CN102571646A - Timing estimation and adjustment method and device in OFDM (Orthogonal Frequency Division Multiplexing) system - Google Patents
Timing estimation and adjustment method and device in OFDM (Orthogonal Frequency Division Multiplexing) system Download PDFInfo
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Abstract
The invention discloses a timing estimation and adjustment method and device in an OFDM (Orthogonal Frequency Division Multiplexing) system. According to the method, in a method for determining the timing position, a mode that a position of a tap, which is greater than a certain threshold, is forwards found instead of a traditional mode that a maximum position of the tap is used. According to the method, the timing positions of special fading channels can be found more accurately but for general fading channels, the tap meeting the conditions cannot be forwards found generally; and at the same time, the method for determining the timing position is consistent with a traditional method. Therefore, according to the timing estimation and adjustment method and device disclosed by the invention, the timing positions of channels with higher time varying speed or special channel models can be found, and thus the positioning accuracy of the timing positions can be increased.
Description
Technical field
The present invention relates to a kind of OFDM timing estimation and adjustment technology
Background technology
In the last few years, received people's extensive concern with OFDM (Orthogonal Frequency Division Multiplexing is called for short " OFDM ") for the multi-carrier transmission technology of representative.The main thought of OFDM is to convert high-speed data signal to parallel low speed sub data flow, is modulated to subsequently on the subcarrier of each quadrature to transmit.Under the ideal situation, the signal on each orthogonal sub-carriers can mutual interference.Signal bandwidth on each subcarrier is less than the correlation bandwidth of channel, so the bandwidth on each subcarrier only is the sub-fraction of former channel width, and it is relatively easy that channel equalization becomes.Because OFDM technology spectrum efficiency is high, can easier tackle the intersymbol interference that multipath transmisstion causes, thereby in wireless mobile communications, obtained increasing application, and generally believed it is the core technology of following 4G.
Ofdm system is avoided intersymbol interference through introducing Cyclic Prefix (Cyclic Prefix is called for short " CP ").CP is exactly that last part data with each OFDM symbol copy to before this OFDM symbol, makes the intersymbol interference that multidiameter delay avoids multipath transmisstion to cause under the prerequisite less than the length of Cyclic Prefix.
The prerequisite of terminal and base station communication be obtain with the base station synchronously, the initial synchronisation of terminal and base station mainly is to accomplish through cell search process, accomplishes terminal after the initial synchronisation and also will continue to keep synchronous with the base station.Because moving of terminal, variation of channel condition or the like, the synchronized relation of terminal and base station possibly change at any time, so the terminal need estimate this synchronized relation at any time and in time adjust the timing at terminal, so just is unlikely step-out.
The ofdm system transmitting terminal is at first encoded data, carries out digital modulation then, after this data flow segmentation is gone here and there and changes; Every segment data is carried out contrary FFT (Inverse Fast FourierTransform; Be called for short " IFFT "), be transformed to time-domain signal to frequency-region signal, then carry out and go here and there conversion; Add CP simultaneously, send to communication channel through sending module then; Then opposite at receiving terminal; At first receive time-domain signal through receiver module; Then go CP, string and conversion, time-domain signal converted into frequency-region signal, carry out and go here and there processing such as conversion, digital demodulation, decoding at frequency domain afterwards through FFT (Fast FourierTransform, be called for short " FFT ").
Fig. 1 is the sketch map of OFDM frequency-region signal.Ofdm system base unit in time is the OFDM symbol, and the base unit on frequency is a subcarrier, and the least unit on time and the frequency is called Resource Unit (Resource Element is called for short " RE ").RS among Fig. 1 representes reference signal (Reference Signal is called for short " RS "), mainly is to be used for channel estimating, and a RS takies a RE.Usually, RS can be divided into two row on time domain: the 1st reference signal and the 2nd reference signal.The 1st reference signal is positioned at the 1st OFDM symbol of each time slot, and the 2nd reference signal is positioned at the 3rd OFDM symbol of inverse of each time slot; On frequency domain, generally per 6 number of sub-carrier are inserted a reference signal, and are as shown in Figure 1.
The FFT module is handled respectively each OFDM symbol.An OFDM symbol is seen from frequency domain and mainly comprised direct current subcarrier, effective subcarrier, empty subcarrier, and is as shown in Figure 2.Middle direct current subcarrier mainly is to be used to remove DC component, is not used for transmitting data, and effective subcarrier of both sides is used for transmitting data, and the empty subcarrier at two ends mainly is to be used for disturbing outside the isolation strip, does not also transmit data.
Prior art timing estimation method commonly used utilizes RS to realize; A kind of method is to utilize the phase difference of adjacent R S on the frequency domain to carry out timing estimation; The cardinal principle of this method is that to utilize timing offset on the time domain to be reflected on the frequency domain be exactly certain phase place rotation; But this method is difficult to accurately estimate regularly under multidiameter fading channel, mainly is that phase deviation information can not accurately reflect the timing offset of time domain again after the stack because different multidiameters causes out of phase rotation on the frequency domain.
Another kind method is to utilize the frequency domain channel of RS to estimate, transforms to time domain then, obtains the time domain channel impulse response, finds prominent tap in the time domain channel impulse response again, and position regularly, terminal is promptly thought in the position of this tap.And the method for regularly adjusting generally is according to the certain level and smooth or average reception timing of going receiver control afterwards of the timing process that estimates.
Because RS only effectively exists in the subcarrier scope; In empty subcarrier, do not exist; And before transforming to time domain, must obtain the channel estimating in the whole bandwidth, method commonly used at present is the method for approximate or interpolation; Promptly go the channel estimating at approximate empty subcarrier place, or utilize the method for interpolation to obtain the channel estimating at empty subcarrier place according to the channel estimating in the effective bandwidth with the channel estimating in the effective bandwidth.Because RS is spacedly distributed, therefore when obtaining the channel estimating at empty subcarrier place, still to go to obtain according to the interval of RS.
Specifically, above-mentioned frequency domain channel timing estimation and method of adjustment are as shown in Figure 3.Data cache module shown in Fig. 3 mainly is to be used for data cachedly, is the indispensable module of ofdm system and go CP and FFT module, mainly is to be used to remove Cyclic Prefix and to carry out fast Fourier transform.Mainly introduce timing estimation and regularly adjustment below.
Timing estimation method:
Method of estimation commonly used at present is least square method (Least Square; Be called for short " LS "); Obtain the channel estimating at each RS place in effective subcarrier through this method, i.e. the channel estimating located of
among Fig. 4.
Step 2, empty RS channel estimating are obtained:
Empty RS position; Promptly think the regularity of distribution according to normal RS; Also should transmit RS in empty subcarrier relevant position, locate shown in the position like
among Fig. 4.The channel estimating at empty RS place can use the channel estimating at the most contiguous RS place approximate, for example R ' among Fig. 4
N+1, R '
N+2Use R Deng the position
N-1The channel estimating at place is approximate, and R '
-1Use R Deng the position
0The channel estimating at place is approximate; Perhaps carry out interpolation, for example R ' with the channel estimating of closing on several RS place
N+1, R '
N+2Use R Deng the position
N-1, R
N-2... Channel estimating interpolation at the place obtains, and interpolation method can be linear interpolation, polynomial interopolation etc.
Step 3, RS extract:
Extract the channel estimating of RS place and empty RS place (empty RS place is meant the regularity of distribution according to RS, should be the position of RS in empty sub-carrier positions), obtain frequency domain sequence ..., R '
-2, R '
-1, R
0..., R
N-2, R
N-1, R '
N, R '
N+1..., the total length of sequence does
N wherein
FFTBe the length of FFT, δ
RSBe the frequency domain interval of RS, unit is the subcarrier number.
Step 4, IFFT:
To the sequence that obtains in the step 3 ..., R '
-2, R '
-1, R
0..., R
N-2, R
N-1, R '
N, R '
N+1... Carry out the IFFT conversion, obtain the time domain channel impulse response, { h
0, h
1, h
M-1}=IFFT{ ..., R '
-2, R '
-1, R
0..., R
N-2, R
N-1, R '
N, R '
N+1..., { h
0, h
1, h
M-1It is each tap of time domain channel impulse response.
Step 5, the maximum tap position of searching and output timing:
Calculate each tap power | h
0|
2, | h
1|
2, | h
M-1|
2,
The expression plural number is asked the mould operation, seeks prominent tap and corresponding position thereof, and timing position is promptly thought in this position.
The result who repeatedly measures is carried out level and smooth or average.
Timing adjusting method:
Go to adjust the timing of receiver according to level and smooth or averaged result.
The shortcoming of above-mentioned technology is:
1) this method according to the maximum power tap position as timing position; Become channel or some special channel models (for example giving birth to the model that goes out) faster during for some; The tap position of maximum power might not be real timing position; If according to the tap position timing of maximum power, possibly cause valid data too much to run out of the data processing window, thereby cause step-out always;
2) owing to estimate to exist all the time error; Therefore remove to adjust receiver according to the timing value of estimating and regularly also have certain error all the time, because ofdm system has adopted Cyclic Prefix, if the timing of therefore estimating shifts to an earlier date slightly; Then the data processing window can comprise portion C P and lose last partial data; Shown in Fig. 5 (a), because CP partly is the repetition of an OFDM symbol last part, therefore this situation is little to performance impact; If the opposite definite time delay of estimating, then the data processing window will be lost the partial data of front, but also can introduce the interference of next OFDM symbol, and shown in Fig. 5 (b), this moment is bigger to Effect on Performance.
When 3) channel estimating at RS place being transformed to time domain, because the frequency domain interval δ of RS
RSBe not necessarily 2 integral number power, thereby cause M also to be not necessarily 2 integral number power, so also just increased the computation complexity of IFFT.
Summary of the invention
The technical problem that the present invention mainly solves provides timing estimation and method of adjustment and device in a kind of ofdm system; Even if become channel or some special channel models faster when making for some; Also can find timing position exactly, improve the accuracy of timing position location.
In order to solve the problems of the technologies described above, the invention provides timing estimation and method of adjustment in a kind of ofdm system, comprise following steps:
Each reference signal place in effective subcarrier carries out channel estimating;
Each empty reference signal place in the empty subcarrier carries out channel estimating;
Extract the channel estimating at said each reference signal and empty reference signal place, obtain the frequency domain sequence of each channel estimating;
Resulting frequency domain sequence is carried out contrary FFT, obtain the time domain channel impulse response;
Calculate the power of each tap in the said time domain channel impulse response, seek prominent tap and corresponding position thereof, from the sampling point of N forward of this position, seek power and surpass α P
MaxThe most forward tap, with this tap position as timing position; Wherein N is greater than 0 length less than Cyclic Prefix, and α is a predetermined threshold value,, 0＜α＜1, P
MaxMaximum power for said each tap;
According to said timing position adjustment receiving terminal regularly.
As the improvement of technique scheme, this N can be 1/2 circulating prefix-length.
As the improvement of technique scheme, said each reference signal place of void in the empty subcarrier is carried out in the step of channel estimating,
Channel estimating, the approximate channel estimating that obtains said empty reference signal place with reference signal place in the most contiguous effective subcarrier of said empty reference signal; Perhaps
Reference signal place channel estimating interpolation obtains the channel estimating at said empty reference signal place at least two effective subcarriers that close on said empty reference signal.
As the improvement of technique scheme, said according to before the timing position adjustment receiving terminal step regularly, can also comprise following steps:
Said timing position is deducted a lead;
Said according in the timing position adjustment receiving terminal step regularly, according to the timing position adjustment receiving terminal that deducts lead regularly.
As the improvement of technique scheme, said lead is generally 1/32 to 1/4 of circulating prefix-length.
As the improvement of technique scheme, in the step of the channel estimating at each reference signal of said extraction and empty reference signal place, the integral number power according to 2 is for extract the channel estimating at said each reference signal and empty reference signal place at interval.
Improvement as technique scheme; Said according in 2 integral number power the step for the channel estimating of extracting each reference signal and empty reference signal place at interval; If the integral number power according to 2 is not the position of reference signal for the position of extracting at interval, then use the channel estimating of the reference signal position nearest to replace apart from this position.
As the improvement of technique scheme, said according in 2 integral number power the step for the channel estimating of extracting each reference signal and empty reference signal place at interval, for the regular circulation prefix, saidly be spaced apart 8; For extended cyclic prefix, saidly be spaced apart 2.
As the improvement of technique scheme, this method can also also comprise following steps:
At least carry out twice channel estimation steps and calculate said timing position, said at least two timing positions that calculate are carried out level and smooth or average according to channel estimation results;
Said according in the timing position adjustment receiving terminal step regularly, according to said timing position adjustment receiving terminal after level and smooth or average regularly.
The present invention also provides timing estimation and adjusting device in a kind of ofdm system, comprises:
First channel estimation module is used for each reference signal place of effective subcarrier is carried out channel estimating;
The second channel estimation module is used for each empty reference signal place of empty subcarrier is carried out channel estimating;
Extraction module is used to extract the channel estimating at said each reference signal and empty reference signal place, obtains the frequency domain sequence of each channel estimating;
Contrary FFT module is used for resulting frequency domain sequence is carried out contrary FFT, obtains the time domain channel impulse response;
The timing position computing module is used for calculating the power of each tap of said time domain channel impulse response, seeks prominent tap and corresponding position thereof, from the sampling point of N forward of this position, seeks power and surpasses α P
MaxThe most forward tap, with this tap position as timing position; Wherein N is greater than 0 length less than Cyclic Prefix, and α is a predetermined threshold value, 0＜α＜1, P
MaxMaximum power for said each tap;
Timing adjustment module is used for the timing position adjustment receiving terminal timing of confirming according to said timing position computing module.
Embodiment of the present invention compared with prior art; The main distinction and effect thereof are: confirming the method for timing position, is not the position of the maximum tap of traditional use, but seeks the position greater than the tap of certain thresholding forward; This method can find timing position more accurately for some special fading channels; And to general fading channel, look for forward and generally can not find qualified tap, should confirm that the method for timing position was consistent with traditional method this moment.Even if become channel or some special channel models faster when therefore embodiment of the present invention is for some, also can find timing position exactly, improve the accuracy of timing position location.
Adjustment method regularly in the embodiment of the present invention; Not directly to remove to adjust receiving terminal regularly according to result regularly; But timing results is deducted the adjustment more afterwards of a fixing lead; This method can make full use of the effect of ofdm system Cyclic Prefix, further reduces the influence that possible timing error causes.If the timing that estimate this moment shifts to an earlier date slightly, then the data processing window can comprise portion C P and lose last partial data, because CP partly is the repetition of an OFDM symbol last part, therefore this moment is little to performance impact; If the definite time delay of estimating; Then can offset with the lead that is deducted; The data processing window can not lost the partial data of front equally; Effectively prevent to lose the interference of previous section data, the next OFDM symbol of introducing, avoid the considerable influence that therefore performance is produced because of the definite time delay of estimating.
When extracting the frequency domain channel estimation is not the channel estimating of directly extracting the RS place; But extract for the interval according to 2 integral number power; If extracting the position is not the position of RS; Then the channel estimating with the most contiguous RS position substitutes, and this method can more be simplified calculating when with IFFT frequency domain channel being estimated to transform to time domain, reduce amount of calculation.
Description of drawings
Below in conjunction with accompanying drawing and embodiment the present invention is done further explain.
Fig. 1 is the sketch map of OFDM frequency-region signal in the prior art;
Fig. 2 is the sketch map of an OFDM symbol on frequency domain in the prior art;
Fig. 3 is the structure drawing of device of timing estimation and adjustment in the prior art;
Fig. 4 is that empty subcarrier place channel estimating is obtained sketch map in the prior art;
Fig. 5 is the design sketch that regularly shifts to an earlier date or lag behind in the prior art;
Fig. 6 is timing estimation and a method of adjustment flow chart in the first embodiment of the invention ofdm system;
Fig. 7 is that first embodiment of the invention frequency domain channel estimating is extracted sketch map.
Embodiment
For making the object of the invention, technical scheme and advantage clearer, will combine accompanying drawing that execution mode of the present invention is done to describe in detail further below.
First embodiment of the invention relates to timing estimation and method of adjustment in a kind of ofdm system, and is as shown in Figure 6.Data cache module shown in the figure mainly is to be used for data cachedly, all is the indispensable module of ofdm system and go CP and FFT module, mainly is to be used to remove Cyclic Prefix and to carry out fast Fourier transform.Facing timing estimation and method of adjustment down specifically introduces.
In the step 601, each RS place in effective subcarrier is carried out channel estimating.Promptly obtain the channel estimating that
among Fig. 7 (a) locates.Method of estimation commonly used at present is a least square method.
In the step 602, each the empty RS place in the empty subcarrier is carried out channel estimating.In this execution mode, be defaulted as in the empty subcarrier with effective subcarrier in the same RS of existence, be called empty RS.The position distribution of empty RS in empty subcarrier is identical with RS position regularity of distribution in effective subcarrier; Promptly think the regularity of distribution according to normal RS; The position that also should transmit RS at empty subcarrier place,
in accompanying drawing 7 (a) locates shown in the position.
The channel estimating at empty RS place can be similar to the channel estimating at the most contiguous RS place and obtain.R ' among Fig. 7 (a) for example
N+1, R '
N+2Use R Deng the position
N-1The channel estimating at place is approximate, and R '
-1Use R Deng the position
0The channel estimating at place is approximate.
Perhaps, the channel estimating at empty RS place also can be carried out interpolation, for example R ' with the channel estimating of closing on several RS place
N+1, R '
N+2Use R Deng the position
N-1, R
N-2... Channel estimating interpolation at the place obtains, and interpolation method can be linear interpolation, polynomial interopolation etc.
In the step 603, the integral number power δ ' according to 2 is for extracting at interval the channel estimating at RS place and empty RS place, obtain frequency domain sequence ..., R "
-2, R "
-1, R "
0..., R "
N '-2, R "
N '-1, R "
N ', R "
N '+1... }, the total length of sequence does
N wherein
FFTBe the length of FFT, δ
RSBe the frequency domain interval of RS, unit is the subcarrier number.If for the position of extracting at interval is not the position of RS or empty RS, then use apart from the nearest RS in this position or the channel estimating of empty RS position to replace according to δ '.Like R in the accompanying drawing 7 (b) "
-1With R '
-1Replace R "
0Use R
0Replace R "
1Use R
1Replace ..., R "
N '-1With R '
NReplace or the like.Usually, to conventional CP, δ ' can get 8, and to expansion CP, δ ' can get 2.
Through directly not extracting the channel estimating at RS place when frequency domain channel is estimated extracting, but according to 2 integral number power for extracting at interval, make and when frequency domain channel being estimated to transform to time domain, can more simplify calculating, the minimizing amount of calculation with IFFT.
In the step 604, to the frequency domain sequence that obtains in the step 603 ..., R "
-2, R "
-1, R "
0..., R "
N '-2, R "
N '-1, R "
N ', R "
N '+1... } and carry out the IFFT conversion, obtain the time domain channel impulse response:
{h
0，h
1…，h
M-1}＝IFFT{...，R″
-2，R″
-1，R″
0，...，R″
N′-2，R″
N′-1，R″
N′，R″
N′+1，...}
{ h
0, h
1, h
M-1It is each tap of time domain channel impulse response.。
In the step 605, calculate each tap in the above-mentioned time domain channel impulse response power | h
0|
2, | h
1|
2, | h
M-1|
2, wherein
The expression plural number is asked the mould operation, seeks prominent tap and corresponding position thereof, and promptly maximum power is P
Max, correspondence position is L
MaxThe L from this position
MaxRise in N the sampling point forward, seek power and surpass α P
MaxThe most forward tap, this tap position is regarded as timing position.Wherein N is greater than 0 less than CP length, and preferred values does
τ
CPBe the length of CP, α is a predetermined threshold value, 0＜α＜1, common desirable 1/2.The above-mentioned process of seeking tap forward can be described below:
break；
}
}
Because when confirming timing position; Be not to use the position of traditional maximum tap, but seek the position greater than the tap of certain thresholding forward, this method can find timing position more accurately for some special fading channels; And to general fading channel; Look for forward and generally can not find qualified tap, should confirm that the method for timing position was consistent with traditional method this moment, even if become channel or some special channel models faster during therefore for some; Also can find timing position exactly, improve the accuracy of timing position location.
In practical application; Can repeatedly carry out channel estimating to each reference signal; And, promptly repeat above-mentioned steps 601 to step 605, in step 606 according to channel estimation results calculating timing position; The timing position that repeatedly calculates is carried out smoothly perhaps on average, obtain the timing position of finally confirming.
In the step 607, the final timing position of confirming in the step 606 is fixedly deducted a lead τ
A, τ
ACan be according to the difference of system bandwidth and difference, 1/32～1/4 of general desirable CP length.
In the step 608, according to deducting lead timing position adjustment receiving terminal afterwards in the step 607 regularly.
Owing to be not directly to remove to adjust receiving terminal regularly according to result regularly; But timing results is deducted the adjustment more afterwards of a fixing lead; This method can make full use of the effect of ofdm system Cyclic Prefix, further reduces the influence that possible timing error causes.If the timing that estimate this moment shifts to an earlier date slightly, then the data processing window can comprise portion C P and lose last partial data, because CP partly is the repetition of an OFDM symbol last part, therefore this moment is little to performance impact; If the definite time delay of estimating; Then can offset with the lead that is deducted; The data processing window can not lost the partial data of front equally; Effectively prevent to lose the interference of previous section data, the next OFDM symbol of introducing, avoid the considerable influence that therefore performance is produced because of the definite time delay of estimating.
Second embodiment of the invention relates to timing estimation and adjusting device in a kind of ofdm system, comprises: first channel estimation module is used for each reference signal place of effective subcarrier is carried out channel estimating; The second channel estimation module is used for each empty reference signal place of empty subcarrier is carried out channel estimating; Extraction module is used to extract the channel estimating at each reference signal and empty reference signal place, obtains the frequency domain sequence of each channel estimating; Contrary FFT module is used for resulting frequency domain sequence is carried out contrary FFT, obtains the time domain channel impulse response; The timing position computing module is used for calculating the power of each tap of time domain channel impulse response, seeks prominent tap and corresponding position thereof, from the individual sampling point of N (preferred values is 1/2 CP length) forward of this position, seeks power and surpasses α P
MaxThe most forward tap, with this tap position as timing position; Wherein N is greater than 0 length less than Cyclic Prefix, and α is a predetermined threshold value, 0＜α＜1, P
MaxMaximum power for each tap; Timing adjustment module is used for the timing position adjustment receiving terminal timing of confirming according to the timing position computing module.This predetermined threshold value can be 1/2.Through above-mentioned timing position computing module, even if become channel or some special channel models faster during for some, also can find timing position exactly, improve the accuracy of timing position location.
As the improvement of technique scheme, the second channel estimation module is carried out channel estimating to each reference signal place of the void in the empty subcarrier in the following manner:
Channel estimating, the approximate channel estimating that obtains empty reference signal place with reference signal place in the most contiguous effective subcarrier of empty reference signal; Perhaps, reference signal place channel estimating interpolation obtains the channel estimating at empty reference signal place at least two effective subcarriers that close on empty reference signal.
As the improvement of technique scheme, this device can also comprise and subtracts the lead module, is used for timing position is deducted a lead; Timing adjustment module according to the timing position adjustment receiving terminal that deducts lead regularly.This lead is generally 1/32 to 1/4 of circulating prefix-length.If the timing that estimate this moment shifts to an earlier date slightly, then the data processing window can comprise portion C P and lose last partial data, and is because CP partly is the repetition of an OFDM symbol last part, therefore little to performance impact; If the definite time delay of estimating; Then can offset with the lead that is deducted; The data processing window can not lost the partial data of front equally; Effectively prevent to lose the interference of previous section data, the next OFDM symbol of introducing, avoid the considerable influence that therefore performance is produced because of the definite time delay of estimating.
As the improvement of technique scheme, extraction module extracts the channel estimating at each reference signal and empty reference signal place according to 2 integral number power for the interval.If the integral number power according to 2 is not the position of reference signal for the position of extracting at interval, then use the channel estimating of the reference signal position nearest to replace apart from this position.For the regular circulation prefix, this interval can get 8; For extended cyclic prefix, this interval can get 2.This method can more be simplified calculating when with IFFT frequency domain channel being estimated to transform to time domain, reduce amount of calculation.
As the improvement of technique scheme, this device can also comprise level and smooth module.The timing position computing module calculates at least two timing positions according at least twice channel estimation results respectively, and this level and smooth module is used at least two timing positions that calculate are carried out level and smooth or average; Timing adjustment module according to the timing position adjustment receiving terminal after level and smooth or average regularly.
Though through reference some preferred implementation of the present invention; The present invention is illustrated and describes; But those of ordinary skill in the art should be understood that and can do various changes to it in form with on the details, and without departing from the spirit and scope of the present invention.
Claims (18)
1. timing estimation and method of adjustment in the orthogonal frequency division multiplex OFDM system is characterized in that, comprise following steps:
Each reference signal place in effective subcarrier carries out channel estimating;
Each empty reference signal place in the empty subcarrier carries out channel estimating;
Extract the channel estimating at said each reference signal and empty reference signal place, obtain the frequency domain sequence of each channel estimating;
Resulting frequency domain sequence is carried out contrary FFT, obtain the time domain channel impulse response;
Calculate the power of each tap in the said time domain channel impulse response, seek prominent tap and corresponding position thereof, from the sampling point of N forward of this position, seek power and surpass α P
MaxThe most forward tap, with this tap position as timing position; Wherein N is greater than 0 length less than Cyclic Prefix, and α is a predetermined threshold value, 0＜α＜1, P
MaxMaximum power for said each tap;
According to said timing position adjustment receiving terminal regularly.
2. timing estimation and method of adjustment in the ofdm system according to claim 1 is characterized in that, said N is 1/2 circulating prefix-length.
3. timing estimation and method of adjustment in the ofdm system according to claim 1 is characterized in that, said each reference signal place of void in the empty subcarrier carried out in the step of channel estimating,
Channel estimating, the approximate channel estimating that obtains said empty reference signal place with reference signal place in the most contiguous effective subcarrier of said empty reference signal; Perhaps
Reference signal place channel estimating interpolation obtains the channel estimating at said empty reference signal place at least two effective subcarriers that close on said empty reference signal.
4. timing estimation and method of adjustment in the ofdm system according to claim 1 is characterized in that, and be said according to before the timing position adjustment receiving terminal step regularly, also comprises following steps:
Said timing position is deducted a lead;
Said according in the timing position adjustment receiving terminal step regularly, according to the timing position adjustment receiving terminal that deducts lead regularly.
5. timing estimation and method of adjustment in the ofdm system according to claim 4 is characterized in that, said lead is 1/32 to 1/4 of a circulating prefix-length.
6. timing estimation and method of adjustment in the ofdm system according to claim 1; It is characterized in that; In the step of the channel estimating at each reference signal of said extraction and empty reference signal place, the integral number power according to 2 is for extract the channel estimating at said each reference signal and empty reference signal place at interval.
7. timing estimation and method of adjustment in the ofdm system according to claim 6; It is characterized in that; Said according in 2 integral number power the step for the channel estimating of extracting each reference signal and empty reference signal place at interval; If the integral number power according to 2 is not the position of reference signal for the position of extracting at interval, then use the channel estimating of the reference signal position nearest to replace apart from this position.
8. timing estimation and method of adjustment in the ofdm system according to claim 6; It is characterized in that; Said according in 2 integral number power the step for the channel estimating of extracting each reference signal and empty reference signal place at interval, for the regular circulation prefix, saidly be spaced apart 8; For extended cyclic prefix, saidly be spaced apart 2.
9. according to timing estimation and method of adjustment in any described ofdm system in the claim 1 to 8, it is characterized in that, also comprise following steps:
At least carry out twice channel estimation steps and calculate said timing position, said at least two timing positions that calculate are carried out level and smooth or average according to channel estimation results;
Said according in the timing position adjustment receiving terminal step regularly, according to said timing position adjustment receiving terminal after level and smooth or average regularly.
10. timing estimation and adjusting device in the ofdm system is characterized in that, comprise:
First channel estimation module is used for each reference signal place of effective subcarrier is carried out channel estimating;
The second channel estimation module is used for each empty reference signal place of empty subcarrier is carried out channel estimating;
Extraction module is used to extract the channel estimating at said each reference signal and empty reference signal place, obtains the frequency domain sequence of each channel estimating;
Contrary FFT module is used for resulting frequency domain sequence is carried out contrary FFT, obtains the time domain channel impulse response;
The timing position computing module is used for calculating the power of each tap of said time domain channel impulse response, seeks prominent tap and corresponding position thereof, from the sampling point of N forward of this position, seeks power and surpasses α P
MaxThe most forward tap, with this tap position as timing position; Wherein N is greater than 0 length less than Cyclic Prefix, and α is a predetermined threshold value, 0＜α＜1, P
MaxMaximum power for said each tap;
Timing adjustment module is used for the timing position adjustment receiving terminal timing of confirming according to said timing position computing module.
11. timing estimation and adjusting device is characterized in that in the ofdm system according to claim 10, said N is 1/2 circulating prefix-length.
12. timing estimation and adjusting device is characterized in that in the ofdm system according to claim 10, said second channel estimation module is carried out channel estimating to each reference signal place of the void in the empty subcarrier in the following manner:
Channel estimating, the approximate channel estimating that obtains said empty reference signal place with reference signal place in the most contiguous effective subcarrier of said empty reference signal; Perhaps
Reference signal place channel estimating interpolation obtains the channel estimating at said empty reference signal place at least two effective subcarriers that close on said empty reference signal.
13. timing estimation and adjusting device is characterized in that in the ofdm system according to claim 10, also comprise to subtract the lead module, are used for said timing position is deducted a lead;
Said timing adjustment module according to the timing position adjustment receiving terminal that deducts lead regularly.
14. timing estimation and adjusting device is characterized in that in the ofdm system according to claim 13, said lead is 1/32 to 1/4 of a circulating prefix-length.
15. timing estimation and adjusting device is characterized in that in the ofdm system according to claim 10, said extraction module extracts the channel estimating at said each reference signal and empty reference signal place according to 2 integral number power for the interval.
16. timing estimation and adjusting device in the ofdm system according to claim 15; It is characterized in that; Said extraction module is when extracting the channel estimating at each reference signal and empty reference signal place at interval according to 2 integral number power; If the integral number power according to 2 is not the position of reference signal for the position of extracting at interval, then use the channel estimating of the reference signal position nearest to replace apart from this position.
17. timing estimation and adjusting device is characterized in that in the ofdm system according to claim 15, for the regular circulation prefix, saidly are spaced apart 8; For extended cyclic prefix, saidly be spaced apart 2.
18., it is characterized in that according to timing estimation and adjusting device in any described ofdm system in the claim 10 to 17, also comprise level and smooth module,
Said timing position computing module calculates at least two said timing positions according at least twice channel estimation results respectively, and said level and smooth module is used for said at least two timing positions that calculate are carried out level and smooth or average;
Said timing adjustment module according to said timing position adjustment receiving terminal after level and smooth or average regularly.
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| CN104301087A (en) * | 2014-09-24 | 2015-01-21 | 重庆邮电大学 | Timing error correcting method for digital phase modulation signal |
| CN106878205A (en) * | 2015-12-10 | 2017-06-20 | 电信科学技术研究院 | A kind of timing offset method of estimation, device and terminal |
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