CN101848183B - Channel Estimation Method and Device in Multiple-Input Multiple-Output Orthogonal Frequency Division Multiplexing System - Google Patents

Abstract

The invention relates to channel estimation method and device in a multiple input multiple output OFDM (Orthogonal Frequency Division Multiplexing) system. The method comprises the following steps that the system codes the pilot subcarrier data of each transmitting antenna to generate time domain OFDM signals and then transmitting the time domain OFDM signals to a receiving antenna; the system extracts continuous pilot subcarrier block data on each receiving antenna to obtain pilot receiving data on each transmitting antenna; the system obtains time domain channel response values after obtaining the frequency response of all pilot subcarriers on each transmitting antenna by carrying out frequency domain LS (Least Square) channel estimation on the pilot receiving data on each transmitting antenna; the system carries out peak search, peak point diffusion coefficient calculation and offset iteration on the obtained time domain channel response values and carries out FFT (Fast Fourier Transform Algorithm) transformation processing on the outputted valid time domain multipath channel response values to obtain channel frequency response values of each subcarrier on each transmitting antenna to complete channel estimation. By applying the invention, the problem of path diffusion phenomenon when the time domain channel estimation is carried out is solved, and meanwhile, partial noise is restrained, and finally, the channel estimation precision is improved.

Description

Channel Estimation Method and Device in Multiple-Input Multiple-Output Orthogonal Frequency Division Multiplexing System

technical field

The invention relates to the field of wireless communication, in particular to a channel estimation method and device in a multiple-input multiple-output orthogonal frequency division multiplexing system.

Background technique

For MIMO-OFDM (Multi-Input Multiple-Output Orthogonal Frequency Division Multiplexing) systems with virtual subcarriers, the existing channel estimation methods are mainly frequency domain interpolation methods, namely linear interpolation, Gaussian interpolation, Wiener filter interpolation and transform domain However, the existing variable domain interpolation can only effectively suppress part of the noise, but it cannot suppress the time-domain path diffusion effect caused by the existence of virtual subcarriers, so that when the signal-to-noise ratio is high, the channel estimation has a "floor effect" , the performance deterioration caused by the time-domain path diffusion makes the accuracy of channel estimation deviate greatly.

It can be seen that a new channel estimation technical solution is currently needed to solve the above-mentioned problems existing in the frequency domain interpolation method used in the current MIMO-OFDM system with virtual subcarriers.

Contents of the invention

The technical problem to be solved by the present invention is to provide a channel estimation method and device in a multiple-input multiple-output OFDM system, which solves the problem of suppressing the phenomenon of time-path diffusion in time-domain channel estimation, and can effectively suppress some noise, which ultimately improves the accuracy of channel estimation.

In order to solve the above problems, the present invention provides a channel estimation method in a multiple-input multiple-output OFDM system, comprising:

After the system encodes the pilot subcarrier data of each transmitting antenna and the Walsh orthogonal code assigned by the corresponding transmitting antenna, the coded pilot subcarrier block and data subcarrier form an orthogonal frequency division in the frequency domain Multiplexing the OFDM signal; after performing inverse fast Fourier transform IFFT to the OFDM signal in the frequency domain on each transmitting antenna, generating an OFDM signal in the time domain and transmitting it to the receiving antenna;

The system performs fast Fourier transform (FFT) transformation processing on the time-domain OFDM signal received on each receiving antenna, extracts the continuous pilot subcarrier block data on each receiving antenna, and is orthogonal to the Walsh of each transmitting antenna matching the transmitting end. The codes are multiplied and accumulated to obtain the pilot reception data on each transmit antenna;

The system performs frequency domain LS channel estimation on the pilot received data on each transmit antenna, and obtains the frequency response of all pilot subcarriers on each transmit antenna, and then obtains the time domain channel response value according to the transform domain method; The time-domain channel response value of the time-domain channel response value is obtained through peak search, peak point spread coefficient calculation and offset iteration, and the effective time-domain multipath channel response value is output, and the channel frequency response value of each data subcarrier on each transmitting antenna is obtained to complete the channel estimation.

Further, the above method may further include, after the system encodes the pilot subcarrier data of each transmitting antenna and the Walsh orthogonal code allocated by the corresponding transmitting antenna, and encodes the coded pilot subcarrier block and data subcarrier block Form the OFDM signal in the frequency domain; after performing IFFT transformation on the OFDM signal in the frequency domain on each transmitting antenna, generate the OFDM signal in the time domain and transmit it to the receiving antenna, which is specifically divided into the following steps:

The system encodes the continuous pilot subcarrier block data on the transmitting antennas with the Walsh orthogonal codes assigned to the corresponding transmitting antennas, and encodes the non-pilot subcarriers in the continuous pilot blocks and the data in the non-pilot data blocks The data on the subcarriers is completed by constellation mapping of the bit streams on the individual transmit antennas, and the coded pilot subcarrier blocks and the data subcarriers after constellation mapping are completed to form OFDM signals in the frequency domain;

The system performs IFFT transformation on the OFDM signal in the frequency domain on each transmitting antenna, performs parallel-to-serial conversion and adds a cyclic prefix at the same time, generates an OFDM signal in the time domain, and transmits it to the receiving antenna through a wireless multiple-input multiple-output MIMO channel .

Further, the above method may also include that the system performs FFT transformation processing on the time-domain OFDM signal received on each receiving antenna, and extracts continuous pilot subcarrier block data on each receiving antenna, specifically referring to:

After the system removes the cyclic prefix and serial-to-parallel conversion of the time-domain OFDM signal received on each receiving antenna, it generates an OFDM signal in the frequency domain on each receiving antenna through FFT transformation processing, and extracts the continuous signal on each receiving antenna. Pilot subcarrier block data.

Further, the above method may also include that the system performs frequency-domain LS channel estimation on the pilot received data on each transmitting antenna, and after obtaining the frequency responses of all pilot subcarriers on each transmitting antenna, according to the transform domain Way to obtain the time domain channel response value, specifically refers to:

The system performs frequency-domain LS channel estimation on the pilot received data on each transmitting antenna, obtains the frequency response of all pilot subcarriers on each transmitting antenna, inserts several zeros, and then performs IFFT transformation to obtain The time-domain channel response value, wherein the number of inserted zeros is determined by the number of pilot subcarriers, the number of FFT points, and the insertion interval of pilot subcarriers.

Further, the above method may further include that the system outputs an effective time-domain multipath channel response value through peak search, peak point spread coefficient calculation, and offset iteration for the obtained time-domain channel response value, and obtains each transmitting antenna The channel frequency response value of each data subcarrier is used to complete the channel estimation, which is specifically divided into the following steps:

For the obtained time-domain channel response value, the system determines the peak value and its corresponding position by performing a peak search, then calculates the diffusion coefficient of the sample point at this position on all time-domain sample points, and converts it from the initially obtained time-domain channel response value to Offset in the domain channel response value, and then perform a new round of peak search iterations until the searched peak value drops below the set threshold, stop the iteration, and perform FFT transformation processing on the output effective time domain multipath channel response value, The channel frequency response value of each data subcarrier on each transmitting antenna is obtained to complete channel estimation.

The present invention also provides a channel estimation device in a multiple-input multiple-output OFDM system, including an antenna encoding module, an antenna decoding module and a radial diffusion suppression module, wherein,

The antenna encoding module is configured to encode the pilot subcarrier data of each transmitting antenna and the Walsh orthogonal code assigned by the corresponding transmitting antenna, and then form the encoded pilot subcarrier blocks and data subcarriers Orthogonal frequency division multiplexing OFDM signal in the frequency domain; after performing inverse fast Fourier transform IFFT to the OFDM signal in the frequency domain on each transmitting antenna, generate an OFDM signal in the time domain and transmit it to the antenna decoding module;

The antenna decoding module is used to perform fast Fourier transform (FFT) transform processing on the received time-domain OFDM signal on each receiving antenna, extract continuous pilot subcarrier block data on each receiving antenna, and match each The Walsh orthogonal codes of the root transmit antennas are multiplied and accumulated to obtain the pilot reception data on each transmit antenna, and sent to the radial diffusion suppression module;

The diameter diffusion suppression module is used to perform frequency-domain LS channel estimation on the pilot received data on each transmitting antenna, and obtain the frequency responses of all pilot subcarriers on each transmitting antenna, and then obtain the time Domain channel response value; through peak search, peak point spread coefficient calculation and offset iteration for the obtained time domain channel response value, the effective time domain multipath channel response value output is obtained to obtain the channel of each data subcarrier on each transmitting antenna The frequency response value completes the channel estimation.

Further, the above device may further include, after the antenna encoding module encodes the pilot subcarrier data of each transmitting antenna and the Walsh orthogonal code allocated by the corresponding transmitting antenna, and encodes the encoded pilot subcarrier block and data The subcarriers form the OFDM signal in the frequency domain; after performing IFFT transformation on the OFDM signal in the frequency domain on each transmitting antenna, the OFDM signal in the time domain is generated, specifically referring to:

The antenna encoding module encodes the continuous pilot subcarrier block data on the transmitting antenna and the Walsh orthogonal codes allocated by the corresponding transmitting antennas, and encodes the non-pilot subcarriers and non-pilot data blocks in the continuous pilot block The data on the inner data subcarrier is completed by the bit stream on each transmit antenna through constellation mapping, and the coded pilot subcarrier block and the data subcarrier after the constellation mapping are completed to form an OFDM signal in the frequency domain; The OFDM signal in the frequency domain on the antenna is subjected to IFFT transformation, parallel-to-serial conversion is performed and a cyclic prefix is added at the same time, and an OFDM signal in the time domain is generated.

Further, the above-mentioned device may further include that the antenna decoding module performs FFT transformation processing on the time-domain OFDM signal received on each receiving antenna, and extracts continuous pilot subcarrier block data on each receiving antenna, specifically referring to:

After the antenna decoding module removes the cyclic prefix and serial-to-parallel conversion of the time-domain OFDM signal received on each receiving antenna, it generates an OFDM signal in the frequency domain on each receiving antenna through FFT transformation processing, and extracts the OFDM signal on each receiving antenna. Consecutive pilot subcarrier block data of .

Further, the above-mentioned device may further include that the channel diffusion suppression module performs frequency-domain LS channel estimation on the pilot received data on each transmitting antenna, and after obtaining the frequency responses of all pilot subcarriers on each transmitting antenna, Obtaining the channel response value in the time domain according to the transformation domain method, specifically refers to:

The radial diffusion suppression module performs frequency-domain LS channel estimation on the pilot received data on each transmitting antenna, and after obtaining the frequency responses of all pilot subcarriers on each transmitting antenna, inserts several zeros, and then performs IFFT Transform to obtain the time-domain channel response value, wherein the number of inserted zeros is determined by the number of pilot subcarriers, the number of FFT points, and the insertion interval of pilot subcarriers.

Further, the above-mentioned device may further include that the effective time-domain multi-path channel response value outputted by the path diffusion suppression module through peak search, calculation of peak point spread coefficient and cancellation iteration for the obtained time-domain channel response value is obtained. The channel frequency response value of each data subcarrier on each transmit antenna specifically refers to:

For the obtained time-domain channel response value, the said diameter diffusion suppression module determines the peak value and its corresponding position by performing a peak search, calculates the diffusion coefficient of the sampling point at this position on all time-domain sample points, and converts it from the initially obtained Offset the obtained time-domain channel response value, and then perform a new round of peak search iterations until the searched peak value drops below the set threshold, stop the iteration, and perform FFT on the output effective time-domain multipath channel response value Transform processing to obtain the channel frequency response value of each data subcarrier on each transmit antenna.

Compared with the prior art, the application of the present invention suppresses the channel diffusion effect of the MIMO-OFDM system with virtual subcarriers during channel estimation, weakens the "floor effect" to a large extent, and also suppresses Part of the noise is eliminated, the accuracy of channel estimation is effectively improved, and its complexity is low, and its implementation is relatively simple.

Description of drawings

Fig. 1 is the flow chart of channel estimation method in the multiple-input multiple-output OFDM system of the present invention;

Fig. 2 is the schematic diagram of channel estimation in the input multiple output OFDM system in the example;

Fig. 3 is a structural schematic diagram in the antenna coding module in the example;

Fig. 4 is a structural schematic diagram in the antenna decoding module in the example;

Fig. 5 is a schematic diagram of the structure of the median diameter diffusion suppression module of the example.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

The implementation condition of the present invention is aimed at the MIMO-OFDM system with virtual sub-carriers. (Wherein, MIMO channel condition: block fading (that is, the frequency channel response is constant on the same subcarrier within multiple OFDM symbols) + white noise). The implementation of the present invention can be realized through memory and multiple calculators (such as multipliers, adders, etc.).

The MIMO-OFDM system of _NT × _NR is taken as an example below, (wherein, _NT is a transmitting antenna, and _NR is a receiving antenna) the channel estimation method in the multiple-input multiple-output OFDM system of the present invention includes The following steps:

Step 110, the system encodes the continuous pilot subcarrier block data on the transmitting antennas and the Walsh (Walsh) orthogonal codes allocated by the corresponding transmitting antennas, and encodes the non-pilot subcarriers and non-pilot subcarriers in the continuous pilot blocks. The data on the data subcarriers in the pilot data block is completed by the bit streams on the individual transmit antennas through constellation mapping, and the coded pilot subcarrier blocks and the data subcarriers after constellation mapping are completed to form OFDM signals in the frequency domain;

The system connects the continuous pilot subcarrier blocks on _NT transmitting antennas (the length of the pilot block is N _C , and the data on each pilot subcarrier is all "1") with the corresponding Walsh normal Cross-code (the code length is also N _C ) is multiplied (i.e., encoded), and the data on the non-pilot subcarriers in the continuous pilot block and the data subcarriers in the non-pilot data block are transmitted by each individual transmit antenna The bitstream is done through constellation mapping.

Step 120, the system performs IFFT transformation of _NFFT points on the OFDM signal in the frequency domain on each transmitting antenna, performs parallel-to-serial conversion (P/S) and adds a cyclic prefix (CP) at the same time to generate an OFDM signal in the time domain, Transmission to the receiving antenna through a wireless MIMO channel;

The system performs IFFT (inverse fast Fourier transform) transformation of _NFFT points on each transmitting antenna, and then undergoes parallel-to-serial conversion (P/S) and adds cyclic prefix (CP) to become an OFDM signal in the time domain. The fading channel is transmitted to the receiver.

Step 130, after the system removes the cyclic prefix and serial-to-parallel conversion (S/P) of the time-domain OFDM signal received on each receiving antenna, the system generates each receiving antenna through FFT (fast Fourier transform) transformation processing of _NFFT points For the OFDM signal in the upper frequency domain, extract the continuous pilot subcarrier block data on each receiving antenna;

The system first removes the cyclic prefix (CP) and serial-to-parallel conversion (S/P) of the received data on each receiving antenna, and then processes through the FFT transformation of _NFFT points, and finally extracts the continuous pilot subcarriers on each receiving antenna block data.

Step 140, the system multiplies and accumulates the Walsh orthogonal code of each transmitting antenna matched with the transmitting end, and the extracted pilot subcarrier block data on each receiving antenna to obtain the Pilot receiving data;

The system multiplies and accumulates the Walsh orthogonal code of each transmitting antenna matched with the transmitting end with the pilot subcarrier block data on each receiving antenna extracted in step 130 and accumulates it to obtain each The pilot on the transmitting antenna receives data, that is, the interference caused by other transmitting antennas is removed at the same time.

Step 150, the system performs frequency-domain LS channel estimation on the pilot received data on each transmit antenna, and after obtaining the frequency responses of all pilot subcarriers on each transmit antenna, according to the transform domain method (that is, inserting several zeros) , and then perform the IFFT transformation of the _MFFT point to obtain the time-domain channel response value of the _MFFT point;

Through the frequency domain LS channel estimation method, the system can first obtain the frequency response of all pilot subcarriers on each transmitting antenna, and insert several zeros (the number is determined by the number of pilot subcarriers N _p , the number of FFT points N _FFT and The insertion interval ΔN _f of the pilot subcarrier is determined), and then the IFFT transformation of the _MFFT point is performed.

Step 160, the system first performs a peak search for the obtained _MFFT point time-domain channel response value, determines the peak value and its corresponding position, and then calculates the diffusion coefficient of the sampling point at this position on all time-domain sample points, and calculates it from The initially obtained _MFFT point time-domain channel response value is offset, and then a new round of peak search iterations is performed until the searched peak value drops below the set threshold, the iteration is stopped, and the effective _MFFT point time-domain multiplicity is output. channel response value, and set all other sample points to 0;

Step 170. The system performs _NFFT point FFT transformation on the obtained _MFFT point time-domain multipath channel response value to obtain the channel frequency response value of each data subcarrier on each transmitting antenna, and completes channel estimation.

The present invention will be further described below in conjunction with specific examples.

The symbols in Figure 2 are explained as follows:

第n_t(n_t＝1，2，…N_T)根发送天线上由导频子载波与数据子载波组成的第n个OFDM符号频域数据块向量；

The nth OFDM symbol frequency-domain data block vector composed of pilot subcarriers and data subcarriers on the n _t (n _t =1, 2, ... N _T ) root transmitting antenna;

第n_t(n_t＝1，2，…N_T)根发送天线上由导频子载波与数据子载波组成

The n _t (n _t = 1, 2, ... N _T ) transmitting antenna is composed of pilot subcarriers and data subcarriers

The nth OFDM symbol time-domain data block vector of ;

h(n): The time-domain impulse response of a wireless MIMO channel, usually expressed by its discrete tapped delay line model as

第n_r(n_r＝1，2，…N_R)根接收天线上的时域接收信号；

The time-domain received signal on the n _rth (n _r =1, 2, ... N _R ) receiving antenna;

第n_r(n_r＝1，2，…N_R)根接收天线上去循环前缀(CP)后的频域接收信号；

The frequency-domain received signal after removing the cyclic prefix (CP) on the n _r (n _r =1, 2, ... N _R ) receiving antenna;

The time-domain channel impulse response between the n _t transmitting antenna and the n _r receiving antenna;

The frequency domain response of the channel between the n _t transmitting antenna and the n _r receiving antenna;

A: The antenna encoding module completes the orthogonal encoding of the upper pilot subcarrier data of each transmitting antenna;

B: Antenna decoding module, which completes the inverse processing of module A, mainly composed of a multiplier and an accumulator;

C: Radial diffusion suppression module, which completes the time-domain radial diffusion and noise suppression.

The process of the signal flow described in Figure 2 is:

(1) Module A outputs pilot subcarrier data on each transmit antenna;

(2) Generation of time-domain transmission signals on each transmission antenna:

${\mathrm{<span\; class="notranslate">\; x</span>}}_{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; CP</span>}}{\mathrm{<span\; class="notranslate">\; f</span>}}_{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; FFT</span>}}}^{\mathrm{<span\; class="notranslate">\; h</span>}}{\mathrm{<span\; class="notranslate">\; x</span>}}_{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1,2</span>}<span\; class="notranslate">\; ,</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}}<span\; class="notranslate">\; )</span>$

为归一化的傅里叶变换矩阵。Among them, T _CP adds the matrix for the cyclic prefix,

is the normalized Fourier transform matrix.

(3) After the above transmitted signal passes through the wireless MIMO channel, the receiving form at the receiving end is:

${\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\underset{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; h</span>}}_{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}}^{\mathrm{<span\; class="notranslate">\; cir</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&eta;</span>}}_{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>$

产生的循环矩阵，为高斯噪声。in, By

The resulting circulant matrix, is Gaussian noise.

(4) Further perform FFT change processing on the received data on each of the above receiving antennas to obtain its frequency domain receiving vector as:

${\mathrm{<span\; class="notranslate">\; Y</span>}}_{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; f</span>}}_{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; FFT</span>}}}{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>$

$<span\; class="notranslate">\; =</span>\underset{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}\mathrm{<span\; class="notranslate">\; diag</span>}<span\; class="notranslate">\; \{</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \}</span>{\stackrel{<span\; class="notranslate">\; ~</span>}{\mathrm{<span\; class="notranslate">\; f</span>}}}_{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; FFT</span>}}}{\mathrm{<span\; class="notranslate">\; h</span>}}_{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&xi;</span>}}_{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>$

(5) Module B performs orthogonal separation on the extracted pilot subcarrier data on each antenna;

(6) The output of module C is an effective time-domain multipath channel response value, and the channel frequency response of each data subcarrier on each transmitting antenna is finally obtained by _NFFT point FFT transformation:

${\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; h</span>}}}_{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; k</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; FFT</span>}<span\; class="notranslate">\; [</span>{\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; h</span>}}}_{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span><span\; class="notranslate">\; .</span>$

The internal structure of module A is shown in Figure 3.

The symbols in Figure 3 are explained as follows:

The Walsh orthogonal code assigned by the n _t (n _t =1, 2, ... N _T )th transmit antenna, and has Among them, the different Walsh orthogonal codes assigned to each transmitting antenna have the following orthogonal characteristics, namely

The coded time-domain data block of the k _p -th pilot subcarrier on the n _t (n _t =1, 2, ... N _T )th transmitting antenna, and has

The signal flow process described in Figure 3 is: Right now

The internal structure of module B is shown in Figure 4.

The symbols in Figure 4 are explained as follows:

第n_r(n_r＝1，2，…N_R)根接收信号中所提取的第k_p个导频子载波处的连续导频块向量，且有

或者

The continuous pilot block vector at the k _pth pilot subcarrier extracted from the n _r (n _r =1, 2, ... _NR ) root received signal, and has

or

${\mathrm{<span\; class="notranslate">\; Y</span>}}_{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span><span\; class="notranslate">\; [</span>\underset{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; h</span>}}_{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&xi;</span>}}_{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span>\underset{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\overset{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}}{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; h</span>}}_{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; C</span>}}_{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&xi;</span>}}_{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ]</span><span\; class="notranslate">\; ;</span>$

第n_t(n_t＝1，2，…N_T)根发送天线到n_r(n_r＝1，2，…N_R)根接收天线之间的第k_p(p＝0，1，…N_P-1)个导频子载波处的接收数据。

_The k _{p (} p=0 _, 1 _{, .} . _. N _P -1) received data at pilot subcarriers.

The signal flow process described in Figure 4 is:

The internal structure of module C is shown in Figure 5.

The symbols in Figure 5 are explained as follows:

第n_t(n_t＝1，2，…N_T)根发送天线到n_r(n_r＝1，2，…N_R)根接收天线之间初始的时域信道冲激响应估计；

The initial time-domain channel impulse response estimation between the n _t (n _t =1, 2, ... N _T ) transmitting antenna and the n _r (n _r = 1, 2, ... _NR ) receiving antenna;

n _max ^(m) : the position of the peak point after the mth iteration,

The diffusion coefficient of the peak point position on all samples after the mth iteration;

After M times of iterative cancellation, the time-domain channel impulse between the n _t (n _t =1, 2, ... _NT )th transmitting antenna and the n _r (n _r =1, 2, ... _NR ) receiving antenna Response estimates.

The signal flow process described in Figure 5 is:

(1) update the input signal,

(2) Perform peak search,

(3) Calculate the diffusion coefficient,

${\mathrm{<span\; class="notranslate">\; g</span>}}_{{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; t</span>}}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; max</span>}}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{\frac{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; j</span>}\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; max</span>}}}{{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; FFT</span>}}}}{\mathrm{<span\; class="notranslate">\; e</span>}}^{\frac{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; j\&pi;</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; max</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; FFT</span>}}}\frac{\mathrm{<span\; class="notranslate">\; sin</span>}\frac{\mathrm{<span\; class="notranslate">\; \&pi;</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; max</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; N</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}}{{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; FFT</span>}}}}{\mathrm{<span\; class="notranslate">\; sin</span>}\frac{\mathrm{<span\; class="notranslate">\; \&pi;</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; no</span>}}_{\mathrm{<span\; class="notranslate">\; max</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; FFT</span>}}}}<span\; class="notranslate">\; .</span>}$

A channel estimation device in a multiple-input multiple-output OFDM system of the present invention includes an antenna encoding module, an antenna decoding module and a radial diffusion suppression module, wherein,

The antenna encoding module is configured to encode the pilot subcarrier data of each transmitting antenna and the Walsh orthogonal code assigned by the corresponding transmitting antenna, and then form the encoded pilot subcarrier blocks and data subcarriers Orthogonal frequency division multiplexing OFDM signal in the frequency domain; after performing inverse fast Fourier transform IFFT to the OFDM signal in the frequency domain on each transmitting antenna, generate an OFDM signal in the time domain and transmit it to the antenna decoding module;

The antenna decoding module is used to perform fast Fourier transform (FFT) transform processing on the received time-domain OFDM signal on each receiving antenna, extract continuous pilot subcarrier block data on each receiving antenna, and match each The Walsh orthogonal codes of the root transmit antennas are multiplied and accumulated to obtain the pilot reception data on each transmit antenna, and sent to the radial diffusion suppression module;

The diameter diffusion suppression module is used to perform frequency-domain LS channel estimation on the pilot received data on each transmitting antenna, and obtain the frequency responses of all pilot subcarriers on each transmitting antenna, and then obtain the time Domain channel response value; through peak search, peak point spread coefficient calculation and offset iteration for the obtained time domain channel response value, the effective time domain multipath channel response value output is obtained to obtain the channel of each data subcarrier on each transmitting antenna The frequency response value completes the channel estimation.

After the antenna encoding module encodes the pilot subcarrier data of each transmitting antenna and the Walsh orthogonal code assigned by the corresponding transmitting antenna, the encoded pilot subcarrier block and data subcarrier form an OFDM signal in the frequency domain; After performing IFFT transformation on the OFDM signal in the frequency domain on each transmitting antenna, an OFDM signal in the time domain is generated, specifically referring to:

The antenna encoding module encodes the continuous pilot subcarrier block data on the transmitting antenna and the Walsh orthogonal codes allocated by the corresponding transmitting antennas, and encodes the non-pilot subcarriers and non-pilot data blocks in the continuous pilot block The data on the inner data subcarrier is completed by the bit stream on each transmit antenna through constellation mapping, and the coded pilot subcarrier block and the data subcarrier after the constellation mapping are completed to form an OFDM signal in the frequency domain; The OFDM signal in the frequency domain on the antenna is subjected to IFFT transformation, parallel-to-serial conversion is performed and a cyclic prefix is added at the same time, and an OFDM signal in the time domain is generated.

The antenna decoding module performs FFT transformation processing on the time-domain OFDM signal received on each receiving antenna, and extracts the continuous pilot subcarrier block data on each receiving antenna, specifically referring to:

After the antenna decoding module removes the cyclic prefix and serial-to-parallel conversion of the time-domain OFDM signal received on each receiving antenna, it generates an OFDM signal in the frequency domain on each receiving antenna through FFT transformation processing, and extracts the OFDM signal on each receiving antenna. Consecutive pilot subcarrier block data of .

The radial spread suppression module performs frequency-domain LS channel estimation on the pilot received data on each transmitting antenna, and obtains the time-domain channel response according to the transform domain method after obtaining the frequency responses of all pilot subcarriers on each transmitting antenna value, specifically:

The radial diffusion suppression module performs frequency-domain LS channel estimation on the pilot received data on each transmitting antenna, and after obtaining the frequency responses of all pilot subcarriers on each transmitting antenna, inserts several zeros, and then performs IFFT Transform to obtain the time-domain channel response value, wherein the number of inserted zeros is determined by the number of pilot subcarriers, the number of FFT points, and the insertion interval of pilot subcarriers.

The path diffusion suppression module performs peak search, peak point spread coefficient calculation and offset iteration on the obtained time-domain channel response value, and the effective time-domain multi-path channel response value outputted obtains each data subcarrier on each transmitting antenna. Channel frequency response value, specifically refers to:

For the obtained time-domain channel response value, the said diameter diffusion suppression module determines the peak value and its corresponding position by performing a peak search, calculates the diffusion coefficient of the sampling point at this position on all time-domain sample points, and converts it from the initially obtained Offset the obtained time-domain channel response value, and then perform a new round of peak search iterations until the searched peak value drops below the set threshold, stop the iteration, and perform FFT on the output effective time-domain multipath channel response value Transform processing to obtain the channel frequency response value of each data subcarrier on each transmit antenna.

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person familiar with the technology can easily think of changes or replacements within the technical scope disclosed in the present invention. , should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the protection scope of the claims.

Claims (6)

1. A channel estimation method in a multiple-input multiple-output orthogonal frequency division multiplexing system is characterized by comprising the following steps:

after the system encodes the pilot frequency subcarrier data of each transmitting antenna and the Walsh orthogonal code distributed by the corresponding transmitting antenna, the system combines the encoded pilot frequency subcarrier block and the data subcarrier into an Orthogonal Frequency Division Multiplexing (OFDM) signal of a frequency domain; after the Inverse Fast Fourier Transform (IFFT) is carried out on the OFDM signal of the frequency domain on each transmitting antenna, the OFDM signal of a time domain is generated and transmitted to a receiving antenna;

the system carries out Fast Fourier Transform (FFT) conversion processing on the time domain OFDM signals received by each receiving antenna, extracts continuous pilot frequency subcarrier block data on each receiving antenna, multiplies and accumulates the continuous pilot frequency subcarrier block data with Walsh orthogonal codes of each transmitting antenna matched with a transmitting end to obtain pilot frequency receiving data on each transmitting antenna;

the system carries out frequency domain LS channel estimation on pilot frequency receiving data on each transmitting antenna to obtain frequency responses of all pilot frequency subcarriers on each transmitting antenna, and then obtains a time domain channel response value according to a transform domain mode; the system performs frequency domain LS channel estimation on pilot frequency receiving data on each transmitting antenna to obtain frequency responses of all pilot frequency subcarriers on each transmitting antenna, inserts a plurality of zeros, and performs IFFT to obtain a time domain channel response value, wherein the number of inserted zeros is determined by the number of pilot frequency subcarriers, the number of FFT points and the insertion interval of the pilot frequency subcarriers;

the system outputs effective time domain multipath channel response values to the obtained time domain channel response values through peak value search, peak value point diffusion coefficient calculation and offset iteration, obtains channel frequency response values of data subcarriers on each transmitting antenna, and completes channel estimation; after the system determines the peak value and the corresponding position of the peak value through peak value search for the obtained time domain channel response value, the diffusion coefficient of the sampling point at the position on all time domain sampling points is calculated and is counteracted from the initially obtained time domain channel response value, a new round of peak value search iteration is carried out again until the searched peak value is reduced to be below a set threshold, the iteration is stopped, the FFT conversion processing is carried out on the output effective time domain multipath channel response value, the channel frequency response value of each data subcarrier on each transmitting antenna is obtained, and the channel estimation is completed.

2. The channel estimation method of claim 1,

the system encodes the pilot frequency subcarrier data of each transmitting antenna and the Walsh orthogonal code distributed by the corresponding transmitting antenna, and then forms the OFDM signal of the frequency domain by the encoded pilot frequency subcarrier block and the data subcarrier; after performing IFFT on the OFDM signal in the frequency domain on each transmitting antenna, generating an OFDM signal in the time domain and transmitting the OFDM signal to a receiving antenna, specifically comprising the following steps:

the system encodes the continuous pilot frequency sub-carrier block data on the transmitting antenna and Walsh orthogonal codes distributed by corresponding transmitting antennas, completes the data on non-pilot frequency sub-carriers in the continuous pilot frequency blocks and data sub-carriers in the non-pilot frequency data blocks by bit streams on the independent transmitting antennas through constellation mapping, and forms OFDM signals of a frequency domain by the encoded pilot frequency sub-carrier blocks and the data sub-carriers after the constellation mapping is completed;

the system carries out IFFT transformation on the OFDM signals of the frequency domain on each transmitting antenna, carries out parallel-serial conversion and adds a cyclic prefix at the same time, generates the OFDM signals of a time domain, and transmits the OFDM signals to a receiving antenna through a wireless MIMO channel.

3. The channel estimation method of claim 1 or 2,

the system performs FFT processing on the time domain OFDM signal received by each receiving antenna, extracts continuous pilot frequency subcarrier block data on each receiving antenna, and specifically comprises the following steps:

the system removes the cyclic prefix and carries out serial-parallel conversion on the time domain OFDM signals received on each receiving antenna, generates the OFDM signals of the frequency domain on each receiving antenna through FFT conversion processing, and extracts the continuous pilot frequency subcarrier block data on each receiving antenna.

4. A channel estimation device in a MIMO OFDM system is disclosed, which is characterized in that,

comprises an antenna coding module, an antenna decoding module and a path diffusion suppression module, wherein,

the antenna coding module is used for coding the pilot frequency subcarrier data of each transmitting antenna and the Walsh orthogonal code distributed by the corresponding transmitting antenna and then forming the coded pilot frequency subcarrier block and the data subcarrier into an Orthogonal Frequency Division Multiplexing (OFDM) signal of a frequency domain; after the Inverse Fast Fourier Transform (IFFT) is carried out on the OFDM signal of the frequency domain on each transmitting antenna, the OFDM signal of a time domain is generated and transmitted to the antenna decoding module;

the antenna decoding module is used for performing Fast Fourier Transform (FFT) conversion processing on the received time domain OFDM signals on each receiving antenna, extracting continuous pilot frequency subcarrier block data on each receiving antenna, multiplying and accumulating the continuous pilot frequency subcarrier block data with Walsh orthogonal codes of each transmitting antenna matched with the transmitting end to obtain pilot frequency receiving data on each transmitting antenna, and transmitting the pilot frequency receiving data to the path diffusion suppression module;

the path diffusion suppression module is used for performing frequency domain LS channel estimation on pilot frequency receiving data on each transmitting antenna to obtain frequency responses of all pilot frequency subcarriers on each transmitting antenna and then obtaining a time domain channel response value according to a transform domain mode, wherein the path diffusion suppression module performs frequency domain LS channel estimation on the pilot frequency receiving data on each transmitting antenna to obtain frequency responses of all pilot frequency subcarriers on each transmitting antenna, inserts a plurality of zeros, and then performs IFFT to obtain a time domain channel response value, wherein the number of the inserted zeros is determined by the number of the pilot frequency subcarriers, the number of FFT points and the insertion interval of the pilot frequency subcarriers; and performing peak search, peak point diffusion coefficient calculation and cancellation iteration on the obtained time domain channel response value to output an effective time domain multipath channel response value, obtain a channel frequency response value of each data subcarrier on each transmitting antenna, and complete channel estimation, wherein the path diffusion suppression module performs peak search on the obtained time domain channel response value to determine a peak value and a corresponding position thereof, calculates the diffusion coefficient of a sampling point at the position on all time domain sample points, cancels the diffusion coefficient from the initially obtained time domain channel response value, performs a new round of peak search iteration until the searched peak value is reduced below a set threshold, stops iteration, performs FFT (fast Fourier transform) processing on the output effective time domain multipath channel response value, and obtains the channel frequency response value of each data subcarrier on each transmitting antenna.

5. The channel estimation apparatus of claim 4,

the antenna coding module codes the pilot frequency subcarrier data of each transmitting antenna and the Walsh orthogonal code distributed by the corresponding transmitting antenna, and then forms the OFDM signal of the frequency domain by the coded pilot frequency subcarrier block and the data subcarrier; after performing IFFT on the OFDM signal in the frequency domain on each transmit antenna, an OFDM signal in the time domain is generated, which specifically means:

the antenna coding module codes continuous pilot frequency sub-carrier block data on the sending antenna and Walsh orthogonal codes distributed by corresponding sending antennas, completes data on non-pilot frequency sub-carriers in continuous pilot frequency blocks and data sub-carriers in non-pilot frequency data blocks through constellation mapping by bit streams on independent sending antennas, and forms OFDM signals of a frequency domain by the coded pilot frequency sub-carrier blocks and the data sub-carriers after the constellation mapping is completed; and after carrying out IFFT transformation on the OFDM signal of the frequency domain on each transmitting antenna, carrying out parallel-serial conversion and adding a cyclic prefix, and generating the OFDM signal of the time domain.

6. The channel estimation apparatus of claim 4 or 5,

the antenna decoding module performs FFT processing on the time domain OFDM signal received on each receiving antenna, and extracts continuous pilot subcarrier block data on each receiving antenna, specifically:

the antenna decoding module removes cyclic prefix and performs serial-parallel conversion on the time domain OFDM signals received by each receiving antenna, generates frequency domain OFDM signals on each receiving antenna through FFT conversion processing, and extracts continuous pilot frequency subcarrier block data on each receiving antenna.

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