Otfs timing synchronization method based on edge detection correction of star-ground uplink link

Abstract

The application provides an OTFS timing synchronization method based on edge detection correction of a satellite-ground uplink, comprising: designing an embedded pilot and zero padding frame structure for communication data symbols of a satellite-ground uplink, performing OTFS modulation to obtain a transmission signal stream; constructing a DT domain model of a satellite-ground communication channel through which the transmission signal stream passes to obtain a received signal; based on the received signal, directly multiplexing a pilot signal used for channel estimation and equalization to calculate a timing metric curve; performing first-stage frame detection based on the timing metric curve to determine a candidate synchronization position through autocorrelation results in a time dimension; and performing edge detection correction on the candidate synchronization position through a second-stage screening mechanism to obtain a precise timing synchronization position. The application significantly reduces the false alarm probability of detection and significantly improves the frame synchronization accuracy on the basis of not improving the first-stage frame detection missed detection rate.

Description

Technical Field

[0001] This invention relates to the field of satellite-to-ground uplink edge detection and correction technology, specifically to an OTFS precise timing synchronization method based on satellite-to-ground uplink edge detection and correction, and also to a corresponding system, computer terminal, and computer-readable storage medium. Background Technology

[0002] Recently, Orthogonal Time-Frequency-Space (OTFS) modulation has emerged as a promising waveform candidate for sixth-generation (6G) wireless communication systems, particularly in non-terrestrial network (NTN) scenarios such as low Earth orbit (LEO) satellite communications. This growing interest stems from the unique advantages of OTFS, especially its robustness to channel impairments caused by high mobility environments through signal processing in the delay-Doppler (DD) domain, and its compatibility with existing wireless infrastructure. The extremely high speeds and long propagation distances characteristic of LEO satellite-to-ground links lead to significant Doppler shifts and power losses, thereby reducing receiver timing synchronization performance. Therefore, resolving the critical issue of physical layer timing synchronization is essential for achieving reliable and high-performance data transmission in future integrated space-air-ground networks.

[0003] In RZP-OTFS (Reduced Zero-Padding Orthogonal Time-Frequency-Space) systems, frame synchronization is the primary prerequisite for correct decoding at the receiver. However, existing frame synchronization schemes mainly face the following technical challenges: (1) There is an inherent contradiction between the false alarm rate and the false alarm probability in single-stage frame detection: Traditional frame synchronization algorithms usually adopt a single-stage detection mechanism, which determines the frame start position by setting a single decision threshold. In low signal-to-noise ratio or high Doppler scenarios, the decision threshold must be lowered to reduce the false alarm rate, but this will inevitably lead to a sharp increase in the false alarm probability; conversely, raising the threshold to reduce false alarms will increase the risk of false alarms. This contradiction is particularly prominent in high-speed moving scenarios.

[0004] (2) The RZP structure places higher demands on frame synchronization accuracy: RZP-OTFS uses a reduced zero-fill guard interval to replace the traditional cyclic prefix (CP) or full zero-fill (ZP). Although this improves spectral efficiency, it also reduces the guard redundancy between frames. Under these conditions, small deviations in frame synchronization position are more likely to cause inter-symbol interference (ISI), making the requirements for synchronization accuracy more stringent than those of the traditional OTFS structure.

[0005] (3) The requirements for synchronization mechanisms differ between continuous and bursty services: continuous service streams require frame synchronization to have continuous and stable tracking capabilities, while bursty services require the receiver to quickly acquire the frame start position in a very short time. Existing synchronization schemes are often designed for a single service type and are difficult to flexibly switch between and accommodate both service modes.

[0006] (4) Traditional synchronization methods rely on high-overhead preamble sequences: Traditional OTFS frame synchronization methods usually require the insertion of special preambles or training sequences to complete synchronization, which increases additional transmission overhead and reduces the effective spectral efficiency of the system. Summary of the Invention

[0007] To address the aforementioned shortcomings in the prior art, this invention provides a precise OTFS timing synchronization method based on satellite-to-ground uplink edge detection and correction, and also relates to a corresponding system, computer terminal, and computer-readable storage medium.

[0008] According to a first aspect of the present invention, an OTFS timing synchronization method based on satellite-to-ground uplink edge detection correction is provided, comprising: For the communication data symbols of the satellite-to-ground uplink, an embedded pilot and zero-fill frame structure is designed, and OTFS modulation is performed to obtain the transmission signal stream; Construct a DT domain model of the satellite-to-ground communication channel through which the transmitted signal stream passes, and obtain the received signal; Based on the received signal, the pilot signal used for channel estimation and equalization is directly multiplexed to calculate the timing metric curve; based on the timing metric curve, a first-stage frame detection is performed, and candidate synchronization positions are determined by the autocorrelation results in the time dimension; the candidate synchronization positions are edge-detected and the timing offset is corrected by a second-stage screening mechanism to obtain the accurate timing synchronization position.

[0009] According to a second aspect of the present invention, an OTFS timing synchronization method based on satellite-to-ground uplink edge detection correction is provided, comprising: The OTFS modulation module is used to design embedded pilot and zero-fill frame structures for communication data symbols of the satellite-to-ground uplink, perform OTFS modulation, and obtain the transmission signal stream. The channel model construction module is used to construct the DT domain model of the satellite-to-ground communication channel through which the transmitted signal stream passes, and to obtain the received signal. A two-stage frame synchronization module is provided. Based on the received signal, the module directly reuses the pilot signal used for channel estimation and equalization to calculate the timing metric curve. Based on the timing metric curve, a first-stage frame detection is performed to determine candidate synchronization positions by autocorrelation results in the time dimension. A second-stage screening mechanism is used to perform edge detection on the candidate synchronization positions and correct the timing offset to obtain the accurate timing synchronization position.

[0010] According to a third aspect of the present invention, a computer terminal is provided, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it can be used to perform the methods described above in the present invention, or to run the system described above in the present invention.

[0011] According to a fourth aspect of the present invention, a computer-readable storage medium is provided having a computer program stored thereon, which, when executed by a processor, can be used to perform the methods described above in the present invention, or to run the system described above in the present invention.

[0012] By adopting the above technical solution, the present invention has at least one of the following beneficial effects compared with the prior art: This invention significantly reduces the false alarm probability without increasing the false negative rate: It employs a two-stage cascaded detection architecture. The first stage performs coarse frame detection, using a low threshold to ensure the capture probability of the frame start position (i.e., maintaining a low false negative rate). The second stage, based on the structural characteristics of a single RZP-OTFS frame in the delay-time domain, performs temporal dimension edge detection and precise correction on the candidate frame start positions output from the first stage. Through the filtering mechanism of the second stage, false alarm candidates generated by the low threshold in the first stage are effectively eliminated, allowing the system to significantly reduce the false alarm probability while maintaining a low false negative rate in the first stage. This cascaded strategy of "coarse detection + fine filtering" fundamentally resolves the inherent contradiction between the false negative rate and the false alarm probability in traditional single-stage detection.

[0013] Significantly improved frame synchronization accuracy: The two-stage processing architecture upgrades frame synchronization from a "single coarse estimation" to a refined process of "coarse estimation + fine correction". The edge detection and correction in the second stage can control the estimation error of the frame start position within a smaller range, achieving higher synchronization accuracy compared to the traditional single-stage method, thus effectively resisting the ISI risk caused by the reduction of the guard interval in the RZP structure.

[0014] Balancing continuous and bursty traffic transmission: The two-stage architecture inherently possesses the flexibility to adapt to different traffic flows. For continuous traffic flows, the first stage maintains continuous tracking, while the second stage performs periodic fine-tuning to achieve stable and reliable continuous synchronization. For bursty traffic flows, the first stage can quickly capture the frame start position (low false negative rate ensures capture speed), while the second stage rapidly completes precise positioning after capture. The division of labor and cooperation between the two stages enables the system to achieve excellent synchronization performance under both traffic modes, eliminating the need to design independent synchronization schemes for different traffic flows.

[0015] No additional preamble sequence required, saving transmission overhead: This invention fully utilizes the inherent structural characteristics of RZP-OTFS frames in the delay-time domain for synchronization detection, eliminating the need to insert preambles or dedicated training sequences into the transmitted signal. This not only saves valuable transmission resources and improves the effective spectral efficiency of the system, but also reduces the peak-to-average power ratio (PAPR) problem at the transmitter.

[0016] Maintaining robust performance in low signal-to-noise ratio and high-mobility scenarios: Because the two-stage architecture does not rely on a single threshold decision, and the second stage performs accurate edge detection based on frame structure features, this invention can still maintain reliable synchronization performance in low signal-to-noise ratio regimes. Meanwhile, the delay-time domain processing method is naturally resistant to the Doppler effect, enabling it to maintain excellent frame synchronization accuracy even in high-speed mobile scenarios.

[0017] This invention significantly reduces the false alarm probability and improves frame synchronization accuracy without increasing the false alarm rate through a two-stage cascaded detection architecture. It takes into account both continuous and bursty service modes, and requires no additional preamble overhead. This provides an efficient, reliable and service-adaptive frame synchronization solution for the RZP-OTFS system. Attached Figure Description

[0018] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram of the RZP OTFS modulation process based on inverse Zak transform in a preferred embodiment of the present invention.

[0019] Figure 2 This is a comparison chart of false alarm probability curves for timed synchronization in a preferred embodiment of the present invention, with and without the second stage. Detailed Implementation

[0020] The embodiments of the present invention are described in detail below: These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention.

[0021] In existing technologies, the following technical problems are usually encountered when synchronizing RZP-OTFS frames: 1. There is an inherent contradiction between the missed detection rate and the false alarm probability in single-stage frame detection; 2. The RZP structure places higher demands on frame synchronization accuracy; 3. There are differences in the synchronization mechanism requirements between continuous services and bursty services; 4. Traditional synchronization methods rely on high-overhead preamble sequences.

[0022] To address the aforementioned issues, one embodiment of the present invention provides an OTFS precise timing synchronization method based on satellite-to-ground uplink edge detection and correction. This method is designed for RZP-OTFS signals and proposes a two-stage frame synchronization algorithm based on the Gardner bit synchronization principle. It aims to use the OTFS waveform, which has stronger anti-Doppler performance than OFDM waveforms, by introducing time-dimensional edge detection and correction of the OTFS physical layer single-frame structure in the time-delay domain. Without increasing the false alarm rate of the first-stage frame detection, the second-stage screening mechanism significantly reduces the false alarm probability and significantly improves the frame synchronization accuracy. This achieves a low-complexity precise timing synchronization method in low-Earth orbit satellite-to-ground communication scenarios and can accommodate both continuous and bursty service flows.

[0023] Specifically, such as Figure 1 As shown, the OTFS timing synchronization method based on satellite-to-ground uplink edge detection correction provided in this embodiment may include: S1, for the communication data symbols of the satellite-to-ground uplink, an embedded pilot and zero-fill frame structure is designed, and OTFS modulation is performed to obtain the transmission signal stream; S2, construct the DT domain model of the satellite-to-ground communication channel through which the transmitted signal stream passes, and obtain the received signal; S3: Based on the received signal, the pilot signal used for channel estimation and equalization is directly multiplexed to calculate the timing metric curve; the first-stage frame detection is performed based on the timing metric curve, and the candidate synchronization position is determined by the autocorrelation result in the time dimension; the candidate synchronization position is edge detected and the timing offset is corrected by the second-stage screening mechanism to obtain the accurate timing synchronization position.

[0024] In some preferred embodiments, S1 above, which designs embedded pilot and zero-fill frame structures for the communication data symbols of the satellite-to-ground uplink and performs OTFS modulation to obtain the transmission signal stream, may further include: OTFS modulation is performed using the inverse Zak transform, such as... Figure 1 shown. Specifically: S11, define the DD domain delay and Doppler lattice number as follows: and Then the DD field symbol is represented as , , In the formula, For the time delay axis coordinates in the DD domain mesh, Let the Doppler axis coordinates be in the DD domain mesh; let the power magnitude be The embedded pilot signal surrounding the guard interval is placed in the DD domain grid coordinates. In the middle, in the formula, The pilot position delay axis coordinates; S12, OTFS modulation is performed using the inverse Zak transform; wherein, the DD domain symbols Mapped to DT domain symbol , represented as: (1) In the formula, , These represent the time delay axis coordinates and the time axis coordinates in the DT domain mesh, respectively. Here, e is the complex exponential phase rotation factor, and e is the natural constant. The imaginary unit, ; S13, DT field symbol The sampling points are converted into a serial data stream through parallel-to-serial conversion. The generated signal and Having a conversion relationship In the formula, This is the index of the sampling points for the received discrete-time information symbols; S14, with a length of Reduced zero padding (RZP) is added to the beginning or end of the OTFS block to form the final transmitted signal stream. More preferably, the length... The RZP length is selected based on the channel delay spread. Specifically, if the RZP length is less than the delay spread, inter-symbol interference (ISI) will occur, leading to a severe degradation in system performance. Therefore, ideally, a "complete" RZP length should cover the worst channel environment. However, an excessively long RZP introduces a large amount of redundancy, reducing spectral efficiency. Specifically, here, based on the 3GPP TDL-D time tap model, the path with the longest delay can be found, and the number of sampling points converted from the delay of this path at the designed sampling rate can be calculated, along with its length. It only needs to be greater than the number.

[0025] In some preferred embodiments, the embedded pilot in S1 is preferably an impulse pilot.

[0026] In some preferred embodiments, S2 above, which involves constructing a DT domain model of the satellite-to-ground communication channel through which the transmitted signal stream passes and obtaining the received signal, may further include: S21 employs a satellite-to-ground time-delay tapped line channel model to construct a DT domain model of the satellite-to-ground communication channel through which the transmitted signal flow passes. Represented as: (2) In the formula, The total number of transmission paths, , , , Let represent the path complex gain, time delay tap, angle of arrival, and Doppler tap of the i-th path, respectively. S22, subject to normalized timing offset and carrier frequency offset Affected received signal Represented as: (3) In the formula, The variance is Complex Gaussian white noise channel, The total length of the last OTFS frame. , t This is the index of the sampling points for the received discrete-time domain information symbols.

[0027] In some preferred embodiments, S3 above, which directly multiplexes the pilot signal used for channel estimation and equalization based on the received signal to calculate the timing metric curve, may further include: In this preferred embodiment, a timing synchronization estimator in the DT domain is proposed for the OTFS satellite-to-ground communication system. This estimator does not require any additional preamble overhead and directly reuses the pilot signals used for channel estimation and equalization. In satellite-to-ground uplink scenarios, this method is more practically valuable than existing methods for extracting weak channel multipath gain. The OTFS frames equipped with this timing synchronization estimator have an RZP prefix / suffix and a padding length of at least [value missing]. This is to distinguish between the edges and the interior. Specifically: S31, such as Figure 1 As shown, the power is (dB), and the embedded pilot around the guard interval is placed in the DD domain grid coordinates. In the 4-QAM modulation format, the data symbol power is set to 1 (dB), and the noise power is... (dB), The signal-to-noise ratio is ; the delay axis width is . The purpose of the guard interval is to prevent pilot signals and data from interfering with each other due to channel fading and shifting. Figure 1 In this configuration, the transmitted data is arranged in a DD domain grid, and the guard interval between the pilot and the data is (2... L P +1)× N -1.

[0028] S32, perform inverse Zak transform (IDZT) on the pilot signal, that is, transform the pilot signal from the DD domain to the DT domain, then the pilot signal corresponds to the... The DT domain grid signal of the row is a series with constant amplitude and linear phase difference , The signal The coordinates of the pilot position delay axis are shown. The transmitted signal undergoes parallel-to-serial conversion, is prefixed or suffixed with RZP, and after reaching the receiver via the channel, it undergoes another parallel-to-serial conversion to obtain the received signal's DT domain grid. Figure 1 Set the padding zero length to This is precisely the minimum length with zero padding that the designed two-stage timing synchronization method must satisfy.

[0029] S33, the timing measurement curve is defined as follows: (4) (5) (6) In the formula, For timed measurement calculations, multiple locations The calculation results form a timing measurement curve. The autocorrelation value calculated by shifting the signal by one bit is the numerator of the formula for calculating the timing metric. The signal power, used for normalization, is the denominator in the formula for calculating timing metrics. For signal sampling point index, For the satellite-side received signal, For the conjugate of the received signal, k is the time axis index (horizontal coordinate) after the information symbol is transformed from the one-dimensional time domain to the two-dimensional DT domain. In this embodiment, .

[0030] When calculating the autocorrelation value of a signal shifted by one bit, the pilot signal is distinguished from other random communication data symbols by the amplitude and phase properties of the converted pilot signal.

[0031] The amplitude and phase properties of the pilot signal distinguish it from other random data symbols in formula (5), which is a key basis for the first stage of the timing estimation algorithm. Adjacent symbols ( l The phase difference of (=1) is very small when N is large, and can be approximately equal to no phase difference. Therefore, the result of conjugate multiplication is approximately equal to the square of its constant amplitude. However, after adjacent random data symbols are modulated by QAM, their conjugate multiplication results usually cancel each other out, and are approximately equal to 0.

[0032] By using the amplitude and phase properties of the pilot signal and calculation formulas (4-6), the pilot signal can be distinguished from other random data symbols, guard intervals, and burst service transmission intervals. In formula (5), adjacent symbols ( l The phase difference of (=1) is very small when N is large, and can be approximately equal to no phase difference. Therefore, the conjugate multiplication result is approximately equal to the square of its constant amplitude. After QAM modulation, the conjugate multiplication result of adjacent random data symbols usually cancels out and is approximately equal to 0. The data transmitted by adjacent guard intervals and burst service transmission intervals is itself 0, with only Gaussian random white noise, and its conjugate result is also approximately equal to 0. That is to say, only the pilot symbol to be found will get a result close to 1 (the denominator of formula (6) is responsible for normalization) after calculation formula (4).

[0033] In some preferred embodiments, S3 above, which involves performing a first-stage frame detection based on a timing metric curve and determining candidate synchronization positions through autocorrelation results in the time dimension, and then performing edge detection correction on the candidate synchronization positions through a second-stage screening mechanism to obtain accurate timing synchronization positions, may further include: This step proposes a two-stage frame synchronization timing synchronization algorithm; wherein: In the first stage, timing measurements are performed on each received frame of data using a timing metric curve, and the results are compared with the estimated values ​​measured along with the signal. or prior Information-based floating threshold A hard decision is performed to determine candidate synchronization positions; the first stage aims to determine these positions. The hard decision calculation process involves a simple judgment logic: when a signal is at a certain sampling point... d The timing metric calculated at the location is greater than or equal to the threshold. T When the point is considered a candidate synchronization timing point, its location is cached for the second stage of edge detection and correction; when the timing metric is less than the threshold... T If the point is not considered a candidate synchronization timing point, the information of that point is not cached, and the timing metric value of the next signal sampling point is directly calculated.

[0034] In the second stage, sharp edges at the start of frames are detected using the idle RZP region in the time dimension to eliminate cross-frame timing ambiguity of pilot signals during adjacent frame transmission; this edge metric function can be found. It has maximum and minimum values ​​only at the beginning and end of the current frame, and is almost zero elsewhere. Furthermore, this edge measurement function... It can also be used to correct timing errors by using peak and valley location information, which helps predict the arrival time of the next frame in continuous service stream transmission, i.e., advance timing.

[0035] (7) In the formula, , which is the time axis index (horizontal axis) after the information symbol is transformed from the one-dimensional time domain to the two-dimensional DT domain; The calculation range in the time axis dimension of the two-dimensional DT domain is defined as the range spanning from the start of the RZP before an OTFS frame to the end of that frame, extended by another RZP length. Assuming the current candidate synchronization position is the correct frame start position, the calculation range covers the entire frame in the DT domain time dimension, the zero-padding of the current frame, and the edge detection results of the zero-padding of the next frame. Within this range, peak positions where the edge detection results are close to 1 are sought. This is the estimated start position of the frame selected in the second stage; The entire solution process is summarized as Algorithm 1. The complexity of the first stage of this algorithm is O(n log n). Linear stage, complexity after entering the second stage is The overall complexity of the proposed solution is constant, meaning it is O(n log n). Linear level. If the two-stage algorithm uses a point-by-point matching and comparison algorithm, the complexity is O(n log n). Linear order, overall complexity of the solution is The quadratic time complexity is thus reduced to quadratic. Therefore, the proposed solution reduces the overall system time complexity to [dimension-wise]. The linear stage can reduce computational latency, avoid memory overflow, prevent triggering hardware resource limits, and ensure the stable operation of downstream components.

[0036] Finally, the estimated frame start position selected in the second stage is not actually the true start of a frame, but only the pilot start position. Therefore, two offsets need to be subtracted, namely the pilot start position. and Prefix length. This refers to the final precise timing synchronization position. The calculation formula is shown in equation (8): (8) In the formula, To achieve the final precise timing synchronization position, the pilot and RZP lengths need to be offset from the results obtained in the two-stage selection. This refers to the estimated start position of the frames selected in the second stage. This is the starting position of the pilot signal. To reduce the length of zero padding.

[0037] The core program example of the two-stage frame synchronization timing synchronization algorithm implemented in this step is shown below: The performance of the technical solution provided in the above embodiments of the present invention will be further illustrated below with a simulation verification example.

[0038] In this simulation verification example, the default system parameters are set as follows: Ka-band carrier frequency 30GHz, system bandwidth BW=2MHz, delay points M=32, Doppler points N=32, RZP length 5M, and 4-QAM signal. The channel delay spread model used in the simulation experiment is the 3GPP PTN-TDL-D model. If the RZP length is less than the delay spread, inter-symbol interference (ISI) will occur, leading to a severe degradation in system performance. Therefore, ideally, a "complete" RZP length needs to cover the worst channel environment. However, an excessively long RZP introduces a large amount of redundancy, reducing spectral efficiency. Specifically, based on the 3GPP TDL-D time tap model, the path with the longest delay can be found, and the number of sampling points and length of that path's delay at the designed sampling rate can be calculated. The number only needs to be greater than the required quantity. Channel simulation of a low-Earth orbit satellite-to-ground communication system was performed at an orbital altitude of 1200 km. The satellite's transmitting antenna is a parabolic antenna with a beam coverage radius of 100 km. The simulation only considers the uplink direction and small-scale fading. The large-scale time delay between the satellite and the ground has been pre-compensated based on ephemeris messages, leaving only the residual delay to be estimated.

[0039] The missed detection probability and false alarm probability of the OTFS timing synchronization method for frame synchronization provided in the above embodiments of the present invention were analyzed. Regardless of whether the subsequent step of second-stage edge detection and correction was added, no missed detection occurred for each correct frame start position during continuous frame transmission.

[0040] When considering the probability of false alarms, the positive effects of the proposed second-stage edge detection and correction step have already been demonstrated. Figure 2This has been confirmed. When the signal-to-noise ratio is 10dB, the false alarm probability is reduced by 97.35%. In summary, when the signal-to-noise ratio is greater than 10dB, the technical solution provided in the above embodiments of the present invention, and the proposed two-stage frame synchronization algorithm, can achieve a low false detection rate with low computational complexity.

[0041] Based on the same inventive concept, another embodiment of the present invention provides an OTFS timing synchronization system based on satellite-to-ground uplink edge detection correction, which may include: The OTFS modulation module is used to design embedded pilot and zero-fill frame structures for communication data symbols of the satellite-to-ground uplink, perform OTFS modulation, and obtain the transmission signal stream. The channel model construction module is used to construct the DT domain model of the satellite-to-ground communication channel through which the transmitted signal stream passes, and to obtain the received signal. The two-stage frame synchronization module directly reuses the pilot signal used for channel estimation and equalization based on the received signal to calculate the timing metric curve; it performs the first-stage frame detection based on the timing metric curve and determines the candidate synchronization position by autocorrelation results in the time dimension; and it performs edge detection on the candidate synchronization position and corrects the timing offset through the second-stage screening mechanism to obtain the accurate timing synchronization position.

[0042] It should be noted that the steps in the method provided by the present invention can be implemented using corresponding modules, devices, units, etc. in the system. Those skilled in the art can refer to the technical solution of the method to realize the composition of the system. That is, the embodiments in the method can be understood as preferred examples for building the system, and will not be elaborated here.

[0043] Based on the same inventive concept, other embodiments of the present invention provide a computer terminal, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it can be used to perform any of the methods in the above embodiments of the present invention, or to run any of the systems in the above embodiments of the present invention.

[0044] Optionally, the memory is used to store programs; the memory may include volatile memory, such as random-access memory (RAM), such as static random-access memory (SRAM), double data rate synchronous dynamic random-access memory (DDR SDRAM), etc.; the memory may also include non-volatile memory, such as flash memory. The memory is used to store computer programs (such as application programs and functional modules that implement the above methods), computer instructions, etc., and the aforementioned computer programs and computer instructions can be partitioned and stored in one or more memories. Furthermore, the aforementioned computer programs, computer instructions, data, etc., can be accessed by the processor.

[0045] A processor is used to execute computer programs stored in memory to implement the various steps of the methods or various modules of the systems involved in the above embodiments. For details, please refer to the relevant descriptions in the preceding method and system embodiments.

[0046] The processor and memory can be separate structures or integrated structures. When the processor and memory are separate structures, they can be coupled together via a bus.

[0047] Based on the same inventive concept, other embodiments of the present invention provide a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, can be used to perform the method of any of the above embodiments of the present invention, or to run the system of any of the above embodiments of the present invention.

[0048] Computer-readable media include computer storage media and communication media, wherein communication media include any medium that facilitates the transfer of computer programs from one place to another. Storage media can be any available medium accessible to a general-purpose or special-purpose computer. An exemplary storage medium is coupled to a processor, enabling the processor to read information from and write information to the storage medium. Of course, the storage medium can also be a component of the processor. The processor and storage medium can reside in an ASIC. Alternatively, the ASIC can reside in a user device. Of course, the processor and storage medium can also exist as discrete components in a communication device.

[0049] Any matters not covered in the above embodiments of the present invention are well-known in the art.

[0050] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. An OTFS timing synchronization method based on satellite-to-ground uplink edge detection and correction, characterized in that, include: For the communication data symbols of the satellite-to-ground uplink, an embedded pilot and zero-fill frame structure is designed, and OTFS modulation is performed to obtain the transmission signal stream; Construct a DT domain model of the satellite-to-ground communication channel through which the transmitted signal stream passes, and obtain the received signal; Based on the received signal, the pilot signal used for channel estimation and equalization is directly multiplexed to calculate the timing metric curve; based on the timing metric curve, the first-stage frame detection is performed, and the candidate synchronization position is determined by the autocorrelation result of the time dimension. The candidate synchronization positions are edge-detected and the timing offset is corrected through a second-stage screening mechanism to obtain the accurate timing synchronization position.

2. The OTFS timing synchronization method based on satellite-to-ground uplink edge detection and correction according to claim 1, characterized in that, The communication data symbols for the satellite-to-ground uplink are designed with embedded pilot and zero-fill frame structures, and OTFS modulation is performed to obtain the transmission signal stream, including: Define the DD domain delay and Doppler lattice number as follows: and Then the symbolic representation of the DD field is as follows: , , In the formula, The time delay axis coordinates in the DD domain mesh. These are the Doppler axis coordinates in the DD domain grid; With power magnitude The embedded pilot signal surrounding the guard interval is placed in the DD domain grid coordinates. In the middle, in the formula, The pilot position delay axis coordinates; OTFS modulation is performed using the inverse Zak transform; where the DD domain symbols are... Mapped to DT domain symbol , is represented as: (1) In the formula, , These represent the time delay axis coordinates and the time axis coordinates in the DT domain mesh, respectively. Here, e is the complex exponential phase rotation factor, and e is the natural constant. The imaginary unit, ; DT field symbol The sampling points are converted into a serial data stream through parallel-to-serial conversion. The generated signal and Having a conversion relationship In the formula, This is the index of the sampling points for the received discrete-time information symbols; The length is The reduced zero padding is added to the beginning or end of the OTFS block to form the final transmission signal stream.

3. The OTFS timing synchronization method based on satellite-to-ground uplink edge detection and correction according to claim 2, characterized in that, The length The selection is based on the channel delay spread.

4. The OTFS timing synchronization method based on satellite-to-ground uplink edge detection and correction according to claim 1, characterized in that, The process of constructing the DT domain model of the satellite-to-ground communication channel through which the transmitted signal stream passes, and obtaining the received signal, includes: Using a satellite-to-ground time-delay tapped line channel model, a DT domain model of the satellite-to-ground communication channel through which the transmitted signal stream passes is constructed. Represented as: (2) In the formula, The total number of transmission paths, , , , They represent the first The path complex gain, delay tap, angle of arrival, and Doppler tap of each path; Subject to normalized timing offset and carrier frequency offset Affected received signal Represented as: (3) In the formula, The variance is Complex Gaussian white noise channel, The total length of the last OTFS frame. , t This is the index of the sampling points for the received discrete-time domain information symbols.

5. The OTFS timing synchronization method based on satellite-to-ground uplink edge detection and correction according to claim 1, characterized in that, The step of directly multiplexing the pilot signals used for channel estimation and equalization based on the received signal to calculate the timing metric curve includes: Performing an inverse Zak transform on the embedded pilot signal to convert it from the DD domain to the DT domain, the pilot signal corresponds to the [missing information - likely a specific domain or region]. The DT domain grid signal of the row is a series with constant amplitude and linear phase difference The signal , The pilot position delay axis coordinates; The timing metric curve is calculated as follows: (4) (5) (6) In the formula, For timed measurement calculations, multiple locations The calculation results form a timing measurement curve. The autocorrelation value is calculated by shifting the signal by one bit. For signal power, For signal sampling point index, For the satellite-side received signal, For the conjugate of the received signal, k For the time axis index after information symbols are transformed from the one-dimensional time domain to the two-dimensional DT domain; Specifically, when calculating the autocorrelation value of a signal shifted by one bit, the pilot signal is distinguished from other random communication data symbols by the amplitude and phase properties of the converted pilot signal.

6. The OTFS timing synchronization method based on satellite-to-ground uplink edge detection and correction according to claim 1, characterized in that, The first-stage frame detection is performed based on the timing metric curve, and candidate synchronization positions are determined by the autocorrelation results in the time dimension. A second-stage screening mechanism is used to perform edge detection and correct timing offsets on the candidate synchronization positions to obtain accurate timing synchronization positions, including: In the first stage, timing measurements are performed on each received frame of data using the aforementioned timing metric curve, and the results are compared with the estimated values ​​measured along with the signal. or prior Information-based floating threshold Make a hard decision to determine the candidate synchronization position; In the second stage, for the current candidate synchronization position, sharp edges of the frame start are detected using the idle zero-padding region in the time dimension to obtain the estimated frame start position; timing offset correction is then performed on the estimated frame start position to obtain the final accurate timing synchronization position; wherein, the edge detection results... The calculation is shown in formula (7): (7) In the formula, , k For the time axis index after information symbols are transformed from the one-dimensional time domain to the two-dimensional DT domain; Assuming the current candidate synchronization position is the correct frame start position, the calculation range covers the entire frame in the DT domain time dimension, the zero-padding of the current frame, and the edge detection results of the next frame with zero padding. Within this range, the peak position where the edge detection result is close to 1 is searched. This is the estimated start position of the frame selected in the second stage; For the estimated frame start position Perform timed offset and Correction is performed to obtain the final precise timing synchronization position. : (8) In the formula, This is the starting position of the pilot signal. To reduce the length of zero padding.

7. An OTFS timing synchronization method based on satellite-to-ground uplink edge detection and correction, characterized in that, include: The OTFS modulation module is used to design embedded pilot and zero-fill frame structures for communication data symbols of the satellite-to-ground uplink, perform OTFS modulation, and obtain the transmission signal stream. The channel model construction module is used to construct the DT domain model of the satellite-to-ground communication channel through which the transmitted signal stream passes, and to obtain the received signal. A two-stage frame synchronization module, based on the received signal, directly multiplexes the pilot signal used for channel estimation and equalization to calculate a timing metric curve; performs first-stage frame detection based on the timing metric curve, and determines candidate synchronization positions by autocorrelation results in the time dimension; The candidate synchronization positions are edge-detected and the timing offset is corrected through a second-stage screening mechanism to obtain the accurate timing synchronization position.

8. A computer terminal, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it can be used to perform the method of any one of claims 1-6, or to run the system of claim 7.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by a processor, the computer program can be used to perform the method of any one of claims 1-6, or to run the system of claim 7.

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