CN101577692B - Channel estimating method of orthogonal frequency division multiplexing system and device thereof - Google Patents

Abstract

The invention discloses a channel estimating method of an orthogonal frequency division multiplexing system and a device thereof. The method comprises the following steps of: obtaining initial channeltime domain impulse response; obtaining channel time domain impulse response corresponding to an effective multidiameter delay position in the initial channel time domain impulse response and generat ing an interference matrix according to the effective multidiameter delay position; multiplying the channel time domain impulse response corresponding to the multidiameter delay position by the inverse of the interference matrix to obtain the channel time domain impulse response after modification; and carrying out Fourier transformation to the channel time domain impulse response after modification to obtain channel frequency domain response estimation. In the method and the device, by constructing the multidiameter interference, the inverse of the interference matrix is multiplied by the effective channel time domain impulse response so as to restrict the energy leakage, therefore, the problem of the energy leakage caused by the incoming of virtual subcarrier as well as the floor effect can be effectively eliminated, the estimation precision of the channel is improved, and the system complexity can be controlled by rapid matrix algorithm.

Description

A kind of channel estimation methods of ofdm system and device

Technical field

The present invention relates to the wireless mobile telecommunication technology field, relate in particular to a kind of channel estimation methods and device of ofdm system.

Background technology

OFDM (OFDM) technology has improved spectrum efficiency with multiplexing on the different orthogonal subcarrier behind the high-speed data-flow serial to parallel conversion when between the minimizing data, disturbing.And the subchannel that each subcarrier is corresponding is the frequency-flat fading channel, has effectively reduced the intersymbol interference that multipath fading causes.At present, the OFDM technology is able to extensive use in WLAN, enhancement mode 3-G (Generation Three mobile communication system) etc.

For guaranteeing the superperformance of ofdm system in the wireless mobile communications environment, receiving terminal need provide to be estimated wireless fading channel as far as possible accurately.Therefore, channel estimating is the important step that can not lack in the ofdm system frenulum signal processing.

Fig. 1 illustrates the system schematic that data are sent and received in the ofdm system.As shown in Figure 1, at transmitting terminal, data are through chnnel coding, modulation, Space Time Coding, and the signal of generation and pilot tone signal carry out the resource mapping together, launch after handling through IFFT variation, framing again.At receiving terminal, after separating through FFT conversion, pilot data, the pilot signal of separation is used for channel estimating, deciphers the data of sending through operation reduction such as demodulation, channel decodings again when according to the result of channel estimating isolated data-signal being carried out sky.

In the ofdm system of reality, for avoiding sending the influence that signal receives low pass filter, the parton carrier wave of reserving band edge that system distributes usually is as the virtual subnet carrier wave.Because the pilot frequency sequence that falls in the virtual carrier scope can't provide the channel information in this frequency domain scope; If the channel frequency domain response estimation value of lost part frequency domain information is carried out inverse fourier transform; The time domain impulse response that obtains will receive the influence of energy leakage and the phase mutual interference causes the decline of precision of channel estimation.Existing channel estimation technique is Considering Energy leakage effect not mostly, in time domain limited sampled point is carried out intercepting, has lost effective time domain impulse response, floor effect occurs.Therefore, demand a kind of method of effective elimination energy leakage influence urgently, improve the precision of channel estimation in the real system.

Summary of the invention

The technical problem that the present invention will solve provides a kind of channel estimation methods of ofdm system, the precision of channel estimation in can the raising system.

The present invention provides a kind of channel estimation methods of ofdm system, comprising: the patterns available to being positioned at effective subcarrier scope is carried out channel frequency domain response estimation, carries out inverse Fourier transform, obtains initial channel time domain impulse response; With the corresponding channel time domain impulse response in effective multidiameter delay position, generate interference matrix in the acquisition initial channel time domain impulse response according to effective multidiameter delay position; Contrary and the channel time domain impulse response corresponding with effective multidiameter delay position of interference matrix multiplied each other, obtain revised channel time domain impulse response; Revised channel time domain impulse response is carried out Fourier transform, obtain channel frequency domain response estimation.

Based on an embodiment of channel estimation methods of the present invention, this method is also confirmed said effective multidiameter delay position based on preset effective diameter decision threshold.Wherein, this preset effective diameter decision threshold Thr is:

$\mathrm{Thr}=\mathrm{\ρP}\sqrt{2N_{\mathrm{av}}}/\mathrm{\ξ}$

Wherein, ρ=J ₀(2 π f _DΔ mT _s), J ₀For 0 rank Bessel function of the first kind, T _sBe OFDM symbol period, f _DBe maximum doppler frequency, ξ is the SNR estimation value, and P is a frequency pilot sign power, N _AvBe the OFDM symbolic number that to add up in order to calculating decision threshold Thr.

According to an embodiment of channel estimation methods of the present invention, generate interference matrix according to said effective multidiameter delay position through following formula:

Wherein ${\mathrm{\δ}}_{i,j}(l_p,l_q)=W_N^{{\mathrm{\β}}_{l_q,l_p}}\frac{\mathrm{Sin}(\mathrm{\π}(l_q-l_p+{\mathrm{\α}}_i)N_e/N)}{\mathrm{Sin}(\mathrm{\π}(l_q-l_p+{\mathrm{\α}}_i)D_f/N)},$

l ₀, l ₁..., l _{L '-1}Be said effective multidiameter delay position,

Be the phase rotation coefficient of different transmitting antenna time domain impulse responses, α _iBe the shift factor of different transmitting antenna time domain impulse responses, N is an IFFT length, N _eBe effective sub-carrier number, D _fBe the frequency pilot sign frequency domain interval.

Further, for the ofdm system of frequency division multi-antenna pilot,

α _i=0; Perhaps, divide the ofdm system of multi-antenna pilot for sign indicating number,

α _i=(i-1) K ₀, D _f=1, K wherein ₀The spacing of time domain impulse response on time shaft for each transmitting antenna.

According to an embodiment of channel estimation methods of the present invention, the step of revised channel time domain impulse response being carried out Fourier transform acquisition channel frequency domain response estimation comprises: revised channel time domain impulse response is mended 0 make number of samples extend to the FFT/IFFT of system length N; Channel time domain impulse response sequence to after the expansion is carried out the FFT conversion, obtains the channel frequency domain response on each number of sub-carrier.

Another technical problem that the present invention will solve provides a kind of channel estimating apparatus of ofdm system, the precision of channel estimation in can the raising system.

The present invention provides a kind of channel estimating apparatus of ofdm system; Comprise: initial time domain impulse response acquisition module; Be used for the patterns available that is positioned at effective subcarrier scope is carried out channel frequency domain response estimation; Said channel frequency domain response estimation is carried out inverse Fourier transform obtain initial channel time domain impulse response, send said initial channel time domain impulse response; Effective time domain impulse response acquisition module; Be used to receive initial channel time domain impulse response from said initial time domain impulse response acquisition module; Obtain in the said initial channel time domain impulse response and the effective corresponding channel time domain impulse response in multidiameter delay position transmission and the corresponding channel time domain impulse response in said effective multidiameter delay position; The interference matrix acquisition module is used for generating interference matrix according to said effective multidiameter delay position, sends said interference matrix; Time domain impulse response correcting module; Be used to receive from said effective time domain impulse response acquisition module with the corresponding channel time domain impulse response in said effective multidiameter delay position; Reception is from the said interference matrix of said interference matrix acquisition module; Contrary and the channel time domain impulse response corresponding with said multidiameter delay position of said interference matrix multiplied each other, obtain revised channel time domain impulse response, send said revised channel time domain impulse response; The frequency domain response estimation acquisition module; Be used to receive said revised channel time domain impulse response from said time domain impulse response correcting module; Said revised channel time domain impulse response is carried out Fourier transform, obtain revised channel frequency domain response estimation.

Further, this channel estimating apparatus also comprises: effective multidiameter delay position acquisition module, be used for confirming said effective multidiameter delay position according to preset effective diameter decision threshold, and send said effective multidiameter delay position; Said when effective city impulse response acquisition module also be used to receive said effective multidiameter delay position from said effective multidiameter delay position acquisition module; Said interference matrix acquisition module also is used to receive the said effective multidiameter delay position from said effective multidiameter delay position acquisition module.

Further, above-mentioned frequency domain response estimation acquisition module makes number of samples extend to the FFT/IFFT of system length N to said revised channel time domain impulse response benefit 0; Channel time domain impulse response sequence to after the said expansion is carried out the FFT conversion, obtains the revised channel frequency domain response on each number of sub-carrier.

Channel estimation methods provided by the invention and device through the interference of structure multipath, multiply by the inhibition energy leakage with the contrary of interference matrix with efficient channel time domain impulse response mutually, eliminate floor effect, improve channel estimated accuracy.

Description of drawings

Fig. 1 illustrates the system schematic that data are sent and received in the ofdm system;

Fig. 2 illustrates the flow chart of an embodiment of the channel estimation methods of ofdm system of the present invention;

Fig. 3 illustrates the flow chart of another embodiment of the channel estimation methods of ofdm system of the present invention;

Fig. 4 illustrates the block diagram of an embodiment of the channel estimating apparatus of ofdm system of the present invention;

Fig. 5 illustrates the block diagram of another embodiment of the channel estimating apparatus of ofdm system of the present invention.

Embodiment

With reference to the accompanying drawings the present invention is more comprehensively described, exemplary embodiment of the present invention wherein is described.In the accompanying drawings, identical label is represented identical or similar assembly or element.

Fig. 2 illustrates the flow chart of an embodiment of the channel estimation methods of ofdm system of the present invention.

As shown in Figure 2, in step 202, the patterns available that is positioned at effective subcarrier scope is carried out channel frequency domain response estimation, carry out inverse Fourier transform then, obtain initial channel time domain impulse response.For example, the channel frequency domain is estimated and can be carried out based on least square or minimum mean square error criterion through on each pilot sub-carrier, carrying out.

In step 204, obtain in the initial channel time domain impulse response and the effective corresponding channel time domain impulse response in multidiameter delay position, and according to effective multidiameter delay position generation interference matrix.Effectively multi-path location can be through confirming according to predefined effective diameter decision threshold; For the known system of channel multi-path time delay, can directly confirm effective multidiameter delay position according to known multidiameter delay information.For the unknown system of channel multi-path time delay, the method that keeps multipath comprises also preceding Lmax point is all remained that wherein Lmax is a maximum multipath time delay; Perhaps, by amplitude from big to small, keep the individual point of L ', L ' is an empirical value, and is different in the different channels environment.

In step 206, the contrary and channel time domain impulse response corresponding with effective multidiameter delay position of interference matrix multiplied each other, obtain revised channel time domain impulse response;

In step 208, revised channel time domain impulse response is carried out Fourier transform, obtain revised channel frequency domain response estimation.

Fig. 3 illustrates the flow chart of another embodiment of the channel estimation methods of ofdm system of the present invention.

As shown in Figure 3, in step 302, receive signal, the signal that receives is carried out the FFT conversion, will pass through in the reception signal of FFT conversion frequency pilot sign will be separated.

In step 304; Try to achieve channel frequency domain response estimation according to least square or minimum mean square error criterion; Behind IFFT, obtain initial time domain impulse response estimated value

i, j representes i root transmitting antenna and j root reception antenna respectively.

In step 306,, seek effective multidiameter delay position l according to predefined effective diameter decision threshold ₀, l ₁..., l _{L '-1}, keep and the corresponding efficient channel time domain impulse response in effective multidiameter delay position ${\tilde{h}}_{i,j}={[{\hat{h}}_{i,j}\left(l_0\right),{\hat{h}}_{i,j}\left(l_1\right),...{\hat{h}}_{i,j}\left(l_{L^{\′}-1}\right)]}^T.$

In step 308, according to the corresponding interference δ of each multidiameter delay of effective multidiameter delay position reconstruct of confirming _{I, j}, and structure interference matrix A _{I, j}:

Wherein ${\mathrm{\δ}}_{i,j}(l_p,l_q)=W_N^{{\mathrm{\β}}_{l_q,l_p}}\frac{\mathrm{Sin}(\mathrm{\π}(l_q-l_p+{\mathrm{\α}}_i)N_e/N)}{\mathrm{Sin}(\mathrm{\π}(l_q-l_p+{\mathrm{\α}}_i)D_f/N)},$

Be the phase rotation coefficient of different transmitting antenna time domain impulse responses, α _iShift factor for different transmitting antenna time domain impulse responses.According to different pilot tone mode (for example, frequency division multi-antenna pilot, sign indicating number divide multi-antenna pilot), these two parameters are different.

Use interference matrix A _{I, j}The contrary efficient channel time domain impulse response that multiply by ${\tilde{h}}_{i,j}={[{\hat{h}}_{i,j}\left(l_0\right),{\hat{h}}_{i,j}\left(l_1\right),...{\hat{h}}_{i,j}\left(l_{L^{\′}-1}\right)]}^T,$ The time domain impulse response that obtains revising

${\stackrel{\‾}{h}}_{i,j}=A_{i,j}^{-1}{\tilde{h}}_{i,j}---\left(2\right)$

In step 310; The time domain impulse response of revising

is added 0 to N point; Carry out the FFT conversion then, the channel frequency domain response estimation that obtains revising.

According to one embodiment of present invention,, can obtain predefined effective decision threshold Thr according to following formula for the unknown system of channel multi-path time delay:

$\mathrm{Thr}=\mathrm{\ρP}\sqrt{2N_{\mathrm{av}}}/\mathrm{\ξ}---\left(3\right)$

Wherein, ρ=J ₀(2 π f _DΔ mT _s), J ₀For 0 rank Bessel function of the first kind, T _sBe OFDM symbol period, f _DBe maximum doppler frequency, ξ is the SNR estimation value, and P is a frequency pilot sign power, N _AvBe the OFDM symbolic number that to add up in order to calculating decision threshold Thr.According to formula (3) initial channel time domain impulse response being carried out effective diameter keeps:

${\tilde{h}}_{i,j}\left(n\right)=\left\{\begin{array}{cc}{\hat{h}}_{i,j}\left(n\right),& {\left|{\hat{h}}_{i,j}\left(n\right)\right|}^2\≥\mathrm{Thr}\\ 0,& \mathrm{else}\end{array}\right.---\left(4\right)$

According to one embodiment of present invention, for the unknown system of channel multi-path time delay,, seek effective multidiameter delay position according to predefined decision threshold.And can a plurality of dual-mode antennas be united statistics to reaching a plurality of frequency pilot signs, to confirm effective multidiameter delay position l ₀, l ₁..., l _{L '-1}

According to one embodiment of present invention, for channel multi-path time delay system, can confirm effective multidiameter delay position l directly according to known multidiameter delay information ₀, l ₁..., l _{L '-1}, and the time domain impulse response that effective multidiameter delay position is corresponding keeps:

${\tilde{h}}_{i,j}={[{\hat{h}}_{i,j}\left(l_0\right),{\hat{h}}_{i,j}\left(l_1\right),...{\hat{h}}_{i,j}\left(l_{L^{\′}-1}\right)]}^T.$

According to one embodiment of present invention, can be with interference matrix A _{I, j}Be modified to the complex conjugate symmetrical matrix, find the solution more precise channels time domain impulse response, thereby reach the effect that reduces computation complexity with Qiao Lisiji (Cholesky) decomposition method.

It may be noted that method of the present invention is applicable to that the single-shot list is received, single-shot is overcharged or the ofdm communication system of MIMO.

Through a concrete application examples method of the present invention is further explained below.

In this application examples, the FFT/IFFT length of supposing ofdm system is N, and effectively sub-carrier number is N _e, the virtual subnet carrier number is N-N _eThe frequency-region signal Y that receives on the receiver j root antenna _j[k] is:

Y _j[k]＝H _j，i[k]P _i[k]+V _j[k]，k∈Ω _uc (5)

Wherein, H _{J, i}The channel frequency domain response of [k] expression i root transmitting antenna to the j root reception antenna, P _i[k] is the frequency pilot sign of i root transmitting antenna, Ω _UcBe effectively subcarrier set.

The first step: on each pilot sub-carrier, carry out estimating, and carry out the IFFT conversion and obtain initial channel time domain impulse response

based on the channel frequency domain of least square or minimum mean square error criterion

For the ofdm system of frequency division multi-antenna pilot method, promptly on the corresponding subcarrier of each transmitting antenna divided by separately pilot frequency sequence, obtain the noisy channel frequency domain response estimation value of each transmitting antenna:

${\hat{H}}_{j,i}\left[k\right]=Y_j\left[k\right]/P_i\left[k\right]=H_{j,i}\left[k\right]+V_j\left[k\right]/P_i\left[k\right],k\∈{\mathrm{\Ω}}_{\mathrm{uc}}---\left(6\right)$

To each transmitting antenna

Carry out N/D respectively _fPoint IFFT conversion obtains the initial channel time domain impulse response of each transmitting antenna

Wherein N is an IFFT length, D _fBe the frequency pilot sign frequency domain interval.

Dividing the ofdm system of multi-antenna pilot method for sign indicating number, is example with the exponential type pilot tone, and the conjugation that is about to first transmitting antenna frequency pilot sign multiply by frequency-region signal Y _j[k] obtains the adding up of noisy channel frequency domain response estimation value of each transmitting antenna:

$\hat{H}\left[k\right]=Y_j\left[k\right]P_i^{*}\left[k\right]/{\left|P_i\right[k\left]\right|}^2=\underset{i=1}{\overset{T_x}{\mathrm{\Σ}}}{H}_{j,i}\left[k\right]e^{-j2\mathrm{\πk}(i-1)K_0/N}+{\hat{V}}_j\left[k\right],k\∈{\mathrm{\Ω}}_{\mathrm{uc}}---\left(7\right)$

To frequency-region signal

Carry out N point IFFT conversion, obtain the initial channel time domain impulse response of all transmitting antennas

Time domain impulse response non-overlapping copies on time shaft of each transmitting antenna, its spacing is K ₀

Second step: set effective diameter decision threshold Thr according to above-mentioned formula (3), from the initial channel time domain impulse response

of first step gained, seeking effectively according to above-mentioned formula (4), many

can confirm effective multidiameter delay position through the statistics of uniting to a plurality of transmitting antennas and a plurality of frequency pilot signs.

The 3rd step: effective multidiameter delay position reconstruct each multidiameter delay corresponding interference definite according to above-mentioned steps ${\mathrm{\δ}}_{i,j}(l_p,l_q)=W_N^{{\mathrm{\β}}_{l_q,l_p}}\mathrm{Sin}(\·\mathrm{\π}(l_q-l_p+{\mathrm{\α}}_i)N_e/N)/\mathrm{Sin}(\mathrm{\π}(l_q-l_p+{\mathrm{\α}}_i)D_f/N).$

For different pilot tone modes, disturb δ _{I, j}Different.For example, for the ofdm system of frequency division multi-antenna pilot method, α _i=0.Divide the ofdm system of multi-antenna pilot method for sign indicating number,

α _i=(i-1) K ₀, D _f=1.

Then according to δ _{I, j}Formula (1) structure interference matrix A through the front _{I, j}

With the time domain impulse response that keeps in second step

With interference matrix A _{I, j}Anti-phase take advantage of (referring to top formula (2)), to eliminate energy leakage that the virtual subnet carrier wave introduces, obtain channel time domain impulse response more accurately to the influence that channel estimating causes

Preferably, A _{I, j}Be deformed into the complex conjugate symmetrical matrix.With frequency division multi-antenna pilot mode is example, will

With

Merge new interference matrix

(p, q) individual element does ${\widetilde{\mathrm{\δ}}}_i(l_p,l_q)=W_N^{((l_q-l_p)D_f/2)}\mathrm{Sin}(\mathrm{\π}(l_q-l_p)N_e/N)/\mathrm{Sin}(\mathrm{\π}(l_q-l_p)D_f/N),$ This interference matrix

Be the complex conjugate symmetrical matrix.Cholesky capable of using decomposes the solving equation group and replaces matrix inversion, thereby reaches the effect that reduces computation complexity.

The 4th step: the 3rd step gained channel time domain impulse response is estimated ${\stackrel{\‾}{h}}_{i,j}={[{\stackrel{\‾}{h}}_{i,j}\left(l_0\right),{\hat{h}}_{i,j}\left(l_1\right),...{,\hat{h}}_{i,j}\left(l_{L^{\′}-1}\right)]}^T$ Carry out Fourier transform after adding 0 to N point, obtain revised channel frequency domain response estimation.

Fig. 4 illustrates the block diagram of an embodiment of the channel estimating apparatus of ofdm system of the present invention.As shown in Figure 4, this channel estimating apparatus comprises initial time domain impulse response acquisition module 41, effectively time domain impulse response acquisition module 42, interference matrix acquisition module 43, time domain impulse response correcting module 44 and frequency domain response estimation acquisition module 45.Wherein, Initial time domain impulse response acquisition module 41 is used for the patterns available that is positioned at effective subcarrier scope is carried out channel frequency domain response estimation; Channel frequency domain response estimation is carried out inverse Fourier transform; Obtain initial channel time domain impulse response, send the initial channel time domain impulse response that obtains and arrive effective time domain impulse response acquisition module 42.Effective time domain impulse response acquisition module 42; Be used to receive initial channel time domain impulse response from initial time domain impulse response acquisition module 41; With the corresponding channel time domain impulse response in effective multidiameter delay position, send and the corresponding channel time domain impulse response in effective multidiameter delay position in the acquisition initial channel time domain impulse response.Interference matrix acquisition module 43 is used for generating interference matrix according to effective multidiameter delay position, sends interference matrix.Time domain impulse response correcting module 44; Be used to receive the channel time domain impulse response corresponding with effective multidiameter delay position from effective time domain impulse response acquisition module 42; Reception is from the interference matrix of interference matrix acquisition module 43; Contrary and the channel time domain impulse response corresponding with effective multidiameter delay position of interference matrix multiplied each other, obtain revised channel time domain impulse response, send revised channel time domain impulse response to frequency domain response estimation acquisition module 45.Frequency domain response estimation acquisition module 45 is used to receive the revised channel time domain impulse response from time domain impulse response correcting module 44, and revised channel time domain impulse response is carried out Fourier transform, obtains revised channel frequency domain response estimation.

Fig. 5 illustrates the block diagram of another embodiment of the channel estimating apparatus of ofdm system of the present invention.The channel estimating apparatus of Fig. 5 is compared with Fig. 4; Increased effective multidiameter delay position acquisition module 56; Be used for confirming effective multidiameter delay position, send effective multidiameter delay position to effective time domain impulse response acquisition module 42 and interference matrix acquisition module 43 according to preset effective diameter decision threshold.Effectively acquisition module 56 receives effective multidiameter delay position to time domain impulse response acquisition module 43 from effective multidiameter delay position.Effective multidiameter delay position of interference matrix acquisition module 43 acquisition module 56 from effective multidiameter delay position.Other module is described can be referring to the description of respective modules among Fig. 4, for for purpose of brevity, this no longer auspicious stating.

Wherein, the preset effective diameter decision threshold Thr that effective multidiameter delay position acquisition module 56 adopts among Fig. 5 does

Wherein, ρ=J ₀(2 π f _DΔ mT _s), T _sBe OFDM symbol period, f _DBe maximum doppler frequency, ξ is the SNR estimation value, and P is a frequency pilot sign power, N _AvBe the OFDM symbolic number that to add up in order to calculating decision threshold Thr.

According to an embodiment of channel estimating apparatus of the present invention, the effective diameter decision threshold that effective multidiameter delay position acquisition module basis is preset is through adding up definite said effective multidiameter delay position to a plurality of dual-mode antennas to reaching uniting of a plurality of frequency pilot signs.In addition, the interference matrix acquisition module generates interference matrix A through top formula (1) according to effective multidiameter delay position _{I, j}

According to an embodiment of channel estimating apparatus of the present invention, time domain impulse response correcting module is modified to the complex conjugate symmetrical matrix with interference matrix, calculates the contrary of interference matrix through the fast algorithm that adopts matrix inversion, to reduce computation complexity.

According to an embodiment of channel estimating apparatus of the present invention, the frequency domain response estimation acquisition module mends 0 to revised channel time domain impulse response makes number of samples extend to the FFT/IFFT of system length N; Channel time domain impulse response sequence to after the expansion is carried out the FFT conversion, obtains the revised channel frequency domain response on each number of sub-carrier.

Method and apparatus of the present invention is through the interference of structure multipath; The contrary of interference matrix multiply by the inhibition energy leakage mutually with efficient channel time domain impulse response; Be applicable to single antenna and many antennas ofdm system, can be applied to flexibly or the system of Unknown Channel multidiameter delay information.The method can effectively be eliminated the Energy Leaking that the virtual subnet carrier wave is introduced, and eliminates floor effect, improves precision of channel estimation, and can be through quick matrix algorithm control system complexity.

Description of the invention provides for example with for the purpose of describing, and is not the disclosed form that exhaustively perhaps limit the invention to.Many modifications and variations are obvious for the ordinary skill in the art.Selecting and describing embodiment is for better explanation principle of the present invention and practical application, thereby and makes those of ordinary skill in the art can understand the various embodiment that have various modifications that the present invention's design is suitable for special-purpose.

Claims (11)

1. the channel estimation methods of an ofdm system is characterized in that, comprising:

Patterns available to being positioned at effective subcarrier scope is carried out channel frequency domain response estimation, carries out inverse Fourier transform, obtains initial channel time domain impulse response;

Obtain in the said initial channel time domain impulse response and the effective corresponding channel time domain impulse response in multidiameter delay position, according to said effective multidiameter delay position generation interference matrix;

Multiply each other with the contrary of said interference matrix with the corresponding channel time domain impulse response in said effective multidiameter delay position, obtain revised channel time domain impulse response;

Said revised channel time domain impulse response is carried out Fourier transform, obtain channel frequency domain response estimation.

2. the channel estimation methods of ofdm system according to claim 1 is characterized in that, also comprises step:

Effective diameter decision threshold based on preset is confirmed said effective multidiameter delay position.

3. the channel estimation methods of ofdm system according to claim 2 is characterized in that, said preset effective diameter decision threshold Thr is:

Wherein, ρ=J ₀(2 π f _DΔ mT _s), J ₀For 0 rank Bessel function of the first kind,Ts is the OFDM symbol period, f _DBe maximum doppler frequency, ξ is the SNR estimation value, and P is a frequency pilot sign power, N _AvBe the OFDM symbolic number that to add up in order to calculating decision threshold Thr.

4. according to the channel estimation methods of claim 2 or 3 described ofdm systems, it is characterized in that the preset effective diameter decision threshold of said basis confirms that the step of said effective multidiameter delay position comprises:

Based on preset effective diameter decision threshold through to a plurality of dual-mode antennas to and the statistics of uniting of a plurality of frequency pilot signs confirm said effective multidiameter delay position.

5. the channel estimation methods of ofdm system according to claim 1 is characterized in that, generates interference matrix through following formula according to said effective multidiameter delay position:

Wherein

l ₀, l ₁..., l _{L '-1}Be said effective multidiameter delay position,

Be the phase rotation coefficient of different transmitting antenna time domain impulse responses, α _iBe the shift factor of different transmitting antenna time domain impulse responses, N is an IFFT length, N _eBe effective sub-carrier number, D _fBe the frequency pilot sign frequency domain interval.

6. the channel estimation methods of ofdm system according to claim 1 is characterized in that, saidly said revised channel time domain impulse response is carried out the step that Fourier transform obtains channel frequency domain response estimation comprises:

Said revised channel time domain impulse response is mended 0 makes number of samples extend to the FFT/IFFT of system length N;

Channel time domain impulse response sequence to after the said expansion is carried out the FFT conversion, obtains the channel frequency domain response on each number of sub-carrier.

7. the channel estimating apparatus of an ofdm system is characterized in that, comprising:

Initial time domain impulse response acquisition module; Be used for the patterns available that is positioned at effective subcarrier scope is carried out channel frequency domain response estimation; Said channel frequency domain response estimation is carried out inverse Fourier transform obtain initial channel time domain impulse response, send said initial channel time domain impulse response;

Effective time domain impulse response acquisition module; Be used to receive initial channel time domain impulse response from said initial time domain impulse response acquisition module; Obtain in the said initial channel time domain impulse response and the effective corresponding channel time domain impulse response in multidiameter delay position transmission and the corresponding channel time domain impulse response in said effective multidiameter delay position;

The interference matrix acquisition module is used for generating interference matrix according to said effective multidiameter delay position, sends said interference matrix;

Time domain impulse response correcting module; Be used to receive from said effective time domain impulse response acquisition module with the corresponding channel time domain impulse response in said effective multidiameter delay position; Reception is from the said interference matrix of said interference matrix acquisition module; Multiply each other with the contrary of said interference matrix with the corresponding channel time domain impulse response in said effective multidiameter delay position, obtain revised channel time domain impulse response, send said revised channel time domain impulse response;

The frequency domain response estimation acquisition module; Be used to receive said revised channel time domain impulse response from said time domain impulse response correcting module; Said revised channel time domain impulse response is carried out Fourier transform, obtain revised channel frequency domain response estimation.

8. the channel estimating apparatus of ofdm system according to claim 7 is characterized in that, also comprises:

Effectively multidiameter delay position acquisition module is used for confirming said effective multidiameter delay position according to preset effective diameter decision threshold, sends said effective multidiameter delay position;

Said effective time domain impulse response acquisition module also is used to receive the said effective multidiameter delay position from said effective multidiameter delay position acquisition module; Said interference matrix acquisition module also is used to receive the said effective multidiameter delay position from said effective multidiameter delay position acquisition module.

9. the channel estimating apparatus of ofdm system according to claim 8; It is characterized in that the effective diameter decision threshold that acquisition module basis in said effective multidiameter delay position is preset is through confirming said effective multidiameter delay position to a plurality of dual-mode antennas to the statistics of uniting that reaches a plurality of frequency pilot signs.

10. the channel estimating apparatus of ofdm system according to claim 7 is characterized in that, said interference matrix acquisition module generates interference matrix through following formula according to said effective multidiameter delay position:

Wherein

l ₀, l ₁..., l _{L '-1}Be said effective multidiameter delay position,

Be the phase rotation coefficient of different transmitting antenna time domain impulse responses, α _iBe the shift factor of different transmitting antenna time domain impulse responses, N is an IFFT length, N _eBe effective sub-carrier number, D _fBe the frequency pilot sign frequency domain interval.

11. the channel estimating apparatus of ofdm system according to claim 7 is characterized in that, said frequency domain response estimation acquisition module mends 0 to said revised channel time domain impulse response makes number of samples extend to the FFT/IFFT of system length N; Channel time domain impulse response sequence to after the said expansion is carried out the FFT conversion, obtains the revised channel frequency domain response on each number of sub-carrier.

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