An OTFS signal detection method, device and readable storage medium

Abstract

This application provides an OTFS signal detection method, apparatus, and readable storage medium. The method includes: performing constellation modulation based on task data and mapping it to the time-delay-Doppler domain; constructing a time-frequency bidispersive channel model to obtain the received signal at the receiver; performing an orthogonal time-delay-Doppler modulation OTFS inverse transform on the received signal to obtain the received signal in the time-delay-Doppler domain; estimating a portion of the transmitted signal using interference-free region information symbols in the received signal in the time-delay-Doppler domain; calculating interference symbols of non-direct paths and eliminating interference at the corresponding positions of the received signal in the time-delay-Doppler domain; and iterative updating of the interference-free region and convergence of the full-domain detection. This application can significantly suppress symbol interference caused by out-of-bounds cyclic shifts, achieve refined processing of complex scattering paths, and reliably recover symbols of direct paths.

Description

Technical Field

[0001] This application relates to the field of communication technology, and in particular to an OTFS signal detection method, apparatus and readable storage medium. Background Technology

[0002] With the continuous development of low-altitude communication and future integrated air-space-ground networks, the communication needs of low-altitude unmanned aerial vehicles (UAVs) in scenarios such as emergency communication, urban management, logistics transportation, and environmental monitoring are constantly increasing. In the low-altitude three-dimensional spatial environment, the wireless propagation path is affected by factors such as the ground surface, buildings, vegetation, and the structure of the UAV, exhibiting obvious time delay spread, Doppler spread, and dynamic characteristics of rapid changes in the propagation path over time. These propagation laws place higher demands on the modulation methods, signal detection strategies, and channel processing methods of wireless communication systems, requiring a physical layer technology system that can adapt to low-altitude high-speed movement, strong multipath, and complex reflection environments to ensure link stability and communication reliability.

[0003] In mobile communication modulation technology, Orthogonal Frequency-Division Multiplexing (OFDM), as a typical multi-carrier modulation method, is widely used to address frequency-selective fading. OFDM achieves parallel transmission through an orthogonal subcarrier structure and uses a cyclic prefix to suppress interference between multipath paths. Its main processing steps include: information symbol mapping, modulation and demodulation based on IFFT (Inverse Fast Fourier Transform) / FFT (Fast Fourier Transform), addition and removal of the cyclic prefix, frequency-domain pilot-assisted channel estimation, frequency-domain equalization, and symbol decision. In frequency-selective fading environments, OFDM, by processing each subcarrier independently in the frequency domain, allows multipath effects to be compensated for in a relatively clear way during frequency-domain equalization. Its overall architecture is relatively standardized, and its engineering implementation is quite mature. However, in high-speed mobile scenarios, the frequency-domain structure is susceptible to Doppler spread, causing the channel to change rapidly over time in the frequency domain, thus affecting the stability of frequency-domain equalization and the accuracy of channel estimation.

[0004] Against this backdrop, Orthogonal Time-Frequency Space (OTFS) modulation, a transform-domain modulation method based on the time-delay-Doppler domain, was proposed to address propagation environments with significant time-varying and Doppler spread characteristics. The basic idea of ​​OTFS is to map information symbols to the time-delay-Doppler domain, making the channel exhibit a relatively stable and sparse structure in this domain, facilitating the handling of dynamic channel changes caused by high-speed movement. In a typical OTFS signal processing link, the transmitter transforms the time-delay-Doppler domain symbols to the time-frequency domain using ISFFT (Inverse Symplectic Finite Fourier Transform), and then obtains the time-domain signal for air interface transmission through Heisenberg transform. The receiver maps the received signal back to the time-delay-Doppler domain through Wegener transform and SFFT (Symplectic Finite Fourier Transform), thus forming a received symbol matrix with a two-dimensional convolutional structure. In parametric channel models, multipath components are typically characterized by parameters such as time delay, Doppler, gain, and phase, and the signal propagation process is described through a multipath superposition structure. This architecture enables OTFS to characterize channel properties in the time delay-Doppler domain, providing fundamental technical conditions for analyzing low-altitude propagation patterns and researching signal detection algorithms.

[0005] However, existing technologies suffer from problems such as severe performance degradation of OFDM due to high-speed movement, insufficient utilization of channel sparsity, and high complexity of existing detection algorithms. Summary of the Invention

[0006] The technical problem to be solved by this application is to provide an OTFS signal detection method, apparatus and readable storage medium to address the above-mentioned shortcomings of the prior art.

[0007] In a first aspect, this application provides an OTFS signal detection method, the method comprising: S1: Based on the mission data sent by the low-altitude UAV communication terminal or ground control station, perform constellation modulation and map it into the time delay-Doppler domain; S2: Based on the multipath propagation characteristics and Doppler effect of low-altitude air-to-ground links, a time-frequency dual-dispersion channel model is constructed to obtain the received signal at the receiver. S3: Perform an inverse OTFS transform on the received signal to convert the received signal from the time domain to the time-delay-Doppler domain, thus obtaining the time-delay-Doppler domain received signal. S4: Based on the line-of-sight path and ground object reflection path characteristics in low-altitude UAV communication, partial transmitted signals are estimated by utilizing the interference-free zone information symbols in the time-delay-Doppler domain received signals. S5: Based on the multipath characteristics in the low-altitude communication environment, calculate the interference symbols of non-direct paths and eliminate the interference at the corresponding position of the received signal in the time-delay-Doppler domain; S6: Iterative update of the interference-free region and convergence of global detection: Dynamically update the interference-free region based on the current detection results, and repeat S4 and S5 to gradually expand the detection range from local to global.

[0008] In some embodiments, S1 includes: Define the time delay dimension as M, the Doppler dimension as N, and the time delay-Doppler domain transmitted signal as... At the transmitting end, the time-delayed Doppler domain signal Two-dimensional time-domain signals are obtained by inverse symplectic finite Fourier transform (ISFFT) and Heisenberg transform. : ; in, Represents the N-point inverse Fourier transform matrix; Two-dimensional time-domain signals After parallel-to-serial conversion, the transmitted signal in the time domain is obtained. .

[0009] In some embodiments, S2 includes: Send signals in the time domain After time-frequency bicolor dispersive channel Transmission occurs during this process, where the time-frequency bidispersive channel matrix... for:

[0010] in, L Indicates that the channel has K One transmission path, i Indicates the first i Path, and These represent the index values ​​for time delay and Doppler frequency shift, respectively. Indicates the first i The fading coefficient of the path; the first path i The delay of the path is , , Representing the time delay matrix, we can obtain , I For the identity matrix; the first i Doppler for each path , , Representing the Doppler matrix, we can obtain , , ; The received signal at the receiving end is obtained by analyzing both the case where the boundary crossing phenomenon occurs and the case where the boundary crossing phenomenon does not occur. Here, "out of bounds" refers to the received signal falling outside the M×N two-dimensional grid in the time-delay-Doppler domain, where M is the time delay dimension range and N is the Doppler dimension range.

[0011] In some embodiments, including: When no boundary crossing occurs and ; The time-domain received signal at the receiving end matrix form for:

[0012] Among them, the information symbols are The size of the information symbol is , Represents the time delay axis index coordinate. Represents the Doppler axis index coordinates; right After serial-to-parallel conversion, a two-dimensional time-domain received signal is obtained. .

[0013] In some embodiments, including: When a boundary violation occurs or ; The time-domain received signal at the receiving end matrix form for:

[0014] Among them, the information symbols are The size of the information symbol is , Represents the time delay axis index coordinate. Represents the Doppler axis index coordinates; right After serial-to-parallel conversion, a two-dimensional time-domain received signal is obtained. .

[0015] In some embodiments, S3 includes: The time-delay-Doppler domain received signal is obtained using the following formula. : .

[0016] In some embodiments, S4 includes: By estimating the direct path component using signals from interference-free areas, a preliminary recovery of the main communication path can be achieved.

[0017] in, This represents the additional phase matrix corresponding to the first path. Represents deconvolution operation. Represents the inverse operation of the Hadamard product; Among them, the time-delay-Doppler domain channel matrix The expression is: .

[0018] In some embodiments, S5 includes: Interference symbols for non-direct paths as follows:

[0019] in, ; Receiving signals Eliminate interference at appropriate locations: .

[0020] Secondly, this application provides an OTFS signal detection device, the device comprising: The modulation mapping module is configured to perform constellation modulation on mission data sent by low-altitude UAV communication terminals or ground control stations and map it into the time-delay-Doppler domain. The channel model module is configured to construct a time-frequency dual-dispersion channel model based on the multipath propagation characteristics and Doppler effect of low-altitude air-to-ground links, and obtain the received signal at the receiver. The signal conversion module is configured to perform an inverse orthogonal time delay-Doppler modulation (OTFS) transform on the received signal, converting the received signal from the time domain to the time delay-Doppler domain, and obtaining the time delay-Doppler domain received signal. The signal estimation module is configured to estimate part of the transmitted signal based on the characteristics of line-of-sight path and ground object reflection path in low-altitude UAV communication, using the interference-free zone information symbols in the time-delay-Doppler domain received signal. The interference cancellation module is configured to calculate the interference symbols of non-direct paths based on the multipath characteristics in the low-altitude communication environment, and cancel the interference at the corresponding position of the received signal in the time-delay-Doppler domain. The iterative update module is configured to perform iterative updates in the interference-free area and convergence of the global detection: it dynamically updates the interference-free area based on the current detection results and repeatedly performs signal estimation and interference cancellation, so that the detection range gradually expands from the local area to the global area.

[0021] Thirdly, this application provides an OTFS signal detection device, including a memory and a processor, wherein the memory stores a computer program, and the processor is configured to run the computer program to implement the OTFS signal detection method described in the first aspect above.

[0022] Fourthly, this application provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the OTFS signal detection method described in the first aspect.

[0023] The OTFS signal detection method, apparatus, and readable storage medium provided in this application include: performing constellation modulation on mission data transmitted by a low-altitude UAV communication terminal or ground control station and mapping it to the time-delay-Doppler domain; constructing a time-frequency bicolor channel model based on the multipath propagation characteristics and Doppler effect of the low-altitude air-to-ground link to obtain the received signal at the receiver; performing an orthogonal time-delay-Doppler modulation OTFS inverse transform on the received signal to convert the received signal from the time domain to the time-delay-Doppler domain, obtaining the time-delay-Doppler domain received signal; estimating part of the transmitted signal using interference-free area information symbols in the time-delay-Doppler domain received signal based on the line-of-sight direct path and ground object reflection path characteristics in low-altitude UAV communication; calculating interference symbols for non-direct paths based on the multipath characteristics in the low-altitude communication environment and eliminating interference at the corresponding positions of the time-delay-Doppler domain received signal; iterative updating of the interference-free area and convergence of the entire detection range: dynamically updating the interference-free area based on the current detection results and repeatedly performing signal estimation and interference elimination, so that the detection range gradually expands from local to global. This application can significantly suppress symbol interference caused by out-of-bounds cyclic shifts, enabling refined processing of complex scattering paths and reliable recovery of symbols from direct paths. Attached Figure Description

[0024] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0025] Figure 1 A schematic diagram of the OTFS signal detection method provided in the embodiments of this application; Figure 2 A schematic diagram of the OTFS signal processing flow for low-altitude UAV communication provided in an embodiment of this application; Figure 3This is a schematic diagram of the "out-of-bounds" phenomenon cyclic shift provided in an embodiment of this application; Figure 4 A comparative diagram illustrating the complexity of the OTFS signal detection method for low-altitude UAV communication provided in the embodiments of this application; Figure 5 This is a performance simulation comparison diagram of the OTFS signal detection method for low-altitude UAV communication provided in the embodiments of this application; Figure 6 This is a schematic diagram of the structure of an OTFS signal detection device provided in an embodiment of this application; Figure 7 This is a schematic diagram of another OTFS signal detection device provided in an embodiment of this application.

[0026] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0027] To enable those skilled in the art to better understand the technical solution of this application, the embodiments of this application will be further described in detail below with reference to the accompanying drawings.

[0028] It is understood that the specific embodiments and accompanying drawings described herein are merely for explaining this application and are not intended to limit this application.

[0029] It is understood that, without conflict, the various embodiments and features in the embodiments of this application can be combined with each other.

[0030] It is understood that, for ease of description, only the parts relevant to this application are shown in the accompanying drawings, while parts unrelated to this application are not shown in the drawings.

[0031] It is understood that each unit or module involved in the embodiments of this application may correspond to only one entity structure, or may be composed of multiple entity structures, or multiple units or modules may be integrated into one entity structure.

[0032] It is understood that the terms "first," "second," etc., used in the embodiments of this application are used to distinguish different objects or to distinguish different treatments of the same object, rather than to describe a specific order of objects.

[0033] It is understood that, without conflict, the functions and steps marked in the flowcharts and block diagrams of this application may occur in a different order than those marked in the accompanying drawings.

[0034] It is understood that the flowcharts and block diagrams of this application illustrate the possible architecture, functions, and operations of systems, apparatuses, devices, and methods according to various embodiments of this application. Each block in a flowchart or block diagram may represent a unit, module, program segment, or code, containing executable instructions for implementing the specified function. Furthermore, each block or combination of blocks in the block diagrams and flowcharts may be implemented using a hardware-based system to implement the specified function, or using a combination of hardware and computer instructions.

[0035] It is understood that the units and modules involved in the embodiments of this application can be implemented by software or by hardware. For example, the units and modules can be located in the processor.

[0036] It is understood that the specific values ​​of each parameter in this application are merely illustrative examples, and in practical applications, the parameters can be optimized and adjusted based on specific requirements.

[0037] Currently, existing technologies have the following drawbacks: 1. High-speed movement leads to severe performance degradation of OFDM: Traditional methods cannot cope with the high Doppler scenarios of low-altitude UAVs.

[0038] 2. Insufficient utilization of channel sparsity: Multipath propagation exists in complex low-altitude environments, but the sparse structure is not fully utilized.

[0039] 3. Existing detection algorithms have high complexity: ZF (Zero Forcing) / MMSE (Minimum Mean Square Error) require inverse matrices in linear calculations, and MP (Matching Pursuit) algorithms have many iterations, making them unsuitable for low-altitude real-time communication.

[0040] Based on the aforementioned shortcomings, this application aims to construct an OTFS signal detection method for low-altitude UAV communication to address the performance bottlenecks caused by high-speed movement, multipath sparsity, and real-time computational load. Specifically, it includes: 1. To address the Doppler spread caused by high-speed movement, a detection framework is designed that can stably characterize channel properties in the time-delay-Doppler domain, thereby improving detection accuracy in high-speed environments.

[0041] 2. By utilizing the sparse structure characteristics of low-altitude channels and employing a hierarchical detection strategy, the sparsity of multipath can be effectively utilized to improve detection efficiency.

[0042] 3. By constructing a lightweight detection process, the overall detection complexity is significantly reduced, thereby meeting the real-time requirements of low-altitude UAV communication scenarios.

[0043] This application relates to an OTFS signal detection method based on the time delay-Doppler domain. Its technical solution consists of multiple steps, and there are clear logical relationships, data flow relationships and functional coupling relationships between the steps.

[0044] In the method flow of this application, the various steps form a processing structure that unfolds layer by layer from the transmitting end to the receiving end, and from the time domain to the time-delay-Doppler domain. Within the OTFS transform domain framework, this application constructs a processing mechanism that can reduce computational complexity and improve detection accuracy, forming a complete signal detection process.

[0045] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will now be described with reference to the accompanying drawings.

[0046] This application provides an OTFS signal detection method. The processing flow of this method can be implemented by electronic devices, such as computers, handheld smart terminals, etc. For ease of explanation, the embodiments of this application are described with the computer as the subject of the method execution.

[0047] Figure 1 This is a schematic diagram of the OTFS signal detection method provided in an embodiment of this application. Figure 2 This is a schematic diagram of the OTFS signal processing flow for low-altitude UAV communication provided in an embodiment of this application, as shown below. Figure 1 as well as Figure 2 As shown, this application provides an OTFS signal detection method, the method comprising S1-S6, as follows: S1: Based on the mission data sent by the low-altitude UAV communication terminal or ground control station, perform constellation modulation and map it into the time delay-Doppler domain; In low-altitude UAV communication scenarios, assuming an ideal single-path channel, its fading coefficient is... The delay is Doppler frequency shift is ,in, l and k These represent the index values ​​for time delay and Doppler frequency shift, respectively; the information symbols are... The size of the information symbol is ,in Represents the time delay axis index coordinate. This represents the Doppler axis index coordinates. Then, in the time-delay-Doppler domain, the transmitted information symbols... It can be represented as follows:

[0048] To address the Doppler spread caused by low-altitude drones during flight, a time delay dimension is reserved at the end. M A blank unit is reserved at both ends of the Doppler dimension. N A blank cell is used to reduce signal "out-of-bounds" caused by high-speed movement. After OTFS transformation, the signal is converted to the time domain for transmission via air-to-ground link.

[0049] In some embodiments, S1 includes: Define the time delay dimension as M, the Doppler dimension as N, and the time delay-Doppler domain transmitted signal as... At the transmitting end, the time-delayed Doppler domain signal Two-dimensional time-domain signals are obtained by inverse symplectic finite Fourier transform (ISFFT) and Heisenberg transform. : ; in, Represents the N-point inverse Fourier transform matrix; Two-dimensional time-domain signals After parallel-to-serial conversion, the transmitted signal in the time domain is obtained. .

[0050] Figure 3 This is a schematic diagram of the "out-of-bounds" phenomenon cyclic shift provided in the embodiments of this application, such as... Figure 3 As shown, during the transmission process, Performing a two-dimensional convolution between the matrix and the channel matrix can potentially cause the received signal to "cross the boundary." "Crossing the boundary" refers to the received signal... In the time-delay-Doppler domain, only defined as Within a two-dimensional grid, where the time delay dimension ranges from 1 to 2. The range of Doppler dimensions is When the symbol of the actual received signal falls outside the grid position of this range, it is considered to have "crossed the boundary". By reserving M blank units at the end of the time delay dimension of the time delay-Doppler domain signal and N blank units at both ends of the Doppler dimension, the phenomenon of "crossing the boundary" of the received signal can be effectively avoided.

[0051] S2: Based on the multipath propagation characteristics and Doppler effect of low-altitude air-to-ground links, a time-frequency dual-dispersion channel model is constructed to obtain the received signal at the receiver. In low-altitude UAV communication, the channel exhibits delay spread and Doppler characteristics, the sources of which include building reflection, ground scattering, and UAV body reflection. In some embodiments, S2 includes: Send signals in the time domain After time-frequency bicolor dispersive channel Transmission occurs during this process, where the time-frequency bidispersive channel matrix... for:

[0052] in, L Indicates that the channel has K One transmission path, i Indicates the first i Path, and These represent the index values ​​for time delay and Doppler frequency shift, respectively. Indicates the first i The fading coefficient of the path; the first path i The delay of the path is , , Representing the time delay matrix, we can obtain , I For the identity matrix; the first i Doppler for each path , , Representing the Doppler matrix, we can obtain , , ; The received signal at the receiving end is obtained by analyzing both the case where the boundary crossing phenomenon occurs and the case where the boundary crossing phenomenon does not occur. Here, "out of bounds" refers to the received signal falling outside the M×N two-dimensional grid in the time-delay-Doppler domain, where M is the time delay dimension range and N is the Doppler dimension range.

[0053] In some embodiments, including: When no boundary crossing occurs and ; The time-domain received signal at the receiving end matrix form for:

[0054] Among them, the information symbols are The size of the information symbol is , Represents the time delay axis index coordinate. Represents the Doppler axis index coordinates; right After serial-to-parallel conversion, a two-dimensional time-domain received signal is obtained. .

[0055] In some embodiments, including: When a boundary violation occurs or ; The time-domain received signal at the receiving end matrix form for:

[0056] Among them, the information symbols are The size of the information symbol is , Represents the time delay axis index coordinate. Represents the Doppler axis index coordinates; right After serial-to-parallel conversion, a two-dimensional time-domain received signal is obtained. .

[0057] S3: Perform an inverse OTFS (Orthogonal Time Delay-Doppler Modulation) transform on the received signal to convert the received signal... The signal is obtained by converting from the time domain to the time-delay-Doppler domain. ; In some embodiments, S3 includes: obtaining the time-delay-Doppler domain received signal using the following formula. : .

[0058] S4: Based on the characteristics of line-of-sight path and ground object reflection path in low-altitude UAV communication, the signal is received using the time-delay-Doppler domain. The interference-free area information symbols in the data are used to estimate part of the transmitted signal. ; In low-altitude UAV communication, direct path signals correspond to air-to-ground line-of-sight links, while non-direct paths are mostly paths generated by reflections from ground objects or buildings. In some embodiments, S4 includes: By estimating the direct path component using signals from interference-free areas, a preliminary recovery of the main communication path can be achieved.

[0059] in, This represents the additional phase matrix corresponding to the first path. Represents deconvolution operation. Represents the inverse operation of the Hadamard product; Among them, the time-delay-Doppler domain channel matrix The expression is: .

[0060] In a two-dimensional convolution model based on the time-delay-Doppler domain, information symbols are... and delay-Doppler domain channel matrix The received signal is obtained by performing two-dimensional convolution. .

[0061] The received signal obtained after two-dimensional convolution The expression is:

[0062] Received signal The amplitude is:

[0063] For the same information symbol The received signal obtained through a time-domain-based linear product model is The received signal obtained through a two-dimensional convolution model based on the time-delay-Doppler domain is .in, and The two have the same amplitude, differing only in phase, that is, in The result is appended with an information symbol Delay-Doppler Domain Channel The relevant phase value can then be obtained. .

[0064] The expression for the additional phase matrix P is as follows:

[0065] In a single-path channel, two model results can be obtained according to formula (3-14). and The equivalent conversion relationship between them is as follows:

[0066] in, It represents the Hadamardi (or Hadama) stack.

[0067] S5: Based on the multipath characteristics in low-altitude communication environments, calculate the interference symbols of non-direct paths. And receive signals in the time-delay-Doppler domain. Eliminate interference at the appropriate locations; In some embodiments, S5 includes: Interference symbols for non-direct paths as follows:

[0068] in, ; Receiving signals Eliminate interference at appropriate locations: .

[0069] S6: Iterative update of interference-free area and convergence of global detection: As path interference is gradually eliminated, the area originally covered by interference will be transformed into a new interference-free area. This step dynamically updates the interference-free area based on the current detection results and repeats S4 and S5 to gradually expand the detection range from local to global.

[0070] To verify the effectiveness and superiority of the low-altitude OTFS signal detection method proposed in this application, a systematic comparative analysis of the performance differences between the proposed method and traditional detection methods is conducted based on simulation results under typical low-altitude UAV communication channel conditions.

[0071] Figure 4 This is a schematic diagram comparing the complexity of the OTFS signal detection method for low-altitude UAV communication provided in the embodiments of this application, as shown below. Figure 4 As shown, the overall complexity difference between the hierarchical path cancellation and iterative update mechanism proposed in this application and traditional ZF, MMSE and MP algorithms is demonstrated.

[0072] Traditional ZF / MMSE methods require inverse operations on the equivalent channel matrix, which significantly increases complexity when the number of multipaths is large or the grid size is high, making it difficult to meet the real-time processing requirements of low-altitude UAVs. The method in this application relies on the sparse structure of the delay-Doppler domain, which only needs to perform hierarchical processing on direct paths and a few non-direct paths, and adopts a local iterative update strategy, which significantly reduces the amount of computation. The complexity curve is better than traditional algorithms under various parameter scales, fully demonstrating its lightweight characteristics.

[0073] Figure 5 This is a performance simulation comparison diagram of the OTFS signal detection method for low-altitude UAV communication provided in the embodiments of this application, as shown in the figure. Figure 5 As shown, the comparison of the bit error rate (BER) performance of the proposed method and the benchmark detection algorithm in typical low-altitude high-speed scenarios is presented. The results show that when the Doppler spread is high, the traditional OFDM correlation detection method is affected by rapid channel changes, and the BER reduction is limited. The traditional OTFS correlation detection method is still limited in performance when facing severe out-of-bounds convolution and multipath interference. The proposed method, through the structure of "interference-free direct path estimation + non-direct path step-by-step cancellation + iterative full-domain detection", can reduce the error accumulation problem caused by out-of-bounds interference.

[0074] This application provides an OTFS signal detection method, which has the following advantages: (1) This application addresses the two-dimensional boundary crossing problem in the time-delay-Doppler domain of low-altitude UAV communication by proposing a structured mechanism for constructing a guard band in the time-delay-Doppler dimension. This mechanism not only adapts parameters according to the dynamic physical characteristics of the low-altitude channel, but also significantly suppresses symbol interference caused by boundary crossing cyclic shift by limiting the effective scope of the two-dimensional convolution.

[0075] (2) This application proposes an interference-free region identification mechanism by taking advantage of the stable and predictable propagation characteristics of low-altitude LOS paths. This mechanism extracts the structured region that is not affected by scattering and reflection paths in the time-delay-Doppler two-dimensional domain, and thereby realizes the reliable recovery of the direct path symbol.

[0076] (3) Given the naturally separable parameters of low-altitude multipath in the time-delay-Doppler domain, this application proposes a path-by-path interference cancellation mechanism. By parameterizing each non-direct path and performing targeted cancellation at the corresponding grid position in the two-dimensional domain, a refined processing of complex scattering paths is achieved.

[0077] It should be understood that although the steps in the flowcharts of the above embodiments are shown sequentially according to the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless explicitly stated herein, there is no strict order restriction on the execution of these steps, and they can be executed in other orders. Moreover, at least some of the steps in the figures 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, and their execution order is not necessarily sequential, but can be performed alternately or in turn with other steps or at least some of the sub-steps or stages of other steps.

[0078] Figure 6 This is a schematic diagram of the OTFS signal detection device provided in the embodiments of this application, as shown below. Figure 6 As shown, this application provides an OTFS signal detection device, the device comprising: The modulation mapping module 11 is configured to perform constellation modulation on mission data sent by the low-altitude UAV communication terminal or ground control station and map it into the time delay-Doppler domain. Channel model module 12 is configured to construct a time-frequency dual-dispersion channel model based on the multipath propagation characteristics and Doppler effect of low-altitude air-to-ground links to obtain the received signal at the receiver. The signal conversion module 13 is configured to perform an inverse orthogonal time delay-Doppler modulation (OTFS) transform on the received signal, converting the received signal from the time domain to the time delay-Doppler domain, and obtaining the time delay-Doppler domain received signal. The signal estimation module 14 is configured to estimate part of the transmitted signal based on the characteristics of line-of-sight path and ground object reflection path in low-altitude UAV communication, using the interference-free zone information symbols in the time-delay-Doppler domain received signal. The interference cancellation module 15 is configured to calculate the interference symbols of non-direct paths based on the multipath characteristics in the low-altitude communication environment, and cancel the interference at the corresponding position of the received signal in the time-delay-Doppler domain. The iterative update module 16 is set to iterative update of the interference-free area and convergence of the global detection: dynamically update the interference-free area according to the current detection results, and repeatedly perform signal estimation and interference cancellation, so that the detection range gradually expands from the local to the global range.

[0079] Regarding the limitations on the OTFS signal detection device, please refer to the limitations on the OTFS signal detection method in the above embodiments of this application, which will not be repeated here.

[0080] Figure 7 Another schematic diagram of the OTFS signal detection device provided in the embodiments of this application is shown below. Figure 7 As shown, the device includes a memory 22 and a processor 21. The memory stores a computer program, and the processor is configured to run the computer program to perform the methods described in the above embodiments of this application.

[0081] The memory is connected to the processor. The memory can be flash memory, read-only memory or other types of memory. The processor can be a central processing unit or a microcontroller.

[0082] In some embodiments, this application provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the methods described in the above embodiments of this application.

[0083] The computer-readable storage medium includes volatile or non-volatile, removable or non-removable media implemented in any method or technology for storing information, such as computer-readable instructions, data structures, computer program modules or other data. Computer-readable storage media include, but are not limited to, RAM (Random Access Memory), ROM (Read-Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), flash memory or other memory technologies, CD-ROM (Compact Disc Read-Only Memory), DVD or other optical disc storage, cartridges, magnetic tapes, disk storage or other magnetic storage devices, or any other medium that can be used to store desired information and is accessible to a computer.

[0084] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of this application, and this application is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and substance of this application, and these modifications and improvements are also considered to be within the scope of protection of this application.

Claims

1. An OTFS signal detection method, characterized in that, The method includes: S1: Based on the mission data sent by the low-altitude UAV communication terminal or ground control station, perform constellation modulation and map it into the time delay-Doppler domain; S2: Based on the multipath propagation characteristics and Doppler effect of low-altitude air-to-ground links, a time-frequency dual-dispersion channel model is constructed to obtain the received signal at the receiver. S3: Perform an inverse OTFS transform on the received signal to convert the received signal from the time domain to the time-delay-Doppler domain, thus obtaining the time-delay-Doppler domain received signal. S4: Based on the line-of-sight path and ground object reflection path characteristics in low-altitude UAV communication, partial transmitted signals are estimated by utilizing the interference-free zone information symbols in the time-delay-Doppler domain received signals. S5: Based on the multipath characteristics in the low-altitude communication environment, calculate the interference symbols of non-direct paths and eliminate the interference at the corresponding position of the received signal in the time-delay-Doppler domain; S6: Iterative update of the interference-free region and convergence of global detection: Dynamically update the interference-free region based on the current detection results, and repeat S4 and S5 to gradually expand the detection range from local to global.

2. The OTFS signal detection method according to claim 1, characterized in that, S1 includes: Define the time delay dimension as M, the Doppler dimension as N, and the time delay-Doppler domain transmitted signal as... At the transmitting end, the time-delayed Doppler domain signal Two-dimensional time-domain signals are obtained by inverse symplectic finite Fourier transform (ISFFT) and Heisenberg transform. : ； in, Represents the N-point inverse Fourier transform matrix; Two-dimensional time-domain signals After parallel-to-serial conversion, the time-domain transmitted signal is obtained. .

3. The OTFS signal detection method according to claim 2, characterized in that, S2 includes: Send signals in the time domain After time-frequency bicolor dispersive channel Transmission occurs during this process, where the time-frequency bidispersive channel matrix... for: in, L Indicates that the channel has K One transmission path, i Indicates the first i Path, and These represent the index values ​​for time delay and Doppler frequency shift, respectively. Indicates the first i The fading coefficient of the path; the first path i The delay of the path is , , Representing the time delay matrix, we can obtain , I For the identity matrix; the first i Doppler for each path , , Representing the Doppler matrix, we can obtain , , ; The received signal at the receiving end is obtained by analyzing both the case where the boundary crossing phenomenon occurs and the case where the boundary crossing phenomenon does not occur. Here, "out of bounds" refers to the received signal falling outside the M×N two-dimensional grid in the time-delay-Doppler domain, where M is the time delay dimension range and N is the Doppler dimension range.

4. The OTFS signal detection method according to claim 3, characterized in that, include: When no boundary crossing occurs and ; The time-domain received signal at the receiving end matrix form for: Among them, the information symbols are The size of the information symbol is , Represents the time delay axis index coordinate. Represents the Doppler axis index coordinates; right After serial-to-parallel conversion, a two-dimensional time-domain received signal is obtained. .

5. The OTFS signal detection method according to claim 3, characterized in that, include: When a boundary violation occurs or ; The time-domain received signal at the receiving end matrix form for: Among them, the information symbols are The size of the information symbol is , Represents the time delay axis index coordinate. Represents the Doppler axis index coordinates; right After serial-to-parallel conversion, a two-dimensional time-domain received signal is obtained. .

6. The OTFS signal detection method according to claim 1, characterized in that, S3 includes: The time-delay-Doppler domain received signal is obtained using the following formula. : 。 7. The OTFS signal detection method according to claim 1, characterized in that, S4 includes: By estimating the direct path component using signals from interference-free areas, a preliminary recovery of the main communication path can be achieved. in, This represents the additional phase matrix corresponding to the first path. Represents deconvolution operation. Represents the inverse operation of the Hadamard product; Among them, the time-delay-Doppler domain channel matrix The expression is: 。 8. The OTFS signal detection method according to claim 1, characterized in that, S5 includes: Interference symbols for non-direct paths as follows: in, ; Receiving signals Eliminate interference at appropriate locations: 。 9. An OTFS signal detection device, characterized in that, The device includes: The modulation mapping module is configured to perform constellation modulation on mission data sent by low-altitude UAV communication terminals or ground control stations and map it into the time-delay-Doppler domain. The channel model module is configured to construct a time-frequency dual-dispersion channel model based on the multipath propagation characteristics and Doppler effect of low-altitude air-to-ground links, and obtain the received signal at the receiver. The signal conversion module is configured to perform an inverse orthogonal time delay-Doppler modulation (OTFS) transform on the received signal, converting the received signal from the time domain to the time delay-Doppler domain, and obtaining the time delay-Doppler domain received signal. The signal estimation module is configured to estimate part of the transmitted signal based on the characteristics of line-of-sight path and ground object reflection path in low-altitude UAV communication, using the interference-free zone information symbols in the time-delay-Doppler domain received signal. The interference cancellation module is configured to calculate the interference symbols of non-direct paths based on the multipath characteristics in the low-altitude communication environment, and cancel the interference at the corresponding position of the received signal in the time-delay-Doppler domain. The iterative update module is configured to perform iterative updates in the interference-free area and convergence of the global detection: it dynamically updates the interference-free area based on the current detection results and repeatedly performs signal estimation and interference cancellation, so that the detection range gradually expands from the local area to the global area.

10. An OTFS signal detection device, characterized in that, It includes a memory and a processor, wherein the memory stores a computer program and the processor is configured to run the computer program to implement the OTFS signal detection method as described in any one of claims 1-8.

11. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the OTFS signal detection method as described in any one of claims 1-8.

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