CN102143113A - Channel estimation method and device - Google Patents
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Abstract
The embodiment of the invention discloses a channel estimation method and device for improving system performance. The method disclosed by the embodiment of the invention comprises the steps of: carrying out least squares criterion (LS) channel estimation on an OFDM (Orthogonal Frequency Division Multiplexing) channel by using a block-type pilot frequency to obtain an LS estimation result; carrying out frequency domain to time domain conversion on the LS estimation result to obtain time domain channel impulse response of N sampling points, wherein N is number of the sampling points; for each sampling point, calculating an energy set of time domain channel impulse response of a plurality of sampling points beginning from the sampling point; determining N-L sampling points to be subjected to zero setting according to the obtained energy set, wherein L is the length of OFDM circulating prefixes; carrying out zero setting on numerical values of the N-L sampling points to be subjected to zero setting; and carrying out time domain to frequency domain conversion on current numerical values of the N sampling points to obtain a channel estimation result. The embodiment of the invention also provides a channel estimation device. Channel estimation effect can be effectively enhanced by adopting the embodiment of the invention.
Description
Technical field
The present invention relates to the signal processing field, relate in particular to a kind of channel estimation methods and device.
Background technology
Along with people to the broadband demand of communicating by letter, wireless communication system is just developed rapidly to the broadband by the arrowband.OFDM (OFDM, Orthogonal Frequency Division Multiplexing) technology is a kind of special multi-carrier transmission technology, it is converted into parallel low rate information symbol by the information symbol with two-forty, parallel transmission on the subcarrier of a plurality of quadratures has resisted the frequency selective fading phenomenon that broadband system runs into effectively in wireless transmission then.
Channel condition information is mainly used in receiving terminal and carries out coherent detection to received signal, to offset the adverse effect of wireless channel to signal.At present, channel estimation methods mainly contains non-blind estimation, blind estimation and half-blindness is estimated three kinds.Utilizing the auxiliary channel estimation technique of pilot tone is a kind of effective non-blind estimating method that obtains channel condition information low complex degree and low energy consumption.When the block ofdm system that distributes of pilot tone is carried out channel estimating, can obtain frequency domain channel state information according to criterion of least squares (LS, Least Square) or least mean-square error (MMSE, Minimum Mean Square Error) criterion.
Channel estimation methods based on LS is simple, but evaluated error is bigger, and higher based on the channel estimation methods precision of MMSE, but computational process needs channel statistical knowledge, and more complicated.
A kind of channel estimation methods of the prior art adopts the method for DFT filtering to estimating to carry out noise reduction process based on the frequency domain channel of LS, to approach the channel estimating effect based on MMSE.As shown in Figure 1, implementation procedure based on DFT filtering comprises: at first utilize block pilot tone to carry out the LS channel estimating, utilize the channel estimating that obtains by fast adverse Fourier transform (IFFT then, Inverse Fast Fourier Transform) calculates time domain channel impulse response (CIR, Channel Impulse Response), then to exceeding the whole zero setting of time-domain sampling value of circulating prefix-length.At last, the CIR estimated result that obtains is transformed into frequency domain, finishes channel estimating.
But in the OFDM of reality wireless system, systematic sampling might not be the integral multiple of multipath channel time delay at interval, and promptly multipath channel is non-sampling interval channel.At this moment, when adopting based on discrete Fourier transform (DFT) (DFT, Discrete Fourier Transform) during the OFDM channel estimation methods of filtering, the response of channel time domain after the IFFT computing might not all concentrate on the sampled point in the circulating prefix-length interval of front, and the stronger sampled point of some energy occurs at the end, thereby cause the energy leakage phenomenon.This phenomenon can make the traditional mean square error estimated performance of method of estimation in middle high s/n ratio zone based on DFT filtering plateau phenomenon occur, has had a strong impact on systematic function.
Summary of the invention
The embodiment of the invention provides a kind of channel estimation methods and device, can improve systematic function.
The channel estimation methods that the embodiment of the invention provides comprises: utilize block pilot tone that the orthogonal frequency division multiplex OFDM channel is carried out criterion of least squares LS channel estimating and obtain the LS estimated result; The conversion that described LS estimated result is carried out frequency domain to time domain obtains the time domain channel impulse response of N sampled point, and described N is a sampling number; For each sampled point, calculate continuous several sampled points that begin from this sampled point the time domain channel impulse response can duration set; According to N-L the sampled point can duration set determining to treat zero setting that obtains, described L is the length of OFDM Cyclic Prefix; With the described numerical value zero setting for the treatment of N-L sampled point of zero setting; The current numerical value of N sampled point is carried out time domain obtain channel estimation results to the conversion of frequency domain.
The channel estimating apparatus that the embodiment of the invention provides comprises: the LS processing unit is used to utilize block pilot tone that the orthogonal frequency division multiplex OFDM channel is carried out criterion of least squares LS channel estimating and obtains the LS estimated result; First converter unit is used for the conversion that described LS estimated result carries out frequency domain to time domain is obtained the time domain channel impulse response of N sampled point, and described N is a sampling number; The zero setting processing unit, be used for for each sampled point, the time domain channel impulse response of continuous several sampled points that calculating begins from this sampled point can duration set, determine to treat N-L sampled point of zero setting according to the energy duration set that obtains, described L is the length of OFDM Cyclic Prefix, with the described numerical value zero setting for the treatment of N-L sampled point of zero setting; Second converter unit is used for current numerical value to N sampled point and carries out time domain and obtain channel estimation results to the conversion of frequency domain.
As can be seen from the above technical solutions, the embodiment of the invention has the following advantages: in the embodiment of the invention, can be according to the time domain channel impulse response calculating energy set of the N that an obtains sampled point, N sampled point then obtains N energy duration set, can determine N-L the sampled point for the treatment of zero setting by duration set according to N that obtains afterwards, and carry out zero setting, owing to when determining to treat the sampled point of zero setting, considered the energy of each sampled point, so when multipath channel is that non-sampling interval is during channel, the sampled point that some energy at end are stronger can't be by direct zero setting, so can avoid energy leakage, thereby improve systematic function.
Description of drawings
Fig. 1 is the OFDM channel estimating schematic diagram of prior art based on DFT filtering;
Fig. 2 is embodiment schematic diagram of channel estimation methods of the present invention;
Fig. 3 is another embodiment schematic diagram of channel estimation methods of the present invention;
Fig. 4 is another embodiment schematic diagram of channel estimation methods of the present invention;
Fig. 5 is the OFDM channel estimating schematic diagram that the present invention is based on DFT filtering;
Fig. 6 is a time domain channel impulse response schematic diagram of the present invention;
Fig. 7 is embodiment schematic diagram of channel estimating apparatus of the present invention;
Fig. 8 is simulation result schematic diagram of the present invention;
Fig. 9 is another simulation result schematic diagram of the present invention;
Figure 10 is another simulation result schematic diagram of the present invention;
Figure 11 is another simulation result schematic diagram of the present invention.
Embodiment
The embodiment of the invention provides a kind of channel estimation methods and device, can improve systematic function.
See also Fig. 2, embodiment of channel estimation methods of the present invention comprises:
201, utilize block pilot tone that the OFDM channel is carried out the LS channel estimating and obtain the LS estimated result;
The channel estimation methods of present embodiment is based on the LS channel estimating, obtains the LS estimated result so the OFDM channel that at first can utilize block pilot tone that needs are carried out channel estimating carries out the LS channel estimating.
Specifically carry out the common practise of the process of LS channel estimating, specifically do not do qualification herein for those skilled in the art.
202, the conversion that the LS estimated result is carried out frequency domain to time domain obtains the time domain channel impulse response of N sampled point;
After obtaining the LS estimated result, can obtain the time domain channel impulse response of N sampled point to the conversion that this LS estimated result carries out frequency domain to time domain, wherein, N is a sampling number.
203, for each sampled point, calculate continuous several sampled points that begin from this sampled point the time domain channel impulse response can duration set;
The LS estimated result is carried out obtain after the conversion of frequency domain to time domain the time domain channel impulse response of N sampled point.
At each sampled point, the time domain channel impulse response of continuous several sampled points that calculating begins from this sampled point can duration set, then can obtain N energy duration set, the energy sum of the time domain channel impulse response that this energy duration set promptly is these several sampled points.
Need to prove that after the time domain channel impulse response of each sampled point was determined, the process of energy of calculating the time domain channel impulse response of each sampled point was those skilled in the art's common practise, does not specifically do qualification herein.
204, determine to treat N-L sampled point of zero setting according to the energy duration set that obtains;
Adopting the mode of DFT filtering is in order to reduce The noise, thereby improve the accuracy of channel estimating, the process of this DFT filtering promptly is the numerical value that only keeps L sampled point in N the sampled point, the whole zero setting of numerical value of remaining N-L sampled point, thereby the reduction The noise, this L is the length of OFDM Cyclic Prefix.
In the present embodiment, obtained after N the energy duration set, can determine to treat N-L sampled point of zero setting according to this N energy duration set.
205, will treat the numerical value zero setting of N-L sampled point of zero setting;
206, the current numerical value of N sampled point is carried out time domain and obtain channel estimation results to the conversion of frequency domain.
Treat after the numerical value zero setting of N-L sampled point of zero setting, then can carry out time domain to the current numerical value of N sampled point and obtain channel estimation results, thereby finish the OFDM channel estimating to the conversion of frequency domain.
In the present embodiment, can be according to the time domain channel impulse response calculating energy set of the N that an obtains sampled point, N sampled point then obtains N energy duration set, can determine N-L the sampled point for the treatment of zero setting by duration set according to N that obtains afterwards, and carry out zero setting, owing to when determining to treat the sampled point of zero setting, considered the energy of each sampled point, so when multipath channel is that non-sampling interval is during channel, the sampled point that some energy at end are stronger can't be by direct zero setting, so can avoid energy leakage, thereby improve systematic function.
In the present embodiment, specifically can determine to treat N-L sampled point of zero setting in several ways, describe for example below:
(1), determine to treat N-L sampled point of zero setting by the maximized mode of energy:
See also Fig. 3, another embodiment of channel estimation methods of the present invention comprises:
301, utilize block pilot tone that the OFDM channel is carried out the LS channel estimating and obtain the LS estimated result;
The channel estimation methods of present embodiment is based on the LS channel estimating, obtains the LS estimated result so the OFDM channel that at first can utilize block pilot tone that needs are carried out channel estimating carries out the LS channel estimating.
Specifically carry out the common practise of the process of LS channel estimating, specifically do not do qualification herein for those skilled in the art.
302, the conversion that the LS estimated result is carried out frequency domain to time domain obtains the time domain channel impulse response of N sampled point;
After obtaining the LS estimated result, can obtain the time domain channel impulse response of N sampled point to the conversion that this LS estimated result carries out frequency domain to time domain, wherein, N is a sampling number.
The conversion of the frequency domain to time domain in the present embodiment can be contrary fast fourier transform (IFFT, Inverse Fast Fourier Transform), also can specifically not do qualification herein for the conversion of the frequency domain to time domain of other modes.
303,, calculate the energy duration set of the time domain channel impulse response of continuous L the sampled point that begins from this sampled point for each sampled point;
The LS estimated result is carried out obtain after the conversion of frequency domain to time domain the time domain channel impulse response of N sampled point.
At each sampled point, the time domain channel impulse response of continuous L the sampled point that calculating begins from this sampled point can duration set, then can obtain N energy duration set, this energy duration set promptly is the energy sum of the time domain channel impulse response of this L sampled point, and this L is the length of OFDM Cyclic Prefix.
In the present embodiment, it is continuous that a continuous L sampled point does not refer in particular to the numbering of sampled point, and be meant the starting point that each sampled point all can one group of L sampled point, for example, for last sampled point, thereafter the sampled point that does not have other then uses L-1 sampled point and this last sampled point of beginning to form L sampled point.
Need to prove that after the time domain channel impulse response of each sampled point was determined, the process of energy of calculating the time domain channel impulse response of each sampled point was those skilled in the art's common practise, does not specifically do qualification herein.
304, determine L sampled point of the energy duration set correspondence of energy maximum in N the energy duration set;
Adopting the mode of DFT filtering is in order to reduce The noise, thereby improve the accuracy of channel estimating, the process of this DFT filtering promptly is the numerical value that only keeps L sampled point in N the sampled point, the whole zero setting of numerical value of remaining N-L sampled point, thus reduce The noise.
In the present embodiment, obtained can the energy of this N energy duration set being compared after N the energy duration set, therefrom selected the energy duration set of energy maximum, determined the pairing L of this an energy duration set sampled point afterwards again.
305, will except that the energy maximum can duration set the numerical value zero setting of other N-L sampled point L the sampled point of correspondence;
What step 304 had been determined the energy maximum can duration set after L the sampled point of correspondence, the energy that then means the time domain channel impulse response of this L sampled point has great function to the OFDM channel estimating, and in order to carry out DFT filtering, then can be with the numerical value zero setting of N-L sampled point except this L sampled point, to reduce The noise.
306, the current numerical value of N sampled point is carried out time domain and obtain channel estimation results to the conversion of frequency domain.
Treat after the numerical value zero setting of N-L sampled point of zero setting, then can carry out time domain to the current numerical value of N sampled point and obtain channel estimation results, thereby finish the OFDM channel estimating to the conversion of frequency domain.
Time domain in the present embodiment can be fast fourier transform (FFT, Fast Fourier Transform) to the conversion of frequency domain, also can arrive the conversion of frequency domain for the time domain of other modes, does not specifically do qualification herein.
In the present embodiment, can be according to the time domain channel impulse response calculating energy set of the N that an obtains sampled point, N sampled point then obtains N energy duration set, determine the energy duration set of energy maximum in N the energy duration set afterwards, and will except that the energy maximum can duration set the numerical value zero setting of other N-L sampled point L the sampled point of correspondence, owing to when determining to treat the sampled point of zero setting, considered the energy of each sampled point, so when multipath channel is that non-sampling interval is during channel, the sampled point that some energy at end are stronger can't be by direct zero setting, so can avoid energy leakage, thereby improve systematic function.
(2), determine to treat N-L sampled point of zero setting by the mode of energy minimization:
See also Fig. 4, another embodiment of channel estimation methods of the present invention comprises:
401, utilize block pilot tone that the OFDM channel is carried out the LS channel estimating and obtain the LS estimated result;
The channel estimation methods of present embodiment is based on the LS channel estimating, obtains the LS estimated result so the OFDM channel that at first can utilize block pilot tone that needs are carried out channel estimating carries out the LS channel estimating.
Specifically carry out the common practise of the process of LS channel estimating, specifically do not do qualification herein for those skilled in the art.
402, the conversion that the LS estimated result is carried out frequency domain to time domain obtains the time domain channel impulse response of N sampled point;
After obtaining the LS estimated result, can obtain the time domain channel impulse response of N sampled point to the conversion that this LS estimated result carries out frequency domain to time domain, wherein, N is a sampling number.
The conversion of the frequency domain to time domain in the present embodiment can be IFFT, also can specifically not do qualification herein for the conversion of the frequency domain to time domain of other modes.
403,, calculate the energy duration set of the time domain channel impulse response of continuous L the sampled point that begins from this sampled point for each sampled point;
The LS estimated result is carried out obtain after the conversion of frequency domain to time domain the time domain channel impulse response of N sampled point.
At each sampled point, the time domain channel impulse response of N continuous-L the sampled point that calculating begins from this sampled point can duration set, then can obtain N energy duration set, this energy duration set promptly is the energy sum of the time domain channel impulse response of this N-L sampled point, and this L is the length of OFDM Cyclic Prefix.
In the present embodiment, it is continuous that a continuous N-L sampled point does not refer in particular to the numbering of sampled point, and be meant the starting point that each sampled point all can one group of N-L sampled point, for example, for last sampled point, thereafter the sampled point that does not have other then uses N-L-1 sampled point and this last sampled point of beginning to form N-L sampled point.
Need to prove that after the time domain channel impulse response of each sampled point was determined, the process of energy of calculating the time domain channel impulse response of each sampled point was those skilled in the art's common practise, does not specifically do qualification herein.
404, determine N-L sampled point of the energy duration set correspondence of energy minimum in N the energy duration set;
Adopting the mode of DFT filtering is in order to reduce The noise, thereby improve the accuracy of channel estimating, the process of this DFT filtering promptly is the numerical value that only keeps L sampled point in N the sampled point, the whole zero setting of numerical value of remaining N-L sampled point, thus reduce The noise.
In the present embodiment, obtained can the energy of this N energy duration set being compared after N the energy duration set, therefrom selected the energy duration set of energy minimum, determined the pairing N-L of this an energy duration set sampled point afterwards again.
405, with the energy minimum can duration set the numerical value zero setting of N-L sampled point of correspondence;
What step 404 had been determined the energy minimum can duration set after N-L the sampled point of correspondence, the energy that then means the time domain channel impulse response of this N-L sampled point can be not helpful to the OFDM channel estimating, can bring The noise on the contrary, in order to carry out DFT filtering, then can be with numerical value zero setting, to reduce The noise except this N-L sampled point.
406, the current numerical value of N sampled point is carried out time domain and obtain channel estimation results to the conversion of frequency domain.
Treat after the numerical value zero setting of N-L sampled point of zero setting, then can carry out time domain to the current numerical value of N sampled point and obtain channel estimation results, thereby finish the OFDM channel estimating to the conversion of frequency domain.
Time domain in the present embodiment can be FFT to the conversion of frequency domain, also can arrive the conversion of frequency domain for the time domain of other modes, does not specifically do qualification herein.
In the present embodiment, can be according to the time domain channel impulse response calculating energy set of the N that an obtains sampled point, N sampled point then obtains N energy duration set, determine the energy duration set of energy minimum in N the energy duration set afterwards, and with this energy minimum can duration set the numerical value zero setting of N-L sampled point of correspondence, owing to when determining to treat the sampled point of zero setting, considered the energy of each sampled point, so when multipath channel is that non-sampling interval is during channel, the sampled point that some energy at end are stronger can't be by direct zero setting, so can avoid energy leakage, thereby improve systematic function.
For ease of understanding, describe with the process of an instantiation below channel estimating of the present invention, see also Fig. 5:
(1), on frequency domain, at first the OFDM channel is carried out the LS channel estimating, obtain the LS estimated result H that N is ordered
LS(0)～H
LS(N-1);
(2), the LS estimated result carried out IFFT handle, obtain the time domain channel impulse response h of N sampled point on the time domain
LS(0)～h
LS(N-1);
(3), carry out the selection in zero setting interval according to the time domain channel impulse response of each sampled point;
The selection in concrete zero setting interval sees also Fig. 6, the figure as a result that time domain channel impulse response schematic diagram shown in Figure 6 is based on parameter that following table 1 describes after handling, and sample rate is 10MHz:
Table 1
In Fig. 6, the number N of sampled point is 64, i.e. 0～63 shown in the figure, and the length L of Cyclic Prefix is 32, the abscissa of Fig. 6 is represented sampled point, total coordinate representation normalization amplitude, and this normalization amplitude can characterize the energy size, the normalization amplitude is big more, and then energy is big more, and vice versa.
As seen in Figure 6, though most concentration of energy on some sampled points of front, several sampled points at end also have more intense energy, and energy leakage has promptly taken place.
In the channel estimation methods of prior art based on DFT filtering, L sampled point before only getting, the equal zero setting of the numerical value of remaining sampled point, as shown in Figure 6, have only the numerical value of 0～No. 31 sampled point to keep in the prior art, and the numerical value zero setting of 32 to No. 63 sampled points, zero setting promptly of the prior art interval is [32 to 63].
Present embodiment determines that in the maximized mode of energy the zero setting interval is that example describes:
Since No. 0 sampled point, calculate continuous 32 sampled points that begin from each sampled point the time domain channel impulse response can duration set.
In the present embodiment, can obtain 64 sampling intervals altogether, 32 sampled points are arranged in each interval, concrete, sampling interval is [0 to 31], [1 to 32], [2 to 33], ... [32 to 63], [33 to 63,0], [34 to 63,0,1], [35 to 63,0 to 2] ... [62 to 63,0 to 29], [63,0 to 30].
From 64 above-mentioned sampling intervals as can be seen, each sampled point all can become the starting point of a sampling interval.
At above-mentioned 64 sampling intervals, calculate the energy sum of the time domain channel impulse response of 32 sampled points in each sampling interval respectively, thereby obtain 64 energy duration sets.
Again 64 energy duration sets are compared afterwards, determine the energy duration set of energy maximum, and determine the pairing sampled point of this energy duration set, in the present embodiment, because some sampled points at end have stronger energy, so when calculating energy is gathered, the energy that includes the sampling interval of end sampled point can be bigger, the sampling interval of supposing the energy duration set of energy maximum is [59 to 63,0 to 26], then remaining 32 sampled points, i.e. [27 to 58], then for treating the sampled point of zero setting, then the interval of the zero setting in the present embodiment is [27 to 58].
Present embodiment is determined the zero setting interval in the maximized mode of energy, is understandable that, in actual applications, can determine the zero setting interval in the mode of energy minimization equally, and detailed process is similar, repeats no more herein.
N the result who obtains after the zero setting is hDFT (0)～hDFT (N-1), and the numerical value that N-L result arranged among this N result is 0.
The process of the zero setting interval selection in the present embodiment can be realized that concrete false code can be as follows by software:
h_improved_dft_matrix＝[]；
for?ii＝1:CP
H_improved_dft_matrix=[h_improved_dft_matrix; [h_improved_dft (1:ii) h_improved_dft (end-(CP-ii)+1:end)]]; // be starting point with each sampled point, calculate the time domain channel impulse response
end
Tmp=sum (abs (h_improved_dft_matrix) .^2,2); // selection ceiling capacity
[val, idx]=max (tmp); // determine the starting point of ceiling capacity correspondence
H_improved_dft=[h_improved_dft (1:idx) zeros (1, N-CP) h_improved_dft (end-(CP-idx)+1:end)]; // zero setting is handled
H_improved_dft=ffh (h_improved_dft); // carry out the FFT processing to obtain channel estimation results
Need to prove that the above-mentioned false code that provides in the present embodiment only is a concrete example, be understandable that, in actual applications, can adopt the false code of other types or the process that program realizes the zero setting interval selection equally, do not do qualification herein.
(4), carry out FFT and handle, obtain OFDM channel estimation results H
DFT(0)～H
DFT(N-1).
Above the channel estimation methods in the embodiment of the invention is described, below the channel estimating apparatus in the embodiment of the invention is described, see also Fig. 7, the channel estimating apparatus in the embodiment of the invention comprises:
Zero setting processing unit 703, be used for for each sampled point, the time domain channel impulse response of continuous several sampled points that calculating begins from this sampled point can duration set, determine to treat N-L sampled point of zero setting according to the energy duration set that obtains, L is the length of OFDM Cyclic Prefix, will treat the numerical value zero setting of N-L sampled point of zero setting;
Zero setting processing unit 703 in the present embodiment can further include:
Perhaps,
Zero setting processing unit 703 in the present embodiment can further include:
Detailed process that zero setting processing unit 703 in the present embodiment is performed and earlier figures 2 and embodiment illustrated in fig. 3 in the content class described seemingly, specifically repeat no more herein.
In the embodiment of the invention, zero setting processing unit 703 can be according to the time domain channel impulse response calculating energy set of the N that an obtains sampled point, N sampled point then obtains N energy duration set, can determine N-L the sampled point for the treatment of zero setting by duration set according to N that obtains afterwards, and carry out zero setting, owing to when determining to treat the sampled point of zero setting, considered the energy of each sampled point, so when multipath channel is that non-sampling interval is during channel, the sampled point that some energy at end are stronger can't be by direct zero setting, so can avoid energy leakage, thereby improve systematic function.
Below the effect of the channel estimating in the embodiment of the invention is analyzed:
One, at indoor environment (ITU Indoor A):
Concrete experiment parameter is as shown in table 2 below:
Table 2
Modulation system is 4-QAM, systematic sampling rate 10MHz, N=1024, L=256, k=6, the maximum length 32 of multipath channel identification under the systematic sampling rate.
See also Fig. 8, Fig. 8 is the schematic diagram of signal to noise ratio (snr) and mean square error (MSE) relation, wherein, what curve 801 was represented is LS performance for estimating channel curve, what curve 802 was represented is existing LS performance for estimating channel curve based on DFT filtering, and what curve 803 was represented is the performance curve of the channel estimation methods in the present embodiment.
As seen from Figure 8, plateau phenomenon has appearred in the LS channel estimating based on DFT filtering of prior art when signal to noise ratio improves, and mean square error is difficult to descend, and in the scheme of the embodiment of the invention, even signal to noise ratio improves, also can effectively reduce mean square error.
See also Fig. 9, Fig. 9 is the schematic diagram of signal to noise ratio (snr) and bit error rate (BER) relation, wherein, what curve 901 was represented is LS performance for estimating channel curve, what curve 902 was represented is existing LS performance for estimating channel curve based on DFT filtering, what curve 903 was represented is the performance curve of the channel estimation methods in the present embodiment, and curve 904 is perfect performance curves.
As seen from Figure 9, LS channel estimating bit error rate when signal to noise ratio improves based on DFT filtering of prior art is difficult to descend, and in the scheme of the embodiment of the invention, even signal to noise ratio improves, also can effectively reduce bit error rate, and more approach perfect performance.
Two, at vehicle environment (ITU VehicularA):
Shown in the table 1, modulation system is 4-QAM to concrete experiment parameter, systematic sampling rate 10MHz, N=1024, L=256, k=6, the maximum length 32 of multipath channel identification under the systematic sampling rate as described above.
See also Figure 10, Figure 10 is the schematic diagram of signal to noise ratio (snr) and mean square error (MSE) relation, wherein, what curve 1001 was represented is LS performance for estimating channel curve, what curve 1002 was represented is existing LS performance for estimating channel curve based on DFT filtering, and what curve 1003 was represented is the performance curve of the channel estimation methods in the present embodiment.
As seen from Figure 10, plateau phenomenon has appearred in the LS channel estimating based on DFT filtering of prior art when signal to noise ratio improves, and mean square error is difficult to descend, and in the scheme of the embodiment of the invention, even signal to noise ratio improves, also can effectively reduce mean square error.
See also Figure 11, Figure 11 is the schematic diagram of signal to noise ratio (snr) and bit error rate (BER) relation, wherein, what curve 1101 was represented is LS performance for estimating channel curve, what curve 1102 was represented is existing LS performance for estimating channel curve based on DFT filtering, what curve 1103 was represented is the performance curve of the channel estimation methods in the present embodiment, and curve 1104 is perfect performance curves.
As seen from Figure 11, LS channel estimating bit error rate when signal to noise ratio improves based on DFT filtering of prior art is difficult to descend, and in the scheme of the embodiment of the invention, even signal to noise ratio improves, also can effectively reduce bit error rate, and more approach perfect performance.
By above-mentioned Fig. 8 to Figure 11 as can be known, no matter be indoor environment or vehicle environment, the effect of the channel estimation methods in the embodiment of the invention all is better than in the prior art LS channel estimation methods based on DFT filtering, so the channel estimation methods in the embodiment of the invention can effectively improve systematic function.
One of ordinary skill in the art will appreciate that all or part of step that realizes in the foregoing description method is to instruct relevant hardware to finish by program, this program can be stored in a kind of computer-readable recording medium, the above-mentioned storage medium of mentioning can be a read-only memory, disk or CD etc.
More than a kind of channel estimation methods provided by the present invention and device are described in detail, for one of ordinary skill in the art, thought according to the embodiment of the invention, part in specific embodiments and applications all can change, therefore, this description should not be construed as limitation of the present invention.
Claims (10)
1. a channel estimation methods is characterized in that, comprising:
Utilize block pilot tone that the orthogonal frequency division multiplex OFDM channel is carried out criterion of least squares LS channel estimating and obtain the LS estimated result;
The conversion that described LS estimated result is carried out frequency domain to time domain obtains the time domain channel impulse response of N sampled point, and described N is a sampling number;
For each sampled point, calculate continuous several sampled points that begin from this sampled point the time domain channel impulse response can duration set;
According to N-L the sampled point can duration set determining to treat zero setting that obtains, described L is the length of OFDM Cyclic Prefix;
With the described numerical value zero setting for the treatment of N-L sampled point of zero setting;
The current numerical value of N sampled point is carried out time domain obtain channel estimation results to the conversion of frequency domain.
2. method according to claim 1 is characterized in that, and is described for each sampled point, calculates the comprising by duration set of time domain channel impulse response of continuous several sampled points that begin from this sampled point:
For each sampled point, calculate the energy duration set of the time domain channel impulse response of continuous L the sampled point that begins from this sampled point.
3. method according to claim 2 is characterized in that, what described basis obtained can determine that N-L sampled point treating zero setting comprises by duration set:
Determine L sampled point of the energy duration set correspondence of energy maximum in N the energy duration set;
Will except that described energy maximum can duration set other N-L sampled points conducts L the sampled point of correspondence treat N-L sampled point of zero setting.
4. method according to claim 1 is characterized in that, and is described for each sampled point, calculates the comprising by duration set of time domain channel impulse response of continuous several sampled points that begin from this sampled point:
For each sampled point, calculate the energy duration set of the time domain channel impulse response of N continuous-L the sampled point that begins from this sampled point.
5. method according to claim 4 is characterized in that, what described basis obtained can determine that N-L sampled point treating zero setting comprises by duration set:
Determine N-L sampled point of the energy duration set correspondence of energy minimum in N the energy duration set;
With described N-L definite sampled point as the N-L that treats a zero setting sampled point.
6. according to each described method in the claim 1 to 5, it is characterized in that,
Being transformed to of described frequency domain to time domain against fast fourier transform IFFT;
Described time domain is transformed to fast fourier transform FFT to frequency domain.
7. a channel estimating apparatus is characterized in that, comprising:
The LS processing unit is used to utilize block pilot tone that the orthogonal frequency division multiplex OFDM channel is carried out criterion of least squares LS channel estimating and obtains the LS estimated result;
First converter unit is used for the conversion that described LS estimated result carries out frequency domain to time domain is obtained the time domain channel impulse response of N sampled point, and described N is a sampling number;
The zero setting processing unit, be used for for each sampled point, the time domain channel impulse response of continuous several sampled points that calculating begins from this sampled point can duration set, determine to treat N-L sampled point of zero setting according to the energy duration set that obtains, described L is the length of OFDM Cyclic Prefix, with the described numerical value zero setting for the treatment of N-L sampled point of zero setting;
Second converter unit is used for current numerical value to N sampled point and carries out time domain and obtain channel estimation results to the conversion of frequency domain.
8. device according to claim 7 is characterized in that, described zero setting processing unit comprises:
First computing module is used for for each sampled point, calculates the energy duration set of the time domain channel impulse response of continuous L the sampled point that begins from this sampled point;
First determination module, be used for determining N can duration set energy maximum can the duration set correspondence L sampled point, will treat N-L sampled point of zero setting except that other N-L sampled points conducts L the sampled point of the energy duration set correspondence of described energy maximum;
First processing module is used for the numerical value zero setting for the treatment of N-L sampled point of zero setting with described.
9. device according to claim 7 is characterized in that, described zero setting processing unit comprises:
Second computing module is used for for each sampled point, calculates the energy duration set of the time domain channel impulse response of N continuous-L the sampled point that begins from this sampled point;
Second determination module, be used for determining N can duration set energy minimum can the duration set correspondence N-L sampled point, will treat N-L sampled point of zero setting except that N-L sampled point conduct of the energy duration set correspondence of described energy minimum;
Second processing module is used for the numerical value zero setting for the treatment of N-L sampled point of zero setting with described.
10. according to each described device in the claim 7 to 9, it is characterized in that described first converter unit is contrary fast fourier transform IFFT unit;
Described second converter unit is fast fourier transform FFT unit.
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| CN104253771A (en) * | 2013-06-27 | 2014-12-31 | 富士通株式会社 | Multi-parameter joint estimation method and apparatus |
| CN105141555A (en) * | 2014-05-27 | 2015-12-09 | 恩智浦有限公司 | System and method for performing channel estimation on an ofdm signal |
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| CN101115046A (en) * | 2007-09-04 | 2008-01-30 | 西安电子科技大学 | Modified type LS channel estimation method for OFDM system |
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| CN105141555A (en) * | 2014-05-27 | 2015-12-09 | 恩智浦有限公司 | System and method for performing channel estimation on an ofdm signal |
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| CN108650197B (en) * | 2018-03-29 | 2021-01-29 | 江苏中科羿链通信技术有限公司 | Improved DFT-S-OFDM channel estimation response noise reduction method |
| CN111277521A (en) * | 2019-12-19 | 2020-06-12 | 南京六九零二科技有限公司 | Channel estimation and noise filtering method of single carrier frequency domain equalization system |
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