Unimodal multi-pilot structure and its channel estimation method in OTFS system

Abstract

The present invention discloses a single-peak multi-pilot structure and channel estimation method in an OTFS system. The structure includes an OTFS transmission frame, which includes data symbols, common multi-pilot symbols, and single-peak pilot symbols. The method includes the following steps: setting an OTFS transmission frame, dividing the OTFS transmission frame into three parts, including data symbols, common multi-pilot symbols, and single-peak pilot symbols; using the receiving end delay Doppler grid area l p ≤l≤l p +l max ,k p ‑k max ≤k≤k p +k max The structure of the present invention can effectively estimate the fractional Doppler value, and the single-peak pilot power used is lower than the pilot power used in the single pilot transmission frame scheme. The channel estimation method designed based on this pilot transmission frame structure can effectively estimate the channel state information in the presence of fractional Doppler.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless communications, and more particularly relates to a single-peak multi-pilot structure in an OTFS system and a channel estimation method thereof. Background Art

[0002] Orthogonal Time-Frequency-Space (OTFS) modulation technology has garnered widespread attention for its excellent performance in high-speed scenarios. The delay-Doppler domain representation of dual-frequency selective channels is sparse, compact, and separable. Previously, some scholars proposed a transmission frame structure for embedded pilots and, based on this, a threshold-based channel estimation method. Others have modeled the OTFS channel estimation problem as a sparse signal recovery problem, achieving good channel estimation performance in both integer delay and integer Doppler cases. However, in actual OTFS systems, due to insufficient Doppler resolution, fractional Doppler must be considered. The delay-Doppler domain representation of dual-frequency selective channels is no longer sparse, and the estimation performance of threshold-based channel estimation methods and channel estimation modeled as a sparse signal recovery problem deteriorates.

[0003] Therefore, a new unimodal multi-pilot structure and its channel estimation method in OTFS system are urgently needed. Summary of the Invention

[0004] The present invention proposes a single-peak multi-pilot structure and a channel estimation method thereof in an OTFS system.

[0005] In order to solve at least one of the above technical problems, according to one aspect of the present invention, a unimodal multi-pilot structure in an OTFS system is provided, wherein the OTFS transmission frame includes data symbols, ordinary multi-pilot symbols and unimodal pilot symbols;

[0006] The common multi-pilot symbol is a pilot symbol whose pilot power is the same as the data symbol power;

[0007] The single-peak pilot symbol is a pilot symbol whose pilot power is greater than the data symbol power;

[0008] The symbols in the OTFS transmission frame are arranged as follows:

[0009]

[0010] Among them, x p1 is a single-peak pilot, and the coordinates of the delay-Doppler grid are [l p ,k p ], x p2 is a common pilot, distributed around the single-peak pilot, l max and k maxare the maximum delay and Doppler value of the channel, respectively, x d There is no guard interval between the data symbol and the pilot symbol. In order to reduce the interference of the data symbol on the pilot symbol at the receiving end, Q pilot symbols are added along the Doppler axis. The range of Q is

[0011] According to one aspect of the present invention, a channel estimation method based on a unimodal multi-pilot structure in an OTFS system is provided, comprising the following steps:

[0012] Set the OTFS transmission frame and divide the OTFS transmission frame into three parts, including data symbols, common multi-pilot symbols and single-peak pilot symbols;

[0013] The common multi-pilot symbol is a pilot symbol whose pilot power is the same as the data symbol power;

[0014] The single-peak pilot symbol is a pilot symbol whose pilot power is greater than the data symbol power;

[0015] The symbols in the OTFS transmission frame are arranged as follows:

[0016]

[0017] Among them, x p1 is a single-peak pilot, and the coordinates of the delay-Doppler grid are [l p ,k p ], x p2 is a common pilot, distributed around the single-peak pilot, l max and k max are the maximum delay and Doppler value of the channel, respectively, x d For data symbols, Q pilots are set along the Doppler axis between the data symbols and the pilot symbols, and the range of Q is

[0018] Using the receiving end delay Doppler grid area l p ≤l≤l p +l max ,k p -k max ≤k≤k p +k max The channel estimation is performed on the received signal within the delay-Doppler grid area at the receiving end. The received signal within the delay-Doppler grid area at the receiving end is expressed as follows:

[0019]

[0020] in is the additional phase deviation, is the Doppler basis function, k * =k i+κ i -(k-k'), k i and κ i are the integer and fractional parts of the path Doppler, respectively, l i is the path delay, P is the number of paths, g i is the channel gain, [·] M It is the modulo M operation.

[0021] The channel estimation method is specifically as follows:

[0022] Step 1: Consider the receiving signal area of ​​the single-peak pilot at the receiving end, that is, the delay-Doppler grid area l at the receiving end p ≤l≤l p +l max ,k p -k max ≤k≤k p +k max The received signal within is traversed and searched. The first traversal search order is to fix the delay axis l = l p , traverse the search along the Doppler axis, the range traversed along the Doppler axis is k p -k max ≤k≤k p +k max , find the grid point y[l,k] with the largest received signal power, and the received signal power at this grid point is greater than the threshold Γ, select As the threshold, N0 is the channel noise power, which means there is a delay of l0=ll p , the integer Doppler value is k0=kk p path.

[0023] Step 2: Use the obtained initial time delay and integer Doppler estimate to perform correlation operations, as shown below:

[0024]

[0025] Where d∈(k0-0.5:step:k0+0.5), step is the search step size. A value of 0.1 typically achieves good channel estimation performance. The smaller the value, the closer the resulting Doppler value is to the actual Doppler value. The value of d at the maximum value in equation (3) is the fractional portion of the Doppler value, κ0. After steps one and two, a channel path with a delay of l0 and a Doppler value of k0+κ0 is obtained.

[0026] Step 3: The signal in the pilot reception area can be the superposition of the transmitted signal through multiple paths. The received signal is expressed as follows:

[0027]

[0028] It is divided into three parts. The first part indicates that the delay is l0=ll p , the received signal under the path with Doppler value k0+κ0, the second part is the received signal under the other paths, and the third part is the received signal after the data symbol passes through the path and the channel Gaussian white noise, denoted as I l,k The gain g0 of this path can be calculated as follows:

[0029]

[0030] In formula (5), since the multi-pilot transmission frame mode is adopted, x[l p ,k'] is a known pilot signal. In order to reduce the interference of other paths and noise, the received signal when |y[l,k]| is maximized can be selected as the operation, that is, l=l0+l p ,k=k0+k p The received signal at is used to calculate the channel gain g0. Due to the influence of fractional Doppler, the received signal will be affected by the surrounding 2N i The sum of the denominators in formula (5) includes the influence of the 2N transmitted signals. i Send a signal.

[0031] Step 4: After the above steps, the delay value l0, Doppler value k0+κ0 and channel gain g0 of a certain path can be estimated. Calculate the received pilot signal y after all pilots (single-peak pilots and ordinary multi-pilots) pass through the path. pilot [l,k], subtract the received pilot signal y from the original received signal y[l,k] pilot [l,k], and get the new signal y'[l,k]=y[l,k]-y pilot [l, k], this is to reduce interference when estimating another path, that is, the second part in equation (4) can be reduced, and then steps 1, 2, 3 and 4 are repeated to finally obtain the initial channel state information.

[0032] Step 5: After the initial channel state information is obtained through the above operations, the initial channel state information depends largely on the estimation of the Doppler value. If the Doppler value deviation is large, it will lead to inaccurate channel gain estimation, which will affect the performance of the entire channel estimation. Therefore, the initial state information needs to be corrected. Assuming that the number of paths obtained by the initial estimation is P, when correcting the information of a certain path, first calculate the received pilot signal y after all pilots have passed through P-1 paths except the path pilot [l,k], then subtract the received pilot signal y from the original received signal y[l,k] pilot[l,k], and obtain the new received signal y'[l,k]=y[l,k]-y pilot [l,k], the new received signal y'[l,k] can be considered the received signal after the transmitted signal has passed through this path. Repeat steps 2 and 3 to re-estimate the channel fractional Doppler value, correct the initial Doppler value, and calculate the path gain again using equation (5). The correction of other path information also uses the above method, that is, when correcting a path, subtract the influence of other paths.

[0033] Step 6: Repeat the steps in step 5 and set two stopping conditions for the algorithm. Condition 1 sets a maximum number of iterations and stops when the maximum number of iterations is exceeded. Condition 2 compares the NMSE performance of the two channel estimates. If the current estimation cannot improve the NMSE performance of the channel estimation, stop.

[0034] According to another aspect of the present invention, a computer-readable storage medium is provided, on which a computer program is stored. When the program is executed by a processor, the steps of the channel estimation method based on a unimodal multi-pilot structure in an OTFS system of the present invention are implemented.

[0035] According to another aspect of the present invention, a computer device is provided, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, the steps of the channel estimation method based on a unimodal multi-pilot structure in an OTFS system of the present invention are implemented.

[0036] Compared with the existing technology, the beneficial effects of the present invention are:

[0037] The single-peak multi-pilot unguarded interval pilot transmission frame structure of the present invention can effectively estimate the fractional Doppler value, and the single-peak pilot power used is lower than the pilot power used in the single-pilot transmission frame scheme. The channel estimation method designed based on the pilot transmission frame structure can effectively estimate the channel state information in the presence of fractional Doppler. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings of the embodiments will be briefly introduced below. Obviously, the drawings in the following description only relate to some embodiments of the present invention, but are not intended to limit the present invention.

[0039] Figure 1 The frame structure is transmitted for a single-peak multi-pilot without a guard interval pilot;

[0040] Figure 2 Comparison of NMSE performance of channel estimation under different single-peak pilot signal-to-noise ratios;

[0041] Figure 3 The bit error rate curve is obtained by using the estimated channel information under different single-peak pilot signal-to-noise ratios for data detection;

[0042] Figure 4 In order to use different N i The bit error rate curve is obtained by performing data detection on the channel information obtained below. DETAILED DESCRIPTION

[0043] To make the purpose, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0044] Unless otherwise defined, technical or scientific terms used herein shall have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0045] Example 1:

[0046] Figure 1 This is the transmission frame structure of a single-peak multi-pilot with no guard interval. M and N are the number of grid points along the delay axis and along the Doppler axis of the delay-Doppler grid in the OTFS system, respectively. The OTFS transmission frame is divided into three parts, including data symbols, normal multi-pilots, and single-peak pilots. Normal multi-pilots are pilots whose pilot power is the same as the data symbol power, while single-peak pilots are pilots whose pilot power is greater than the data symbol power. The symbols in the OTFS transmission frame are arranged as follows:

[0047]

[0048] Among them, x p1 is a single-peak pilot, and the coordinates of the delay-Doppler grid are [l p , k p ], x p2 is a common pilot, distributed around the single-peak pilot, l max and k max are the maximum delay and Doppler value of the channel, respectively, x d There is no guard interval between the data symbol and the pilot symbol. In order to reduce the interference of the data symbol on the pilot symbol at the receiving end, Q pilot symbols are added along the Doppler axis. The range of Q is

[0049] According to the symbol arrangement of the single-peak multi-pilot non-guard interval pilot transmission frame, the delay Doppler grid area l at the receiving end can be used. p ≤l≤l p +l max , k p -kmax ≤k≤k p +k max The channel estimation is performed on the received signal within the area. The received signal in this area can be expressed as follows:

[0050]

[0051] in is the additional phase deviation, is the Doppler basis function, k * =k i +κ i -(kk′), k i and κ i are the integer and fractional parts of the path Doppler, respectively, l i is the path delay, P is the number of paths, g i is the channel gain, [·] M It is the modulo M operation.

[0052] The specific steps of the channel estimation algorithm are as follows:

[0053] Step 1: Consider the receiving signal area of ​​the single-peak pilot at the receiving end, that is, the delay-Doppler grid area l at the receiving end p ≤l≤l p +l max , k p -k max ≤k≤k p +k max The received signal within is traversed and searched. The first traversal search order is to fix the delay axis l = l p , traverse the search along the Doppler axis, the range traversed along the Doppler axis is k p -k max ≤k≤k p +k max , find the grid point y[l, k] with the largest received signal power, and the received signal power at this grid point is greater than the threshold Γ, select As the threshold, N0 is the channel noise power, which means there is a delay of l0=ll p , the integer Doppler value is k0=kk p path.

[0054] Step 2: Use the obtained initial time delay and integer Doppler estimate to perform correlation operations, as shown below:

[0055]

[0056] Where d∈(k0-0.5:step:k0+0.5), step is the search step size. A value of 0.1 typically achieves good channel estimation performance. The smaller the value, the closer the resulting Doppler value is to the actual Doppler value. The value of d at the maximum value in equation (3) is the fractional portion of the Doppler value, κ0. After steps one and two, a channel path with a delay of l0 and a Doppler value of k0+κ0 is obtained.

[0057] Step 3: The signal in the pilot reception area can be the superposition of the transmitted signal through multiple paths. The received signal is expressed as follows:

[0058]

[0059] It is divided into three parts. The first part indicates that the delay is l0=ll p , the received signal under the path with Doppler value k0+κ0, the second part is the received signal under the other paths, and the third part is the received signal after the data symbol passes through the path and the channel Gaussian white noise, denoted as I l，k The gain g0 of this path can be calculated as follows:

[0060]

[0061] In formula (5), since the multi-pilot transmission frame mode is adopted, x[l p , k′] is a known pilot signal. In order to reduce the interference of other paths and noise, the received signal when |y[l, k]| is maximized can be selected as the operation, that is, l=l0+l p , k=k0+k p The received signal at is used to calculate the channel gain g0. Due to the influence of fractional Doppler, the received signal will be affected by the surrounding 2N i The sum of the denominators in formula (5) includes the influence of the 2N transmitted signals. i Send a signal.

[0062] Step 4: After the above steps, the delay value l0, Doppler value k0+κ0 and channel gain g0 of a certain path can be estimated. Calculate the received pilot signal y after all pilots (single-peak pilots and ordinary multi-pilots) pass through the path. pilot [l, k], subtract the received pilot signal y from the original received signal y[l, k] pilot [l, k], and obtain the new signal y′[l, k]=y[l, k]-y pilot [l, k], this is to reduce interference when estimating another path, that is, the second part in equation (4) can be reduced, and then steps 1, 2, 3 and 4 are repeated to finally obtain the initial channel state information.

[0063] Step 5: After the initial channel state information is obtained through the above operations, the initial channel state information depends largely on the estimation of the Doppler value. If the Doppler value deviation is large, it will lead to inaccurate channel gain estimation, which will affect the performance of the entire channel estimation. Therefore, the initial state information needs to be corrected. Assuming that the number of paths obtained by the initial estimation is P, when correcting the information of a certain path, first calculate the received pilot signal y after all pilots have passed through P-1 paths except the path pilot [l, k], then subtract the received pilot signal y from the original received signal y[l, k] pilot [l, k], and obtain the new received signal y′[l, k]=y[l, k]-y pilot [l, k], the new received signal y′[l, k] can be considered the received signal after the transmitted signal has passed through this path. Repeat steps 2 and 3 to re-estimate the channel fractional Doppler value, correct the initial Doppler value, and calculate the path gain again using equation (5). The correction of other path information also uses the above method, that is, when correcting a path, subtract the influence of other paths.

[0064] Step 6: Repeat the steps in step 5 and set two stopping conditions for the algorithm. Condition 1 sets a maximum number of iterations and stops when the maximum number of iterations is exceeded. Condition 2 compares the NMSE performance of the two channel estimates. If the current estimation cannot improve the NMSE performance of the channel estimation, stop.

[0065] Simulation example:

[0066] Basic parameter settings: OTFS delay-Doppler domain grid size is M=32, N=32, carrier frequency f c is 4GHz, the subcarrier spacing Δf is 15KHz, and the maximum channel delay k max is 4, the maximum Doppler value k max The value of Q is 2. The power of the common pilot is consistent with the power of the data symbol, and 4QAM symbols are used.

[0067] Figure 2 The following curves describe the NMSE performance of channel estimation under different single-peak pilot signal-to-noise ratios as the data symbol signal-to-noise ratio changes. The NMSE is calculated as follows:

[0068]

[0069] y p [l,k] and The original pilot signal and the pilot signal obtained using the estimated channel state information are shown in Figure 2. Simulations were conducted on the channel estimation performance when the single-peak pilot signal-to-noise ratio (SNR) was 20, 24, and 30 dB higher than the data symbol SNR. It was found that as the pilot SNR increased, the channel estimation performance improved.

[0070] Figure 3 The description is about using the channel state information estimated when the single-peak pilot signal-to-noise ratio is (20, 30) dB higher than the data symbol signal-to-noise ratio for data detection. The MMSE detector is used, and the resulting bit error rate curve shows that the bit error rate values ​​under the two pilot signal-to-noise ratios are very close to the bit error rate value under the known channel state, which indirectly illustrates the accuracy of the channel estimation. The channel state information obtained under low single-peak pilot signal-to-noise ratio is sufficient for symbol detection.

[0071] Figure 4 The description is that when the data symbol SNR is 20dB and the single-peak pilot SNR is 20dB higher than the data symbol SNR, the bit error rate of data monitoring decreases with the parameter N when calculating the channel gain in formula (5). i The curve of the change shows that when the value is 4, better bit error rate performance can be obtained. Then increase N i The value of N does not significantly improve the bit error rate performance. i The increase of will bring about the increase of calculation amount, so the parameter N is selected i A value of 4 is more appropriate.

[0072] Example 2:

[0073] The computer-readable storage medium of this embodiment stores a computer program thereon, which, when executed by a processor, implements the steps of the channel estimation method based on a single-peak multi-pilot structure in an OTFS system in embodiment 1.

[0074] The computer-readable storage medium of this embodiment may be an internal storage unit of the terminal, such as a hard disk or memory of the terminal; the computer-readable storage medium of this embodiment may also be an external storage device of the terminal, such as a plug-in hard disk, a smart memory card, a secure digital card, a flash memory card, etc. equipped on the terminal; further, the computer-readable storage medium may also include both an internal storage unit of the terminal and an external storage device.

[0075] The computer-readable storage medium of this embodiment is used to store computer programs and other programs and data required by the terminal. The computer-readable storage medium can also be used to temporarily store data that has been output or is to be output.

[0076] Example 3:

[0077] The computer device of this embodiment includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, the steps of the channel estimation method based on the unimodal multi-pilot structure in the OTFS system of embodiment 1 are implemented.

[0078] In this embodiment, the processor can be a central processing unit, or other general-purpose processors, digital signal processors, application-specific integrated circuits, off-the-shelf programmable gate arrays or other programmable logic devices, discrete gate 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, etc. The memory can include read-only memory and random access memory, and provide instructions and data to the processor. A part of the memory can also include non-volatile random access memory. For example, the memory can also store information about the device type.

[0079] Those skilled in the art will appreciate that the disclosed contents of the embodiments may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a hardware embodiment, a software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage and optical storage, etc.) containing computer-usable program code.

[0080] The present invention is described with reference to the flowcharts and / or block diagrams of the methods and computer program products according to the embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as the combination of the processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions; these computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0081] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0082] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 The steps for the function specified in one or more boxes.

[0083] Those skilled in the art will appreciate that all or part of the processes in the above-described method embodiments can be implemented by instructing related hardware through a computer program. The program can be stored in a computer-readable storage medium, and when executed, the program can include the processes in the above-described method embodiments. The storage medium can be a magnetic disk, an optical disk, a read-only memory (ROM), or a random access memory (RAM).

[0084] The examples described in the present invention are merely descriptions of the preferred embodiments of the present invention and are not intended to limit the concept and scope of the present invention. Without departing from the design concept of the present invention, various modifications and improvements made to the technical solutions of the present invention by engineers and technicians in this field should fall within the scope of protection of the present invention.

Claims

1. A channel estimation method based on a single-peak multi-pilot structure in an OTFS system, characterized in that: The steps include: Set the OTFS transmission frame and divide the OTFS transmission frame into three parts, including data symbols, common multi-pilot symbols and single-peak pilot symbols; The common multi-pilot symbol is a pilot symbol whose pilot power is the same as the data symbol power; The single-peak pilot symbol is a pilot symbol whose pilot power is greater than the data symbol power; The symbols in the OTFS transmission frame are arranged as follows: （1） in, is a single-peak pilot, and its coordinates on the delay-Doppler grid are , It is a common pilot, distributed around the single-peak pilot. and are the maximum delay and Doppler values ​​of the channel respectively, For data symbols, the data symbols and pilot symbols are set along the Doppler axis pilots, The range is ; Using the receiving end delay Doppler grid area The channel estimation is performed on the received signal within the delay-Doppler grid area at the receiving end. The received signal within the delay-Doppler grid area at the receiving end is expressed as follows: （2） in is the additional phase deviation, is the Doppler basis function, , and are the integer and fractional parts of the path Doppler, is the path delay, is the number of paths, is the channel gain, It is the modulo M operation; The specific steps are: Step 1: Delay-Doppler grid area at the receiving end Perform traversal search for the received signal within; Step 2: Perform calculations using the obtained initial time delay and integer Doppler estimation values; Step 3: The transmitted signal is superimposed through multiple paths to form a signal in the pilot receiving area; Step 4: Estimate the delay value of a certain path through the above steps , Doppler value and channel gain ; Calculate the received pilot signal after all pilots pass through this path , the original received signal Subtract the received pilot signal , get a new signal , so that when estimating another path, the interference is reduced, that is, the second part in equation (4) is reduced, and then steps 1, 2, 3 and 4 are repeated, and finally the initial channel state information can be obtained; Step 5: After the above operations, the initial channel state information is obtained. The initial channel state information depends largely on the estimation of the Doppler value. If the Doppler value deviation is large, the initial state information needs to be corrected. Assume that the number of paths obtained by the initial estimation is When correcting the information of a certain path, first calculate the number of pilots passing through the path other than the path. Received pilot signal after the action of the paths , and then the original received signal Subtract the received pilot signal , get the new received signal , the new received signal at this time Consider it as the received signal after the transmitted signal has passed through this path, repeat the operations of steps 2 and 3, re-estimate the fractional Doppler value of the channel, correct the initial Doppler value, and calculate the path gain again using formula (5); the correction of other path information also adopts the above method, that is, when correcting a certain path, subtract the influence of other paths; Step 6: Repeat the steps in step 5 and set two stopping conditions for the algorithm. Condition 1 sets a maximum number of iterations and stops when the maximum number of iterations is exceeded. Condition 2 compares the NMSE performance of the two channel estimates. If the current estimation cannot improve the NMSE performance of the channel estimation, stop.

2. The method according to claim 1, characterized in that Step 1 is as follows: Consider the receiving signal area of ​​the single-peak pilot at the receiving end, that is, the delay Doppler grid area of ​​the receiving end The received signal in the traversal search is firstly fixed in the delay axis. , traverse and search along the Doppler axis, the range traversed along the Doppler axis is , find the grid point with the maximum received signal power , and the received signal power at this grid point is greater than the threshold , select As the threshold, is the channel noise power, then there is a delay of , the integer Doppler value is path.

3. The method according to claim 2, characterized in that Step 2 is as follows: using the obtained initial time delay and integer Doppler estimation value, perform correlation operation, as shown below: （3） in, , is the search step size. The smaller the value, the closer the obtained Doppler value is to the actual Doppler value, so that Equation (3) can obtain the maximum value. The value is the fractional part of the Doppler value ; After steps one and two, we get a delay value of , the Doppler value is channel path.

4. The method according to claim 3, wherein Step 3: The signal in the pilot reception area is the result of the superposition of the transmitted signal through multiple paths. The received signal is expressed as follows: （4） It is divided into three parts. The first part indicates the delay is , the Doppler value is The second part is the received signal under the action of the path, the second part is the received signal under the action of other paths, and the third part is the received signal after the data symbol passes through the path and the channel Gaussian white noise, which is recorded as ; The gain of this path It can be obtained by the following formula: （5） In formula (5), since the multi-pilot transmission frame mode is adopted, is a known pilot signal. In order to reduce the interference of other paths and noise, we select The received signal at the maximum is used as the calculation, and you can choose The received signal at is used to calculate the channel gain Due to the influence of fractional Doppler, the received signal will be affected by the surrounding The sum of the denominators in Equation (5) includes the influence of the transmitted signal. Send a signal.

5. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps of the channel estimation method based on a single-peak multi-pilot structure in an OTFS system are implemented as described in any one of claims 1 to 4.

6. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the program, the steps of the channel estimation method based on a unimodal multi-pilot structure in an OTFS system are implemented as described in any one of claims 1 to 4.

Images