lock-out pulse was in q1.When judging timing signal and being in q4, " late " register of second only increases by 1.Judge when regularly being in q2 or q3, two registers all only deduct 1, but are not less than 0.Any time, any counter reached at 4 o'clock, counter circuit 62 moves only such amount to the commutator pulse that signal generator 58 produces, this amount is corresponding to additional smoothly (n on for hithermost 4 samplings of next symbol (perhaps for the further processing that illustrates later has the more time, for example being the symbol after the leaning on of second or the 3rd regulation that follow-up signal is such)
Max-n
Min)/4.Commutator pulse is a counter or slow counter moves to direct motion direction or retrograde direction early in response to what reach 4 value.
Other register correspondences of counter circuit 62 are in regularly whether being positioned at scope n
MinTo n
MaxOutside increase or reduce.When producing this situation on continuous 4 cycles, counter circuit 62 carries out initialization action.
When retuning new office or the result of this initialization action of carrying out after the energized signal generator 58 is set at n
MinAnd n
MaxCentre position place produce timing signal.Also can comprise the change filter characteristic in the initialization action, as described later.
The timing that each signal generator 58 moves lock-out pulse, the output of FFT14 produce the out of phase rotation of carrier wave.For promoting this processing, counter circuit 62 outputs of timing recovery circuit 50 are illustrated in the signal of the change amount that applies on the lock-out pulse, and this signal is received by phase rotation device 15.Phase rotation device 15 comprises search list, the precalculated phase place rotation that this table storage is corresponding with the probable value of the signal indication of origin self-timing restore circuit 50.Therefore, when receiving this signal, derive appropriate value, and each compound sampling in the FFT output is only adjusted corresponding amount from search list.As its alternative method, phase rotation device 15 can comprise the device that rotates in response to from the calculated signals phase place of timing recovery circuit 50.The reason that the adjustment of phase place promotes is:
(a) timing recovery circuit 50 produce the adjustment amount of expression lock-out pulses signal,
(b) as previously mentioned, timing recovery circuit constitute with less frequency adjust,
(c) adjustment amount of level and smooth appended synchronization pulse, reduce thus the different adjustment in the timing that may be applied to lock-out pulse number,
(d) timing recovery circuit can specify in advance the timing variable effect that is subjected to lock-out pulse initial symbol,
(e) owing to only after timing recovery circuit 50 detects ejusdem generis continuous timing error, carry out adjustment regularly, wish in advance, for example judging that carrying out suitable phase place rotation when only having 1 or 2 symbols that timing error is arranged determines, can have more time be used for action,
(f) the change calculated in advance that applies also is stored in the search list.
With reference to figure 5, the output of fifo register 46 also is sent to has conduct other fifo registers 64 to the function of the sliding window summation averaging device of L2 continuous sampling group addition again.Sampling rate divided by F1, addition L2 up-to-date sampling.The best actual Ng that equals of L1XL2.The existing addition averager 36 of these 2 summation averaging devices 46 and 64 the circuit that is combined in the prior art that is equal to Fig. 3 on the function.Peak value searching circuit 66 is delivered in the output of summation averaging device 64, the maximum sampling of this electric circuit inspection size, and derive the angle of this sampling, it draws the reckoning value of small frequency shift (FS).Then, the signal of representing this frequency shift (FS) is sent to the frequency adjustment circuit 12 by the sampling phase rotation frequency of amendment that receives.
Among this embodiment, the successive value addition in 64 pairs of symbols of L2 summation averaging device is average, or it is average to carry out addition on (postponing correctly to obtain small frequency reckoning value) respective value in continuous symbol.
Receiver by power amplification or be tuned to during new office, wish to pin as far as possible apace new signal.This handles preferably the sign-on from initial reception.At this moment, the value of Ns, i.e. the symbolic number that symbol addition averager 48 is considered begins with 1, thereby owing to avoided the undue long-term interval of considering that signal changes betwixt, make and not allow described value is brought up to more than the smaller number (for example 8), then can increase on the symbol of each new reception.
Because Ns from minimum value, then increases, wish to change in the starting stage value of L1 and L2.L1 is preferably from bigger value (certainly most can be compared to Ng the most much smaller), and its reason is, as not like this, and Ns value hour, the output of L1 summation averaging device becomes irregular excessively easily.For example L1 is set at 64, on the other hand, makes Ns equal at 1 o'clock, for the synchronizing signal of first symbol, obtain the first good timing reckoning value.When L1 is set in bigger value at first, preferably L2 is set for little value, to make compensation.
The table of Fig. 8 represents that these values are the examples how to change.
The 9th and the value of later symbol be retained in the value of the 8th symbol.
It is not only effective in disturbing about the simple multichannel of Fig. 4 explanation to understand the present invention, also is effective at signal under received other states in the path more than 2.Under this environment, the waveform of Fig. 4 (e) becomes more complicated trapezoidal wave.But, under the situation that expands into the whole protection gap periods of repetition that postpones, can use technology of the present invention to judge corresponding to the window that should produce synchronizing signal.
With reference to the cycle of the existence at the top that is in symbol protection repetition at interval, shown in the situation of above-mentioned embodiment, notice that this may not be the time that is fit to produce synchronizing signal.In the foregoing description, degree of overlapping with repeating data is arranged corresponding to the cycle that should send signal.The selection of appropriate intervals is subjected to a plurality of factor affecting, should regard protection as the top of signal or terminal and (as above-mentioned embodiment) at interval as whether and whether use the terminal that is used for the regulation symbol period but not the timing signal at top.What more should note a bit is that above-mentioned explanation is not consider the delay of for example FIFO summation averaging device 46 generations.In the above-described embodiments, in fact, owing to consider this delay, preferably carry out and-(L1)/2 the corresponding correction of sampling.
In the foregoing description, multiply by 1 sampling by complex conjugate and make the sampling at interval in sampling period of spaced apart only Nu relevant with other samplings.Other structures also can.For example, such as the other side all British patent BPA9920446.3 number (Britain attorney docket J00041703GB) the record, correlator operates by the difference of taking out by the absolute value of the sampling of Nu sampling period separation.
Window for regulation is carried out the sampling of fast fourier transform has so far illustrated the present invention with the OFDM receiver structure that uses lock-out pulse.But the present invention uses in other environment of the lock-out pulse on the border that the expression symbol must be arranged.For example, such pulse is effective in the transponder that does not carry out complete FFT demodulation.
One of the hardware of the functional part available dedicated of being put down in writing here or software are implemented.
As mentioned above; because the lock-out pulse production method relevant with the present invention is a kind of method of lock-out pulse that produces the character boundary of the ofdm signal that expression comprises the significant character cycle that is spaced apart by protection; comprise step: a part of corresponding the data in the data in each protection at interval and each effective period; the signal of expression by the degree of correlation between the sampling that separates received signal corresponding to the cycle of symbol live part is provided; thus; signal provides expression to confirm as the output at relevant interval intentionally in each symbol; but also comprise son that the maximal correlation degree wherein appears in judgement at interval supplying with the step of lock-out pulse at this son at interval, so realization comprises the reduction of the reduction in processing time and the processing power of acquisition time when avoiding intersymbol interference (ISI).
Claims (16)
1. the method for the lock-out pulse of a character boundary that produces the ofdm signal that expression comprises the significant character cycle of being separated at interval by protection; each protects a part of corresponding of interior data of interior at interval data and each effective period; the method comprising the steps of: the signal of expression by the degree of correlation between the sampling of the received signal of separating corresponding to the cycle of symbol live part is provided; thus; signal pin provides expression wherein to confirm as the output at significant relevant interval to each symbol; but also comprise and determine the degree of correlation that in described interval, changes, thereby detecting the maximal correlation degree wherein appears and son at interval with this son at interval in the step of supply lock-out pulse.
2. according to the method for claim 1, it is characterized in that by the signal applicable threshold of the expression degree of correlation is judged described son at interval.
3. according to the method for claim 2, it is characterized in that described threshold value is variable.
4. according to the method for claim 3, it is characterized in that described threshold value represents to depend on the peaked value of the signal of the expression degree of correlation.
5. according to the method for aforementioned any one claim; it is characterized in that representing that signal quilt before utilizing the signal of judging described son interval of the described degree of correlation is average; should on average in fact make each by the mean value of the continuous sampling of average output sampled representation defined amount, the number of samples in the described defined amount actual specific protection at interval be few.
6. according to the method for claim 5, it is characterized in that the average output of described quilt is illustrated in the average value of addition on a plurality of symbols.
7. according to the method for claim 6, when it is characterized in that number that the average output of described quilt is added average symbol increases in collection phase, for on average adjusting so that reduce number of samples continuous in the described collection phase, by by the mean value of the described continuous number of samples of average each output sampled representation.
8. according to claim 5,6 or 7 method, it is characterized in that handling before the average output of described quilt, average again, so that the signal of the accurate frequency shift (FS) of expression to be provided.
9. according to the method for aforementioned any one claim, it is characterized in that comprising the step of only when the error overshoot threshold value that current timing is calculated, adjusting the timing of lock-out pulse.
10. according to the method for aforementioned any one claim, it is characterized in that comprising and only on the symbol period of defined amount, judge the step of adjusting the timing of lock-out pulse when having that the symbol period of defined amount is more than 1 because of the error due to the current timing.
11., it is characterized in that the amount of the timing adjustment of lock-out pulse corresponding to a plurality of sampling periods according to the method for aforementioned any one claim.
12. the method for the ofdm signal of decoding, the method comprising the steps of:
Receive ofdm signal;
Use the described method of aforementioned arbitrary claim to produce a lock-out pulse;
Use described lock-out pulse a fast fourier transform to be applied to the compound sampling of deriving from ofdm signal.
13., it is characterized in that also comprising step according to the method for claim 12: when the timing of lock-out pulse changes, provide the signal of expression intensity of variation, to conversion sampling apply the phase place rotation of determining by this signal.
14., it is characterized in that the rotation of described phase place determined by the value of the search list of address appointment according to the signal of the intensity of variation of the timing of expression lock-out pulse according to the method for claim 13.
15. lock-out pulse generating means, be used for producing lock-out pulse according to the method for one of claim 1 to 11, this lock-out pulse generating means comprises: be used to provide the correlator of expression by the signal of the degree of correlation between the sampling of the received signal of separating corresponding to the cycle of symbol live part, thereby this signal provides expression to confirm as the output at significant relevant interval in each symbol; Be used to determine the degree of correlation that in described interval, changes, thus detect the maximal correlation degree wherein appears and son at interval device and this son at interval in the synchronous generator of supply lock-out pulse.
16. an OFDM receiver comprises:
Be used to receive the device of ofdm signal;
A kind of lock-out pulse generating means, be used for producing lock-out pulse according to the method for one of claim 1 to 11, this lock-out pulse generating means comprises: be used to provide the correlator of expression by the signal of the degree of correlation between the sampling of the received signal of separating corresponding to the cycle of symbol live part, thereby this signal pin provides expression wherein to confirm as the output at significant relevant interval to each symbol; Be used to determine the degree of correlation that in described interval, changes, thus detect the maximal correlation degree wherein appears and son at interval device and this son at interval in the synchronous generator of supply lock-out pulse;
Be used to use described lock-out pulse that a fast fourier transform is applied to from the fast Fourier transform circuit of the compound sampling of ofdm signal derivation.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9920447A GB2353681B (en) | 1999-08-27 | 1999-08-27 | OFDM frame synchronisation |
| GB9920447.1 | 1999-08-27 | ||
| DE10063990A DE10063990B4 (en) | 1999-08-27 | 2000-12-21 | OFDM frame synchronization |
Related Child Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNA200510078514XA Division CN1694445A (en) | 1999-08-27 | 2000-08-24 | Synchronizing pulse generating method and method of receiving OFDM signal |
| CNA2005100785154A Division CN1694446A (en) | 1999-08-27 | 2000-08-24 | Synchronizing pulse generating method and method of receiving OFDM signal |
Publications (2)
| Publication Number | Publication Date |
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| CN1336001A CN1336001A (en) | 2002-02-13 |
| CN1214437C true CN1214437C (en) | 2005-08-10 |
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| Application Number | Title | Priority Date | Filing Date |
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| CNB008024278A Expired - Lifetime CN1214437C (en) | 1999-08-27 | 2000-08-24 | Synchronizing pulse generating method and method of receiving OFDM signal |
Country Status (4)
| Country | Link |
|---|---|
| CN (1) | CN1214437C (en) |
| DE (1) | DE10063990B4 (en) |
| GB (3) | GB2353681B (en) |
| WO (1) | WO2001017150A1 (en) |
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|---|---|---|---|---|
| JP3789275B2 (en) * | 2000-02-28 | 2006-06-21 | 三菱電機株式会社 | Subcarrier frequency signal demodulator |
| GB2364866B (en) * | 2000-07-12 | 2004-05-19 | Conexant Systems Inc | Television receiver |
| ATE345618T1 (en) | 2001-03-09 | 2006-12-15 | Flarion Technologies Inc | METHOD FOR SYMBOL TACT SYNCHRONIZATION IN COMMUNICATION SYSTEMS |
| US7206367B1 (en) * | 2001-07-10 | 2007-04-17 | Sigmatel, Inc. | Apparatus and method to synchronize multimedia playback over a network using out-of-band signaling |
| GB2419263B (en) * | 2002-07-05 | 2006-10-18 | British Broadcasting Corp | OFDM receivers |
| EP1469647B1 (en) * | 2003-04-17 | 2007-01-10 | Mitsubishi Electric Information Technology Centre Europe B.V. | OFDM symbol synchronisation |
| GB2417864A (en) | 2004-09-01 | 2006-03-08 | Univ Bristol | Determining time of receipt of a signal on the basis of a falling edge of a derivative of a correlation function |
| US7425778B2 (en) | 2005-04-14 | 2008-09-16 | Schweitzer Engineering Laboratories, Inc. | Apparatus and method for compensating secondary currents used in differential protection to correct for a phase shift introduced between high voltage and low voltage transformer windings |
| US7602852B2 (en) | 2005-04-21 | 2009-10-13 | Telefonaktiebolaget L M Ericsson (Publ) | Initial parameter estimation in OFDM systems |
| CN101563900B (en) * | 2006-10-16 | 2012-07-18 | 皇家飞利浦电子股份有限公司 | Method for determining symbol synchronization information for OFDM signals and device thereof |
| CN103888154B (en) * | 2014-03-31 | 2017-10-20 | 四川九洲空管科技有限责任公司 | A kind of multichannel is anti-interference with anti-aliasing pulse train coding/decoding method |
| CN104361383A (en) * | 2014-10-31 | 2015-02-18 | 上海复亚微电子有限公司 | Decoding method for FM0 (bi-phase space coding) of ultrahigh-frequency RFID (radio frequency identification) reader and writer |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SE514986C2 (en) * | 1995-03-01 | 2001-05-28 | Telia Ab | Method and device for synchronization with OFDM systems |
| GB2306084B (en) * | 1995-10-30 | 2000-02-16 | British Broadcasting Corp | Correlation of OFDM signals |
| EP0772332A3 (en) * | 1995-11-02 | 2000-10-11 | British Broadcasting Corporation | Synchronisation of OFDM signals |
| GB2307155B (en) * | 1995-11-02 | 1999-09-15 | British Broadcasting Corp | Synchronisation of OFDM signals |
| CA2183140C (en) * | 1996-08-12 | 2001-11-20 | Grant Mcgibney | Ofdm timing and frequency recovery system |
| JPH10190610A (en) * | 1996-12-24 | 1998-07-21 | Fujitsu Ten Ltd | Receiver of multicarrier system |
| JPH10209998A (en) * | 1997-01-20 | 1998-08-07 | Sony Corp | Demodulation device |
| JP3726856B2 (en) * | 1997-05-02 | 2005-12-14 | ソニー株式会社 | Receiving apparatus and receiving method |
| GB2361157B (en) * | 1997-05-02 | 2001-12-05 | British Broadcasting Corp | Improvements to OFDM symbol synchronization |
| FR2764143A1 (en) * | 1997-05-27 | 1998-12-04 | Philips Electronics Nv | METHOD FOR DETERMINING A SYMBOL TRANSMISSION FORMAT IN A TRANSMISSION SYSTEM AND SYSTEM |
| EP0915597B1 (en) * | 1997-11-05 | 2007-02-14 | Sony Deutschland GmbH | Synchronisation of digital communication systems |
| JP3981898B2 (en) * | 1998-02-20 | 2007-09-26 | ソニー株式会社 | Signal receiving apparatus and method, and recording medium |
| FI106592B (en) * | 1998-05-07 | 2001-02-28 | Nokia Multimedia Network Termi | Method and arrangement to achieve and maintain symbol synchronization especially in an OFDM system |
| EP1041790B1 (en) * | 1999-03-30 | 2004-11-24 | Nec Corporation | Symbol timing recovery for OFDM demodulator |
| US7058002B1 (en) * | 1999-04-22 | 2006-06-06 | Nippon Telegraph And Telephone Corporation | OFDM packet communication receiver |
| EP1063824B1 (en) * | 1999-06-22 | 2006-08-02 | Matsushita Electric Industrial Co., Ltd. | Symbol synchronisation in multicarrier receivers |
-
1999
- 1999-08-27 GB GB9920447A patent/GB2353681B/en not_active Expired - Lifetime
- 1999-08-27 GB GB0208805A patent/GB2373693B/en not_active Expired - Lifetime
- 1999-08-27 GB GB0208803A patent/GB2373692C/en not_active Expired - Lifetime
-
2000
- 2000-08-24 WO PCT/JP2000/005704 patent/WO2001017150A1/en active Application Filing
- 2000-08-24 CN CNB008024278A patent/CN1214437C/en not_active Expired - Lifetime
- 2000-12-21 DE DE10063990A patent/DE10063990B4/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| CN1336001A (en) | 2002-02-13 |
| GB2353681B (en) | 2003-01-15 |
| GB9920447D0 (en) | 1999-11-03 |
| GB2373693A (en) | 2002-09-25 |
| GB0208803D0 (en) | 2002-05-29 |
| GB2373692A (en) | 2002-09-25 |
| DE10063990B4 (en) | 2011-08-11 |
| GB2353681A (en) | 2001-02-28 |
| GB2373693B (en) | 2003-01-15 |
| DE10063990A1 (en) | 2002-06-27 |
| GB0208805D0 (en) | 2002-05-29 |
| WO2001017150A1 (en) | 2001-03-08 |
| GB2373692B (en) | 2003-01-15 |
| GB2373692C (en) | 2007-12-31 |
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