CN102571646B - 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
- Publication number
- CN102571646B CN102571646B CN201010606650.2A CN201010606650A CN102571646B CN 102571646 B CN102571646 B CN 102571646B CN 201010606650 A CN201010606650 A CN 201010606650A CN 102571646 B CN102571646 B CN 102571646B
- Authority
- CN
- China
- Prior art keywords
- timing
- reference signal
- channel estimating
- empty
- estimation
- 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
Landscapes
- Synchronisation In Digital Transmission Systems (AREA)
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, the Multicarrier Transmission Technology that was representative with OFDM (Orthogonal Frequency Division Multiplexing is called for short " OFDM ") has been subject to people's extensive concern.OFDM main thought is to convert high-speed data signal to parallel low speed sub data flow, is modulated to subsequently on each orthogonal subcarrier and transmits.Ideally, the signal in each orthogonal sub-carriers can mutual interference.Signal bandwidth on each subcarrier is less than the correlation bandwidth of channel, and therefore the bandwidth on each subcarrier is only 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, obtain increasing application, and be generally considered the core technology of following 4G.
Ofdm system is avoided intersymbol interference by introducing Cyclic Prefix (Cyclic Prefix is called for short " CP ").CP be exactly by the last part data Replica of each OFDM symbol to before this OFDM symbol, the intersymbol interference that makes multidiameter delay avoid multipath transmisstion to cause under the prerequisite of length that is less than Cyclic Prefix.
Terminal and the prerequisite of base station communication are to obtain and synchronize of base station, and the initial synchronisation of terminal and base station is mainly to complete by cell search process, complete terminal after initial synchronisation and also will continue synchronizeing of maintenance and base station.Due to the movement of terminal, variation of channel condition etc., the synchronized relation of terminal and base station may change at any time, and therefore terminal need to be estimated this synchronized relation the timing of adjustment terminal in time at any time, is so just unlikely step-out.
First ofdm system transmitting terminal encodes data, then carry out Digital Modulation, after this data flow segmentation is gone here and there and changed, every segment data is carried out to contrary fast fourier transform (Inverse Fast FourierTransform, be called for short " IFFT "), frequency-region signal is transformed to time-domain signal, then carry out parallel-serial conversion, add CP simultaneously, then send to communication channel by sending module; Contrary at receiving terminal, first receive time-domain signal by receiver module, then go CP, string conversion, by fast fourier transform (Fast FourierTransform, be called for short " FFT "), time-domain signal be converted to frequency-region signal, carry out the processing such as parallel-serial conversion, digital demodulation, decoding at frequency domain afterwards.
Fig. 1 is the schematic diagram of OFDM frequency-region signal.Ofdm system base unit is in time OFDM symbol, and the base unit in frequency is subcarrier, and the least unit in time and frequency is called Resource Unit (Resource Element is called for short " RE ").RS in Fig. 1 represents reference signal (Reference Signal is called for short " RS "), is mainly used for channel estimating, and a RS takies a RE.Conventionally, in time domain, RS can be divided into two row: 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, every 6 subcarriers insert a reference signal under normal circumstances, as shown in Figure 1.
FFT module is processed respectively each OFDM symbol.An OFDM symbol mainly comprises direct current subcarrier, effective subcarrier, empty subcarrier from frequency domain, as shown in Figure 2.Middle direct current subcarrier is mainly used for removing 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 is mainly for disturbing outside isolation strip, does not also transmit data.
The conventional timing estimation method of prior art utilizes RS to realize, a kind of method is to utilize the phase difference of adjacent R S on frequency domain to carry out timing estimation, the cardinal principle of this method is that to utilize timing offset in time domain to be reflected on frequency domain be exactly certain phase rotating, but this method is difficult to accurately estimate timing under multidiameter fading channel, mainly that after stack, phase deviation information can not accurately reflect the timing offset of time domain again because different multidiameters causes out of phase rotation on frequency domain.
Another kind method is to utilize the channel estimation in frequency domain of RS, then transforms to time domain, obtains time domain channel impulse response, then finds prominent tap in time domain channel impulse response, the position of this tap to think the position of terminal timing.And the method for timing adjustment is generally through certain level and smooth or average reception timing of removing to control receiver afterwards according to the timing estimating.
Because RS only effectively exists within the scope of subcarrier, in empty subcarrier, do not exist, and before transforming to time domain, must obtain the channel estimating in whole bandwidth, conventional method is the method for approximate or interpolation at present, go the channel estimating at approximate empty subcarrier place by the channel estimating in effective bandwidth, or utilize the method for interpolation to obtain the channel estimating at empty subcarrier place according to the channel estimating in effective bandwidth.Because RS is spacedly distributed, therefore in the time 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 is mainly used for data cached, is the module of ofdm system indispensability and go CP and FFT module, is mainly used for removing Cyclic Prefix and carries out fast Fourier transform.Article timing estimation and timing adjustment below.
Timing estimation method:
Step 1, RS place channel estimating:
At present conventional method of estimation is least square method (Least Square is called for short " LS "), obtain the channel estimating at each RS place in effective subcarrier by the method, in Fig. 4
the channel estimating at place.
Step 2, empty RS channel estimating are obtained:
Empty RS position, thinks according to the regularity of distribution of normal RS, also should transmit RS, in empty subcarrier relevant position in Fig. 4
shown in position, place.The channel estimating at empty RS place can be approximate by the channel estimating at the most contiguous RS place, for example R ' in Fig. 4
n+1, R '
n+2deng position R
n-1the channel estimating at place is approximate, and R '
-1deng position R
0the channel estimating at place is approximate; Or carry out interpolation, for example R ' by the channel estimating of closing on several RS place
n+1, R '
n+2deng position R
n-1, R
n-2... channel estimating interpolation at 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 refers to 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 is
wherein N
fFTfor the length of FFT, δ
rSfor the frequency domain interval of RS, unit is subcarrier number.
Step 4, IFFT:
To the sequence obtaining in step 3 ..., R '
-2, R '
-1, R
0..., R
n-2, R
n-1, R '
n, R '
n+1... carry out IFFT conversion, obtain 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, find maximum tap position and output timing:
Calculate each tap power | h
0|
2, | h
1|
2, | h
m-1|
2,
expression plural number is asked modulo operation, finds prominent tap and corresponding position thereof, and timing position is thought in this position.
Step 6, level and smooth or average:
The result of repeatedly measuring is carried out level and smooth or average.
Timing adjusting method:
Go to adjust the timing of receiver according to level and smooth or average result.
The shortcoming of above-mentioned technology is:
1) the method according to maximum power tap position as timing position, during for some, become channel faster or channel model (for example raw model that goes out) that some are special, the tap position of maximum power might not be real timing position, if always according to the tap position timing of maximum power, may cause valid data to run out of too much data processing window, thereby cause step-out;
2) owing to estimating to exist all the time error, therefore go to adjust receiver timing according to the timing value of estimating and also have all the time certain error, because ofdm system has adopted Cyclic Prefix, if the timing of therefore estimating shifts to an earlier date slightly, data processing window can comprise part CP and lose last partial data, as shown in Fig. 5 (a), because CP part is the repetition of an OFDM symbol last part, therefore this situation is little to performance impact; If the contrary definite time delay of estimating, data processing window will be lost partial data above, but also can introduce the interference of next OFDM symbol, as shown in Fig. 5 (b), now larger on the impact of performance.
3) while the channel estimating at RS place being transformed to time domain, due to the frequency domain interval δ of RS
rSnot necessarily 2 integral number power, thus also 2 integral number power not necessarily of M caused, so also just increase the computation complexity of IFFT.
Summary of the invention
The technical problem that the present invention mainly solves is to provide timing estimation and method of adjustment and device in a kind of ofdm system, even if become channel faster or channel model that some are special while making for some, also can find exactly timing position, 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 is carried out to channel estimating;
Each empty reference signal place in empty subcarrier is carried out to channel estimating;
Extract the channel estimating at described each reference signal and empty reference signal place, obtain the frequency domain sequence of each channel estimating;
Obtained frequency domain sequence is carried out to contrary fast fourier transform, obtain time domain channel impulse response;
Calculate the power of each tap in described time domain channel impulse response, find prominent tap and corresponding position thereof, from this position, N sampling point forward, searching power exceedes α P
maxthe most forward tap, using this tap position as timing position; Wherein N is greater than 0 length that is less than Cyclic Prefix, and α is predetermined threshold value,, 0 < α < 1, P
maxfor the maximum power of described each tap;
Adjust receiving terminal timing according to described timing position.
As the improvement of technique scheme, this N can be 1/2 circulating prefix-length.
As the improvement of technique scheme, described the each reference signal of void in empty subcarrier place is carried out in the step of channel estimating,
By the channel estimating at reference signal place in the most contiguous effective subcarrier of described empty reference signal, the approximate channel estimating that obtains described empty reference signal place; Or
In at least two effective subcarriers that close on by described empty reference signal, reference signal place channel estimating interpolation obtains the channel estimating at described empty reference signal place.
As the improvement of technique scheme, before the described step of adjusting receiving terminal timing according to timing position, can also comprise following steps:
Described timing position is deducted to a lead;
In the described step of adjusting receiving terminal timing according to timing position, adjust receiving terminal timing according to the timing position that deducts lead.
As the improvement of technique scheme, described 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 the each reference signal of described extraction and empty reference signal place, the integral number power according to 2 is the channel estimating that described each reference signal and empty reference signal place are extracted in interval.
As the improvement of technique scheme, the described integral number power according to 2 is in the step of the interval channel estimating of extracting each reference signal and empty reference signal place, if the integral number power according to 2 is that the position that interval is extracted is not the position of reference signal, use the channel estimating of the reference signal position nearest apart from this position to replace.
As the improvement of technique scheme, the described integral number power according to 2 is in the step of the interval channel estimating of extracting each reference signal and empty reference signal place, for regular circulation prefix, described in be spaced apart 8; For extended cyclic prefix, described in be spaced apart 2.
As the improvement of technique scheme, the method can also also comprise following steps:
At least carry out twice channel estimation steps and calculate described timing position according to channel estimation results, described at least two timing positions that calculate being carried out level and smooth or average;
In the described step of adjusting receiving terminal timing according to timing position, adjust receiving terminal timing according to described timing position smoothly or after average.
The present invention also provides timing estimation and adjusting device in a kind of ofdm system, comprises:
The first channel estimation module, carries out channel estimating for the each reference signal place to effective subcarrier;
Second channel estimation module, carries out channel estimating for the each empty reference signal place to empty subcarrier;
Extraction module, for extracting the channel estimating at described each reference signal and empty reference signal place, obtains the frequency domain sequence of each channel estimating;
Contrary fast fourier transform module, carries out contrary fast fourier transform for the frequency domain sequence to obtained, and obtains time domain channel impulse response;
Timing position computing module, for calculating the power of the each tap of described time domain channel impulse response, finds prominent tap and corresponding position thereof, and from this position, N sampling point forward, searching power exceedes α P
maxthe most forward tap, using this tap position as timing position; Wherein N is greater than 0 length that is less than Cyclic Prefix, and α is predetermined threshold value, 0 < α < 1, P
maxfor the maximum power of described each tap;
Timing adjustment module, for adjusting receiving terminal timing according to the definite timing position of described timing position computing module.
Embodiment of the present invention compared with prior art, the main distinction and effect thereof are: the method for determining timing position, it not the position of the maximum tap of traditional use, but searching is forward greater than the position of the tap of certain thresholding, the 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, now this method of determining timing position is consistent with traditional method.Even if become channel faster or channel model that some are special when therefore embodiment of the present invention is for some, also can find exactly timing position, improve the accuracy of timing position location.
In embodiment of the present invention, adjust the method for timing, not directly to go to adjust receiving terminal timing according to the result of timing, but after being deducted to a fixing lead, timing results adjusts again, the method can make full use of the effect of ofdm system Cyclic Prefix, further reduces the impact that possible timing error causes.If the timing of now estimating shifts to an earlier date slightly, data processing window can comprise part CP and lose last partial data, because CP part is the repetition of an OFDM symbol last part, therefore now little to performance impact; If the definite time delay of estimating, can offset with deducted lead, data processing window can not lost partial data above equally, effectively prevent that the definite time delay because estimating from losing previous section data, introducing the interference of next OFDM symbol, avoid the considerable influence therefore performance being produced.
In the time extracting channel estimation in frequency domain, it not the channel estimating of directly extracting RS place, but be that interval is extracted according to 2 integral number power, if extracting position is not the position of RS, substitute by the channel estimating of the most contiguous RS position, the method can more be simplified calculating in the time channel estimation in frequency domain being transformed to time domain with IFFT, reduces amount of calculation.
Brief description of the drawings
Below in conjunction with the drawings and specific embodiments, the present invention is described in further detail.
Fig. 1 is the schematic diagram of OFDM frequency-region signal in prior art;
Fig. 2 is OFDM symbol schematic diagram on frequency domain in prior art;
Fig. 3 is the structure drawing of device of timing estimation and adjustment in prior art;
Fig. 4 is that in prior art, empty subcarrier place channel estimating is obtained schematic diagram;
Fig. 5 is the design sketch of timing advance or hysteresis in prior art;
Fig. 6 is timing estimation and method of adjustment flow chart in first embodiment of the invention ofdm system;
Fig. 7 is that first embodiment of the invention frequency domain channel estimating is extracted schematic diagram.
Embodiment
For making the object, technical solutions and advantages of the present invention clearer, below in conjunction with accompanying drawing, embodiments of the present invention are described in further detail.
First embodiment of the invention relates to timing estimation and method of adjustment in a kind of ofdm system, as shown in Figure 6.Data cache module shown in figure is mainly used for data cached, is all the module of ofdm system indispensability and go CP and FFT module, is mainly used for removing Cyclic Prefix and carries out fast Fourier transform.Below timing estimation and method of adjustment are specifically introduced.
In step 601, each RS place in effective subcarrier is carried out to channel estimating.Obtain in Fig. 7 (a)
the channel estimating at place.Conventional method of estimation is least square method at present.
In step 602, the each empty RS place in empty subcarrier is carried out to channel estimating.In present embodiment, be defaulted as in empty subcarrier and the same RS of existence in effective subcarrier, be called empty RS.The position distribution of empty RS in empty subcarrier is identical with RS position regularity of distribution in effective subcarrier, thinks according to the regularity of distribution of normal RS, also should transmit the position of RS, at empty subcarrier place in accompanying drawing 7 (a)
shown in position, place.
The channel estimating at empty RS place can obtain with the channel estimating at the most contiguous RS place is approximate.For example, in Fig. 7 (a) R '
n+1, R '
n+2deng position R
n-1the channel estimating at place is approximate, and R '
-1deng position R
0the channel estimating at place is approximate.
For example, or the channel estimating at empty RS place also can be carried out interpolation, R ' by the channel estimating of closing on several RS place
n+1, R '
n+2deng position R
n-1, R
n-2... channel estimating interpolation at place obtains, and interpolation method can be linear interpolation, polynomial interopolation etc.
In step 603, the integral number power δ ' according to 2 is the channel estimating that RS place and empty RS place are extracted in interval, 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 is
wherein N
fFTfor the length of FFT, δ
rSfor the frequency domain interval of RS, unit is subcarrier number.If the position of extracting for interval according to δ ' is not the position of RS or empty RS, use the channel estimating of the RS nearest apart from this position or empty RS position to replace.As R in accompanying drawing 7 (b) "
-1with R '
-1replace R "
0use R
0replace R "
1use R
1replace ..., R "
n '-1with R '
nreplace etc.Usually, to conventional CP, δ ' can get 8, and to expansion CP, δ ' can get 2.
By directly do not extract the channel estimating at RS place in the time extracting channel estimation in frequency domain, but be that interval is extracted according to 2 integral number power, make can more simplify calculating in the time channel estimation in frequency domain being transformed to time domain with IFFT, reduce amount of calculation.
In step 604, to the frequency domain sequence obtaining in step 603 ..., R "
-2, R "
-1, R "
0..., R "
n '-2, R "
n '-1, R "
n ', R "
n '+1... } and carry out IFFT conversion, obtain 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 step 605, calculate each tap in above-mentioned time domain channel impulse response power | h
0|
2, | h
1|
2, | h
m-1|
2, wherein
expression plural number is asked modulo operation, finds prominent tap and corresponding position thereof, and maximum power is P
max, correspondence position is L
max; From this position L
maxrise in N sampling point forward, find power and exceed α P
maxthe most forward tap, this tap position is regarded as to timing position.Wherein N is greater than 0 and is less than CP length, and preferred values is
τ
cPfor the length of CP, α is predetermined threshold value, 0 < α < 1, common desirable 1/2.The above-mentioned process of finding tap forward can be described below:
break；
}
}
Due in the time determining timing position, it not the position that uses traditional maximum tap, but searching is forward greater than the position of the tap of certain thresholding, the 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, now this method of determining timing position is consistent with traditional method, even if become channel faster or channel model that some are special during therefore for some, also can find exactly timing position, improve the accuracy of timing position location.
In actual applications, can repeatedly carry out channel estimating to each reference signal, and calculate timing position according to channel estimation results, repeat above-mentioned steps 601 to step 605, in step 606, the timing position repeatedly calculating is carried out smoothly or on average, obtains final definite timing position.
In step 607, final definite timing position in step 606 is fixedly deducted to 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 step 608, adjust receiving terminal timing according to deducting lead timing position afterwards in step 607.
Because not being directly goes to adjust receiving terminal timing according to the result of timing, but after being deducted to a fixing lead, timing results adjusts again, the method can make full use of the effect of ofdm system Cyclic Prefix, further reduces the impact that possible timing error causes.If the timing of now estimating shifts to an earlier date slightly, data processing window can comprise part CP and lose last partial data, because CP part is the repetition of an OFDM symbol last part, therefore now little to performance impact; If the definite time delay of estimating, can offset with deducted lead, data processing window can not lost partial data above equally, effectively prevent that the definite time delay because estimating from losing previous section data, introducing the interference of next OFDM symbol, avoid the considerable influence therefore performance being produced.
Second embodiment of the invention relates to timing estimation and adjusting device in a kind of ofdm system, comprises: the first channel estimation module, carries out channel estimating for the each reference signal place to effective subcarrier; Second channel estimation module, carries out channel estimating for the each empty reference signal place to empty subcarrier; Extraction module, for extracting the channel estimating at each reference signal and empty reference signal place, obtains the frequency domain sequence of each channel estimating; Contrary fast fourier transform module, carries out contrary fast fourier transform for the frequency domain sequence to obtained, and obtains time domain channel impulse response; Timing position computing module, for calculating the power of the each tap of time domain channel impulse response, find prominent tap and corresponding position thereof, from this position, the individual sampling point of N (the CP length that preferred values is 1/2) forward, find power and exceed α P
maxthe most forward tap, using this tap position as timing position; Wherein N is greater than 0 length that is less than Cyclic Prefix, and α is predetermined threshold value, 0 < α < 1, P
maxfor the maximum power of each tap; Timing adjustment module, for adjusting receiving terminal timing according to the definite timing position of timing position computing module.This predetermined threshold value can be 1/2.By above-mentioned timing position computing module, even if become channel faster or channel model that some are special during for some, also can find exactly timing position, improve the accuracy of timing position location.
As the improvement of technique scheme, second channel estimation module is carried out channel estimating to the each reference signal of the void in empty subcarrier place in the following manner:
By the channel estimating at reference signal place in the most contiguous effective subcarrier of empty reference signal, the approximate channel estimating that obtains empty reference signal place; Or reference signal place channel estimating interpolation obtains the channel estimating at empty reference signal place at least two effective subcarriers that close on by empty reference signal.
As the improvement of technique scheme, this device can also comprise and subtracts lead module, for timing position being deducted to a lead; Timing adjustment module is adjusted receiving terminal timing according to the timing position that deducts lead.This lead is generally 1/32 to 1/4 of circulating prefix-length.If the timing of now estimating shifts to an earlier date slightly, data processing window can comprise part CP and lose last partial data, because CP part is the repetition of an OFDM symbol last part, therefore little to performance impact; If the definite time delay of estimating, can offset with deducted lead, data processing window can not lost partial data above equally, effectively prevent that the definite time delay because estimating from losing previous section data, introducing the interference of next OFDM symbol, avoid the considerable influence therefore performance being produced.
As the improvement of technique scheme, extraction module is the channel estimating that each reference signal and empty reference signal place are extracted in interval according to 2 integral number power.If the integral number power according to 2 is that the position that interval is extracted is not the position of reference signal, use the channel estimating of the reference signal position nearest apart from this position to replace.For regular circulation prefix, this interval can get 8; For extended cyclic prefix, this interval can get 2.The method can more be simplified calculating in the time channel estimation in frequency domain being transformed to time domain with IFFT, reduces amount of calculation.
As the improvement of technique scheme, this device can also comprise level and smooth module.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 level and smooth or average for calculate at least two timing positions are carried out; Timing adjustment module is adjusted receiving terminal timing according to the timing position after level and smooth or average.
Although pass through with reference to some of the preferred embodiment of the invention, the present invention is illustrated and described, but those of ordinary skill in the art should be understood that and can do various changes to it in the form and details, and without departing from the spirit and scope of the present invention.
Claims (18)
1. timing estimation and a method of adjustment in orthogonal frequency division multiplex OFDM system, is characterized in that, comprises following steps:
Each reference signal place in effective subcarrier is carried out to channel estimating;
Each empty reference signal place in empty subcarrier is carried out to channel estimating;
Extract the channel estimating at described each reference signal and empty reference signal place, obtain the frequency domain sequence of each channel estimating;
Obtained frequency domain sequence is carried out to contrary fast fourier transform, obtain time domain channel impulse response;
Calculate the power of each tap in described time domain channel impulse response, find prominent tap and corresponding position thereof, from this position, N sampling point forward, searching power exceedes α P
maxthe most forward tap, using this tap position as timing position; Wherein N is greater than 0 length that is less than Cyclic Prefix, and α is predetermined threshold value, 0< α <1, P
maxfor the maximum power of described each tap;
Adjust receiving terminal timing according to described timing position.
2. timing estimation and method of adjustment in ofdm system according to claim 1, is characterized in that, described N is 1/2 circulating prefix-length.
3. timing estimation and method of adjustment in ofdm system according to claim 1, is characterized in that, described the each reference signal of void in empty subcarrier place is carried out in the step of channel estimating,
By the channel estimating at reference signal place in the most contiguous effective subcarrier of described empty reference signal, the approximate channel estimating that obtains described empty reference signal place; Or
In at least two effective subcarriers that close on by described empty reference signal, reference signal place channel estimating interpolation obtains the channel estimating at described empty reference signal place.
4. timing estimation and method of adjustment in ofdm system according to claim 1, is characterized in that, before the described step of adjusting receiving terminal timing according to timing position, also comprises following steps:
Described timing position is deducted to a lead;
In the described step of adjusting receiving terminal timing according to timing position, adjust receiving terminal timing according to the timing position that deducts lead.
5. timing estimation and method of adjustment in ofdm system according to claim 4, is characterized in that, described lead is circulating prefix-length 1/32 to 1/4.
6. timing estimation and method of adjustment in ofdm system according to claim 1, it is characterized in that, in the step of the channel estimating at the each reference signal of described extraction and empty reference signal place, the integral number power according to 2 is the channel estimating that described each reference signal and empty reference signal place are extracted in interval.
7. timing estimation and method of adjustment in ofdm system according to claim 6, it is characterized in that, the described integral number power according to 2 is in the step of the interval channel estimating of extracting each reference signal and empty reference signal place, if the integral number power according to 2 is that the position that interval is extracted is not the position of reference signal, use the channel estimating of the reference signal position nearest apart from this position to replace.
8. timing estimation and method of adjustment in ofdm system according to claim 6, it is characterized in that, the described integral number power according to 2 is in the step of the interval channel estimating of extracting each reference signal and empty reference signal place, for regular circulation prefix, described in be spaced apart 8; For extended cyclic prefix, described in be spaced apart 2.
9. according to timing estimation and method of adjustment in the ofdm system described in any one in claim 1 to 8, it is characterized in that, also comprise following steps:
At least carry out twice pair of reference signal and empty reference signal and carry out the step of channel estimating and calculate described timing position according to channel estimation results, described at least two timing positions that calculate are carried out level and smooth or average;
In the described step of adjusting receiving terminal timing according to timing position, adjust receiving terminal timing according to described timing position smoothly or after average.
10. timing estimation and an adjusting device in ofdm system, is characterized in that, comprises:
The first channel estimation module, carries out channel estimating for the each reference signal place to effective subcarrier;
Second channel estimation module, carries out channel estimating for the each empty reference signal place to empty subcarrier;
Extraction module, for extracting the channel estimating at described each reference signal and empty reference signal place, obtains the frequency domain sequence of each channel estimating;
Contrary fast fourier transform module, carries out contrary fast fourier transform for the frequency domain sequence to obtained, and obtains time domain channel impulse response;
Timing position computing module, for calculating the power of the each tap of described time domain channel impulse response, finds prominent tap and corresponding position thereof, and from this position, N sampling point forward, searching power exceedes α P
maxthe most forward tap, using this tap position as timing position; Wherein N is greater than 0 length that is less than Cyclic Prefix, and α is predetermined threshold value, 0< α <1, P
maxfor the maximum power of described each tap;
Timing adjustment module, for adjusting receiving terminal timing according to the definite timing position of described timing position computing module.
Timing estimation and adjusting device in 11. ofdm systems according to claim 10, is characterized in that, described N is 1/2 circulating prefix-length.
Timing estimation and adjusting device in 12. ofdm systems according to claim 10, is characterized in that, described second channel estimation module is carried out channel estimating to the each reference signal of the void in empty subcarrier place in the following manner:
By the channel estimating at reference signal place in the most contiguous effective subcarrier of described empty reference signal, the approximate channel estimating that obtains described empty reference signal place; Or
In at least two effective subcarriers that close on by described empty reference signal, reference signal place channel estimating interpolation obtains the channel estimating at described empty reference signal place.
Timing estimation and adjusting device in 13. ofdm systems according to claim 10, is characterized in that, also comprises and subtract lead module, for described timing position being deducted to a lead;
Described timing adjustment module is adjusted receiving terminal timing according to the timing position that deducts lead.
Timing estimation and adjusting device in 14. ofdm systems according to claim 13, is characterized in that, described lead is circulating prefix-length 1/32 to 1/4.
Timing estimation and adjusting device in 15. ofdm systems according to claim 10, is characterized in that, described extraction module is the channel estimating that described each reference signal and empty reference signal place are extracted in interval according to 2 integral number power.
Timing estimation and adjusting device in 16. ofdm systems according to claim 15, it is characterized in that, described extraction module is that interval is while extracting the channel estimating at each reference signal and empty reference signal place according to 2 integral number power, if the integral number power according to 2 is that the position that interval is extracted is not the position of reference signal, use the channel estimating of the reference signal position nearest apart from this position to replace.
Timing estimation and adjusting device in 17. ofdm systems according to claim 15, is characterized in that, for regular circulation prefix, described in be spaced apart 8; For extended cyclic prefix, described in be spaced apart 2.
18. according to claim 10 to timing estimation and adjusting device in the ofdm system described in any one in 17, it is characterized in that, also comprises level and smooth module,
The result that described timing position computing module carries out channel estimating according at least twice pair of reference signal and empty reference signal is respectively calculated at least two described timing positions, and described level and smooth module is level and smooth or average for described at least two timing positions that calculate are carried out;
Described timing adjustment module is adjusted receiving terminal timing according to described timing position smoothly or after average.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201010606650.2A CN102571646B (en) | 2010-12-27 | 2010-12-27 | Timing estimation and adjustment method and device in OFDM (Orthogonal Frequency Division Multiplexing) system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201010606650.2A CN102571646B (en) | 2010-12-27 | 2010-12-27 | Timing estimation and adjustment method and device in OFDM (Orthogonal Frequency Division Multiplexing) system |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN102571646A CN102571646A (en) | 2012-07-11 |
| CN102571646B true CN102571646B (en) | 2014-09-17 |
Family
ID=46416142
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201010606650.2A Active CN102571646B (en) | 2010-12-27 | 2010-12-27 | Timing estimation and adjustment method and device in OFDM (Orthogonal Frequency Division Multiplexing) system |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN102571646B (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104301087A (en) * | 2014-09-24 | 2015-01-21 | 重庆邮电大学 | Timing error correcting method for digital phase modulation signal |
| CN106878205B (en) * | 2015-12-10 | 2019-07-05 | 电信科学技术研究院 | A kind of timing offset estimation method and device |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101378371A (en) * | 2007-08-27 | 2009-03-04 | 株式会社Ntt都科摩 | Method for channel estimation of wideband wireless mobile commutation system and channel estimator |
| CN101431492A (en) * | 2007-11-07 | 2009-05-13 | 中国科学院微电子研究所 | Method for timing estimation of OFDM communication system signal |
-
2010
- 2010-12-27 CN CN201010606650.2A patent/CN102571646B/en active Active
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101378371A (en) * | 2007-08-27 | 2009-03-04 | 株式会社Ntt都科摩 | Method for channel estimation of wideband wireless mobile commutation system and channel estimator |
| CN101431492A (en) * | 2007-11-07 | 2009-05-13 | 中国科学院微电子研究所 | Method for timing estimation of OFDM communication system signal |
Also Published As
| Publication number | Publication date |
|---|---|
| CN102571646A (en) | 2012-07-11 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US7680197B2 (en) | Apparatus and method for sampling timing compensation in multi-carrier system | |
| CN102932289B (en) | Cyclic shifting-based method for estimating shifting number and channel response in orthogonal frequency division multiplexing (OFDM) system | |
| CN106559370B (en) | A kind of method of low complexity OFDM-PON system sample clock frequency deviation compensation | |
| CN103780521A (en) | Sparsity self-adaptive OFDM system channel estimation method | |
| CN101115046A (en) | Modified type LS channel estimation method for OFDM system | |
| CN101924723A (en) | OFDM (Orthogonal Frequency Division Multiplexing) signal demodulation method and device | |
| CN102215204B (en) | Feedback-iteration-based OFDM/OQAM (orthogonal frequency division multiplexing/offset quadrature amplitude modulation) system as well as time-frequency synchronization method thereof | |
| CN101267419A (en) | A time advance adjustment method and device for OFDM symbol timing | |
| Ijaz et al. | Low-complexity time-domain SNR estimation for OFDM systems | |
| CN104253772B (en) | The channel estimation methods of ofdm system | |
| CN102377726B (en) | Timing synchronization method of OFDM (Orthogonal Frequency Division Multiplexing) system | |
| CN103795676A (en) | Doppler frequency offset estimation method based on cyclic accumulation | |
| JP5080400B2 (en) | Wireless terminal, base station, and channel characteristic estimation method | |
| CN102594740B (en) | Method and device for estimating frequency offset | |
| CN102571646B (en) | Timing estimation and adjustment method and device in OFDM (Orthogonal Frequency Division Multiplexing) system | |
| CN102075475A (en) | Combined tracking method for timing deviation and sampling frequency offset | |
| CN101505294A (en) | Synchronization method for OFDM system and synchronization apparatus thereof | |
| CN103297100B (en) | A kind of doppler changing rate method of estimation for ofdm system and system | |
| CN102340864B (en) | OFDM (Orthogonal Frequency Division Multiplexing) timing synchronization algorithm with low complexity and high performance | |
| CN111800366B (en) | OFDM symbol timing synchronization method and receiving device under complex multipath environment | |
| CN104618294B (en) | OFDM integer frequency offsets Method of fast estimating based on training sequence and system | |
| CN103532896A (en) | Timing estimation method and device for variable bandwidth system | |
| CN103986683A (en) | OFDM symbol timing synchronization method based on high carrier number | |
| CN101883068A (en) | Superimposed training sequence time thickness synchronization method | |
| CN106888065A (en) | A kind of clock synchronizing method and terminal |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C06 | Publication | ||
| PB01 | Publication | ||
| C10 | Entry into substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| ASS | Succession or assignment of patent right |
Owner name: DATANG TELECOM TECHNOLOGY INDUSTRY HOLDING CO., LT Free format text: FORMER OWNER: LEADCORE TECHNOLOGY CO., LTD. Effective date: 20141217 |
|
| C41 | Transfer of patent application or patent right or utility model | ||
| COR | Change of bibliographic data |
Free format text: CORRECT: ADDRESS; FROM: 201206 PUDONG NEW AREA, SHANGHAI TO: 100191 HAIDIAN, BEIJING |
|
| TR01 | Transfer of patent right |
Effective date of registration: 20141217 Address after: 100191 Haidian District, Xueyuan Road, No. 1, No. 40, Patentee after: Datang Telecom Technology Industry Holding Co., Ltd. Address before: 201206 Pudong New Area Mingyue Road, Shanghai, No. 1258 Patentee before: Leadcore Technology Co., Ltd. |
|
| TR01 | Transfer of patent right |
Effective date of registration: 20201111 Address after: 100083 Haidian District, Xueyuan Road, No. 29, Patentee after: DATANG MOBILE COMMUNICATIONS EQUIPMENT Co.,Ltd. Address before: 100191 Haidian District, Xueyuan Road, No. 1, No. 40, Patentee before: Datang Telecom Technology Industry Holding Co.,Ltd. |
|
| TR01 | Transfer of patent right |