VDES downlink burst detection method and apparatus

Abstract

The application relates to a VDES downlink burst detection method and device, the method is applied to a terminal of VDES and comprises the following steps: sampling and receiving a baseband signal of a to-be-detected downlink, obtaining an initial synchronization word position and a coarse frequency offset estimation value according to the received signal, obtaining a subsequent each synchronization word rough position based on the initial synchronization word position, determining a real position of the subsequent each synchronization word according to the coarse frequency offset estimation value and the subsequent each synchronization word rough position, intercepting data segments between all adjacent synchronization word positions from the received signal according to the initial synchronization word position and the real position of the subsequent each synchronization word, and splicing the data segments in sequence after pre-compensating the frequency offset of the data segments, so that complete burst effective data is obtained, and burst detection is realized.

Description

Technical Field

[0001] This invention relates to the field of wireless communication technology, and more specifically to a VDES downlink burst detection method and apparatus. Background Technology

[0002] VDES (Very High Frequency Data Exchange System) is a standard developed by the ITU-R (International Telecommunication Union Radiocommunication Sector) for maritime mobile communications, used to support satellite-to-ship and ship-to-satellite communications. Satellite communications are characterized by wide coverage, long communication distances, large frequency offset ranges, and a large number of users within the coverage area, resulting in a relatively harsh communication environment.

[0003] VDE (Wideband VHF Data Exchange) is the primary method for high-speed data transmission in VDES. To match the asymmetric communication needs between ship stations and satellites, the system adopts a design with short uplink time slots and long downlink time slots. Furthermore, in the downlink design, by adding more redundant bits and employing bit interleaving and forward error correction coding techniques, the transient effects of deep fading are homogenized, effectively improving the probability of successful data decoding. However, the VDES system is a burst detection system; to achieve successful data demodulation, burst synchronization word detection is first required to locate the start of the signal.

[0004] In existing technologies, differential synchronization word detection or time-frequency traversal detection methods are typically used to find the position of the first synchronization word of the burst signal. Then, based on this position, the signal start position is deduced, and the data of the corresponding link length is extracted for subsequent demodulation. However, this method ignores the dynamic time delay changes caused by the high-speed movement of the satellite, which leads to decoding failure after directly downsampling and demodulating the extracted data. Summary of the Invention

[0005] The purpose of this invention is to provide a method and apparatus for burst detection in VDES downlink, so as to solve the signal acquisition problem in VDES downlink scenarios with long time slots, large frequency offset, and low signal-to-noise ratio.

[0006] To achieve the above objectives, the present invention provides a VDES downlink burst detection method, which is applied to a VDES terminal and includes:

[0007] The baseband signal of the downlink under test is sampled and received to obtain the received signal;

[0008] The received signal is subjected to time-frequency ergodic detection to obtain the initial synchronization word position and coarse frequency offset estimate.

[0009] The local synchronization word sequence is compensated for frequency offset using the coarse frequency offset estimate to obtain a frequency offset calibrated local sequence.

[0010] Based on the initial synchronization word position and the parameters of the downlink to be detected, the approximate position of each subsequent synchronization word is calculated; based on the approximate position of each synchronization word, a candidate signal segment corresponding to the approximate position of the synchronization word is extracted from the received signal;

[0011] The candidate signal segment corresponding to the rough position of each subsequent synchronization word is subjected to sliding conjugate cross-correlation with the frequency offset calibration local sequence to obtain the correlation power sequence corresponding to the rough position of each subsequent synchronization word.

[0012] The actual position of the subsequent synchronization word is determined based on the relevant power sequence corresponding to the approximate position of each subsequent synchronization word.

[0013] Based on the initial synchronization word position and the actual position of each subsequent synchronization word, the data segments between all adjacent synchronization word positions are extracted from the received signal to obtain the synchronization word interval data segments.

[0014] The frequency offset is pre-compensated for each synchronization word interval data segment using the coarse frequency offset estimate to obtain each compensated synchronization word interval data segment; the compensated synchronization word interval data segments are then concatenated in chronological order to obtain complete burst valid data.

[0015] Optionally, based on the coarse position of each synchronization word, a candidate signal segment corresponding to the coarse position of the synchronization word is extracted from the received signal, specifically including:

[0016] Using the approximate position of each subsequent synchronization word as the center, expand N sampling points forward and backward to form a data window. Extract the received signal segment within the data window as the candidate signal segment corresponding to the approximate position of the subsequent synchronization word; where N is a positive integer.

[0017] Optionally, a sliding conjugate cross-correlation operation is performed on the candidate signal segment corresponding to the coarse position of each subsequent synchronization word and the frequency offset calibration local sequence to obtain the correlation power sequence corresponding to the coarse position of each subsequent synchronization word, specifically including:

[0018] For each subsequent coarse synchronization word position, the candidate signal segment corresponding to the subsequent coarse synchronization word position is subjected to a sliding conjugate cross-correlation operation with the frequency offset calibration local sequence. The results of each sliding operation are accumulated and summed to obtain the correlation operation result sequence. The modulus of the correlation operation result sequence is then squared to obtain the correlation power sequence corresponding to the subsequent coarse synchronization word position.

[0019] Optionally, the actual position of the subsequent synchronization word is determined based on the correlation power sequence corresponding to the approximate position of each subsequent synchronization word, specifically including:

[0020] Determine the location of the peak value of the relevant power sequence corresponding to the approximate position of each subsequent synchronization word;

[0021] The true position of each subsequent synchronization word is determined by the peak position of the relevant sequence corresponding to the approximate position of each subsequent synchronization word.

[0022] Optionally, the location of the peak value of the relevant power sequence corresponding to each subsequent coarse position of the synchronization word is determined, specifically including:

[0023] The values ​​in the relevant power sequence corresponding to the rough position of each subsequent synchronization word are continuously fed into the constant false alarm rate detector (CFAR), which determines the peak value and outputs the position of the peak value.

[0024] Another aspect of the present invention provides a VDES downlink burst detection device, which is applied to a VDES terminal and includes:

[0025] The receiving module is used to sample and receive the baseband signal of the downlink under test to obtain the received signal;

[0026] The detection module is used to perform time-frequency traversal detection on the received signal to obtain the initial synchronization word position and coarse frequency offset estimate.

[0027] The first pre-compensation module is used to perform frequency offset compensation on the local synchronization word sequence using the coarse frequency offset estimate to obtain a frequency offset calibrated local sequence.

[0028] The estimation module is used to estimate the approximate position of each subsequent synchronization word based on the initial synchronization word position and the parameters of the downlink to be detected; and based on the approximate position of each synchronization word, to extract the candidate signal segment corresponding to the approximate position of the synchronization word from the received signal.

[0029] The correlation operation module is used to perform sliding conjugate cross-correlation operation on the candidate signal segment corresponding to the coarse position of each subsequent synchronization word and the frequency offset calibration local sequence to obtain the correlation power sequence corresponding to the coarse position of each subsequent synchronization word.

[0030] The determination module is used to determine the true position of the subsequent synchronization word based on the relevant power sequence corresponding to the approximate position of each subsequent synchronization word.

[0031] The extraction module is used to extract the data segments between all adjacent synchronization word positions from the received signal based on the initial synchronization word position and the actual position of each subsequent synchronization word, thus obtaining the synchronization word interval data segments.

[0032] The second pre-compensation module is used to pre-compensate the frequency offset of each synchronization word interval data segment using the coarse frequency offset estimate, so as to obtain each compensated synchronization word interval data segment; the compensated synchronization word interval data segments are then spliced ​​together in chronological order to obtain complete burst valid data.

[0033] Optionally, based on the coarse position of each synchronization word, a candidate signal segment corresponding to the coarse position of the synchronization word is extracted from the received signal, specifically including:

[0034] Using the approximate position of each subsequent synchronization word as the center, expand N sampling points forward and backward to form a data window. Extract the received signal segment within the data window as the candidate signal segment corresponding to the approximate position of the subsequent synchronization word; where N is a positive integer.

[0035] Optionally, a sliding conjugate cross-correlation operation is performed on the candidate signal segment corresponding to the coarse position of each subsequent synchronization word and the frequency offset calibration local sequence to obtain the correlation power sequence corresponding to the coarse position of each subsequent synchronization word, specifically including:

[0036] For each subsequent coarse synchronization word position, the candidate signal segment corresponding to the subsequent coarse synchronization word position is subjected to a sliding conjugate cross-correlation operation with the frequency offset calibration local sequence. The results of each sliding operation are accumulated and summed to obtain the correlation operation result sequence. The modulus of the correlation operation result sequence is then squared to obtain the correlation power sequence corresponding to the subsequent coarse synchronization word position.

[0037] Optionally, the actual position of the subsequent synchronization word is determined based on the correlation power sequence corresponding to the approximate position of each subsequent synchronization word, specifically including:

[0038] Determine the location of the peak value of the relevant power sequence corresponding to the approximate position of each subsequent synchronization word;

[0039] The true position of each subsequent synchronization word is determined by the peak position of the relevant sequence corresponding to the approximate position of each subsequent synchronization word.

[0040] Optionally, the location of the peak value of the relevant power sequence corresponding to each subsequent coarse position of the synchronization word is determined, specifically including:

[0041] The values ​​in the relevant power sequence corresponding to the rough position of each subsequent synchronization word are continuously fed into the constant false alarm rate detector (CFAR), which determines the peak value and outputs the position of the peak value. Attached Figure Description

[0042] Figure 1 This is a flowchart of the VDES downlink burst detection method according to an embodiment of the present invention;

[0043] Figure 2 This is a structural block diagram of a VDES downlink burst detection device according to an embodiment of the present invention. Detailed Implementation

[0044] The preferred embodiments of the present invention are given below with reference to the accompanying drawings and described in detail.

[0045] The VDES downlink frame structure contains multiple synchronization words. The inventive concept of this invention is as follows: First, obtain the position and frequency offset of the first synchronization word of the link to be detected. Then, combine the parameters of the link to be detected to capture subsequent synchronization words one by one until all synchronization words are captured. Then, based on the positions of all captured synchronization words, extract the link data in segments and finally splice them into complete data for subsequent demodulation and decoding. By capturing each synchronization word, it is equivalent to splitting a long burst into multiple short bursts, thereby effectively solving the problem of long time slot timing deviation.

[0046] Based on the above inventive concept, such as Figure 1 As shown, this embodiment of the invention provides a VDES downlink burst detection method, which is applied to a VDES terminal and includes the following steps:

[0047] S100: Sample and receive the baseband signal of the downlink under test at a rate of M times the symbol rate to obtain the received signal.

[0048] The VDES terminal is equipped with a receiver that can sample and receive the baseband signal of the downlink under test at a rate of M times the symbol rate to obtain the received signal, which can be denoted as... M is a positive integer, and its specific value can be set as needed, for example, it can be 8.

[0049] S200: Perform time-frequency ergodic detection on the received signal to obtain the initial synchronization word position and coarse frequency offset estimate.

[0050] The method for performing time-frequency ergodic detection on the received signal can be any suitable method in the prior art, such as the method in patent application with publication number CN113783820A or patent application with publication number CN121690940A, and the present invention does not limit it.

[0051] S300: Use the coarse frequency offset estimate to perform frequency offset pre-compensation on the local synchronization word sequence to obtain the frequency offset calibrated local sequence.

[0052] The method for frequency offset pre-compensation is as follows:

[0053] ,

[0054] ,

[0055] in, To calibrate the local sequence for frequency offset, Here, j is the local synchronization word sequence, and j is the imaginary unit. This is a coarse frequency offset estimate. For symbol period, Where n is the symbol rate and n is the sampling point index. Synchronization word distance, which is the distance between two adjacent synchronization words as defined by the protocol.

[0056] S400: Calculate the approximate position of each subsequent synchronization word based on the initial synchronization word position and the parameters of the downlink to be detected; based on the approximate position of each synchronization word, extract the candidate signal segment corresponding to the approximate position of the synchronization word from the received signal.

[0057] The parameters of the downlink to be detected include synchronization word distance. Synchronized word count and synchronization word length The parameters of the downlink to be tested are specified by ITU-R M.2092-1, which is the core international standard for the Maritime VHF Data Exchange System (VDES) published by the International Telecommunication Union (ITU-R). For example, for downlink link 26, ITU-R M.2092-1 specifies that its synchronization word distance is 2268, the number of synchronization words is 35, and the synchronization word length is 27.

[0058] The formula for estimating the approximate position of each subsequent synchronization word is as follows:

[0059]

[0060] in, This is the initial synchronization word position. This is the approximate position of the i-th synchronization word. .

[0061] In some embodiments, based on the coarse position of each subsequent synchronization word, a candidate signal segment corresponding to the coarse position of that synchronization word is extracted from the received signal, specifically including:

[0062] Using the approximate position of each subsequent synchronization word as the center, expand N sampling points forward and backward to form a data window. Extract the received signal segment within the data window as the candidate signal segment corresponding to the approximate position of the subsequent synchronization word.

[0063] The candidate signal segment corresponding to the approximate position of the i-th synchronization word is: :

[0064]

[0065] N is a positive integer, which is based on the satellite altitude. The corresponding time delay change rate can be calculated based on the satellite orbital altitude, and combined with the receiver's receiving sampling rate, the maximum sampling point deviation within a burst can be calculated as N. For example, when the orbital altitude is 900km, N can be 64.

[0066] S500: For each subsequent coarse position of the synchronization word, perform a sliding conjugate cross-correlation operation on the candidate signal segment corresponding to the subsequent coarse position of the synchronization word and the frequency offset calibration local sequence to obtain the correlation power sequence corresponding to each subsequent coarse position of the synchronization word.

[0067] Step S500 specifically includes:

[0068] For each subsequent coarse synchronization word position, the candidate signal segment corresponding to the subsequent coarse synchronization word position is subjected to a sliding conjugate cross-correlation operation with the frequency offset calibration local sequence. The results of each sliding operation are accumulated and summed to obtain the correlation operation result sequence. The modulus of the correlation operation result sequence is then squared to obtain the correlation power sequence corresponding to the subsequent coarse synchronization word position.

[0069] The sliding window length for the sliding conjugate cross-correlation operation is The formulas for calculating the correlation result sequence and the correlation power sequence are as follows:

[0070]

[0071]

[0072] in, The results of the related calculations are obtained by summing. This is the relevant power sequence.

[0073] S600: Determine the actual position of the subsequent synchronization word based on the correlation power sequence corresponding to the approximate position of each subsequent synchronization word.

[0074] The position of the maximum value of the relevant power sequence corresponds to the actual position of the synchronization word. Step S600 specifically includes:

[0075] Determine the location of the peak value of the relevant power sequence corresponding to the approximate position of each subsequent synchronization word;

[0076] The true position of each subsequent synchronization word is determined by the peak position of the relevant sequence corresponding to the approximate position of each subsequent synchronization word.

[0077] For example, the method for determining the peak position of the relevant power sequence corresponding to each subsequent coarse position of synchronization word is as follows:

[0078] The values ​​in the relevant power sequence corresponding to the rough position of each subsequent synchronization word are continuously fed into the constant false alarm rate detector to find the peak value and output the position of the peak value.

[0079] The actual position of each subsequent synchronization word is calculated as follows:

[0080]

[0081] in, This represents the actual position of the i-th subsequent synchronization word. This indicates the location of the peak value of the relevant power sequence corresponding to the approximate position of each subsequent synchronization word.

[0082] S700: Based on the initial synchronization word position and the actual position of each subsequent synchronization word, extract the data segments between all adjacent synchronization word positions from the received signal to obtain the synchronization word interval data segments.

[0083] The initial synchronization word position and the actual position of each subsequent synchronization word constitute the set of synchronization word positions for the burst signal, denoted as: ,common Each synchronization word position.

[0084] Extract the data segment between all adjacent synchronization word positions from the received signal:

[0085]

[0086] Where k is the synchronization word sequence number. ; For the k-th value in the synchronization word position set, when k=1, When k > 1, ; This is the data segment between the k-th synchronization word position and the (k+1)-th synchronization word position, also known as the k-th synchronization word interval data segment.

[0087] S800: Use the coarse frequency offset estimate to perform frequency offset pre-compensation on each synchronization word interval data segment to obtain each compensated synchronization word interval data segment; then concatenate the compensated synchronization word interval data segments in time order to obtain complete burst valid data.

[0088] The calculation method for the compensated synchronization word interval data segment is as follows:

[0089]

[0090] in, This is the k-th compensated synchronization word interval data segment.

[0091] like Figure 2 As shown, this embodiment of the invention also provides a VDES downlink burst detection device, which is applied to a VDES terminal and includes a receiving module 10, a detection module 20, a first pre-compensation module 30, a calculation module 40, a correlation calculation module 50, a determination module 60, an extraction module 70, and a second pre-compensation module 80.

[0092] The receiving module 10 is used to sample and receive the baseband signal of the downlink under test to obtain the received signal;

[0093] The detection module 20 is used to perform time-frequency traversal detection on the received signal to obtain the initial synchronization word position and coarse frequency offset estimate.

[0094] The first pre-compensation module 30 is used to perform frequency offset compensation on the local synchronization word sequence using the coarse frequency offset estimate to obtain a frequency offset calibrated local sequence.

[0095] The estimation module 40 is used to estimate the approximate position of each subsequent synchronization word based on the initial synchronization word position and the parameters of the downlink to be detected; and based on the approximate position of each synchronization word, to extract the candidate signal segment corresponding to the approximate position of the synchronization word from the received signal.

[0096] The correlation operation module 50 is used to perform sliding conjugate cross-correlation operation on the candidate signal segment corresponding to the coarse position of each subsequent synchronization word and the frequency offset calibration local sequence to obtain the correlation power sequence corresponding to the coarse position of each subsequent synchronization word.

[0097] The determination module 60 is used to determine the true position of the subsequent synchronization word based on the relevant power sequence corresponding to the rough position of each subsequent synchronization word;

[0098] Extraction module 70 is used to extract data segments between all adjacent synchronization word positions from the received signal based on the initial synchronization word position and the actual position of each subsequent synchronization word, to obtain the synchronization word interval data segment.

[0099] The second pre-compensation module 80 is used to perform frequency offset pre-compensation on each synchronization word interval data segment using the coarse frequency offset estimate, so as to obtain each compensated synchronization word interval data segment; the compensated synchronization word interval data segments are then spliced ​​together in time order to obtain complete burst valid data.

[0100] The receiving module 10, the detection module 20, the first pre-compensation module 30, the calculation module 40, the correlation calculation module 50, the determination module 60, the extraction module 70, and the second pre-compensation module 80 are the functional modules corresponding to steps S100-S800 in the method embodiment. For a detailed description, please refer to the description in the method embodiment, which will not be repeated here.

[0101] The VDES downlink burst detection method and apparatus of this invention first obtains the position and frequency offset of the first synchronization word of the link to be detected, and then captures subsequent synchronization words one by one in combination with the parameters of the link to be detected until all synchronization words are captured; then, based on the positions of all captured synchronization words, the link data is extracted in segments and finally spliced ​​into complete data for subsequent demodulation and decoding; by capturing each synchronization word, it is equivalent to splitting a long burst into multiple short bursts, thereby effectively solving the problem of long time slot timing deviation.

[0102] Another embodiment of the present invention provides a readable storage medium having a computer program stored thereon, which, when executed in a computer, causes the computer to perform the steps of the method described in the above embodiments of the present invention.

[0103] Another embodiment of the present invention provides an electronic device, which includes a memory and a processor. The memory stores executable code, and when the processor executes the executable code, it performs the steps of the method in the above embodiments of the present invention.

[0104] The systems, devices, modules, or units described in the above embodiments can be implemented by computer chips or entities, or by products with certain functions. A typical implementation device is a computer. Specifically, a computer can be, for example, a personal computer, laptop computer, cellular phone, camera phone, smartphone, personal digital assistant, media player, navigation device, email device, game console, tablet computer, wearable device, or any combination of these devices.

[0105] For ease of description, the above apparatus is described by dividing it into various functional units. Of course, in implementing this invention, the functions of each unit can be implemented in one or more software and / or hardware components.

[0106] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0107] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0108] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0109] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0110] In a typical configuration, an electronic device includes one or more processors (CPU), input / output interfaces, network interfaces, and memory.

[0111] Memory may include non-persistent storage in computer-readable media, such as random access memory (RAM) and / or non-volatile memory, such as read-only memory (ROM) or flash RAM. Memory is an example of computer-readable media.

[0112] Computer-readable media includes both permanent and non-permanent, removable and non-removable media that can store information by any method or technology. Information can be computer-readable instructions, data structures, modules of programs, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, magnetic magnetic disk storage or other magnetic storage devices, or any other non-transferable medium that can be used to store information accessible by electronic devices. As defined herein, computer-readable media does not include transient computer-readable media, such as modulated data signals and carrier waves.

[0113] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0114] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0115] This invention can be described in the general context of computer-executable instructions, such as program modules, that are executed by a computer. Generally, program modules include routines, programs, objects, components, data structures, etc., that perform a specific task or implement a specific abstract data type. This invention can also be practiced in distributed computing environments where tasks are performed by remote processing devices connected via a communication network. In distributed computing environments, program modules can reside in local and remote computer storage media, including storage devices.

[0116] The various embodiments in this invention are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments.

[0117] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention. Various variations can be made to the above embodiments of the present invention. That is, all simple and equivalent changes and modifications made based on the claims and description of this invention fall within the protection scope of the claims of this patent. All aspects not described in detail in this invention are conventional technical content.

Claims

1. A method of VDES downlink burst detection, the method comprising: Terminals used in VDES, including: The baseband signal of the downlink under test is sampled and received to obtain the received signal; The received signal is subjected to time-frequency ergodic detection to obtain the initial synchronization word position and coarse frequency offset estimate. The local synchronization word sequence is compensated for frequency offset using the coarse frequency offset estimate to obtain a frequency offset calibrated local sequence. Based on the initial synchronization word position and the parameters of the downlink to be detected, the approximate position of each subsequent synchronization word is calculated; based on the approximate position of each synchronization word, a candidate signal segment corresponding to the approximate position of the synchronization word is extracted from the received signal; The candidate signal segment corresponding to the rough position of each subsequent synchronization word is subjected to sliding conjugate cross-correlation with the frequency offset calibration local sequence to obtain the correlation power sequence corresponding to the rough position of each subsequent synchronization word. The actual position of the subsequent synchronization word is determined based on the relevant power sequence corresponding to the approximate position of each subsequent synchronization word. Based on the initial synchronization word position and the actual position of each subsequent synchronization word, the data segments between all adjacent synchronization word positions are extracted from the received signal to obtain the synchronization word interval data segments. The frequency offset is pre-compensated for each synchronization word interval data segment using the coarse frequency offset estimate to obtain each compensated synchronization word interval data segment; the compensated synchronization word interval data segments are then concatenated in chronological order to obtain complete burst valid data.

2. The VDES downlink burst detection method of claim 1, wherein, Based on the approximate position of each synchronization word, a candidate signal segment corresponding to that approximate position is extracted from the received signal, specifically including: Using the approximate position of each subsequent synchronization word as the center, expand N sampling points forward and backward to form a data window. Extract the received signal segment within the data window as the candidate signal segment corresponding to the approximate position of the subsequent synchronization word; where N is a positive integer.

3. The VDES downlink burst detection method according to claim 1, characterized in that, The candidate signal segment corresponding to the coarse position of each subsequent synchronization word is subjected to a sliding conjugate cross-correlation operation with the frequency offset calibration local sequence to obtain the correlation power sequence corresponding to the coarse position of each subsequent synchronization word, specifically including: For each subsequent coarse synchronization word position, the candidate signal segment corresponding to the subsequent coarse synchronization word position is subjected to a sliding conjugate cross-correlation operation with the frequency offset calibration local sequence. The results of each sliding operation are accumulated and summed to obtain the correlation operation result sequence. The modulus of the correlation operation result sequence is then squared to obtain the correlation power sequence corresponding to the subsequent coarse synchronization word position.

4. The VDES downlink burst detection method according to claim 1, characterized in that, The actual position of the subsequent synchronization word is determined based on the relevant power sequence corresponding to the approximate position of each subsequent synchronization word, specifically including: Determine the location of the peak value of the relevant power sequence corresponding to the approximate position of each subsequent synchronization word; The true position of each subsequent synchronization word is determined by the peak position of the relevant sequence corresponding to the approximate position of each subsequent synchronization word.

5. The VDES downlink burst detection method according to claim 4, characterized in that, Determine the location of the peak value of the relevant power sequence corresponding to the approximate position of each subsequent synchronization word, specifically including: The values ​​in the relevant power sequence corresponding to the rough position of each subsequent synchronization word are continuously fed into the constant false alarm rate detector (CFAR), which determines the peak value and outputs the position of the peak value.

6. A VDES downlink burst detection device, characterized in that, Terminals used in VDES, including: The receiving module is used to sample and receive the baseband signal of the downlink under test to obtain the received signal; The detection module is used to perform time-frequency traversal detection on the received signal to obtain the initial synchronization word position and coarse frequency offset estimate. The first pre-compensation module is used to perform frequency offset compensation on the local synchronization word sequence using the coarse frequency offset estimate to obtain a frequency offset calibrated local sequence. The estimation module is used to estimate the approximate position of each subsequent synchronization word based on the initial synchronization word position and the parameters of the downlink to be detected; and based on the approximate position of each synchronization word, to extract the candidate signal segment corresponding to the approximate position of the synchronization word from the received signal. The correlation operation module is used to perform sliding conjugate cross-correlation operation on the candidate signal segment corresponding to the coarse position of each subsequent synchronization word and the frequency offset calibration local sequence to obtain the correlation power sequence corresponding to the coarse position of each subsequent synchronization word. The determination module is used to determine the true position of the subsequent synchronization word based on the relevant power sequence corresponding to the rough position of each subsequent synchronization word; The extraction module is used to extract the data segments between all adjacent synchronization word positions from the received signal based on the initial synchronization word position and the actual position of each subsequent synchronization word, thus obtaining the synchronization word interval data segments. The second pre-compensation module is used to pre-compensate the frequency offset of each synchronization word interval data segment using the coarse frequency offset estimate, so as to obtain each compensated synchronization word interval data segment; the compensated synchronization word interval data segments are then spliced ​​together in chronological order to obtain complete burst valid data.

7. The VDES downlink burst detection device according to claim 6, characterized in that, Based on the approximate position of each synchronization word, a candidate signal segment corresponding to that approximate position is extracted from the received signal, specifically including: Using the approximate position of each subsequent synchronization word as the center, expand N sampling points forward and backward to form a data window. Extract the received signal segment within the data window as the candidate signal segment corresponding to the approximate position of the subsequent synchronization word; where N is a positive integer.

8. The VDES downlink burst detection device according to claim 6, characterized in that, The candidate signal segment corresponding to the coarse position of each subsequent synchronization word is subjected to a sliding conjugate cross-correlation operation with the frequency offset calibration local sequence to obtain the correlation power sequence corresponding to the coarse position of each subsequent synchronization word, specifically including: For each subsequent coarse synchronization word position, the candidate signal segment corresponding to the subsequent coarse synchronization word position is subjected to a sliding conjugate cross-correlation operation with the frequency offset calibration local sequence. The results of each sliding operation are accumulated and summed to obtain the correlation operation result sequence. The modulus of the correlation operation result sequence is then squared to obtain the correlation power sequence corresponding to the subsequent coarse synchronization word position.

9. The VDES downlink burst detection device according to claim 6, characterized in that, The actual position of the subsequent synchronization word is determined based on the relevant power sequence corresponding to the approximate position of each subsequent synchronization word, specifically including: Determine the location of the peak value of the relevant power sequence corresponding to the approximate position of each subsequent synchronization word; The true position of each subsequent synchronization word is determined by the peak position of the relevant sequence corresponding to the approximate position of each subsequent synchronization word.

10. The VDES downlink burst detection device according to claim 9, characterized in that, Determine the location of the peak value of the relevant power sequence corresponding to the approximate position of each subsequent synchronization word, specifically including: The values ​​in the relevant power sequence corresponding to the rough position of each subsequent synchronization word are continuously fed into the constant false alarm rate detector (CFAR), which determines the peak value and outputs the position of the peak value.

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