CN102143113B - 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 signal process field, relate in particular to a kind of channel estimation methods and device.
Background technology
Along with people are to the broadband demand of communicating by letter, wireless communication system is just developed rapidly to broadband by arrowband.OFDM (OFDM, Orthogonal Frequency Division Multiplexing) technology is a kind of special Multicarrier Transmission Technology, it is by being converted into the information symbol of two-forty parallel low rate information symbol, then parallel transmission on the subcarrier of a plurality of quadratures, has resisted the frequency selective fading phenomenon that broadband system runs in wireless transmission effectively.
Channel condition information is mainly used in the receiving terminal detection that is concerned with 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 ofdm system of pilot tone block distribution is carried out to channel estimating, can be according to criterion of least squares (LS, Least Square) or least mean-square error (MMSE, Minimum Mean Square Error) criterion, obtain frequency domain channel state information.
Channel estimation methods based on LS is simple, but evaluated error is larger, and channel estimation methods precision based on MMSE is higher, 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 carry out noise reduction process to the channel estimation in frequency domain based on LS, to approach the channel estimating effect based on MMSE.As shown in Figure 1, implementation procedure based on DFT filtering comprises: first utilize block pilot tone to carry out LS channel estimating, then utilize the channel estimating obtaining by fast adverse Fourier transform (IFFT, Inverse Fast Fourier Transform) calculate 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.Finally, the CIR estimated result obtaining is transformed into frequency domain, completes channel estimating.
But in actual OFDM wireless system, systematic sampling interval might not be the integral multiple of multipath channel time delay, 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, channel time domain response after IFFT computing might not all concentrate on the sampled point in circulating prefix-length interval above, and at end, occur the sampled point that some energy are stronger, thereby cause energy leakage phenomenon.This phenomenon can make traditional method of estimation based on DFT filtering occur plateau phenomenon at the mean square error estimated performance in middle high s/n ratio region, has had a strong impact on systematic function.
Summary of the invention
The embodiment of the present invention provides a kind of channel estimation methods and device, can improve systematic function.
The channel estimation methods that the embodiment of the present invention provides, comprising: utilize block pilot tone to carry out criterion of least squares LS channel estimating to orthogonal frequency division multiplex OFDM channel and obtain LS estimated result; The conversion that described LS estimated result is carried out to frequency domain to time domain obtains the time domain channel impulse response of N sampled point, and described N is sampling number; For each sampled point, calculate the energy aggregation of the time domain channel impulse response of continuous several sampled points that start from this sampled point; According to the energy aggregation obtaining, determine N-L sampled point treating zero setting, described L is the length of OFDM Cyclic Prefix; By the described numerical value zero setting for the treatment of N-L sampled point of zero setting; The current value of N sampled point is carried out to time domain and to the conversion of frequency domain, obtain channel estimation results.
The channel estimating apparatus that the embodiment of the present invention provides, comprising: LS processing unit, obtains LS estimated result for utilizing block pilot tone to carry out criterion of least squares LS channel estimating to orthogonal frequency division multiplex OFDM channel; The first converter unit, obtains the time domain channel impulse response of N sampled point for the conversion that described LS estimated result is carried out to frequency domain to time domain, described N is sampling number; Zero setting processing unit, be used for for each sampled point, the energy aggregation of the time domain channel impulse response of continuous several sampled points that calculating starts from this sampled point, according to the energy aggregation obtaining, determine N-L sampled point treating zero setting, described L is the length of OFDM Cyclic Prefix, by the described numerical value zero setting for the treatment of N-L sampled point of zero setting; The second converter unit, obtains channel estimation results for the current value of N sampled point being carried out to time domain to the conversion of frequency domain.
As can be seen from the above technical solutions, the embodiment of the present invention has the following advantages: in the embodiment of the present invention, can be according to the time domain channel impulse response calculating energy set of the N an obtaining sampled point, N sampled point obtains N energy aggregation, according to N the energy aggregation obtaining, determine N-L the sampled point for the treatment of zero setting afterwards, and carry out zero setting, during due to sampled point determining until zero setting, considered the energy of each sampled point, so when multipath channel is that non-sampling interval is during channel, the stronger sampled point of some energy at end can't be by direct zero setting, so can avoid energy leakage, thereby improved systematic function.
Accompanying drawing explanation
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 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 present invention provides a kind of channel estimation methods and device, can improve systematic function.
Refer to Fig. 2, embodiment of channel estimation methods of the present invention comprises:
201, utilize block pilot tone to carry out LS channel estimating to OFDM channel and obtain LS estimated result;
The channel estimation methods of the present embodiment is based on LS channel estimating, so first can utilize block pilot tone to carry out LS channel estimating and obtain LS estimated result carrying out the OFDM channel of channel estimating.
Specifically carry out the common practise that the process of LS channel estimating is those skilled in the art, specifically do not limit herein.
202, the conversion of LS estimated result being carried out to frequency domain to time domain obtains the time domain channel impulse response of N sampled point;
After obtaining LS estimated result, the conversion that can carry out frequency domain to time domain to this LS estimated result obtains the time domain channel impulse response of N sampled point, and wherein, N is sampling number.
203,, for each sampled point, calculate the energy aggregation of the time domain channel impulse response of continuous several sampled points that start from this sampled point;
LS estimated result is carried out to obtain after the conversion of frequency domain to time domain the time domain channel impulse response of N sampled point.
For each sampled point, the energy aggregation of the time domain channel impulse response of continuous several sampled points that calculating starts from this sampled point, can obtain N energy aggregation, this energy aggregation is the energy sum of the time domain channel impulse response of these several sampled points.
It should be noted that, after the time domain channel impulse response of each sampled point is determined, the common practise that the process of energy of calculating the time domain channel impulse response of each sampled point is those skilled in the art does not specifically limit herein.
204, according to the energy aggregation obtaining, determine N-L sampled point treating zero setting;
Adopting the mode of DFT filtering is in order to fall low noise impact, thereby improve the accuracy of channel estimating, the process of this DFT filtering is the numerical value that only retains L sampled point in N sampled point, the whole zero setting of numerical value of remaining N-L sampled point, thereby fall low noise impact, this L is the length of OFDM Cyclic Prefix.
In the present embodiment, after having obtained N energy aggregation, can determine N-L sampled point treating zero setting according to this N energy aggregation.
205, the numerical value zero setting of N-L sampled point of zero setting will be treated;
206, the current value of N sampled point is carried out to time domain and obtain channel estimation results to the conversion of frequency domain.
After treating the numerical value zero setting of N-L sampled point of zero setting, can carry out time domain to the current value of N sampled point and obtain channel estimation results to the conversion of frequency domain, thereby complete OFDM channel estimating.
In the present embodiment, can be according to the time domain channel impulse response calculating energy set of the N an obtaining sampled point, N sampled point obtains N energy aggregation, according to N the energy aggregation obtaining, determine N-L the sampled point for the treatment of zero setting afterwards, and carry out zero setting, during due to sampled point determining until zero setting, considered the energy of each sampled point, so when multipath channel is that non-sampling interval is during channel, the stronger sampled point of some energy at end can't be by direct zero setting, so can avoid energy leakage, thereby improve systematic function.
In the present embodiment, specifically can determine in several ways N-L sampled point treating zero setting, describe for example below:
(1), by the mode of energy maximization, determine N-L sampled point treating zero setting:
Refer to Fig. 3, another embodiment of channel estimation methods of the present invention comprises:
301, utilize block pilot tone to carry out LS channel estimating to OFDM channel and obtain LS estimated result;
The channel estimation methods of the present embodiment is based on LS channel estimating, so first can utilize block pilot tone to carry out LS channel estimating and obtain LS estimated result carrying out the OFDM channel of channel estimating.
Specifically carry out the common practise that the process of LS channel estimating is those skilled in the art, specifically do not limit herein.
302, the conversion of LS estimated result being carried out to frequency domain to time domain obtains the time domain channel impulse response of N sampled point;
After obtaining LS estimated result, the conversion that can carry out frequency domain to time domain to this LS estimated result obtains the time domain channel impulse response of N sampled point, and wherein, N is 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, for the conversion of the frequency domain to time domain of other modes, specifically not limit herein.
303,, for each sampled point, calculate the energy aggregation of the time domain channel impulse response of continuous L the sampled point starting from this sampled point;
LS estimated result is carried out to obtain after the conversion of frequency domain to time domain the time domain channel impulse response of N sampled point.
For each sampled point, the energy aggregation of the time domain channel impulse response of continuous L the sampled point that calculating starts from this sampled point, can obtain N energy aggregation, this energy aggregation 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 refer to the starting point that each sampled point can one group of L sampled point, for example, for last sampled point, do not have other sampled point, use L-1 sampled point and this last sampled point of beginning to form L sampled point thereafter.
It should be noted that, after the time domain channel impulse response of each sampled point is determined, the common practise that the process of energy of calculating the time domain channel impulse response of each sampled point is those skilled in the art does not specifically limit herein.
304, determine L the sampled point corresponding to energy aggregation of energy maximum in N energy aggregation;
Adopting the mode of DFT filtering is in order to fall low noise impact, thereby improve the accuracy of channel estimating, the process of this DFT filtering is the numerical value that only retains L sampled point in N sampled point, the whole zero setting of numerical value of remaining N-L sampled point, thus low noise impact is fallen.
In the present embodiment, after having obtained N energy aggregation, can compare the energy of this N energy aggregation, therefrom select the energy aggregation of energy maximum, determine again afterwards the corresponding L of this energy aggregation sampled point.
305, by the numerical value zero setting of other N-L sampled point L sampled point corresponding to the energy aggregation except energy maximum;
After step 304 has been determined L the sampled point that the energy aggregation of energy maximum is corresponding, the energy that means the time domain channel impulse response of this L sampled point has great effect to OFDM channel estimating, and in order to carry out DFT filtering, can be by the numerical value zero setting of N-L sampled point except this L sampled point, to fall low noise impact.
306, the current value of N sampled point is carried out to time domain and obtain channel estimation results to the conversion of frequency domain.
After treating the numerical value zero setting of N-L sampled point of zero setting, can carry out time domain to the current value of N sampled point and obtain channel estimation results to the conversion of frequency domain, thereby complete OFDM channel estimating.
Time domain in the present embodiment can be fast fourier transform (FFT, Fast Fourier Transform) to the conversion of frequency domain, also can for the time domain of other modes, arrive the conversion of frequency domain, does not specifically limit herein.
In the present embodiment, can be according to the time domain channel impulse response calculating energy set of the N an obtaining sampled point, N sampled point obtains N energy aggregation, determine afterwards the energy aggregation of energy maximum in N energy aggregation, and by the numerical value zero setting of other N-L sampled point L sampled point corresponding to the energy aggregation except energy maximum, during due to sampled point determining until zero setting, considered the energy of each sampled point, so when multipath channel is that non-sampling interval is during channel, the stronger sampled point of some energy at end can't be by direct zero setting, so can avoid energy leakage, thereby improved systematic function.
(2), by the mode of energy minimization, determine N-L sampled point treating zero setting:
Refer to Fig. 4, another embodiment of channel estimation methods of the present invention comprises:
401, utilize block pilot tone to carry out LS channel estimating to OFDM channel and obtain LS estimated result;
The channel estimation methods of the present embodiment is based on LS channel estimating, so first can utilize block pilot tone to carry out LS channel estimating and obtain LS estimated result carrying out the OFDM channel of channel estimating.
Specifically carry out the common practise that the process of LS channel estimating is those skilled in the art, specifically do not limit herein.
402, the conversion of LS estimated result being carried out to frequency domain to time domain obtains the time domain channel impulse response of N sampled point;
After obtaining LS estimated result, the conversion that can carry out frequency domain to time domain to this LS estimated result obtains the time domain channel impulse response of N sampled point, and wherein, N is sampling number.
The conversion of the frequency domain to time domain in the present embodiment can be IFFT, also can, for the conversion of the frequency domain to time domain of other modes, specifically not limit herein.
403,, for each sampled point, calculate the energy aggregation of the time domain channel impulse response of continuous L the sampled point starting from this sampled point;
LS estimated result is carried out to obtain after the conversion of frequency domain to time domain the time domain channel impulse response of N sampled point.
For each sampled point, the energy aggregation of the time domain channel impulse response of N continuous-L that calculating starts from this sampled point sampled point, can obtain N energy aggregation, this energy aggregation 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 refer to the starting point that each sampled point can one group of N-L sampled point, for example, for last sampled point, do not have other sampled point, use N-L-1 sampled point and this last sampled point of beginning to form N-L sampled point thereafter.
It should be noted that, after the time domain channel impulse response of each sampled point is determined, the common practise that the process of energy of calculating the time domain channel impulse response of each sampled point is those skilled in the art does not specifically limit herein.
404, determine N-L the sampled point corresponding to energy aggregation of energy minimum in N energy aggregation;
Adopting the mode of DFT filtering is in order to fall low noise impact, thereby improve the accuracy of channel estimating, the process of this DFT filtering is the numerical value that only retains L sampled point in N sampled point, the whole zero setting of numerical value of remaining N-L sampled point, thus low noise impact is fallen.
In the present embodiment, after having obtained N energy aggregation, can compare the energy of this N energy aggregation, therefrom select the energy aggregation of energy minimum, determine again afterwards the corresponding N-L of this energy aggregation sampled point.
405, by the numerical value zero setting of N-L sampled point corresponding to the energy aggregation of energy minimum;
After step 404 has been determined N-L the sampled point that the energy aggregation of energy minimum is corresponding, the energy that means the time domain channel impulse response of this N-L sampled point can be not helpful to OFDM channel estimating, can bring the impact of noise on the contrary, in order to carry out DFT filtering, can be by the numerical value zero setting except this N-L sampled point, to fall low noise impact.
406, the current value of N sampled point is carried out to time domain and obtain channel estimation results to the conversion of frequency domain.
After treating the numerical value zero setting of N-L sampled point of zero setting, can carry out time domain to the current value of N sampled point and obtain channel estimation results to the conversion of frequency domain, thereby complete OFDM channel estimating.
Time domain in the present embodiment can be FFT to the conversion of frequency domain, also can for the time domain of other modes, arrive the conversion of frequency domain, does not specifically limit herein.
In the present embodiment, can be according to the time domain channel impulse response calculating energy set of the N an obtaining sampled point, N sampled point obtains N energy aggregation, determine afterwards the energy aggregation of energy minimum in N energy aggregation, and by the numerical value zero setting of N-L sampled point corresponding to the energy aggregation of this energy minimum, during due to sampled point determining until zero setting, considered the energy of each sampled point, so when multipath channel is that non-sampling interval is during channel, the stronger sampled point of some energy at end can't be by direct zero setting, so can avoid energy leakage, thereby improved systematic function.
For ease of understanding, with an instantiation, the process of channel estimating of the present invention is described below, refer to Fig. 5:
(1), on frequency domain, first OFDM channel is carried out to LS channel estimating, obtain the LS estimated result H that N is ordered
lS(0)～H
lS(N-1);
(2), LS estimated result is carried out to IFFT processing, obtain the time domain channel impulse response h of N sampled point in time domain
lS(0)～h
lS(N-1);
(3), according to the time domain channel impulse response of each sampled point, carry out the selection in zero setting interval;
The selection in concrete zero setting interval refers to Fig. 6, and the time domain channel impulse response schematic diagram shown in Fig. 6 is the result figure after the parameter based on following table 1 description is processed, and sample rate is 10MHz:
Table 1
In Fig. 6, the number N of sampled point is 64, i.e. 0～63 shown in figure, and the length L of Cyclic Prefix is 32, the abscissa of Fig. 6 represents sampled point, and total coordinate represents normalization amplitude, and this normalization amplitude can characterize energy size, normalization amplitude is larger, and energy is larger, and vice versa.
As seen in Figure 6, although most concentration of energy on some sampled points above, several sampled points at end also have more intense energy, and energy leakage has occurred.
In the channel estimation methods of prior art based on DFT filtering, only get a front L sampled point, the equal zero setting of numerical value of remaining sampled point, as shown in Figure 6, in prior art, only have the numerical value of 0～No. 31 sampled point to retain, and the numerical value zero setting of 32 to No. 63 sampled points, zero setting of the prior art interval is [32 to 63].
The present embodiment be take the mode of energy maximization and is determined that zero setting interval describes as example:
Since No. 0 sampled point, calculate the energy aggregation of the time domain channel impulse response of continuous 32 sampled points that start from each sampled point.
In the present embodiment, can obtain altogether 64 sampling intervals, in each interval, have 32 sampled points, 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, can find out, each sampled point can become the starting point of a sampling interval.
For above-mentioned 64 sampling intervals, calculate respectively the energy sum of the time domain channel impulse response of 32 sampled points in each sampling interval, thereby obtain 64 energy aggregations.
Again 64 energy aggregations are compared afterwards, determine the energy aggregation of energy maximum, and determine the corresponding sampled point of this energy aggregation, in the present embodiment, because some sampled points at end have stronger energy, so when calculating energy set, the energy that includes the sampling interval of end sampled point can be larger, the sampling interval of supposing the energy aggregation of energy maximum is [59 to 63,0 to 26], remaining 32 sampled points, i.e. [27 to 58],, for treating the sampled point of zero setting, the interval of the zero setting in the present embodiment is [27 to 58].
The present embodiment determines that in the mode of energy maximization zero setting is interval, is understandable that, in actual applications, can determine that zero setting is interval in the mode of energy minimization equally, and detailed process is similar, repeats no more herein.
N the result obtaining after zero setting is hDFT (0)～hDFT (N-1), and the numerical value that has N-L result in this N result is 0.
The process of the zero setting interval selection in the present embodiment can be realized by software, and concrete false code can be as follows:
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)]]; // take each sampled point as starting point, calculate 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 that ceiling capacity is corresponding
H_improved_dft=[h_improved_dft (1:idx) zeros (1, N-CP) h_improved_dft (end-(CP-idx)+1:end)]; // zero setting is processed
H_improved_dft=ffh (h_improved_dft); // carry out FFT processing to obtain channel estimation results
It should be noted that, the above-mentioned false code providing in the present embodiment is only a concrete example, is understandable that, in actual applications, can adopt equally the false code of other types or the process that program realizes zero setting interval selection, does not limit herein.
(4), carry out FFT processing, obtain OFDM channel estimation results H
dFT(0)～H
dFT(N-1).
Above the channel estimation methods in the embodiment of the present invention is described, below the channel estimating apparatus in the embodiment of the present invention is described, refer to Fig. 7, the channel estimating apparatus in the embodiment of the present invention comprises:
The first converter unit 702, obtains the time domain channel impulse response of N sampled point for LS estimated result being carried out to the conversion of frequency domain to time domain, N is sampling number;
Zero setting processing unit 703, be used for for each sampled point, the energy aggregation of the time domain channel impulse response of continuous several sampled points that calculating starts from this sampled point, according to the energy aggregation obtaining, determine N-L sampled point treating zero setting, L is the length of OFDM Cyclic Prefix, will treat the numerical value zero setting of N-L sampled point of zero setting;
The second converter unit 704, obtains channel estimation results for the current value of N sampled point being carried out to time domain to the conversion of frequency domain.
Zero setting processing unit 703 in the present embodiment can further include:
The first computing module 7031, for for each sampled point, calculates the energy aggregation of the time domain channel impulse response of continuous L the sampled point starting from this sampled point;
The first determination module 7032, for determining L the sampled point corresponding to energy aggregation of N energy aggregation energy maximum, other N-L sampled points using L sampled point corresponding to the energy aggregation except energy maximum are as N-L sampled point treating zero setting;
The first processing module 7033, for treating the numerical value zero setting of N-L sampled point of zero setting.
Or,
Zero setting processing unit 703 in the present embodiment can further include:
The second computing module 7034, for for each sampled point, calculates the energy aggregation of the time domain channel impulse response of N continuous-L the sampled point starting from this sampled point;
The second determination module 7035, for determining N-L the sampled point corresponding to energy aggregation of N energy aggregation energy minimum, using N-L sampled point corresponding to the energy aggregation that removes energy minimum as N-L sampled point treating zero setting;
The second processing module 7036, for treating the numerical value zero setting of N-L sampled point of zero setting.
The first converter unit 702 in the present embodiment can be contrary fast fourier transform IFFT unit, and the second converter unit 704 can be fast fourier transform FFT unit.
The detailed process that zero setting processing unit 703 in the present embodiment is performed and the content of earlier figures 2 and middle description embodiment illustrated in fig. 3 are similar, specifically repeat no more herein.
In the embodiment of the present invention, zero setting processing unit 703 can be according to the time domain channel impulse response calculating energy set of the N an obtaining sampled point, N sampled point obtains N energy aggregation, according to N the energy aggregation obtaining, determine N-L the sampled point for the treatment of zero setting afterwards, and carry out zero setting, during due to sampled point determining until zero setting, considered the energy of each sampled point, so when multipath channel is that non-sampling interval is during channel, the stronger sampled point of some energy at end 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 present invention is analyzed:
One, for indoor environment (ITU Indoor A):
Specific 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 systematic sampling rate.
Refer to Fig. 8, Fig. 8 is the schematic diagram of signal to noise ratio (SNR) and mean square error (MSE) relation, wherein, what curve 801 represented is the performance curve of LS channel estimating, what curve 802 represented is the performance curve of the existing LS channel estimating based on DFT filtering, and what curve 803 represented is the performance curve of the channel estimation methods in the present embodiment.
As seen from Figure 8, the LS channel estimating based on DFT filtering of prior art has occurred that when signal to noise ratio improves plateau phenomenon, mean square error are difficult to decline, and in the scheme of the embodiment of the present invention, even if signal to noise ratio improves, also can effectively reduce mean square error.
Refer to Fig. 9, Fig. 9 is the schematic diagram of signal to noise ratio (SNR) and bit error rate (BER) relation, wherein, what curve 901 represented is the performance curve of LS channel estimating, what curve 902 represented is the performance curve of the existing LS channel estimating based on DFT filtering, what curve 903 represented is the performance curve of the channel estimation methods in the present embodiment, and curve 904 is desirable performance curves.
As seen from Figure 9, LS channel estimating based on DFT filtering bit error rate when signal to noise ratio improves of prior art is difficult to decline, and in the scheme of the embodiment of the present invention, even if signal to noise ratio improves, also can effectively reduce bit error rate, and closer to desirable performance.
Two, for vehicle environment (ITU VehicularA):
Specific experiment parameter is as shown in aforementioned table 1, and modulation system is 4-QAM, systematic sampling rate 10MHz, N=1024, L=256, k=6, the maximum length 32 of multipath channel identification under systematic sampling rate.
Refer to Figure 10, Figure 10 is the schematic diagram of signal to noise ratio (SNR) and mean square error (MSE) relation, wherein, what curve 1001 represented is the performance curve of LS channel estimating, what curve 1002 represented is the performance curve of the existing LS channel estimating based on DFT filtering, and what curve 1003 represented is the performance curve of the channel estimation methods in the present embodiment.
As seen from Figure 10, the LS channel estimating based on DFT filtering of prior art has occurred that when signal to noise ratio improves plateau phenomenon, mean square error are difficult to decline, and in the scheme of the embodiment of the present invention, even if signal to noise ratio improves, also can effectively reduce mean square error.
Refer to Figure 11, Figure 11 is the schematic diagram of signal to noise ratio (SNR) and bit error rate (BER) relation, wherein, what curve 1101 represented is the performance curve of LS channel estimating, what curve 1102 represented is the performance curve of the existing LS channel estimating based on DFT filtering, what curve 1103 represented is the performance curve of the channel estimation methods in the present embodiment, and curve 1104 is desirable performance curves.
As seen from Figure 11, LS channel estimating based on DFT filtering bit error rate when signal to noise ratio improves of prior art is difficult to decline, and in the scheme of the embodiment of the present invention, even if signal to noise ratio improves, also can effectively reduce bit error rate, and closer to desirable performance.
From above-mentioned Fig. 8 to Figure 11, no matter be indoor environment or vehicle environment, the effect of the channel estimation methods in the embodiment of the present invention is all better than the LS channel estimation methods based on DFT filtering in prior art, so the channel estimation methods in the embodiment of the present invention can effectively improve systematic function.
One of ordinary skill in the art will appreciate that all or part of step realizing in above-described embodiment method is to come the hardware that instruction is relevant to complete by program, this program can be stored in a kind of computer-readable recording medium, the above-mentioned storage medium of mentioning can be read-only memory, disk or CD etc.
Above 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 present invention, all will change in specific embodiments and applications, therefore, this description should not be construed as limitation of the present invention.
Claims (4)
1. a channel estimation methods, is characterized in that, comprising:
Utilize block pilot tone to carry out criterion of least squares LS channel estimating to orthogonal frequency division multiplex OFDM channel and obtain LS estimated result;
The conversion that described LS estimated result is carried out to frequency domain to time domain obtains the time domain channel impulse response of N sampled point, and described N is sampling number;
For each sampled point, calculate the energy aggregation of the time domain channel impulse response of continuous several sampled points that start from this sampled point;
According to the energy aggregation obtaining, determine N-L sampled point treating zero setting, described L is the length of OFDM Cyclic Prefix;
By the described numerical value zero setting for the treatment of N-L sampled point of zero setting so that when multipath channel be non-sampling interval during channel, the stronger sampled point of energy at end can be by direct zero setting;
The current value of N sampled point is carried out to time domain and to the conversion of frequency domain, obtain channel estimation results;
Described for each sampled point, the energy aggregation that calculates the time domain channel impulse response of continuous several sampled points that start from this sampled point comprises:
For each sampled point, calculate the energy aggregation of the time domain channel impulse response of continuous L the sampled point starting from this sampled point;
Energy aggregation that described basis obtains is determined and is treated that N-L sampled point of zero setting comprises:
Determine L the sampled point corresponding to energy aggregation of energy maximum in N energy aggregation;
Other N-L sampled points using L sampled point corresponding to the energy aggregation except described energy maximum are as N-L sampled point treating zero setting;
Or,
Described for each sampled point, the energy aggregation that calculates the time domain channel impulse response of continuous several sampled points that start from this sampled point comprises:
For each sampled point, calculate the energy aggregation of the time domain channel impulse response of N continuous-L the sampled point starting from this sampled point;
Energy aggregation that described basis obtains is determined and is treated that N-L sampled point of zero setting comprises:
Determine N-L the sampled point corresponding to energy aggregation of energy minimum in N energy aggregation;
Using described definite N-L sampled point as N-L sampled point treating zero setting.
2. method according to claim 1, is characterized in that,
Being transformed to against fast fourier transform IFFT of described frequency domain to time domain;
Described time domain is transformed to fast fourier transform FFT to frequency domain.
3. a channel estimating apparatus, is characterized in that, comprising:
LS processing unit, obtains LS estimated result for utilizing block pilot tone to carry out criterion of least squares LS channel estimating to orthogonal frequency division multiplex OFDM channel;
The first converter unit, obtains the time domain channel impulse response of N sampled point for the conversion that described LS estimated result is carried out to frequency domain to time domain, described N is sampling number;
Zero setting processing unit, be used for for each sampled point, the energy aggregation of the time domain channel impulse response of continuous several sampled points that calculating starts from this sampled point, according to the energy aggregation obtaining, determine N-L sampled point treating zero setting, described L is the length of OFDM Cyclic Prefix, by the described numerical value zero setting for the treatment of N-L sampled point of zero setting so that when multipath channel be non-sampling interval during channel, the stronger sampled point of energy at end can be by direct zero setting;
The second converter unit, obtains channel estimation results for the current value of N sampled point being carried out to time domain to the conversion of frequency domain;
Described zero setting processing unit comprises:
The first computing module, for for each sampled point, calculates the energy aggregation of the time domain channel impulse response of continuous L the sampled point starting from this sampled point;
The first determination module, for determining L the sampled point corresponding to energy aggregation of N energy aggregation energy maximum, other N-L sampled points using L sampled point corresponding to the energy aggregation except described energy maximum are as N-L sampled point treating zero setting;
The first processing module, for by the described numerical value zero setting for the treatment of N-L sampled point of zero setting;
Or,
Described zero setting processing unit comprises:
The second computing module, for for each sampled point, calculates the energy aggregation of the time domain channel impulse response of N continuous-L the sampled point starting from this sampled point;
The second determination module, for determining N-L the sampled point corresponding to energy aggregation of N energy aggregation energy minimum, using N-L sampled point corresponding to the energy aggregation of described energy minimum as N-L sampled point treating zero setting;
The second processing module, for by the described numerical value zero setting for the treatment of N-L sampled point of zero setting.
4. device according to claim 3, is characterized in that, described the first converter unit is contrary fast fourier transform IFFT unit;
Described the second converter unit is fast fourier transform FFT unit.
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| US9608844B2 (en) * | 2014-05-27 | 2017-03-28 | Nxp B.V. | System and method for performing channel estimation on an OFDM signal |
| CN106330792A (en) * | 2016-09-13 | 2017-01-11 | 广东顺德中山大学卡内基梅隆大学国际联合研究院 | In-band noise-filtering channel estimation algorithm and in-band noise-filtering channel estimation based on DTF transform domain |
| CN107135057A (en) * | 2017-05-03 | 2017-09-05 | 哈尔滨工业大学 | A kind of efficient frequency division multiplexing Waveform generation method expanded based on zero hangover DFT |
| 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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