A preamble structure based OFDM time-frequency synchronization method and device

Abstract

The present disclosure relates to a preamble structure-based OFDM time-frequency synchronization method and device. The method comprises: obtaining a received signal, wherein the received signal comprises a preamble structure, the preamble structure is composed of a prefix sequence and a training sequence, the prefix sequence and the training sequence are both based on a ZC sequence, the training sequence is flanked by a prefix sequence, and the training sequence does not comprise a prefix sequence. In the method provided by the present disclosure, since the prefix sequence and the training sequence are different sequences, and the cross-correlation of the ZC sequence is weak, the received signal will not produce a correlation peak in the prefix sequence part during the sliding correlation process, and only when the training sequence is completely aligned can a strong correlation peak be produced, thereby avoiding the platform effect of timing synchronization. Meanwhile, the timing correlation peak at the timing position obtained by the method provided by the present disclosure is relatively sharp, the timing accuracy is high, and the time-frequency synchronization algorithm is simple and easy to implement.

Description

Technical Field

[0001] This disclosure relates to the field of communication technology, and in particular to an OFDM time-frequency synchronization method and apparatus based on a preamble structure. Background Technology

[0002] Orthogonal Frequency Division Multiplexing (OFDM) is a highly efficient digital modulation technique that decomposes a high-speed data stream into multiple low-speed sub-data streams, which are then modulated onto multiple mutually orthogonal subcarriers for transmission. These subcarriers are closely arranged and orthogonal in the frequency domain, fully utilizing spectrum resources and improving spectral efficiency. Because the data is distributed across multiple subcarriers, even if some subcarriers are interfered with or faded, it will not seriously affect the overall signal, thus enhancing the signal's anti-interference and anti-fading performance.

[0003] OFDM system synchronization includes timing synchronization and carrier synchronization. Timing synchronization is used to determine the initial position of FFT (Fast Fourier Transform) demodulation. The timing position plays an important role in ensuring correct FFT demodulation and subsequent carrier frequency offset estimation and correction.

[0004] In burst communication systems, timing synchronization is primarily achieved by capturing the peak value of the timing metric function using a known preamble sequence, thereby achieving frequency synchronization. The preamble sequence mainly consists of sequences with good autocorrelation and cross-correlation properties, such as pseudo-noise (PN) sequences or constant amplitude zero autocorrelation (CAZAC) sequences. The SC algorithm in correlation techniques uses two repeated training sequences for synchronization; however, due to the cyclic prefix in the training sequence, the timing shift estimation function curve exhibits a flat top during sliding correlation operations, affecting the accuracy of timing position acquisition. The Minn algorithm in correlation techniques improves upon the SC algorithm by using four feature sequences for timing synchronization. While eliminating the flat-top effect, it suffers from high sidelobes. The Park algorithm in correlation techniques designs a training sequence structure with conjugate symmetry. Compared to the SC and Minn algorithms, this algorithm exhibits a larger peak value at the correct starting point, improving the accuracy of timing measurement, but still has relatively small sidelobes. Summary of the Invention

[0005] To address the aforementioned technical problems, this disclosure provides an OFDM time-frequency synchronization method and apparatus based on a preamble structure.

[0006] This disclosure provides an OFDM time-frequency synchronization method based on a preamble structure, comprising: acquiring a received signal, wherein the received signal includes a preamble structure, the preamble structure being composed of a prefix sequence and a training sequence, both the prefix sequence and the training sequence being based on ZC sequences, and the training sequence having a prefix sequence segment before and after it, and the training sequence not including the prefix sequence; mapping the received signal by sign bits to obtain received sign bit information; obtaining a correlation function based on the received sign bit information and a local sequence, wherein the local sequence is obtained based on the training sequence; and determining a timing position based on the correlation function to complete the time-frequency synchronization of the received signal.

[0007] Optionally, the above prefix sequence With the above training sequence They are respectively:

[0008] ;

[0009] ;

[0010] Where A and B are the sequence lengths, both A and B are positive integers, and B > A. p , q It is a non-zero integer. p Coprime to A q and B Coprime.

[0011] Optionally, obtaining the correlation function based on the received symbol bit information and the local sequence includes: performing a sliding conjugate correlation operation on the received symbol bit information and the local sequence to obtain the correlation function; the correlation function is... or ,in, For the nth value in the above local sequence, For the above received symbol information, N represents the number of related results, M represents the N related results grouped into groups of M for incoherent accumulation, m represents the starting position of the sliding window, and * represents conjugate.

[0012] Optionally, the above local sequence is ,in, ; This indicates that the sign bit of the data is taken; if the data is greater than 0, the result is 1, and if the data is less than 0, the result is -1. This represents the real part of a complex number. This represents the imaginary part of the complex number. The above training sequence is given.

[0013] Optionally, the above-mentioned received sign bit information ,in, The above received signal; This indicates that the sign bit of the data is taken; if the data is greater than 0, the result is 1, and if the data is less than 0, the result is -1. This represents the real part of a complex number. This represents the imaginary part of a complex number.

[0014] Optionally, determining the timing position based on the aforementioned related functions includes: determining the positioning point corresponding to the maximum value of the aforementioned related functions. The timing position is determined based on the aforementioned positioning points.

[0015] Optionally, it also includes: demodulating the received signal according to the aforementioned timing position, wherein the demodulated received signal is... ,in, Sampling time, , Sampling frequency, This is the initial phase; the frequency offset of the received signal is determined to be... ,in, The phase angle function is a complex number.

[0016] Based on the unified inventive concept, this disclosure also provides an OFDM time-frequency synchronization device based on a preamble structure, comprising: a signal receiving module for acquiring a received signal, wherein the received signal includes a preamble structure, the preamble structure being composed of a prefix sequence and a training sequence, both the prefix sequence and the training sequence being based on ZC sequences, and the training sequence having a prefix sequence segment before and after it, and the training sequence not including the prefix sequence; a first calculation module for mapping the received signal by sign bits to obtain received sign bit information; a second calculation module for obtaining a correlation function based on the received sign bit information and a local sequence, wherein the local sequence is obtained based on the training sequence; and a time-frequency synchronization module for determining a timing position based on the correlation function to complete the time-frequency synchronization of the received signal.

[0017] Based on the unified inventive concept, this disclosure also provides an electronic device, including: a processor; a memory for storing executable instructions; wherein the processor is configured to read the executable instructions from the memory and execute the executable instructions to implement any of the methods described above.

[0018] Based on the unified inventive concept, this disclosure also provides a computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the processor performs any of the above-described methods.

[0019] The technical solution provided in this disclosure has the following advantages compared with the prior art: In the method provided in this disclosure, since the prefix sequence and the training sequence are different sequences, and the cross-correlation of the ZC sequence is weak, no correlation peak will be generated in the prefix sequence part during the sliding correlation process of the received signal. A strong correlation peak will only be generated when it is completely aligned with the training sequence, thus avoiding the plateau effect of timing synchronization. At the same time, the timing correlation peak at the timing position obtained by the method provided in this disclosure is relatively sharp, the timing accuracy is high, and the time-frequency synchronization algorithm is simple and easy to implement. Attached Figure Description

[0020] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure.

[0021] To more clearly illustrate the technical solutions in the embodiments of this disclosure or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 A flowchart illustrating an OFDM time-frequency synchronization method based on a preamble structure provided in this disclosure embodiment;

[0023] Figure 2 A schematic diagram of a leader structure provided in an embodiment of this disclosure;

[0024] Figure 3 A constellation diagram of a ZC sequence;

[0025] Figure 4 This is a schematic diagram illustrating the positional relationship between a leading structure and a sliding window, provided in an embodiment of this disclosure.

[0026] Figure 5 A schematic diagram of simulation test results for a method provided in an embodiment of this disclosure;

[0027] Figure 6 A schematic diagram illustrating simulation test results for another method based on an embodiment of this disclosure;

[0028] Figure 7 A schematic diagram illustrating simulation test results for another method based on an embodiment of this disclosure;

[0029] Figure 8 A schematic diagram of an OFDM time-frequency synchronization device based on a preamble structure is provided in an embodiment of this disclosure;

[0030] Figure 9This is a schematic diagram of the hardware structure of an electronic device provided in an embodiment of this disclosure. Detailed Implementation

[0031] To better understand the above-mentioned objectives, features, and advantages of the embodiments of this disclosure, the solutions of the embodiments of this disclosure will be further described below. It should be noted that, unless otherwise specified, the embodiments of this disclosure and the features within them can be combined with each other.

[0032] Numerous specific details are set forth in the following description in order to provide a full understanding of the embodiments of this disclosure, but the embodiments of this disclosure may also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of the embodiments of this disclosure, and not all embodiments.

[0033] This disclosure provides an OFDM time-frequency synchronization method based on a preamble structure, such as... Figure 1 As shown, it includes:

[0034] S1. Acquire the received signal, wherein the received signal includes a preamble structure, the preamble structure as follows: Figure 2 As shown, from the prefix sequence With training sequence constitute, Represents prefix sequence Length, Represents the training sequence The length of the prefix sequence, in specific implementation. The length can be set according to the maximum multipath delay, training sequence The length can be set according to the minimum signal-to-noise ratio required by the system. In specific implementation, the training sequence... Used for timed synchronization, prefix sequence Then used to determine the training sequence The position. In this embodiment of the disclosure, the prefix sequence With training sequence All are based on ZC sequences, training sequences There is a prefix sequence before and after it. Training sequence Prefix sequences are not included. That is, prefix sequence Not a training sequence It is not part of a sequence, but a separate, independent sequence.

[0035] S2. Map the received signal according to the sign bit to obtain the received sign bit information.

[0036] S3. Obtain the relevant function based on the received symbol bit information and the local sequence, where the local sequence is obtained based on the training sequence, specifically, the local sequence is the bit information of the training sequence.

[0037] S4. Determine the timing position based on the relevant function to complete the time-frequency synchronization of the received signal.

[0038] In related technologies, the conventional prefix sequence is the last segment of data in the training sequence, essentially copying the last segment of data from the training sequence directly to the beginning. Because the prefix sequence partially overlaps with the training sequence, during sliding correlation, in addition to a relatively strong correlation peak when the training sequence is perfectly aligned, a relatively small correlation peak, or sub-peak, is also generated in the prefix sequence. However, in the method provided by the embodiments of this disclosure, since the prefix sequence and the training sequence are different sequences, and the cross-correlation of the ZC sequence is weak, no correlation peak is generated in the prefix sequence during the sliding correlation process. A strong correlation peak is only generated when it is perfectly aligned with the training sequence, avoiding the plateau effect and excessively high sidelobes in timing synchronization. Furthermore, the timing correlation peak at the timing position obtained by the method provided by the embodiments of this disclosure is sharper, resulting in high timing accuracy, and the time-frequency synchronization algorithm is simple and easy to implement.

[0039] ZC (Zadoff-Chu) sequences are a class of complex sequences with good autocorrelation and cross-correlation properties, widely used in communication systems, especially in wireless communication, such as LTE (Long Term Evolution) and 5G technologies. ZC sequences have the following properties: 1) Constant envelope: The amplitude of a signal from a ZC sequence of arbitrary length is constant, i.e., the power is constant. In one specific embodiment, The constellation diagram of the ZC sequence (where N is the length of the sequence) is as follows: Figure 3 As shown, the horizontal axis represents the in-phase component, and the vertical axis represents the quadrature component; 2) Ideal periodic autocorrelation; 3) Weak cross-correlation: after the ZC sequence is cyclically shifted by N, the original sequence only has a correlation peak with the shifted sequence, and the correlation peak with the sequence at other positions is 0. In addition, if the two roots are coprime, the correlation peak of the generated sequence is almost zero; 4) It is still a ZC sequence after Fourier transform. The ZC sequence can be used for both time-domain correlation detection and frequency-domain correlation detection; 5) The peak-to-average power ratio of the ZC sequence is low. Since the ZC sequence is a ZC sequence in both the time and frequency domains and the amplitude is constant, it is beneficial for the RF power amplifier signal to achieve maximum efficiency.

[0040] In one specific embodiment, the ZC sequence expression is referenced to the following formula, and the above prefix sequence and training sequence can be generated according to the following formula:

[0041] ;

[0042] in, It is the length of the sequence, usually a positive integer. It is a non-zero integer, and Coprime, typically taking the value , It is the imaginary unit.

[0043] In some embodiments, the prefix sequence With training sequence They are respectively:

[0044] ; ;

[0045] Where A and B are the sequence lengths, both A and B are positive integers, and B > A. p , q It is a non-zero integer. p Coprime to A q and B Coprime, in specific implementation p and q One can be chosen.

[0046] In one specific embodiment, the prefix sequence With training sequence They are respectively:

[0047] ; .

[0048] Timing deviations can lead to phase and amplitude errors in frequency domain data, and even inter-symbol and inter-code interference. OFDM is highly sensitive to frequency offsets. A fractional multiple of a frequency offset destroys the orthogonality between subcarriers, causing inter-carrier interference and affecting the overall system performance. An integer multiple of a frequency offset causes cyclic shifts in the output subcarriers, resulting in an increased bit error rate in the demodulated data.

[0049] In view of this, in some embodiments, a correlation function is obtained based on the received symbol bit information and the local sequence, including:

[0050] The received sign bit information is correlated with the local sequence using a sliding conjugate correlation operation to obtain the correlation function, which is: or ,in, The nth value in the local sequence. To receive sign bit information, N represents the number of correlation results, M represents the N correlation results grouped into groups of M for incoherent accumulation, m represents the starting position of the sliding window, indicating that the received data starts from point m, selects data of length N to be correlated with the local sequence, and the N correlation results are grouped into groups of M for incoherent accumulation, and * represents conjugate.

[0051] In one specific embodiment, the aforementioned related functions The operation needs to be performed in segments, that is, the relevant functions mentioned above are In another specific embodiment, if the frequency offset is small, segmentation is not required, i.e., the above correlation function is... The timing correlation peak at the final timing position obtained from timing synchronization is the maximum value of the cross-correlation function between the local signal and the received signal at zero frequency offset. If the frequency offset is large, it will cause a phase difference between the received signal and the local signal that varies linearly with time. During coherent integration (correlation function calculation), this changing phase difference will cause the signal contributions at different times within the integration interval to cancel each other out, resulting in the amplitude of the final integration result (correlation peak) being lower than the ideal value. Segmented accumulation operation, by dividing the long integration time into multiple short segments, significantly reduces the phase rotation caused by the frequency offset within each segment, thereby greatly reducing the amplitude attenuation of the coherent correlation peak of the segment. By performing incoherent integration (accumulating the squared magnitude) on the correlation results of the segments, the influence of the phase change between segments caused by the frequency offset on the final accumulation result can be eliminated.

[0052] In some embodiments, the local sequence is ,in, ; This indicates that the sign bit of the data is taken; if the data is greater than 0, the result is 1, and if the data is less than 0, the result is -1. This represents the real part of a complex number. This represents the imaginary part of the complex number. This is the training sequence.

[0053] In some embodiments, receiving sign bit information ,in, To receive signals; This indicates that the sign bit of the data is taken; if the data is greater than 0, the result is 1, and if the data is less than 0, the result is -1. This represents the real part of a complex number. This represents the imaginary part of a complex number.

[0054] In some embodiments, the process of determining the timing position according to the relevant function in S4 above includes:

[0055] Determine the location point corresponding to the maximum value of the relevant function. The timing position is determined based on the positioning point.

[0056] The above analysis shows that the timing offset estimation correlation function exhibits a very sharp main peak. During sliding correlation calculations, the data positions entering the sliding window are as follows: Figure 4As shown, when the data within the sliding window corresponds completely to the local sequence, the correlation function value will show a large main peak. The location of the peak is the timing position. Loc also represents the point corresponding to the maximum value of the timing offset estimation function, i.e., the most ideal timing position.

[0057] In some embodiments, the above method further includes:

[0058] The frequency offset of the received signal is estimated based on the timing position.

[0059] In some embodiments, estimating the frequency offset of the received signal based on the timing position includes:

[0060] Based on the obtained timing position, the received signal needs to be demodulated first. If noise is ignored (the demodulated received signal only has frequency offset remaining), the demodulated received signal is... Further calculations yielded ,but:

[0061] .

[0062] .

[0063] in, Sampling time, , Sampling frequency, For the first phase, It is only a single symbol used to represent and The result of conjugate multiplication.

[0064] This disclosure also provides two simulation test results, such as... Figure 5 and Figure 6 As shown, the simulation parameters include the sampling rate. Training sequence length Frequency offset range .

[0065] Figure 5 The graph shows the relationship between the correlation function value and the starting position of the sliding window, with a signal-to-noise ratio of -5dB and a timing position of 65. As can be seen from the graph, the correlation peak at the starting position of the sliding window (65) is quite sharp, and this peak only occurs during the sliding window and the training sequence. Peak values ​​only occur when fully aligned; side lobes are absent. Figure 6 The graph shows the relationship between timing error detection probability and signal-to-noise ratio (SNR). The horizontal axis represents SNR. As can be seen from the graph, the probability of timing error detection gradually decreases as the SNR increases. When the SNR is greater than -1 dB, the error detection probability is less than 10^(-6). Figure 7The horizontal axis represents the signal-to-noise ratio (SNR), and the vertical axis represents the root mean square error of the frequency offset estimation. As can be seen from the figure, the frequency offset estimation error decreases as the SNR increases.

[0066] It should be noted that the method in this embodiment can be executed by a single device, such as a computer or server. The method can also be applied in a distributed scenario, where multiple devices cooperate to complete the task. In such a distributed scenario, one of these devices may execute only one or more steps of the method in this embodiment, and the multiple devices will interact with each other to complete the method.

[0067] It should be noted that the above description describes some embodiments of this application. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recorded in the claims can be performed in a different order than that shown in the above embodiments and still achieve the desired result. Furthermore, the processes depicted in the drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0068] Based on the same inventive concept, corresponding to any of the methods in the above embodiments, this application also provides an OFDM time-frequency synchronization device based on a preamble structure, such as... Figure 8 As shown, it includes:

[0069] The signal receiving module 10 is used to acquire the received signal, wherein the received signal includes a preamble structure, which is composed of a prefix sequence and a training sequence. Both the prefix sequence and the training sequence are based on ZC sequences. There is a prefix sequence before and after the training sequence, but the training sequence does not include the prefix sequence.

[0070] The first calculation module 20 is used to map the received signal according to the sign bit to obtain the received sign bit information.

[0071] The second calculation module 30 is used to obtain a correlation function based on the received symbol bit information and the local sequence, wherein the local sequence is obtained based on the training sequence.

[0072] The time-frequency synchronization module 40 is used to determine the timing position according to the relevant function and complete the time-frequency synchronization of the received signal.

[0073] In the apparatus provided in the above embodiments of this disclosure, since the prefix sequence and the training sequence are different sequences, and the cross-correlation of the ZC sequence is weak, no correlation peak is generated in the prefix sequence portion during the sliding correlation process of the received signal. A strong correlation peak is only generated when it is completely aligned with the training sequence, thus avoiding the plateau effect and excessively high sidelobes in timing synchronization. Furthermore, the timing correlation peak at the timing position obtained by the apparatus provided in the embodiments of this disclosure is relatively sharp, resulting in high timing accuracy, and the time-frequency synchronization algorithm is simple and easy to implement.

[0074] For ease of description, the above devices are described in terms of function, divided into various modules. Of course, in implementing this application, the functions of each module can be implemented in one or more software and / or hardware.

[0075] The apparatus of the above embodiments is used to implement the corresponding OFDM time-frequency synchronization method based on the preamble structure in any of the foregoing embodiments, and has the beneficial effects of the corresponding method embodiments, which will not be repeated here.

[0076] Figure 9 A schematic diagram of the structure of an electronic device provided in an embodiment of this disclosure is shown.

[0077] like Figure 9 As shown, the electronic device may include a processor 1101 and a memory 1102 storing computer program instructions.

[0078] Specifically, the processor 1101 may include a central processing unit (CPU), an application-specific integrated circuit (ASIC), or one or more integrated circuits that can be configured to implement the embodiments of this application.

[0079] Memory 1102 may include a mass storage device for information or instructions. For example, and not limitingly, memory 1102 may include a hard disk drive (HDD), a floppy disk drive, flash memory, optical disk, magneto-optical disk, magnetic tape, or a Universal Serial Bus (USB) drive, or a combination of two or more of these. Where appropriate, memory 1102 may include removable or non-removable (or fixed) media. Where appropriate, memory 1102 may be internal or external to the integrated gateway device. In a particular embodiment, memory 1102 is a non-volatile solid-state memory. In a particular embodiment, memory 1102 includes read-only memory (ROM). Where appropriate, the ROM may be a mask-programmed ROM, a programmable ROM (PROM), an erasable PROM (EPROM), an electrically erasable programmable PROM (EEPROM), an electrically alterable ROM (EAROM), or flash memory, or a combination of two or more of these.

[0080] The processor 1101 reads and executes computer program instructions stored in the memory 1102 to perform the steps of the OFDM time-frequency synchronization method based on the preamble structure provided in this embodiment of the disclosure.

[0081] In one example, the electronic device may also include a transceiver 1103 and a bus 1104. Wherein, as... Figure 9 As shown, the processor 1101, memory 1102 and transceiver 1103 are connected via bus 1104 and communicate with each other.

[0082] Bus 1104 may include hardware, software, or both. For example, and not limitingly, the bus may include an Accelerated Graphics Port (AGP) or other graphics bus, an Extended Industry Standard Architecture (EISA) bus, a Front Side Bus (FSB), a Hyper Transport (HT) interconnect, an Industrial Standard Architecture (ISA) bus, an Infinite Bandwidth Interconnect, a Low Pin Count (LPC) bus, a memory bus, a MicroChannel Architecture (MCA) bus, a Peripheral Component Interconnect (PCI) bus, a PCI-Express (PCI-X) bus, a Serial Advanced Technology Attachment (SATA) bus, a Video Electronics Standards Association Local Bus (VLB) bus, or other suitable buses, or a combination of two or more of these. Where appropriate, bus 1104 may include one or more buses. Although specific buses are described and illustrated in the embodiments of this application, this application considers any suitable bus or interconnection.

[0083] The following are embodiments of a computer-readable storage medium provided in this disclosure. This computer-readable storage medium and the OFDM time-frequency synchronization method based on a preamble structure in the above embodiments belong to the same inventive concept. For details not described in detail in the embodiments of the computer-readable storage medium, please refer to the embodiments of the OFDM time-frequency synchronization method based on a preamble structure described above.

[0084] This embodiment provides a storage medium containing computer-executable instructions, which, when executed by a computer processor, are used to perform an OFDM time-frequency synchronization method based on a preamble structure.

[0085] Of course, the computer-executable instructions provided in the embodiments of this disclosure are not limited to the above-described method operations, but can also perform related operations in the OFDM time-frequency synchronization method based on the preamble structure provided in any embodiment of this disclosure.

[0086] Based on the above description of the implementation methods, those skilled in the art can clearly understand that this disclosure can be implemented using software and necessary general-purpose hardware, and of course, it can also be implemented using hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of this disclosure, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as a computer floppy disk, read-only memory (ROM), random access memory (RAM), flash memory, hard disk, or optical disk, etc., including several instructions to cause a computer cloud platform (which may be a personal computer, server, or network cloud platform, etc.) to execute the OFDM time-frequency synchronization method based on the preamble structure provided in the various embodiments of this disclosure.

[0087] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, 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 the aforementioned element.

[0088] The foregoing description is merely a specific embodiment of this disclosure, enabling those skilled in the art to understand or implement it. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this disclosure. Therefore, this disclosure is not to be limited to the embodiments described above, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A preamble-based OFDM time-frequency synchronization method, characterized in that, include: Acquire a received signal, wherein the received signal includes a preamble structure, the preamble structure is composed of a prefix sequence and a training sequence, the prefix sequence and the training sequence are both based on ZC sequences, the training sequence is preceded and followed by a segment of the prefix sequence, and the training sequence does not include the prefix sequence; The received signal is mapped according to its sign bit to obtain the received sign bit information; A correlation function is obtained based on the received symbol bit information and the local sequence, wherein the local sequence is obtained based on the training sequence; The timing position is determined according to the relevant function to complete the time-frequency synchronization of the received signal; The prefix sequence s A With the training sequence s n They are respectively: Where A and B are the sequence lengths, both A and B are positive integers, B > A, p and q are non-zero integers, p is coprime to A, and q is coprime to B; The step of obtaining the correlation function based on the received symbol bit information and the local sequence includes: The received symbol bit information and the local sequence are subjected to a sliding conjugate correlation operation to obtain the correlation function; The relevant function is: or Wherein, d(n) is the nth value in the local sequence, r(n) is the received symbol bit information, N represents the number of related results, M represents the N related results being grouped into groups of M for incoherent accumulation, m represents the starting position of the sliding window, and * represents conjugate.

2. The method according to claim 1, characterized in that, The local sequence is {d1, d2, ..., d...} N-1 }, where d n =sign(Re(s) n ))+j*sign(Im(s n ), 0≤n≤N-1; sign(·) represents taking the sign bit of the data; if the data is greater than 0, the result is 1, and if the data is less than 0, the result is -1; Re(·) represents taking the real part of the complex number, Im(·) represents taking the imaginary part of the complex number, s n The training sequence is described above.

3. The method according to claim 1, characterized in that, The received sign bit information r(n) = sign(Re(r′(n))) + j*sign(Im(r′(n))), 0≤n≤N-1, where r′(n) is the received signal; sign(·) represents taking the sign bit of the data, if the data is greater than 0, the result is 1, if the data is less than 0, the result is -1; Re(·) represents taking the real part of the complex data, and Im(·) represents taking the imaginary part of the complex data.

4. The method according to claim 1, characterized in that, Determining the timing position based on the relevant function includes: Determine the location point corresponding to the maximum value of the relevant function. The timing position is determined based on the positioning point.

5. The method according to claim 4, characterized in that, Also includes: The received signal is demodulated according to the timing position, and the demodulated received signal is: Among them, T s T is the sampling time. s =1 / f s f s Sampling frequency, This is the initial phase; The frequency offset of the received signal is determined to be... Where angle(·) is the phase angle function of a complex number.

6. An OFDM time-frequency synchronization device based on a preamble structure, characterized in that, include: A signal receiving module is used to acquire a received signal, wherein the received signal includes a preamble structure, the preamble structure is composed of a prefix sequence and a training sequence, the prefix sequence and the training sequence are both based on ZC sequences, the training sequence is preceded and followed by a segment of the prefix sequence, and the training sequence does not include the prefix sequence. The first calculation module is used to map the received signal according to the sign bit to obtain the received sign bit information; The second calculation module is used to obtain a correlation function based on the received symbol bit information and the local sequence, wherein the local sequence is obtained based on the training sequence; The time-frequency synchronization module is used to determine the timing position according to the correlation function and complete the time-frequency synchronization of the received signal.

7. An electronic device, characterized in that, include: processor; A memory for storing executable instructions; wherein the processor is configured to read the executable instructions from the memory and execute the executable instructions to implement the method of any one of claims 1 to 5.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that, The storage medium stores a computer program that, when executed by a processor, causes the processor to implement the method described in any one of claims 1 to 5.

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