A channel estimation method and device of OFDM, a signal receiving method and device

Abstract

The application provides an OFDM channel estimation method and device, and a signal receiving method and device, which comprises: obtaining LS channel estimation and background noise of OFDM according to OFDM pilot time domain symbol sequences uniformly distributed in subcarriers of OFDM pilot time slots; performing mirror image extension on the LS channel estimation of a first number of subcarriers on two edges of the frequency domain to obtain extended channel estimation, and performing IDFT transformation on the extended channel estimation to obtain an extended time domain symbol sequence of the pilot time domain symbol sequence; filtering the extended time domain symbol sequence by using a cosine window function obtained according to the background noise and the extended time domain symbol sequence to obtain a noise reduction time domain symbol sequence of the pilot time domain symbol sequence; and obtaining the channel estimation of OFDM according to the noise reduction time domain symbol sequence. The technical scheme of the embodiment of the application improves the problem of deterioration of edge subcarrier channel estimation values in the DFT channel estimation method of OFDM, and improves the channel estimation performance of the system.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of wireless communication, and particularly relates to a channel estimation method and device of OFDM, and a signal receiving method and device. BACKGROUND

[0002] Figure 1 The prior art DFT channel estimation method is shown as follows: pilot symbols in time domain are subjected to LS channel estimation after FFT transformation, and then the frequency domain response is subjected to IDFT transformation to time domain. At this time, the time domain channel response energy is concentrated in the front end, and the concentrated range is generally not greater than the CP length in the normal case. Therefore, the channel response within a certain length in time domain can be regarded as useful channel response, and the response outside the length can be regarded as response caused mainly by noise. The effect of suppressing noise is achieved by setting the response outside the length to zero. The length can be the CP length in the normal case. Then the response after noise suppression in time domain is transformed to frequency domain by DFT, and the channel estimation value in the frequency domain is taken as the channel response after noise suppression.

[0003] The main defect of the method is as follows: in the OFDM system, the frequency band range of transmission is usually vacant guard band, i.e. virtual subcarrier. Taking an OFDM system with a sampling rate of 30.72M, a subcarrier interval of 15k and a bandwidth of 20M as an example. The normal FFT point number is 2048, and the effective subcarrier number is 1200. The remaining edge virtual subcarriers do not carry information. The normal LS channel estimation can only obtain the channel response on the 1200 subcarriers within the band. However, for the actual time domain channel response, after 2048-point FFT transformation to the frequency domain, the channel response information should be contained on all the frequency domain points. By comparison, since the virtual subcarriers of the OFDM system do not carry pilot information and have no channel response value, the in-band estimated frequency domain response is equivalent to multiplying the actual frequency domain response by an ideal low-pass filter. For the time domain channel response, it is equivalent to convolving an actual time domain channel response with a sinc function. Since the sinc function is a time domain signal of infinite length in theory, it forms a tail for the original time domain channel response, so that the channel response energy which should be concentrated in a certain length is distributed on all taps in time domain. When using methods such as windowing and zero setting to suppress the time domain channel response outside a certain length, since part of the useful time domain response is also set to zero, the channel response after transformation to the frequency domain is affected. This effect makes the channel estimation value of the edge part of the effective subcarrier greatly different from the real channel response, which deteriorates the performance of channel estimation. SUMMARY

[0004] In view of the above, the embodiment of the present application provides an OFDM channel estimation method and device, a signal receiving method and device, which comprises: obtaining LS channel estimation and background noise of OFDM according to OFDM pilot time domain symbol sequence, wherein the pilot time domain symbol sequence is uniformly distributed in several subcarriers in pilot time slot in frequency domain; performing mirror image extension on the LS channel estimation of the first number of subcarriers at the two edges of the frequency domain, obtaining extended channel estimation, and performing IDFT transformation on the extended channel estimation, obtaining the extended time domain symbol sequence of the pilot time domain symbol sequence; filtering the extended time domain symbol sequence using a cosine window function, obtaining the noise-reduced time domain symbol sequence of the pilot time domain symbol sequence, wherein the cosine window function is obtained according to the background noise and the extended time domain symbol sequence; and obtaining the channel estimation of OFDM according to the noise-reduced time domain symbol sequence. The technical scheme of the embodiment of the present application improves the problem of deterioration of edge subcarrier channel estimation value in the DFT channel estimation method represented by OFDM, and improves the channel estimation performance of the system.

[0005] In the first aspect, the embodiment of the present application provides an OFDM channel estimation method, which comprises: obtaining LS channel estimation and background noise of OFDM according to OFDM pilot time domain symbol sequence, wherein the pilot time domain symbol sequence is uniformly distributed in several subcarriers in pilot time slot in frequency domain; performing mirror image extension on the LS channel estimation of the first number of subcarriers at the two edges of the frequency domain, obtaining extended channel estimation, and performing IDFT transformation on the extended channel estimation, obtaining the extended time domain symbol sequence of the pilot time domain symbol sequence; filtering the extended time domain symbol sequence using a cosine window function, obtaining the noise-reduced time domain symbol sequence of the pilot time domain symbol sequence, wherein the cosine window function is obtained according to the background noise and the extended time domain symbol sequence; and obtaining the channel estimation of OFDM according to the noise-reduced time domain symbol sequence.

[0006] According to the above, the noise-reduced time domain symbol sequence of the pilot time slot is obtained by performing mirror image extension on the LS channel estimation, then performing IDFT transformation, and then filtering by the cosine window function, so as to obtain the channel estimation of OFDM according to the time domain symbol sequence channel estimation. The technical scheme of the embodiment of the present application improves the problem of deterioration of edge subcarrier channel estimation value in the DFT channel estimation method represented by OFDM, and improves the channel estimation performance of the system.

[0007] In a possible implementation of the first aspect, the LS channel estimation and the background noise of the OFDM are obtained according to the OFDM pilot time-domain symbol sequence, comprising: performing FFT transform on the OFDM pilot time-domain symbol sequence to obtain an OFDM pilot frequency-domain symbol sequence; obtaining the LS channel estimation according to the frequency-domain symbol sequence on the subcarriers where the pilot time-domain symbol sequence exists; and obtaining the background noise according to the frequency-domain symbol sequence on the subcarriers where the pilot time-domain symbol sequence does not exist.

[0008] According to the above, the LS channel estimation and the noise estimation can be accurately performed by using the above method on the pilot time-domain symbol sequence uniformly distributed in the pilot time slot on the subcarriers in the frequency domain.

[0009] In a possible implementation of the first aspect, the channel estimation of the OFDM is obtained according to the noise-reduced time-domain symbol sequence, comprising: performing DFT transform on the noise-reduced time-domain symbol sequence, and taking the obtained frequency-domain response as a noise-reduced channel estimation; removing the frequency-domain responses on the first number of subcarriers at both edges of the noise-reduced channel estimation, and obtaining the channel estimation of the full bandwidth of the OFDM by interpolating the frequency-domain responses on the subcarriers where the pilot time-domain symbol sequence does not exist.

[0010] According to the above, after the noise-reduced time-domain symbol sequence of the pilot time-domain symbol sequence reduced by the cosine window function is transformed to the frequency domain by IDFT, the deterioration of the frequency-domain response mainly occurs on the extended edge subcarriers, and the channel response of the original edge subcarriers has less influence, so that the channel estimation value in the entire effective subcarrier range can be obtained by interpolation.

[0011] In a possible implementation of the first aspect, the pilot time-domain symbol sequence is placed on every other subcarrier in the pilot time slot, and the 0 symbol sequence is placed on the other subcarriers.

[0012] According to the above, the pilot time-domain symbol sequence is placed on every other subcarrier in the pilot time slot by using the above method, and the accuracy of the LS channel estimation and the noise estimation is high, and the final channel estimation is improved.

[0013] In a possible implementation of the first aspect, when the OFDM is 20M bandwidth, the first number is 16.

[0014] According to the above, for the 20M OFDM system, the LS channel estimation is extended by 16 subcarriers on both sides, and the final channel estimation is improved.

[0015] In a second aspect, an embodiment of the present application provides a signal receiving method of OFDM, comprising: obtaining a time domain symbol sequence of OFDM after radio frequency demodulation, filtering, synchronization and frequency offset correction of a radio frequency signal received by an air interface; performing channel estimation of OFDM according to the time domain symbol sequence of a pilot time slot by using the method of any one of the first aspect; and obtaining communication data of OFDM according to the time domain symbol sequence of a data time slot by using the channel estimation.

[0016] In a third aspect, an embodiment of the present application provides a channel estimation device of OFDM, comprising: an initial channel estimation module, configured to obtain LS channel estimation and background noise of OFDM according to a pilot time domain symbol sequence of OFDM, wherein the pilot time domain symbol sequence is uniformly distributed in subcarriers of a pilot time slot of OFDM in a frequency domain; an edge mirror extension module, configured to perform mirror extension on the LS channel estimation of a first number of subcarriers at two edges of the frequency domain, to obtain an extended channel estimation, and to perform IDFT transformation on the extended channel estimation, to obtain an extended time domain symbol sequence of the pilot time domain symbol sequence; a windowing and noise reduction filtering module, configured to filter the extended time domain symbol sequence by using a cosine window function, to obtain a noise reduction time domain symbol sequence of the pilot time domain symbol sequence, wherein the cosine window function is obtained according to the background noise and the extended time domain symbol sequence; and a system channel estimation obtaining module, configured to obtain channel estimation of OFDM according to the noise reduction time domain symbol sequence.

[0017] According to the above, the noise reduction time domain symbol sequence of the pilot time slot is obtained by performing mirror extension on the LS channel estimation, performing IDFT transformation, and then filtering by using the cosine window function, so that the channel estimation of OFDM is obtained according to the channel estimation of the time domain symbol sequence. The technical scheme of the embodiment of the present application improves the problem of deterioration of the edge subcarrier channel estimation value in the DFT channel estimation method represented by OFDM, and improves the channel estimation performance of the system.

[0018] In a possible implementation of the third aspect, the obtaining of the LS channel estimation and the background noise of OFDM according to the pilot time domain symbol sequence of OFDM comprises: performing FFT transformation on the pilot time domain symbol sequence to obtain a pilot frequency domain symbol sequence of OFDM; obtaining the LS channel estimation according to the frequency domain symbol sequence on the subcarriers where the pilot time domain symbol sequence exists; and obtaining the background noise according to the frequency domain symbol sequence on the subcarriers where the pilot time domain symbol sequence does not exist.

[0019] According to the above, the LS channel estimation and the noise estimation can be accurately performed on the pilot time domain symbol sequence uniformly distributed in a plurality of subcarriers in the pilot time slot in the frequency domain by using the above method.

[0020] In a possible implementation of the third aspect, the initial channel estimation is specifically configured to include: performing DFT transformation on the noise-reduced time-domain symbol sequence, and taking the obtained frequency-domain response as a noise-reduced channel estimation; removing the frequency-domain responses on the first number of subcarriers at both edges of the noise-reduced channel estimation, and obtaining a channel estimation of the entire OFDM bandwidth by interpolating the frequency-domain responses on the subcarriers on which the pilot time-domain symbol sequence is absent.

[0021] As described above, after the noise-reduced time-domain symbol sequence of the pilot time-domain symbol sequence subjected to cosine window function noise reduction is transformed to the frequency domain by IDFT, the deterioration of the frequency-domain response mainly occurs on the extended edge subcarriers, and the channel response of the original edge subcarriers has less impact, thereby the channel estimation values in the entire effective subcarrier range can be obtained by interpolation.

[0022] In a possible implementation of the third aspect, the pilot time-domain symbol sequence is placed on every other subcarrier in the pilot time slot, and a 0 symbol sequence is placed on the other subcarriers.

[0023] As described above, by using the above device to place the pilot time-domain symbol sequence on every other subcarrier in the pilot time slot, the accuracy of the LS channel estimation and the noise estimation is high, and the final channel estimation is improved.

[0024] In a possible implementation of the third aspect, when the OFDM is 20M bandwidth, the first number is 16.

[0025] As described above, for the 20M OFDM system, the LS channel estimation is extended by 16 subcarriers on both sides, and the final channel estimation is improved.

[0026] In the fourth aspect, an embodiment of the present application provides an OFDM signal receiving device, which includes: a signal receiving module, configured to obtain an OFDM time-domain symbol sequence after radio frequency demodulation, filtering, synchronization, and frequency offset correction on data received by an air interface; a channel estimation module, configured to perform OFDM channel estimation according to the method in any of the embodiments of the first aspect by using the time-domain symbol sequence of the pilot time slot; and a data obtaining module, configured to obtain OFDM communication data by using the time-domain symbol sequence of the data time slot according to the channel estimation.

[0027] In the fifth aspect, an embodiment of the present application provides an OFDM system, which includes: a sending end, configured to uniformly set OFDM pilot time-domain symbol sequences in the frequency domain to subcarriers in an OFDM pilot time slot; and a receiving end, configured to obtain communication data according to the method in the fourth aspect.

[0028] In a sixth aspect, an embodiment of the present application provides a computing device, comprising a bus; a communication interface connected with the bus; at least one processor connected with the bus; and at least one memory connected with the bus and storing program instructions, which, when executed by the at least one processor, cause the at least one processor to perform the method of any of the embodiments of the first aspect or the method of the second aspect.

[0029] In a seventh aspect, an embodiment of the present application provides a computer readable storage medium, which stores program instructions, which, when executed by a computer, cause the computer to perform the method of any of the embodiments of the first aspect or the method of the second aspect. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 Flowchart of a DFT channel estimation method of the prior art;

[0031] Figure 2A Flowchart of a first embodiment of an OFDM channel estimation method of the present application;

[0032] Figure 2B Block distribution of pilot time slots and data time slots of various embodiments of the present application;

[0033] Figure 2C LS channel estimation mirror extension of edge subcarriers of various embodiments of the present application;

[0034] Figure 3A Distribution of pilot time domain symbol sequences in pilot time slots of 20M OFDM in a second embodiment of an OFDM channel estimation method of the present application;

[0035] Figure 3B Flowchart of a second embodiment of an OFDM channel estimation method of the present application;

[0036] Figure 4 Flowchart of an embodiment of an OFDM signal receiving method of the present application;

[0037] Figure 5 Structural diagram of a first embodiment of an OFDM channel estimation device of the present application;

[0038] Figure 6 Structural diagram of a second embodiment of an OFDM channel estimation device of the present application;

[0039] Figure 7 Structural diagram of an embodiment of an OFDM signal receiving device of the present application;

[0040] Figure 8Structural schematic diagram of a computing device embodiment of the present application. DETAILED DESCRIPTION

[0041] In the following description, reference is made to the "some embodiments", which describe a subset of all possible embodiments, but it can be understood that the "some embodiments" can be the same subset or different subsets of all possible embodiments, and can be combined with each other without conflict.

[0042] In the following description, the terms "first\second\third, etc." or module A, module B, module C, etc. are used only to distinguish similar objects or to distinguish different embodiments, and do not represent a specific order for the objects. It can be understood that the specific order or sequence can be interchanged as permitted, so that the embodiments of the application described herein can be implemented in an order other than that illustrated or described herein.

[0043] In the following description, the labels indicating steps such as S110, S120, etc. do not necessarily mean that the steps are executed in this order, and the order of the steps can be interchanged or executed simultaneously as permitted.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs. The terms used herein are only for the purpose of describing the embodiments of the present application and are not intended to limit the present application.

[0045] The embodiments of the present application provide an OFDM channel estimation method and device, a signal receiving method and device, which technical solutions comprise: obtaining LS channel estimation and background noise of OFDM according to OFDM pilot time domain symbol sequence, wherein the pilot time domain symbol sequence is uniformly distributed in a plurality of subcarriers in the pilot time slot in the frequency domain; mirror extending the LS channel estimation of the first number of subcarriers at the two edges of the frequency domain, obtaining an extended channel estimation, and performing IDFT transformation on the extended channel estimation to obtain an extended time domain symbol sequence of the pilot time domain symbol sequence; filtering the extended time domain symbol sequence using a cosine window function to obtain a noise-reduced time domain symbol sequence of the pilot time domain symbol sequence, wherein the cosine window function is obtained according to the background noise and the extended time domain symbol sequence; and obtaining the channel estimation of OFDM according to the noise-reduced time domain symbol sequence. The technical solutions of the embodiments of the present application improve the problem of deterioration of edge subcarrier channel estimation value in the DFT channel estimation method represented by OFDM, and improve the channel estimation performance of the system.

[0046] The embodiments of the present application will be described below in conjunction with the accompanying drawings.

[0047] Firstly, the embodiments of the present application will be described in conjunction with Figure 2A ​Figure 2C An embodiment of a channel estimation method for OFDM is introduced.

[0048] In the embodiment of a channel estimation method for OFDM, LS channel estimation and background noise of OFDM are obtained according to OFDM pilot time domain symbol sequence, wherein the pilot time domain symbol sequence is uniformly distributed in several subcarriers in pilot time slot in frequency domain; the LS channel estimation of the first number of subcarriers at the two edges of the frequency domain is mirror extended to obtain extended channel estimation, and the extended channel estimation is IDFT transformed to obtain the extended time domain symbol sequence of the pilot time domain symbol sequence; the extended time domain symbol sequence is filtered using a cosine window function to obtain the noise-reduced time domain symbol sequence of the pilot time domain symbol sequence, wherein the cosine window function is obtained according to the background noise and the extended time domain symbol sequence; and the channel estimation of OFDM is obtained according to the noise-reduced time domain symbol sequence. The technical solution of the embodiment improves the problem of edge subcarrier channel estimation value deterioration in the DFT channel estimation method represented by OFDM, and improves the channel estimation performance of the system.

[0049] Figure 2A A flow of the embodiment of a channel estimation method for OFDM is shown, including steps S110 to S140.

[0050] S110: LS channel estimation and background noise of OFDM are obtained according to pilot time domain symbol sequence of OFDM pilot time slot, wherein the pilot time domain symbol sequence is uniformly distributed in several subcarriers in the pilot time slot in frequency domain.

[0051] Figure 2B A block distribution diagram of pilot time slot and data time slot is shown. In some embodiments, the length of the pilot time slot is the same as that of the data time slot, and in other embodiments, the length of the data time slot is several times that of the pilot time slot.

[0052] In the pilot time domain symbol sequence, the LS channel estimation is obtained according to the frequency domain response of the subcarriers with pilot time domain symbol sequence, and the background noise of OFDM is obtained according to the frequency domain response of the subcarriers without pilot time domain symbol sequence in the pilot time slot. In some embodiments, pilot data exists in every other subcarrier in the pilot time slot, and in other embodiments, pilot data exists in one subcarrier every several subcarriers in the pilot time slot.

[0053] S120: The LS channel estimation of the first number of subcarriers at the two edges of the frequency domain is mirror extended to obtain the extended channel estimation of OFDM, and the extended channel estimation is IDFT transformed to obtain the extended time domain symbol sequence of the pilot time domain symbol sequence.

[0054] wherein the first number is determined according to the bandwidth of the OFDM, the wider the OFDM, the larger the first number.

[0055] For example, the first number is m, the number of effective subcarriers of the OFDM is n, h(0), h(1), …, h(n-1) are the channel estimates of the OFDM, h(0), h(1), …, h(m-1) are added outwardly at the low end of the subcarriers, and h(n-1), h(n-2), …, h(n-m) are added outwardly at the high end of the subcarriers.

[0056] Figure 2C A schematic diagram of the LS channel estimate mirror extension of the edge subcarriers is shown, wherein n is 600, m is 2, h(0) and h(1) are extended at the low end of the frequency domain, and h(599) and h(598) are extended at the high end of the frequency domain.

[0057] S130: filtering the extended time domain symbol sequence of the pilot time domain symbol sequence using a cosine window function to obtain a denoised time domain symbol sequence of the pilot time domain symbol sequence.

[0058] wherein the cosine window function is obtained according to the background noise and the extended time domain symbol sequence. Specifically, the cosine window function adopts a cosine roll-off waveform, an intensity threshold of a roll-off starting point is set according to the background noise value, and the width of the cosine window is obtained according to the intensity threshold of the roll-off starting point and the extended time domain symbol sequence.

[0059] From the above, since the spectral sidelobes of the cosine window function are very low, the influence on the edge subcarriers is low, and the denoised time domain symbol sequence of the pilot time domain symbol sequence can be used to obtain accurate channel estimates.

[0060] S140: obtaining the channel estimates of the OFDM according to the denoised time domain symbol sequence of the pilot time domain symbol sequence.

[0061] In some embodiments, the denoised time domain symbol sequence of the pilot time domain symbol sequence is transformed to the frequency domain through IDFT, then the frequency domain response values before mirror extension are taken out, and the frequency domain response values of the subcarriers without the pilot time domain symbol sequence are estimated through interpolation, so as to obtain the channel estimation values of the entire effective subcarrier range.

[0062] From the above, after the denoised time domain symbol sequence of the pilot time domain symbol sequence is denoised through the cosine window function, the deterioration of the frequency domain response mainly occurs on the extended edge subcarriers, and the influence of the channel response of the original edge carriers is small, so that the channel estimation values of the entire effective subcarrier range can be obtained through interpolation.

[0063] In summary, the first embodiment of the OFDM channel estimation method extends the LS channel estimation by mirror image and performs IDFT transformation, then obtains the noise-reduced time-domain symbol sequence of the pilot by noise reduction through the cosine window function, and finally obtains the OFDM channel estimation value through DFT and linear interpolation. Because the spectral sidelobes of the cosine window function are very low, the influence on the edge subcarriers is low, and compared with the traditional method, the embodiment obtains more accurate channel estimation value of the entire effective subcarrier range of the OFDM.

[0064] The following will be described in combination with Figure 3A and Figure 3B The second embodiment of the OFDM channel estimation method of the application is introduced.

[0065] The second embodiment of the OFDM channel estimation method is a detailed implementation of the first embodiment of the OFDM channel estimation method, and has all the advantages of the first embodiment of the OFDM channel estimation method.

[0066] The second embodiment of the OFDM channel estimation method takes 20M OFDM as an example, the system FFT point number is 2048, the effective subcarrier number is 1200, the subcarrier interval is 15KHz, and the CP length is 144. The system adopts block pilot.

[0067] Figure 3A The distribution diagram of the pilot time-domain symbol sequence in the pilot time slot in the 1200 effective subcarriers of the 20M OFDM is shown. The pilot frequency-domain sequence x_p(n), n=0, 1, 2, …, 599 at the sending end is placed according to the interval of one subcarrier as shown in the figure. The DC direct current does not place the pilot sequence, and the frequency domain maps 600 pilot sequence values in total.

[0068] Figure 3B The detailed process of the second embodiment of the OFDM channel estimation method is shown, which includes steps S210 to S246.

[0069] S210: FFT transformation, performing FFT transformation on the time-domain symbol sequence of the OFDM pilot time slot to obtain the frequency-domain symbol sequence of the OFDM pilot.

[0070] Among them, the time-domain symbol sequence of the OFDM pilot time slot is obtained by performing radio frequency demodulation, filtering, synchronization, frequency offset correction on the air interface received data.

[0071] S213: LS channel estimation, obtaining the LS channel estimation of the OFDM according to the frequency-domain symbol sequence on the subcarrier where the pilot time-domain symbol sequence exists.

[0072] S216: noise estimation, obtaining the background noise of OFDM according to the frequency domain symbol sequence on the sub-carrier where the pilot time domain symbol sequence does not exist.

[0073] S220: mirror extension, performing mirror extension on the LS channel estimation of the first number of sub-carriers on the two edges in frequency domain to obtain the extended channel estimation. Wherein, the first number is 16 in mirror extension in frequency domain.

[0074] S223: IDFT transformation, performing IDFT transformation on the extended channel estimation to obtain the extended time domain symbol sequence of the pilot time domain symbol sequence.

[0075] S230: window function design, obtaining the cosine window function according to the background noise of OFDM and the extended time domain symbol sequence.

[0076] S233: windowing and noise reduction, filtering the extended time domain symbol sequence of the pilot time domain symbol sequence using the cosine window function to obtain the noise-reduced time domain symbol sequence of the pilot time domain symbol sequence.

[0077] S240: DFT transformation, performing DFT transformation on the noise-reduced time domain symbol sequence, and taking the obtained frequency domain response as the noise-reduced channel estimation.

[0078] S243: removal of extension, removing the frequency domain response on the first number of sub-carriers on the two edges in the noise-reduced channel estimation to obtain the channel estimation of the pilot time domain symbol sequence.

[0079] S246: interpolation estimation, obtaining the channel estimation of OFDM by performing linear interpolation on the channel estimation of the pilot time domain symbol sequence.

[0080] Wherein, the channel estimation values of the sub-carriers where the pilot time domain symbol sequence is not placed are filled by linear interpolation, thereby obtaining the channel estimation values in the effective sub-carrier range of the entire OFDM.

[0081] The following will be described in combination with Figure 4 An embodiment of the OFDM signal receiving method is introduced.

[0082] An embodiment of the OFDM signal receiving method uses the channel estimation of the channel estimation method embodiment one or embodiment two to perform signal receiving, thereby improving the correctness of data receiving.

[0083] Figure 4 A flow of an embodiment of the OFDM signal receiving method is shown, which includes steps S310 to S330.

[0084] S310: after performing radio frequency demodulation, filtering, synchronization and frequency offset correction on the radio frequency signal received by the air interface, obtaining the time domain symbol sequence of OFDM.

[0085] S320: obtaining the channel estimation of the OFDM by using the time domain symbol sequence of the pilot time slot according to the method of the first or second embodiment of the channel estimation method of the OFDM.

[0086] S330: obtaining the communication data of the OFDM by using the time domain symbol sequence of the data time slot according to the channel estimation.

[0087] The following will be described in combination with Figures 5 to 7 The embodiments of the devices of the present application will be introduced.

[0088] Figure 5 An embodiment of the channel estimation device of the OFDM is shown, which comprises an initial channel estimation module 410, an edge mirror extension module 420, a windowing noise reduction filtering module 430 and a system channel estimation module 440.

[0089] The initial channel estimation module 410 is used for obtaining the LS channel estimation and the background noise of the OFDM according to the time domain symbol sequence of the pilot time slot of the OFDM, wherein the pilot time domain symbol sequence is uniformly distributed in a plurality of subcarriers in the pilot time slot in the frequency domain. The principle and advantages thereof please refer to the step S110 of the first embodiment of the channel estimation method of the OFDM.

[0090] The edge mirror extension module 420 is used for mirror extending the LS channel estimation of the first number of subcarriers at the two edges of the frequency domain, obtaining the extended channel estimation, and performing IDFT transformation on the extended channel estimation, to obtain the extended time domain symbol sequence of the pilot time domain symbol sequence. The principle and advantages thereof please refer to the step S120 of the first embodiment of the channel estimation method of the OFDM.

[0091] The windowing noise reduction filtering module 430 is used for filtering the extended time domain symbol sequence by using the cosine window function, to obtain the noise reduction time domain symbol sequence of the pilot time domain symbol sequence, wherein the cosine window function is obtained according to the background noise and the extended time domain symbol sequence. The principle and advantages thereof please refer to the step S130 of the first embodiment of the channel estimation method of the OFDM.

[0092] The system channel estimation module 440 is used for obtaining the channel estimation of the OFDM according to the noise reduction time domain symbol sequence. The principle and advantages thereof please refer to the step S140 of the first embodiment of the channel estimation method of the OFDM.

[0093] Figure 6An embodiment of a structure of a channel estimation device of OFDM is shown, which comprises: an FFT transform module 510, an LS channel estimation module 513, a noise estimation module 516, a mirror extension module 520, an IDFT transform module 523, a window function design module 530, a windowing filtering module 533, a DFT transform module 540, a removal extension module 543, and an interpolation estimation module 546.

[0094] The FFT transform module 510 is used for performing FFT transform on the time domain symbol sequence of the OFDM pilot time slot, to obtain the frequency domain symbol sequence of the OFDM pilot. Its principle and advantages please refer to step S210 of the embodiment two of the channel estimation method of OFDM.

[0095] The LS channel estimation module 513 is used for obtaining the LS channel estimation of OFDM according to the frequency domain symbol sequence on the subcarrier where the pilot time domain symbol sequence exists. Its principle and advantages please refer to step S213 of the embodiment two of the channel estimation method of OFDM.

[0096] The noise estimation module 516 is used for obtaining the background noise of OFDM according to the frequency domain symbol sequence on the subcarrier where the pilot time domain symbol sequence does not exist. Its principle and advantages please refer to step S216 of the embodiment two of the channel estimation method of OFDM.

[0097] The mirror extension module 520 is used for performing mirror extension on the LS channel estimation of the first number of subcarriers on the two edges of the frequency domain, to obtain the extended channel estimation, and performing IDFT transform on the extended channel estimation, to obtain the extended time domain symbol sequence of the pilot time domain symbol sequence. Its principle and advantages please refer to step S220 of the embodiment two of the channel estimation method of OFDM.

[0098] The IDFT transform module 523 is used for performing IDFT transform on the extended channel estimation, to obtain the extended time domain symbol sequence of the pilot time domain symbol sequence. Its principle and advantages please refer to step S223 of the embodiment two of the channel estimation method of OFDM.

[0099] The window function design module 530 is used for obtaining the cosine window function according to the background noise of OFDM and the extended time domain symbol sequence. Its principle and advantages please refer to step S230 of the embodiment two of the channel estimation method of OFDM.

[0100] The windowing filtering module 533 is used for filtering the extended time domain symbol sequence of the pilot time domain symbol sequence using the cosine window function, to obtain the noise reduction time domain symbol sequence of the pilot time domain symbol sequence. Its principle and advantages please refer to step S233 of the embodiment two of the channel estimation method of OFDM.

[0101] The DFT transformation module 540 is used to perform DFT transformation on the noise reduction time domain symbol sequence and use the obtained frequency domain response as the noise reduction channel estimation; its principle and advantages can be referred to step S240 of the second embodiment of an OFDM channel estimation method.

[0102] The extension removal module 543 is used to remove the frequency domain responses of the first number of subcarriers on the two edges of the noise reduction channel estimate to obtain a channel estimate of the pilot time domain symbol sequence. For its principles and advantages, please refer to step S243 of the second embodiment of an OFDM channel estimation method.

[0103] The interpolation estimation module 546 is used to obtain OFDM channel estimation by performing linear interpolation on the channel estimation of the pilot time domain symbol sequence. For its principle and advantages, please refer to step S246 of the second embodiment of an OFDM channel estimation method.

[0104] The embodiment of the present invention also provides an embodiment of an OFDM signal receiving device.

[0105] Figure 7 The structure of an embodiment of an OFDM signal receiving device is shown, which includes: a time domain sequence acquisition module 610, a channel estimation module 620 and a data acquisition module 630.

[0106] The time domain sequence acquisition module 610 is used to perform radio frequency demodulation, filtering, synchronization, and frequency offset correction on the radio frequency signal received at the air interface to obtain an OFDM time domain symbol sequence.

[0107] The channel estimation module 620 is configured to obtain an OFDM channel estimate using the time domain symbol sequence of the pilot time slot according to the method described in the first or second embodiment of the OFDM channel estimation.

[0108] The data acquisition module 630 obtains OFDM communication data using the time domain symbol sequence of the data time slot according to the channel estimation.

[0109] An embodiment of the present invention further provides an OFDM system, comprising a transmitting end and a receiving end;

[0110] The transmitting end is used to evenly arrange the OFDM pilot time domain symbol sequence in the frequency domain to a number of subcarriers in the OFDM pilot time slot.

[0111] The receiving end includes the modules of the first or second embodiment of an OFDM signal receiving device.

[0112] The embodiment of the present invention also provides a computing device, Figure 8 Detailed introduction.

[0113] The computing device 800 includes a processor 810, a memory 820, a communication interface 830, and a bus 840.

[0114] It should be understood that the communication interface 830 in the computing device 800 shown in the figure can be used for communication with other devices.

[0115] The processor 810 can be connected with the memory 820. The memory 820 can be used for storing program codes and data. Therefore, the memory 820 can be a storage unit inside the processor 810, can be an external storage unit independent of the processor 810, or can be a component including the storage unit inside the processor 810 and the external storage unit independent of the processor 810.

[0116] Optionally, the computing device 800 can further include the bus 840. The memory 820 and the communication interface 830 can be connected with the processor 810 through the bus 840. The bus 840 can be a Peripheral Component Interconnect (PCI) bus or an Extended Industry Standard Architecture (EISA) bus, etc. The bus 840 can be divided into an address bus, a data bus, a control bus, etc. For the convenience of representation, only one line is used in the figure, but it does not mean that there is only one bus or only one type of bus.

[0117] It should be understood that in the embodiments of the present application, the processor 810 can be a central processing unit (CPU). The processor can also be other general-purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC), field programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor. Alternatively, the processor 810 uses one or more integrated circuits to execute related programs to implement the technical solutions provided by the embodiments of the present application.

[0118] The memory 820 can include read-only memory and random access memory, and provide instructions and data for the processor 810. A part of the processor 810 can also include a non-volatile random access memory. For example, the processor 810 can also store device type information.

[0119] When the computing device 800 is in operation, the processor 810 is configured to execute the computer-executable instructions stored in the memory 820, which causes the computing device 800 to implement the method embodiments of the present application.

[0120] It should be understood that the computing device 800 according to the embodiments of the present application can correspond to the respective subject performing the method according to the embodiments of the present application, and the above and other operations and / or functions of the respective modules in the computing device 800 are respectively for implementing the corresponding procedures of the method embodiments of the present application, which are not described herein again for the sake of brevity.

[0121] Those skilled in the art can clearly understand that the units and algorithm steps of the examples described in combination with the embodiments disclosed herein can be realized by electronic hardware or a combination of computer software and electronic hardware. Whether the functions are realized in hardware or software manner depends on the specific application and design constraints of the technical solution. The skilled person can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0122] Those skilled in the art can clearly understand that, for the convenience and brevity of the description, the specific working processes of the above-described system, device and unit can refer to the corresponding processes in the foregoing method embodiments, which are not described herein again.

[0123] In several embodiments provided by the present application, it should be understood that the disclosed system, device and method can be implemented by other manners. For example, the above-described device embodiments are only schematic, for example, the division of the units is only a logical function division, and actual implementation can have another division manner, for example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between the units shown or discussed can be indirect coupling or communication connection through some interface, device or unit, and can be electrical, mechanical or other forms.

[0124] The units described as separate components can or can not be physically separate, and the components shown as units can or can not be physical units, i.e., can be located in one place or can be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the embodiment.

[0125] In addition, each functional unit in the embodiments of the present application can be integrated in one processing unit, or each unit can be physically present separately, or two or more units can be integrated in one unit.

[0126] If the functions are realized in the form of software function units and sold or used as independent products, they can be stored in a computer readable storage medium. Based on this understanding, the technical solutions of the present application or the parts of the present application that essentially contribute to the prior art can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes a plurality of instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods described in the various embodiments of the present application. The aforementioned storage medium includes a U disk, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk, and various program code storage media.

[0127] The embodiments of the present application also provide a computer readable storage medium, which stores a computer program. The computer program is executed by a processor to perform the operation steps of the method embodiments.

[0128] The computer storage medium of the embodiments of the present application can adopt any combination of one or more computer readable media. The computer readable medium can be a computer readable signal medium or a computer readable storage medium. The computer readable storage medium can be, but is not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, device or apparatus, or any combination of the above. More specific examples (non-exhaustive list) of the computer readable storage medium include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above. In this document, the computer readable storage medium can be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, device or apparatus.

[0129] The computer readable signal medium can include a data signal propagated in a baseband or as a part of a carrier wave, in which a computer readable program code is borne. Such a propagated data signal can take various forms, including but not limited to an electromagnetic signal, an optical signal or any suitable combination of the above. The computer readable signal medium can also be any computer readable medium that is not a computer readable storage medium and that can transmit, propagate or transport a program for use by or in connection with an instruction execution system, device or apparatus.

[0130] The program code embodied on the computer readable media can be transmitted using any appropriate medium, including, but not limited to, wireless, wire line, optical fiber cable, RF, etc., or any suitable combination of the foregoing.

[0131] Computer program code for carrying out operations of the present application can be written in any combination of one or more programming languages, including an object oriented programming language such as Java, Smalltalk, C++ or the like and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The program code can execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer can be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection can be made to an external computer (for example, through the Internet using an Internet Service Provider).

[0132] Note that the above merely describes the preferred embodiments of the present application and the principles of the technology applied. Those skilled in the art will understand that the present application is not limited to the specific embodiments described herein, and that various obvious changes, reconfigurations and substitutions can be made without departing from the scope of the present application. Therefore, although the present application has been described in detail through the above embodiments, the present application is not limited to the above embodiments, and can include more other equivalent embodiments without departing from the concept of the present application, and all of them belong to the protection scope of the present application.

Claims

1. A channel estimation method for OFDM, characterized in that: include: Obtaining an OFDM LS channel estimate and background noise according to an OFDM pilot time-domain symbol sequence, wherein the pilot time-domain symbol sequence is uniformly distributed in the subcarriers of the pilot time slot in the frequency domain; Performing mirror extension on the LS channel estimates of the first number of subcarriers at two edges of the frequency domain to obtain extended channel estimates, and performing an IDFT transform on the extended channel estimates to obtain an extended time domain symbol sequence of the pilot time domain symbol sequence; Filtering the extended time domain symbol sequence using a cosine window function to obtain a noise-reduced time domain symbol sequence of the pilot time domain symbol sequence, wherein the cosine window function is obtained according to the background noise and the extended time domain symbol sequence; Obtaining an OFDM channel estimate based on the noise-reduced time-domain symbol sequence; The step of obtaining the cosine window function according to the background noise and the extended time domain symbol sequence includes: The cosine window function uses a cosine roll-off waveform, sets the intensity threshold of the roll-off starting point according to the background noise value, and obtains the width of the cosine window according to the intensity threshold of the roll-off starting point and the extended time domain symbol sequence; The obtaining of OFDM LS channel estimation and background noise according to the OFDM pilot time domain symbol sequence includes: Perform an FFT transform on the pilot time domain symbol sequence to obtain an OFDM pilot frequency domain symbol sequence; obtain the LS channel estimate based on the frequency domain symbol sequence on the subcarrier where the pilot time domain symbol sequence exists; and obtain the background noise based on the frequency domain symbol sequence on the subcarrier where the pilot time domain symbol sequence does not exist.

2. The method according to claim 1, characterized in that Obtaining OFDM channel estimation according to the noise reduction time domain symbol sequence includes: Performing a DFT transform on the noise reduction time domain symbol sequence, and using the obtained frequency domain response as a noise reduction channel estimate; The frequency domain responses on the first number of subcarriers at two edges of the noise reduction channel estimate are removed, and the frequency domain responses on the subcarriers where the pilot time domain symbol sequence does not exist are supplemented by interpolation to obtain a channel estimate of the full OFDM bandwidth.

3. The method according to claim 1, characterized in that In the pilot time slot, a pilot time domain symbol sequence is placed on every other subcarrier, and a 0 symbol sequence is placed on other subcarriers.

4. The method according to claim 1, characterized in that When OFDM has a bandwidth of 20 Mbps, the first number is 16.

5. A method for receiving OFDM signals, characterized in that: include: After performing RF demodulation, filtering, synchronization, and frequency offset correction on the RF signal received at the air interface, the OFDM time domain symbol sequence is obtained; Using the time domain symbol sequence of the pilot time slot to perform ODFM channel estimation according to any one of the methods of claims 1 to 4; The OFDM communication data is obtained by using the time domain symbol sequence of the data time slot according to the channel estimation.

6. An OFDM channel estimation device, characterized in that: include: An initial channel estimation module is used to obtain an LS channel estimate and background noise of OFDM based on an OFDM pilot time domain symbol sequence, wherein the pilot time domain symbol sequence is uniformly distributed in the subcarriers of the OFDM pilot time slot in the frequency domain; an edge mirror extension module, configured to mirror extend the LS channel estimates of the first number of subcarriers at two edges of the frequency domain to obtain extended channel estimates, and perform an IDFT transform on the extended channel estimates to obtain an extended time domain symbol sequence of the pilot time domain symbol sequence; a windowing and noise reduction filtering module, configured to filter the extended time domain symbol sequence using a cosine window function to obtain a noise-reduced time domain symbol sequence of the pilot time domain symbol sequence, wherein the cosine window function is obtained based on the background noise and the extended time domain symbol sequence; A channel estimation obtaining module, configured to obtain an OFDM channel estimate based on the noise reduction time domain symbol sequence; The step of obtaining the cosine window function according to the background noise and the extended time domain symbol sequence includes: using a cosine roll-off waveform for the cosine window function, setting an intensity threshold of a roll-off starting point according to a background noise value, and obtaining a cosine window width according to the intensity threshold of the roll-off starting point and the extended time domain symbol sequence; The obtaining of OFDM LS channel estimation and background noise according to the OFDM pilot time domain symbol sequence includes: Perform an FFT transform on the pilot time domain symbol sequence to obtain an OFDM pilot frequency domain symbol sequence; obtain the LS channel estimate based on the frequency domain symbol sequence on the subcarrier where the pilot time domain symbol sequence exists; and obtain the background noise based on the frequency domain symbol sequence on the subcarrier where the pilot time domain symbol sequence does not exist.

7. An OFDM signal receiving device, characterized in that: include: The signal receiving module is used to perform RF demodulation, filtering, synchronization, and frequency offset correction on the data received over the air interface to obtain the OFDM time domain symbol sequence; A channel estimation module, configured to perform ODFM channel estimation according to any one of claims 1 to 4 using the time domain symbol sequence of the pilot time slot; A data acquisition module is used to obtain OFDM communication data using the time domain symbol sequence of the data time slot according to the channel estimation.

8. An OFDM system, characterized in that: include: The transmitting end is used to evenly arrange the OFDM pilot time domain symbol sequence in the frequency domain to the subcarriers of the OFDM pilot time slot; A receiving end, configured to obtain communication data according to the method of claim 5.

9. A computing device, characterized in that include, bus; a communication interface connected to the bus; at least one processor connected to the bus; as well as At least one memory is connected to the bus and stores program instructions, and when the program instructions are executed by the at least one processor, the at least one processor executes the method according to any one of claims 1 to 5.

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