A method, apparatus, and device for high-precision Doppler frequency estimation using OTFS

Abstract

This application relates to an OTFS high-precision Doppler frequency estimation method, apparatus, and device. The method includes: at the receiving end, recovering the same received signal based on the upper boundary parameter value, center point parameter value, and lower boundary parameter value of the Doppler frequency search unit; calculating the cross-correlation function between the recovered received signal and the transmitted signal; performing a coarse Doppler frequency estimate based on the cross-correlation function of the recovered received signal and the transmitted signal using the center point parameter value; inputting the obtained coarse Doppler frequency estimate into a PN code-based red-blue frequency shift discriminator for frequency shift discrimination; and performing a red-shift or blue-shift correction on the coarse Doppler frequency estimate based on the cross-correlation function of the recovered received signal and the transmitted signal using the upper and lower boundary parameter values ​​to obtain the final Doppler frequency estimation result. This method can reduce the computational complexity of Doppler frequency estimation without affecting its accuracy.

Description

Technical Field

[0001] This application relates to the field of satellite communication and navigation integration technology, and in particular to an OTFS high-precision Doppler frequency estimation method, apparatus and equipment. Background Technology

[0002] As the application scenarios for communication and navigation positioning services become increasingly diverse, providing users with simultaneous navigation and communication services using low-Earth orbit (LEO) satellites has become an important research direction. LEO satellites, with their low orbital altitude and excellent Doppler observation capabilities, can precisely compensate for the shortcomings of GNSS (Global Navigation Satellite System). Taking the Iridium system as an example, the signal strength received by its ground receivers is approximately 30 dB (1000 times) stronger than that of GPS (Global Positioning System). Simultaneously, LEO satellites move very quickly relative to ground receivers, providing excellent Doppler observation capabilities. This allows LEO satellites to be used independently for Doppler positioning, serving as a supplementary positioning system when GNSS is unavailable, thus reducing the limitations of positioning and navigation systems.

[0003] Therefore, using the Doppler frequency shift of LEO satellites for user positioning is an important direction in the research of integrated communication and navigation. Satellite navigation and positioning technology based on Doppler velocity measurement employs the hyperboloid intersection positioning principle. Based on the Doppler frequency shift effect, it measures the relative velocity between the user and the navigation satellites, obtaining the distance difference between the user and two navigation satellites, thus forming two or more hyperboloids. The intersection of these hyperboloids forms a hyperboloid intersection point, from which the user's position can be calculated.

[0004] The OTFS (Orthogonal Time-Frequency Modulation) waveform has been proven to outperform existing communication signal schemes in high-Doppler channel scenarios and is robust to delay-Doppler frequency shifts in wireless channels. By using the OTFS modulated waveform to accurately estimate the Doppler frequency domain, high-precision Doppler frequency observations can be obtained, thereby achieving high-precision Doppler localization.

[0005] Currently, there are two main types of Doppler frequency estimation based on OTFS modulated waveforms: The first method utilizes the characteristics of OTFS in the delay-Doppler (DD) domain to estimate the channel's Doppler and delay fading based on the movement of the pilot sequence in the DD domain. However, the estimation accuracy of this type of method is related to its complexity, with high-precision estimation requiring significant complexity. The second method utilizes general signal characteristics, using range and azimuth information to estimate the Doppler frequency. However, this type of method does not consider Doppler frequency estimation schemes in ultra-high dynamic scenarios. Summary of the Invention

[0006] Therefore, it is necessary to provide an OTFS high-precision Doppler frequency estimation method, apparatus, and device that can redshift or blueshift the Doppler frequency estimate of the received signal to recover the signal most relevant to the real signal, and reduce the computational complexity of Doppler frequency estimation without affecting the accuracy of Doppler frequency estimation.

[0007] A high-precision Doppler frequency estimation method for OTFS, the method comprising:

[0008] The receiver signal that has experienced time delay and Doppler is acquired. At the receiver, the same receiver signal is recovered based on the upper boundary parameter value, center point parameter value, and lower boundary parameter value of the Doppler frequency search unit, respectively, to obtain the recovered receiver signal.

[0009] Utilizing the characteristics of OTFS in the time-delay Doppler domain, the cross-correlation function of the received signal and the transmitted signal recovered by the upper boundary parameter value, the center point parameter value, and the lower boundary parameter value is calculated respectively. Based on the cross-correlation function of the received signal and the transmitted signal recovered by the center point parameter value, a coarse Doppler frequency estimate is performed to obtain the coarse Doppler frequency estimate.

[0010] The coarse Doppler frequency estimate is input into a red-blue frequency shift discriminator based on PN code for frequency shift discrimination. Based on the cross-correlation function of the received signal and the transmitted signal recovered by the upper and lower boundary parameter values, the coarse Doppler frequency estimate is red-shifted or blue-shifted to obtain the final Doppler frequency estimation result.

[0011] In one embodiment, the Doppler frequency search unit is formed by dividing the two-dimensional target domain consisting of the Doppler frequency search interval and the time delay search interval into several grids. The length of the grid is the time delay search step size, and the width of the grid is the Doppler frequency search step size. The parameter values ​​in the Doppler frequency search unit are the Doppler frequency estimate and the time delay estimate.

[0012] In one embodiment, the received signal after time delay and Doppler is acquired, and the same received signal is recovered at the receiving end based on the upper boundary parameter value, center point parameter value, and lower boundary parameter value of the Doppler frequency search unit, respectively, to obtain the recovered received signal, including:

[0013] The receiver signal that has experienced time delay and Doppler is acquired. At the receiver, the same receiver signal is linearly transformed based on the Doppler frequency estimate and time delay estimate from the upper boundary parameter value, center point parameter value and lower boundary parameter value of the Doppler frequency search unit, respectively, to obtain the recovered time-domain received signal.

[0014] The recovered time-domain received signal is subjected to Wigner transform and two-dimensional SFFT transform to obtain the recovered time-delay Doppler domain received signal.

[0015] In one embodiment, utilizing the characteristics of OTFS in the time-delay Doppler domain, the cross-correlation function between the received signal and the transmitted signal recovered from the upper boundary parameter value, the center point parameter value, and the lower boundary parameter value is calculated, including:

[0016] The cross-correlation value of the received signal and the transmitted signal in the time-delayed Doppler domain, recovered using different Doppler frequency estimates, exhibits the characteristics of a sinc function. In the time-delayed Doppler domain, the cross-correlation function of the received signal and the transmitted signal in the time-delayed Doppler domain is recovered by calculating the upper boundary parameter value, the center point parameter value, and the lower boundary parameter value, respectively.

[0017] In one embodiment, a coarse Doppler frequency estimate is performed based on the cross-correlation function between the received signal and the transmitted signal recovered from the center point parameter value, resulting in a coarse Doppler frequency estimate, including:

[0018] The cross-correlation function between the received and transmitted signals in the time-delay Doppler domain, recovered by traversing and searching the center point parameter values ​​of different Doppler frequency search units. when When the Doppler frequency estimate is obtained from the parameter value of the current search center point, the Doppler frequency coarse estimate is used.

[0019] In one embodiment, the coarse Doppler frequency estimate is input into a PN code-based red-blue frequency shift discriminator for frequency shift discrimination. Based on the cross-correlation function between the received signal and the transmitted signal recovered from the upper and lower boundary parameter values, the coarse Doppler frequency estimate is red-shifted or blue-shifted to obtain the final Doppler frequency estimation result, including:

[0020] The coarse estimate of the Doppler frequency is input into the red-blue frequency shift discriminator based on the PN code for frequency shift discrimination, and the upper and lower boundary parameter values ​​in the Doppler frequency search unit corresponding to the coarse estimate of the Doppler frequency are obtained. The estimation deviation of the Doppler frequency is calculated based on the cross-correlation function between the received signal and the transmitted signal in the time-delay Doppler domain recovered by the upper and lower boundary parameter values.

[0021] The coarse Doppler frequency estimate is corrected by redshifting or blueshifting based on the estimation bias to obtain the final Doppler frequency estimate.

[0022] In one embodiment, the coarse estimate of the Doppler frequency is corrected by redshift or blueshift based on the estimation bias to obtain the final Doppler frequency estimation result, including:

[0023] The coarse estimate of the Doppler frequency is corrected by redshift or blueshift based on the estimation bias, and expressed as follows:

[0024]

[0025]

[0026] in, This represents the corrected coarse estimate of the Doppler frequency, v. est This is a rough estimate of the Doppler frequency, δ y To estimate the deviation, if δ v >0 is called redshift correction, if δ v <0 is called blue shift correction; This represents the cross-correlation function between the received and transmitted signals in the time-delay Doppler domain, recovered by the upper boundary parameter values. The cross-correlation function between the received and transmitted signals in the time-delay Doppler domain, represented by the lower boundary parameter value, is v. bin The Doppler frequency search step size;

[0027] Will Move to the center of the current Doppler frequency search unit, according to The upper and lower boundary parameter values ​​in the current Doppler frequency search unit are updated, and the same receiver signal is recovered and the cross-correlation function is calculated based on the updated upper and lower boundary parameter values. This process is repeated multiple times until the condition is met. Until then, and the current This serves as the final Doppler frequency estimation result.

[0028] In one embodiment, the transmitting signal is generated by a PN code generator.

[0029] An OTFS high-precision Doppler frequency estimation device, the device comprising:

[0030] The signal recovery module is used to acquire the received signal after time delay and Doppler. At the receiving end, the same received signal is recovered based on the upper boundary parameter value, center point parameter value, and lower boundary parameter value of the Doppler frequency search unit to obtain the recovered received signal.

[0031] The Doppler frequency coarse estimation module is used to utilize the characteristics of OTFS in the time-delay Doppler domain to calculate the cross-correlation function of the received signal and the transmitted signal recovered by the upper boundary parameter value, the center point parameter value, and the lower boundary parameter value, respectively. Based on the cross-correlation function of the received signal and the transmitted signal recovered by the center point parameter value, the Doppler frequency coarse estimation is performed to obtain the Doppler frequency coarse estimation value.

[0032] The Doppler frequency shift correction module is used to input the coarse estimate of the Doppler frequency into the red-blue frequency shift discriminator based on the PN code for frequency shift discrimination, and to perform red-shift or blue-shift correction on the coarse estimate of the Doppler frequency based on the cross-correlation function of the received signal and the transmitted signal recovered by the upper boundary parameter value and the lower boundary parameter value, so as to obtain the final Doppler frequency estimation result.

[0033] A computer device includes a memory and a processor, the memory storing a computer program, and the processor executing the computer program performing the following steps:

[0034] The receiver signal that has experienced time delay and Doppler is acquired. At the receiver, the same receiver signal is recovered based on the upper boundary parameter value, center point parameter value, and lower boundary parameter value of the Doppler frequency search unit, respectively, to obtain the recovered receiver signal.

[0035] Utilizing the characteristics of OTFS in the time-delay Doppler domain, the cross-correlation function of the received signal and the transmitted signal recovered by the upper boundary parameter value, the center point parameter value, and the lower boundary parameter value is calculated respectively. Based on the cross-correlation function of the received signal and the transmitted signal recovered by the center point parameter value, a coarse Doppler frequency estimate is performed to obtain the coarse Doppler frequency estimate.

[0036] The coarse Doppler frequency estimate is input into a red-blue frequency shift discriminator based on PN code for frequency shift discrimination. Based on the cross-correlation function of the received signal and the transmitted signal recovered by the upper and lower boundary parameter values, the coarse Doppler frequency estimate is red-shifted or blue-shifted to obtain the final Doppler frequency estimation result.

[0037] The beneficial effects of this application are as follows: This application makes full use of the robustness of OTFS modulation to Doppler frequency. First, it performs a coarse estimation of Doppler frequency based on the cross-correlation function of the received signal and the transmitted signal recovered from the center point parameter value of the Doppler frequency search unit, and obtains a coarse estimate of Doppler frequency. Then, based on the cross-correlation function of the received signal and the transmitted signal recovered from the upper boundary parameter value and the lower boundary parameter value, it performs a red-shift or blue-shift correction on the coarse estimate of Doppler frequency, so that the peak value of the cross-correlation between the recovered received signal and the transmitted signal reaches the maximum. At the same time, it can reduce the computational complexity of Doppler frequency estimation and make the accuracy of Doppler frequency estimation approach the theoretical limit of Cramer-Rao. Attached Figure Description

[0038] Figure 1 This is a flowchart illustrating an OTFS high-precision Doppler frequency estimation method in one embodiment;

[0039] Figure 2 This is a flowchart illustrating the coarse estimation of Doppler frequency in one embodiment;

[0040] Figure 3 This is a schematic diagram illustrating the results of different recovery parameters in one embodiment.

[0041] Figure 4 This is a flowchart illustrating the process of redshifting or blueshifting a coarse estimate of Doppler frequency in one embodiment.

[0042] Figure 5 This is a schematic diagram of the unbiased characteristic curve and frequency identification curve of the algorithm proposed in this application in one embodiment; wherein, Figure 5 (a) is a schematic diagram of the unbiased characteristic curve of the algorithm proposed in this application. Figure 5 (b) is a schematic diagram of the frequency identification curve of the algorithm proposed in this application;

[0043] Figure 6 This is a schematic diagram comparing the Doppler frequency estimation accuracy of different Doppler frequency estimation methods in one embodiment.

[0044] Figure 7 This is a schematic diagram illustrating the Doppler frequency estimation accuracy corresponding to different OTFS parameters involved in this application in one embodiment;

[0045] Figure 8 This is an internal structural diagram of a computer device in one embodiment. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0047] In one embodiment, such as Figure 1 As shown, a high-precision Doppler frequency estimation method for OTFS is provided, including the following steps:

[0048] Step S1: Obtain the received signal after time delay and Doppler. At the receiving end, recover the same received signal according to the upper boundary parameter value, center point parameter value, and lower boundary parameter value of the Doppler frequency search unit to obtain the recovered received signal.

[0049] Step S2: Utilizing the characteristics of OTFS in the time-delay Doppler domain, calculate the cross-correlation function between the received signal and the transmitted signal recovered by the upper boundary parameter value, the center point parameter value, and the lower boundary parameter value, respectively. Based on the cross-correlation function between the received signal and the transmitted signal recovered by the center point parameter value, perform a coarse estimation of the Doppler frequency to obtain a coarse estimate of the Doppler frequency.

[0050] Step S3: Input the coarse Doppler frequency estimate into the red-blue frequency shift discriminator based on the PN code for frequency shift discrimination, and perform red-shift or blue-shift correction on the coarse Doppler frequency estimate based on the cross-correlation function of the received signal and the transmitted signal recovered by the upper boundary parameter value and the lower boundary parameter value to obtain the final Doppler frequency estimation result.

[0051] In one embodiment, such as Figure 2 As shown, the Doppler frequency search unit is established by searching the Doppler frequency range [-v]. max v max ] and the time delay search interval [0, τ max After dividing the two-dimensional target domain into a grid, several grids are formed, the length of which is the time-delay search step size τ. bin The width of the grid is the Doppler frequency search step size v. bin The parameter values ​​in the Doppler frequency search unit are the Doppler frequency estimate and the time delay estimate.

[0052] In one embodiment, the received signal after time delay and Doppler is acquired, and the same received signal is recovered at the receiving end based on the upper boundary parameter value, center point parameter value, and lower boundary parameter value of the Doppler frequency search unit, respectively, to obtain the recovered received signal, including:

[0053] The receiver signal that has experienced time delay and Doppler is acquired. At the receiver, the same receiver signal is linearly transformed based on the Doppler frequency estimate and time delay estimate from the upper boundary parameter value, center point parameter value and lower boundary parameter value of the Doppler frequency search unit, respectively, to obtain the recovered time-domain received signal.

[0054] The recovered time-domain received signal is subjected to Wigner transform and two-dimensional SFFT transform to obtain the recovered time-delay Doppler domain received signal. Specifically, the steps for recovering the received signal at the receiver based on the center point parameter values ​​of the Doppler frequency search unit include:

[0055] First, for a signal s(t) experiencing a time delay τ0 and a Doppler effect v0, the expression for the received signal is: Where v(t) is additive noise, j is the imaginary unit, t is time, and h(τ0, v0) is the channel gain of the path. The receiver recovers the time-domain received signal y affected by the channel based on the center point parameter value of the Doppler frequency search unit. C (t), denoted as

[0056]

[0057] Where Π(·) represents a linear transformation, that is, the received signal r(t) undergoes a linear transformation. Get yC (t), y C (t) is the center point parameter value (τ) in the Doppler frequency search unit. est v est The recovered time-domain received signal, τ est v is the estimated time delay. est This is the estimated Doppler frequency.

[0058] Then, for y C (t) Perform Wigner transform and two-dimensional SFFT (symplectic finite Fourier transform) to obtain the recovered time-delay Doppler domain received signal y. C [k, l]. Specific steps include:

[0059] The receiving end uses the received pulse waveform g rx (t) Perform matched filtering; this operation is called the cross-blur function. Represented as

[0060]

[0061] For cross-ambiguity function Sampling is performed to obtain the time-frequency domain received signal Y. FT [m, n], denoted as

[0062]

[0063] Where Δf is the subcarrier spacing, T represents the symbol length, n and m are the time axis and frequency axis defined on a resource unit Λ in the time-delay-Doppler domain, τ = nT, v = mΔf indicates that the time axis and frequency axis are sampled for time delay and Doppler frequency in integer multiples of T and Δf, respectively, and Λ = {(nT, mΔf): n, m ∈ Z}, where Z is the range to which n and m belong.

[0064] This transformation from a one-dimensional continuous signal r(t) to a two-dimensional signal Y FT The transformation of [m, n] is called the Discrete Wigner Transform, which is the inverse operation of the Heisenberg Transform. Finally, the receiver performs a Symplectic Finite Fourier Transform (SFFT) to obtain the time-delayed Doppler domain received signal y reconstructed from the center point parameter values. C [k, l], denoted as

[0065]

[0066] Where M is the number of time delay grids, and N is the number of Doppler grids; k and l are parameters defined on a resource unit Λ in the time delay-Doppler domain, which are sampled on the time delay axis and the Doppler axis at integer multiples of Δτ = 1 / MΔf and Δv = 1 / NT, respectively. The interval Δτ on the delay axis is the reciprocal of the bandwidth MΔf, and the interval Δv on the Doppler axis is the reciprocal of the frame length NT.

[0067] In one embodiment, utilizing the characteristics of OTFS in the time-delay Doppler domain, the cross-correlation function between the received signal and the transmitted signal recovered from the upper boundary parameter value, the center point parameter value, and the lower boundary parameter value is calculated, including:

[0068] like Figure 3 As shown, the center point parameter values ​​(τ) in the search unit are used with different Doppler frequencies. est v est The recovered received signal and the transmitted signal are cross-correlation functions calculated in the DD domain. When v est , τ est The cross-correlation function reaches its maximum value when aligned with the channel response; when the estimate is biased, the cross-correlation function and v... est The relationship is that of a sinc function;

[0069] Based on this, the cross-correlation value of the received signal and the transmitted signal in the time-delayed Doppler domain, recovered using different Doppler frequency estimates, exhibits the characteristics of a sinc function. In the time-delayed Doppler domain, the cross-correlation function of the received signal and the transmitted signal is calculated using the upper boundary parameter value, the center point parameter value, and the lower boundary parameter value, respectively. Specifically, through parameter traversal search, without considering estimation bias in the time-delay domain, the center point Doppler frequency parameter v in the center point parameter value is obtained in the DD domain. e The recovered time-delay Doppler domain received signal y C The cross-correlation function between [k, l] and the transmitted signal x[k, l] Represented as

[0070]

[0071] By observing formula (5), it can be found that when the Doppler frequency estimate v est When aligned with the channel response (i.e., the center point Doppler frequency parameter v) e When = 0), cross-correlation function The value of R(v) reaches its maximum when there is a bias in the Doppler frequency estimate. e ) and independent variable v est The relationship is that of a sinc function.

[0072] Therefore, to find the center point parameter value (τ) of the Doppler frequency search unit with strong correlation characteristics, est v estThis application describes the cross-correlation function between the received signal and the transmitted signal in the time-delay Doppler domain, recovered by traversing and searching the center point parameter values ​​of different Doppler frequency search units. when Sometimes, or as Figure 2 As shown, when When the value is greater than a set threshold α, the Doppler frequency estimate v in the current search center point parameter value is... est This serves as a coarse estimate of the Doppler frequency. Specifically, when the receiver searches on a search unit, the carrier frequency and code phase value used correspond to the center position of that search unit.

[0073] In one embodiment, the coarse Doppler frequency estimate is input into a PN code-based red-blue frequency shift discriminator for frequency shift discrimination. Based on the cross-correlation function between the received signal and the transmitted signal recovered from the upper and lower boundary parameter values, the coarse Doppler frequency estimate is red-shifted or blue-shifted to obtain the final Doppler frequency estimation result, including:

[0074] like Figure 4 As shown, the coarse estimate of the Doppler frequency is input into the red-blue frequency shift discriminator based on the PN code for frequency shift discrimination, and the upper boundary parameter value and lower boundary parameter value in the Doppler frequency search unit corresponding to the coarse estimate of the Doppler frequency are obtained. The estimation deviation of the Doppler frequency is calculated based on the cross-correlation function between the received signal and the transmitted signal in the time-delay Doppler domain recovered by the upper boundary parameter value and the lower boundary parameter value.

[0075] The coarse Doppler frequency estimate is corrected by redshifting or blueshifting based on the estimation bias to obtain the final Doppler frequency estimate.

[0076] In one embodiment, the coarse estimate of the Doppler frequency is corrected by redshift or blueshift based on the estimation bias to obtain the final Doppler frequency estimation result, including:

[0077] The coarse estimate of the Doppler frequency is corrected by redshift or blueshift based on the estimation bias, and expressed as follows:

[0078]

[0079]

[0080] in, This represents the corrected coarse estimate of the Doppler frequency, v. est This is a rough estimate of the Doppler frequency, δ v The deviation is estimated using the lead-lag amplitude method, if δ v >0 is called redshift correction, if δ v<0 is called blueshift correction; The received Doppler domain signal y, which is recovered by the upper boundary parameter value, represents the time-delayed signal. U The cross-correlation function between [k, l] and the transmitted signal x[k, l], The time-delayed Doppler domain received signal y is represented by the lower boundary parameter value. L The cross-correlation function between [k, l] and the transmitted signal x[k, l], v bin The Doppler frequency search step size;

[0081] Will Move to the center of the current Doppler frequency search unit, according to The upper and lower boundary parameter values ​​in the current Doppler frequency search unit are updated, and the same receiver signal is recovered and the cross-correlation function is calculated based on the updated upper and lower boundary parameter values. This process is repeated multiple times until the condition is met. Until then, and the current This serves as the final Doppler frequency estimation result.

[0082] It is understandable that the lead-lag amplitude method will produce a certain discrimination error because the amplitude autocorrelation curve does not coincide with the sinc function curve. Considering that the PN code-based red-blue frequency shift discriminator continuously optimizes the Doppler frequency estimate through iterative loops, it will eventually lead to... It reaches a steady state.

[0083] In one embodiment, the transmitting signal is generated by a PN code generator.

[0084] Furthermore, in order to verify the beneficial effects of the OTFS high-precision Doppler frequency estimation method provided in this application, experimental results were also conducted. Figure 5 (a) shows that as the number of iterations increases, the average value of the Doppler frequency estimate gradually converges to the true value, proving that the algorithm proposed in this application has unbiased properties. Figure 5 The curve in (b) illustrates the input-output relationship (the relationship between the actual Doppler frequency input value and the estimated value) of the Red-Blue Frequency Shift Discriminator (RBFD) in the Doppler frequency shift interval from -Δf / 2 to Δf / 2, where the loop signal-to-noise ratio (SNR) is -10 dB. It is evident that the theoretical Doppler frequency value and the estimated Doppler frequency value are very close; therefore, the algorithm proposed in this application exhibits unbiased characteristics throughout the entire estimation interval.

[0085] Figure 6 The algorithm proposed in this application is compared with other Doppler frequency estimation methods, using IEEE 802.11p parameters, carrier frequency f c=5.89GHz, subcarrier spacing Δf = 156.25kHz, delay grid number M = 64, Doppler grid number N = 50, and the CRLB (Cramer-Rao boundary) for this case was plotted. Doppler frequency estimation methods used in the comparison include: fractional Doppler frequency shift estimation methods based on pseudo-random noise (PN) pilots, and classic pilot-based frequency domain CFO (carrier frequency deviation) estimation techniques (Moose method), etc. Figure 6 Analysis shows that the method proposed in this application has an estimation accuracy close to the theoretical limit under low signal-to-noise ratio (SNR) conditions (SNR≥-15dB), and has better estimation performance than other methods.

[0086] Figure 7 The relationship between Doppler frequency estimation accuracy and (log₂ M)×N was simulated. The estimation accuracy of the proposed algorithm is related to (log₂ M)×N. When log₂ M×N is a constant, the Doppler frequency estimation accuracy is approximately equal. Therefore, the value of (log₂ M)×N chosen in the simulation is related to the Doppler frequency estimation accuracy, and varies with the DD domain mesh. As (log2 M)×N increases, the estimation accuracy of the Doppler frequency improves. For the case of (log2 M)×N=6000, when the signal-to-noise ratio is greater than -8dB, the Doppler frequency estimation deviation of the final estimate in this application is less than 1Hz.

[0087] It should be understood that, although Figure 1 , Figure 2 , Figure 4 The steps in the flowchart are shown sequentially as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order in which these steps are executed, and they can be performed in other orders. Figure 1 , Figure 2 , Figure 4 At least some of the steps in the process may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed in turn or alternately with other steps or at least some of the sub-steps or stages of other steps.

[0088] In one embodiment, an OTFS high-precision Doppler frequency estimation device is provided, comprising:

[0089] The signal recovery module is used to acquire the received signal after time delay and Doppler. At the receiving end, the same received signal is recovered based on the upper boundary parameter value, center point parameter value, and lower boundary parameter value of the Doppler frequency search unit to obtain the recovered received signal.

[0090] The Doppler frequency coarse estimation module is used to utilize the characteristics of OTFS in the time-delay Doppler domain to calculate the cross-correlation function of the received signal and the transmitted signal recovered by the upper boundary parameter value, the center point parameter value, and the lower boundary parameter value, respectively. Based on the cross-correlation function of the received signal and the transmitted signal recovered by the center point parameter value, the Doppler frequency coarse estimation is performed to obtain the Doppler frequency coarse estimation value.

[0091] The Doppler frequency shift correction module is used to input the coarse estimate of the Doppler frequency into the red-blue frequency shift discriminator based on the PN code for frequency shift discrimination, and to perform red-shift or blue-shift correction on the coarse estimate of the Doppler frequency based on the cross-correlation function of the received signal and the transmitted signal recovered by the upper boundary parameter value and the lower boundary parameter value, so as to obtain the final Doppler frequency estimation result.

[0092] Specific limitations regarding the OTFS high-precision Doppler frequency estimation device can be found in the limitations of the OTFS high-precision Doppler frequency estimation method described above, and will not be repeated here. Each module in the aforementioned OTFS high-precision Doppler frequency estimation device can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in hardware or independent of the processor in a computer device, or stored in software in the memory of a computer device, so that the processor can call and execute the corresponding operations of each module.

[0093] In one embodiment, a computer device is provided, which may be a terminal, and its internal structure diagram may be as follows: Figure 8 As shown, the computer device includes a processor, memory, network interface, display screen, and input devices connected via a system bus. The processor provides computational and control capabilities. The memory includes non-volatile storage media and internal memory. The non-volatile storage media stores the operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs stored in the non-volatile storage media. The network interface is used to communicate with external terminals via a network connection. When executed by the processor, the computer program implements an OTFS high-precision Doppler frequency estimation method. The display screen can be a liquid crystal display (LCD) or an e-ink display. The input devices can be a touch layer covering the display screen, buttons, a trackball, or a touchpad mounted on the computer device casing, or an external keyboard, touchpad, or mouse.

[0094] Those skilled in the art will understand that Figure 8The structure shown is merely a block diagram of a portion of the structure related to the present application and does not constitute a limitation on the computer device to which the present application is applied. Specific computer devices may include more or fewer components than those shown in the figure, or combine certain components, or have different component arrangements.

[0095] In one embodiment, a computer device is provided, including a memory and a processor, the memory storing a computer program, the processor executing the computer program to perform the following steps:

[0096] The receiver signal that has experienced time delay and Doppler is acquired. At the receiver, the same receiver signal is recovered based on the upper boundary parameter value, center point parameter value, and lower boundary parameter value of the Doppler frequency search unit, respectively, to obtain the recovered receiver signal.

[0097] Utilizing the characteristics of OTFS in the time-delay Doppler domain, the cross-correlation function of the received signal and the transmitted signal recovered by the upper boundary parameter value, the center point parameter value, and the lower boundary parameter value is calculated respectively. Based on the cross-correlation function of the received signal and the transmitted signal recovered by the center point parameter value, a coarse Doppler frequency estimate is performed to obtain the coarse Doppler frequency estimate.

[0098] The coarse Doppler frequency estimate is input into a red-blue frequency shift discriminator based on PN code for frequency shift discrimination. Based on the cross-correlation function of the received signal and the transmitted signal recovered by the upper and lower boundary parameter values, the coarse Doppler frequency estimate is red-shifted or blue-shifted to obtain the final Doppler frequency estimation result.

[0099] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0100] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these modifications and improvements all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A high-precision Doppler frequency estimation method for OTFS, characterized in that, The method includes: The receiver signal that has experienced time delay and Doppler is acquired. At the receiver, the same receiver signal is recovered based on the upper boundary parameter value, center point parameter value, and lower boundary parameter value of the Doppler frequency search unit, respectively, to obtain the recovered receiver signal. Utilizing the characteristics of OTFS in the time-delay Doppler domain, the cross-correlation function of the received signal and the transmitted signal recovered by the upper boundary parameter value, the center point parameter value, and the lower boundary parameter value is calculated respectively. Based on the cross-correlation function of the received signal and the transmitted signal recovered by the center point parameter value, a coarse Doppler frequency estimate is performed to obtain the coarse Doppler frequency estimate. The coarse Doppler frequency estimate is input into a PN code-based red-blue frequency shift discriminator for frequency shift discrimination. Based on the cross-correlation function between the received and transmitted signals recovered from the upper and lower boundary parameter values, the coarse Doppler frequency estimate is red-shifted or blue-shifted to obtain the final Doppler frequency estimation result. Specifically, this includes: inputting the coarse Doppler frequency estimate into a PN code-based red-blue frequency shift discriminator for frequency shift discrimination; obtaining the upper and lower boundary parameter values ​​in the Doppler frequency search unit corresponding to the coarse Doppler frequency estimate; calculating the Doppler frequency estimation deviation based on the cross-correlation function between the received and transmitted signals in the time-delay Doppler domain recovered from the upper and lower boundary parameter values; and red-shifting or blue-shifting the coarse Doppler frequency estimate based on the estimation deviation, expressed as... ； ； in, This represents the corrected coarse estimate of the Doppler frequency. This is a rough estimate of the Doppler frequency. To estimate the deviation, if This is called redshift correction, if This is called blueshift correction; This represents the cross-correlation function between the received and transmitted signals in the time-delay Doppler domain, recovered by the upper boundary parameter values. This represents the cross-correlation function between the received and transmitted signals in the time-delay Doppler domain, recovered by the lower boundary parameter values. The Doppler frequency search step size; Move to the center of the current Doppler frequency search unit, according to The upper and lower boundary parameter values ​​in the current Doppler frequency search unit are updated, and the same receiver signal is recovered and the cross-correlation function is calculated based on the updated upper and lower boundary parameter values. This process is repeated multiple times until the condition is met. Until then, and the current This serves as the final Doppler frequency estimation result.

2. The method according to claim 1, characterized in that, The Doppler frequency search unit is formed by dividing the two-dimensional target domain, which consists of the Doppler frequency search interval and the time delay search interval, into several grids. The length of the grid is the time delay search step size, and the width of the grid is the Doppler frequency search step size. The parameter values ​​in the Doppler frequency search unit are the Doppler frequency estimate and the time delay estimate.

3. The method according to claim 2, characterized in that, Acquire the received signal after time delay and Doppler effect. At the receiving end, reconstruct the same received signal based on the upper boundary parameter value, center point parameter value, and lower boundary parameter value of the Doppler frequency search unit to obtain the recovered received signal, including: The receiver signal that has experienced time delay and Doppler is acquired. At the receiver, the same receiver signal is linearly transformed based on the Doppler frequency estimate and time delay estimate from the upper boundary parameter value, center point parameter value and lower boundary parameter value of the Doppler frequency search unit, respectively, to obtain the recovered time-domain received signal. The recovered time-domain received signal is subjected to Wigner transform and two-dimensional SFFT transform to obtain the recovered time-delay Doppler domain received signal.

4. The method according to claim 3, characterized in that, Utilizing the characteristics of OTFS in the time-delay Doppler domain, the cross-correlation functions of the received signal and the transmitted signal recovered by the upper boundary parameter value, center point parameter value, and lower boundary parameter value are calculated respectively, including: The cross-correlation value of the received signal and the transmitted signal in the time-delayed Doppler domain, recovered using different Doppler frequency estimates, exhibits the characteristics of a sinc function. In the time-delayed Doppler domain, the cross-correlation function of the received signal and the transmitted signal in the time-delayed Doppler domain is recovered by calculating the upper boundary parameter value, the center point parameter value, and the lower boundary parameter value, respectively.

5. The method according to claim 4, characterized in that, Based on the cross-correlation function between the received signal and the transmitted signal recovered from the center point parameter values, a coarse Doppler frequency estimate is performed to obtain a coarse Doppler frequency estimate, including: The cross-correlation function between the received and transmitted signals in the time-delay Doppler domain, recovered by traversing and searching the center point parameter values ​​of different Doppler frequency search units. ,when When the Doppler frequency estimate is obtained from the parameter value of the current search center point, the Doppler frequency coarse estimate is used.

6. The method according to claim 1, 4, or 5, characterized in that, The transmitting signal is generated by a PN code generator.

7. A high-precision Doppler frequency estimation device for OTFS, characterized in that, The device includes: The signal recovery module is used to acquire the received signal after time delay and Doppler. At the receiving end, the same received signal is recovered based on the upper boundary parameter value, center point parameter value, and lower boundary parameter value of the Doppler frequency search unit to obtain the recovered received signal. The Doppler frequency coarse estimation module is used to utilize the characteristics of OTFS in the time-delay Doppler domain to calculate the cross-correlation function of the received signal and the transmitted signal recovered by the upper boundary parameter value, the center point parameter value, and the lower boundary parameter value, respectively. Based on the cross-correlation function of the received signal and the transmitted signal recovered by the center point parameter value, the Doppler frequency coarse estimation is performed to obtain the Doppler frequency coarse estimation value. The Doppler frequency shift correction module is used to input the coarse Doppler frequency estimate into a PN code-based red-blue frequency shift discriminator for frequency shift discrimination, and to perform red-shift or blue-shift correction on the coarse Doppler frequency estimate based on the cross-correlation function of the received signal and the transmitted signal recovered from the upper and lower boundary parameter values, thereby obtaining the final Doppler frequency estimation result. Specifically, the Doppler frequency shift correction module is used to: input the coarse Doppler frequency estimate into the PN code-based red-blue frequency shift discriminator for frequency shift discrimination, obtain the upper and lower boundary parameter values ​​in the Doppler frequency search unit corresponding to the coarse Doppler frequency estimate, calculate the Doppler frequency estimation deviation based on the cross-correlation function of the received signal and the transmitted signal recovered from the upper and lower boundary parameter values ​​in the time-delay Doppler domain, and then perform red-shift or blue-shift correction on the coarse Doppler frequency estimate based on the estimation deviation, expressed as... ； ； in, This represents the corrected coarse estimate of the Doppler frequency. This is a rough estimate of the Doppler frequency. To estimate the deviation, if This is called redshift correction, if This is called blueshift correction; This represents the cross-correlation function between the received and transmitted signals in the time-delay Doppler domain, recovered by the upper boundary parameter values. This represents the cross-correlation function between the received and transmitted signals in the time-delay Doppler domain, recovered by the lower boundary parameter values. The Doppler frequency search step size; Move to the center of the current Doppler frequency search unit, according to The upper and lower boundary parameter values ​​in the current Doppler frequency search unit are updated, and the same receiver signal is recovered and the cross-correlation function is calculated based on the updated upper and lower boundary parameter values. This process is repeated multiple times until the condition is met. Until then, and the current This serves as the final Doppler frequency estimation result.

8. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the method according to any one of claims 1 to 6.

Images