CN101577692A - 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 channel time 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 generating 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 is multiplexing on the different orthogonal subcarrier after with the high-speed data-flow serial to parallel conversion, has improved spectrum efficiency when disturbing between data reducing.And the subchannel of each subcarrier correspondence 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 (wireless local area network), 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 as far as possible accurately to wireless fading channel.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 send and receive 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 when according to the result of channel estimating isolated data-signal being carried out sky, the data that send through operation reduction such as demodulation, channel decodings again.

In the ofdm system of reality, for avoiding sending the influence that signal is subjected to 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 this frequency domain scope interior channel information, 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 be subjected to the influence of energy leakage and the phase mutual interference causes the decline of precision of channel estimation.Existing channel estimation technique is not considered the influence of energy leakage mostly, in time domain limited sampled point is intercepted, and 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 invention provides a kind of channel estimation methods of ofdm system, comprising: the patterns available that is positioned at effective subcarrier scope is carried out channel frequency domain response estimation, carry out inverse Fourier transform, obtain 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.

According to an embodiment of channel estimation methods of the present invention, this method is also determined described effective multidiameter delay position according to default effective diameter decision threshold.Wherein, this default 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), T _sBe OFDM symbol period, f _DBe maximum doppler frequency, ξ is the signal-to-noise ratio (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 described effective multidiameter delay position by following formula:

Wherein ${\mathrm{\δ}}_{i,j}(l_p,l_q)=W_N^{{\mathrm{\β}}_{l_q,l_p}}\frac{\sin (\mathrm{\π}(l_q-l_p+{\mathrm{\α}}_i)N_e/N)}{\sin (\mathrm{\π}(l_q-l_p+{\mathrm{\α}}_i)D_f/N)},$ $W_N^{{\mathrm{\β}}_{l_q,l_p}}=\exp (-j2\mathrm{\π}{\mathrm{\β}}_{l_q,l_p}/N),$ l ₀, l ₁..., l _{L '-1}Be described 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, ${\mathrm{\β}}_{l_p,l_q}=l_{q}i-(l_q-l_p)D_f/2,$ α _i=0; Perhaps, divide the ofdm system of multi-antenna pilot for sign indicating number, ${\mathrm{\β}}_{l_p,l_q}=(l_q-l_p+{\mathrm{\α}}_i)/2,$ 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 after the expansion is carried out the FFT conversion, obtain the channel frequency domain response on each subcarrier.

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 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, described channel frequency domain response estimation is carried out inverse Fourier transform obtain initial channel time domain impulse response, send described initial channel time domain impulse response; Effective time domain impulse response acquisition module, be used to receive initial channel time domain impulse response from described initial time domain impulse response acquisition module, obtain in the described initial channel time domain impulse response and the effective corresponding channel time domain impulse response in multidiameter delay position, send and the corresponding channel time domain impulse response in described effective multidiameter delay position; The interference matrix acquisition module is used for generating interference matrix according to described effective multidiameter delay position, sends described interference matrix; Time domain impulse response correcting module, be used to receive from described effective time domain impulse response acquisition module with the corresponding channel time domain impulse response in described effective multidiameter delay position, reception is from the described interference matrix of described interference matrix acquisition module, contrary and the channel time domain impulse response corresponding with described multidiameter delay position of described interference matrix multiplied each other, obtain revised channel time domain impulse response, send described revised channel time domain impulse response; The frequency domain response estimation acquisition module, be used to receive described revised channel time domain impulse response from described time domain impulse response correcting module, described 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 determining described effective multidiameter delay position according to default effective diameter decision threshold, and send described effective multidiameter delay position; Described effective time domain impulse response acquisition module also is used to receive the described effective multidiameter delay position from described effective multidiameter delay position acquisition module; Described interference matrix acquisition module also is used to receive the described effective multidiameter delay position from described 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 described revised channel time domain impulse response benefit 0; Channel time domain impulse response sequence after the described expansion is carried out the FFT conversion, obtain the revised channel frequency domain response on each subcarrier.

Channel estimation methods provided by the invention and device by 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 send and receive 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 described more fully, 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,, 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 in step 202.For example, the channel frequency domain is estimated and can be carried out based on least square or minimum mean square error criterion by carrying out on each pilot sub-carrier.

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 by determining according to predefined effective diameter decision threshold; For the known system of channel multi-path time delay, can directly determine effective multidiameter delay position according to known multidiameter delay information.For the system of channel multi-path time delay the unknown, 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, received signal is carried out the FFT conversion with the signal that receives, and will in the received signal through the FFT conversion frequency pilot sign 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 represent 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 interference δ of each multidiameter delay correspondence of effective multidiameter delay position reconstruct of determining _{I, j}, and structure interference matrix A _{I, j}:

Wherein ${\mathrm{\δ}}_{i,j}(l_p,l_q)=W_N^{{\mathrm{\β}}_{l_q,l_p}}\frac{\sin (\mathrm{\π}(l_q-l_p+{\mathrm{\α}}_i)N_e/N)}{\sin (\mathrm{\π}(l_q-l_p+{\mathrm{\α}}_i)D_f/N)},$ $W_N^{{\mathrm{\β}}_{l_q,l_p}}=\exp (-j2\mathrm{\π}{\mathrm{\β}}_{l_q,l_p}/N),$

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 h that obtains revising _{I, j}:

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

In step 310, with the time domain impulse response h that revises _{I, j}Add 0 to N point, carry out FFT conversion, the channel frequency domain response estimation that obtains revising then.

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

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

Wherein, ρ=J ₀(2 π f _DΔ mT _s), T _sBe OFDM symbol period, f _DBe maximum doppler frequency, ξ is the signal-to-noise ratio (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 system of channel multi-path time delay the unknown,, seek effective multidiameter delay position according to predefined decision threshold.And a plurality of dual-mode antennas can be united statistics to reaching a plurality of frequency pilot signs, to determine 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 determine effective multidiameter delay position l directly according to known multidiameter delay information ₀, l ₁..., l _{L '-1}, and the time domain impulse response of effective multidiameter delay position correspondence kept:

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

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.

Below by a concrete application examples method of the present invention is further detailed.

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 subcarrier of each transmitting antenna correspondence 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), according to the initial channel time domain impulse response of above-mentioned formula (4) from first step gained Middle effective multidiameter delay position l that seeks ₀, l ₁..., l _{L '-1}, and keep the time domain impulse response of described effective multidiameter delay position correspondence: ${\tilde{h}}_{i,j}={[{\hat{h}}_{i,j}\left(l_0\right),{\hat{h}}_{i,j}\left(l_1\right),...{\hat{h}}_{i,j}\left(l_{L^{\′}-1}\right)]}^T.$ For improving the accuracy that multipath detects, can determine effective multidiameter delay position by the statistics of uniting to a plurality of transmitting antennas and a plurality of frequency pilot signs.

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

For different pilot tone modes, disturb δ _{I, j}Different.For example, for the ofdm system of frequency division multi-antenna pilot method, ${\mathrm{\β}}_{l_p,l_q}=l_{q}i-(l_q-l_p)D_f/2,$ α _i＝0。Divide the ofdm system of multi-antenna pilot method for sign indicating number, ${\mathrm{\β}}_{l_p,l_q}=(l_q-l_p+{\mathrm{\α}}_i)/2,$ α _i＝(i-1)K ₀，D _f＝1。

Then according to δ _{I, j}Formula (1) structure interference matrix A by 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 h more accurately to the influence that channel estimating causes _{I, j}

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

With

Merge new interference matrix

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

Be the complex conjugate symmetrical matrix.Can utilize Cholesky to decompose the solving equation group and replace matrix inversion, thereby reach 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, effective 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 determining 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 default effective diameter decision threshold.Effectively time domain impulse response acquisition module 43 receives effective multidiameter delay position from effective multidiameter delay position acquisition module 56.Interference matrix acquisition module 43 is from effective multidiameter delay position of effective multidiameter delay position acquisition module 56.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 default effective diameter decision threshold Thr that effective multidiameter delay position acquisition module 56 adopts among Fig. 5 is $\mathrm{Thr}=\mathrm{\ρP}\sqrt{2N_{\mathrm{av}}}/\mathrm{\ξ}.$ Wherein, ρ=J ₀(2 π f _DΔ mT _s), T _sBe OFDM symbol period, f _DBe maximum doppler frequency, ξ is the signal-to-noise ratio (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 by adding up definite described 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 by 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 by 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 after the expansion is carried out the FFT conversion, obtain the revised channel frequency domain response on each subcarrier.

Method and apparatus of the present invention is by the interference of structure multipath, the contrary of interference matrix be 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 by quick matrix algorithm control system complexity.

Description of the invention provides for example with for the purpose of describing, and is not exhaustively or limit the invention to disclosed form.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:

The patterns available that is positioned at effective subcarrier scope is carried out channel frequency domain response estimation, carry out inverse Fourier transform, obtain initial channel time domain impulse response;

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

Contrary and the channel time domain impulse response corresponding with described effective multidiameter delay position of described interference matrix multiplied each other, obtain revised channel time domain impulse response;

Described 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:

Determine described effective multidiameter delay position according to default effective diameter decision threshold.

3. the channel estimation methods of ofdm system according to claim 2 is characterized in that, described default 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), Ts is the OFDM symbol period, and fD is a maximum doppler frequency, and ξ is the signal-to-noise ratio (SNR) estimation value, and P is a frequency pilot sign power, the OFDM symbolic number of Nav for adding 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 default effective diameter decision threshold of described basis determines that the step of described effective multidiameter delay position comprises:

According to default effective diameter decision threshold by to a plurality of dual-mode antennas to and the statistics of uniting of a plurality of frequency pilot signs determine described effective multidiameter delay position.

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

Wherein ${\mathrm{\δ}}_{i,j}(l_p,l_q)=W_N^{{\mathrm{\β}}_{l_q,l_p}}\frac{\sin (\mathrm{\π}(l_q-l_p+{\mathrm{\α}}_i)N_e/N)}{\sin (\mathrm{\π}(l_q-l_p+{\mathrm{\α}}_i)D_f/N)},$ $W_N^{{\mathrm{\β}}_{l_q,l_p}}=\exp (-j2\mathrm{\π}{\mathrm{\β}}_{l_q,l_p}/N),$ l ₀, l ₁..., l _{L '-1}Be described 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, describedly described revised channel time domain impulse response is carried out the step that Fourier transform obtains channel frequency domain response estimation comprises:

Described 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 after the described expansion is carried out the FFT conversion, obtain the channel frequency domain response on each subcarrier.

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, described channel frequency domain response estimation is carried out inverse Fourier transform obtain initial channel time domain impulse response, send described initial channel time domain impulse response;

Effective time domain impulse response acquisition module, be used to receive initial channel time domain impulse response from described initial time domain impulse response acquisition module, obtain in the described initial channel time domain impulse response and the effective corresponding channel time domain impulse response in multidiameter delay position, send and the corresponding channel time domain impulse response in described effective multidiameter delay position;

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

Time domain impulse response correcting module, be used to receive from described effective time domain impulse response acquisition module with the corresponding channel time domain impulse response in described effective multidiameter delay position, reception is from the described interference matrix of described interference matrix acquisition module, contrary and the channel time domain impulse response corresponding with described effective multidiameter delay position of described interference matrix multiplied each other, obtain revised channel time domain impulse response, send described revised channel time domain impulse response;

The frequency domain response estimation acquisition module, be used to receive described revised channel time domain impulse response from described time domain impulse response correcting module, described 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 determining described effective multidiameter delay position according to default effective diameter decision threshold, sends described effective multidiameter delay position;

Described effective time domain impulse response acquisition module also is used to receive the described effective multidiameter delay position from described effective multidiameter delay position acquisition module; Described interference matrix acquisition module also is used to receive the described effective multidiameter delay position from described 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 described effective multidiameter delay position is preset is by determining described 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, described interference matrix acquisition module generates interference matrix by following formula according to described effective multidiameter delay position:

Wherein ${\mathrm{\δ}}_{i,j}(l_p,l_q)=W_N^{{\mathrm{\β}}_{l_q,l_p}}\frac{\sin (\mathrm{\π}(l_q-l_p+{\mathrm{\α}}_i)N_e/N)}{\sin (\mathrm{\π}(l_q-l_p+{\mathrm{\α}}_i)D_f/N)},$ $W_N^{{\mathrm{\β}}_{l_q,l_p}}=\exp (-j2\mathrm{\π}{\mathrm{\β}}_{l_q,l_p}/N),$ l ₀, l ₁..., l _{L '-1}Be described 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, described frequency domain response estimation acquisition module mends 0 to described 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 after the described expansion is carried out the FFT conversion, obtain the revised channel frequency domain response on each subcarrier.

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