CN114785653A

CN114785653A - Symbol synchronization method, system, equipment and readable storage medium

Info

Publication number: CN114785653A
Application number: CN202210415360.2A
Authority: CN
Inventors: 纪元法; 林万年; 孙希延; 白杨; 李晶晶; 付文涛; 梁维彬; 贾茜子; 严素清
Original assignee: Guilin University of Electronic Technology
Current assignee: Guilin University of Electronic Technology
Priority date: 2022-04-20
Filing date: 2022-04-20
Publication date: 2022-07-22
Anticipated expiration: 2042-04-20
Also published as: CN114785653B

Abstract

The application provides a symbol synchronization method, a system, a device and a readable storage medium. The method comprises the following steps: truncating the received current frame data by adopting a sliding window, performing correlation operation on each segment of the current frame data and the first terminal head sequence of the local pilot frequency after each truncation to obtain a correlation value, and then taking an absolute value; accumulating the first 16 points of the absolute correlation values, multiplying the accumulated values by a coefficient to perform low-pass filtering, detecting the occurrence of a correlation peak value, after judging that each absolute correlation value is larger than the corresponding dynamic threshold value, storing the magnitude and the position of the absolute correlation value to perform operation judgment, searching to obtain a first section of correlation peak when an operation judgment result is obtained and the operation judgment result conforms to the operation judgment rule of a preset correlation peak, outputting a target frame and completing frame synchronization, and keeping the finally obtained dynamic threshold to the next frame for mean processing. By combining the dynamic threshold detection algorithm and the approximate approximation module algorithm, the searching timing speed and the detection performance during frame synchronization are improved, and the operation amount is effectively reduced.

Description

Symbol synchronization method, system, equipment and readable storage medium

Technical Field

The present application relates to the field of wireless communication technologies, and in particular, to a symbol synchronization method, system, device, and readable storage medium.

Background

With the development of the scientific and technological society and the coming of the era of mobile communication, people put forward more and more diversified multimedia business requirements, and the requirements on the speed and the quality of wireless communication are higher and higher. The existing broadband wireless access technology generally comprises four categories of a wireless personal area network, a wireless local area network, a wireless metropolitan area network and a wireless wide area network, and a network architecture of broadband wireless access is formed together.

In a wireless transmission environment, since a signal undergoes many processes such as reflection, scattering, refraction and the like when propagating in a free space, a receiver receives signals of a plurality of paths with different attenuation amplitudes and phase delays after the signals are transmitted through different paths. Multipath effects can cause intersymbol interference to occur such that the received signal is either very weak or is swamped by various noise. In order to detect a useful signal under a low signal-to-noise ratio condition, a simple and easy-to-implement synchronization technique is important. At present, the mainstream uses the OFDMA technology, which is an OFDM multiple access mode based on the OFDM multiple access mode, and is an access system of a multi-user communication system applying the technology of combining the OFDM with the TDMA, the FDMA or the CDMA multiple access technology. The sensitivity of the OFDM synchronization performance is a factor that most seriously affects the performance of the whole communication system, and OFDM frame synchronization deviation not only causes intersymbol interference, but also causes phase linear rotation of output data of fast fourier transform, thereby reducing the system performance. The existing timing synchronization technology for the downlink of the OFDMA system can be solved by using the timing synchronization scheme of the conventional system, and can be summarized into three general categories: synchronization based on training sequences, synchronization based on cyclic prefixes, blind estimation synchronization. The three algorithms are respectively represented by Schmidl & cox (SC) algorithm, Maximum Likelihood (ML) algorithm and MUSIC algorithm.

However, in the course of research and practice on the prior art, the inventors of the present invention found that the prior art has the following disadvantages: the performance of the blind estimation algorithm is not ideal, the algorithm complexity is very high, and the estimation precision is not as good as that of the training sequence estimation algorithm; although the estimation precision of the training sequence algorithm is high, the training sequence needs to additionally occupy system resources; and the traditional frame synchronization method is easily influenced by a wireless channel when receiving signals, and the bit synchronization based on the phase locking technology is difficult to realize under the condition of extremely low signal-to-noise ratio.

The foregoing description is provided for general background information and is not admitted to be prior art.

Disclosure of Invention

In view of the above technical problems, the present application provides a symbol synchronization method, system, device and readable storage medium, which can improve the search timing speed and detection performance during frame synchronization and effectively reduce the amount of computation.

In order to solve the above technical problem, the present application provides a symbol synchronization method, including the following steps:

receiving current frame data through a receiving antenna;

truncating the received current frame data by adopting a sliding window, performing correlation operation with a local pilot frequency first end head sequence after each truncation, and performing complex modulus to obtain a corresponding absolute correlation value;

performing 16-point accumulation processing on each obtained absolute correlation value, multiplying the accumulated absolute correlation value by a coefficient, and performing low-pass filtering to obtain a dynamic threshold of the current absolute correlation value point;

after the absolute correlation value is judged to be larger than the corresponding dynamic threshold value, the size and the position of the absolute correlation value are saved;

while the sliding window continuously completes the correlation operation of the frame data, the operation judgment is carried out according to the sizes and the positions of all the stored absolute correlation values to obtain an operation judgment result;

searching to obtain a first section of correlation peak when the operation judgment result is judged to accord with the operation judgment rule of the preset correlation peak;

and outputting a target frame according to the first section of correlation peak, then carrying out frame synchronization, and reserving a threshold value finally calculated by the current frame data to a next frame for mean processing.

Optionally, after the receiving the current frame data through the receiving antenna, the method further includes:

and if the current frame data sent by the transmitting end is judged to be a plurality of times of interpolation data, carrying out corresponding a plurality of times of extraction processing on the received current frame data.

Optionally, the correlation operation specifically includes:

and performing approximate simulation and combination operation by adopting a preset piecewise function to obtain an approximate modulus value of the correlation value after performing correlation operation on current frame data truncated by the current sliding window and the first end head sequence of the local pilot frequency, so as to obtain an absolute correlation value.

Optionally, the performing, by taking the first 16 points of accumulation processing on each obtained absolute correlation value, multiplying the obtained absolute correlation value by a coefficient to perform low-pass filtering to serve as a dynamic threshold of the current absolute correlation value point specifically includes:

adopting a 16-point accumulation filter for the absolute correlation value, multiplying the absolute correlation value by a filter coefficient, and performing low-pass filtering to obtain a dynamic threshold value;

and reserving the finally calculated dynamic threshold value to the threshold value of the next frame for mean value operation.

Optionally, the performing operation judgment according to the sizes and the positions of all the stored absolute correlation values to obtain an operation judgment result specifically includes:

and detecting whether the difference value of the adjacent positions corresponding to any absolute correlation value is smaller than a first threshold value or not and the number of the continuous points is larger than a second threshold value until all the absolute correlation values are detected.

Optionally, when it is determined that the operation determination result meets the operation determination rule of the preset correlation peak, searching to obtain a first-stage correlation peak specifically includes:

when the operation judgment result is judged to accord with a preset correlation peak operation judgment rule, detecting to obtain a first section of correlation peak and storing an absolute correlation value and a position corresponding to the first section of correlation peak;

performing single-point search according to left and right preset unit ranges of the position of the first section of correlation peak to obtain a maximum absolute correlation value in the left and right preset unit ranges;

obtaining a corresponding single-point maximum value and a position thereof according to the maximum absolute correlation value, and calculating to obtain a corresponding pilot frequency position;

and extracting corresponding frame data according to the pilot frequency position of the single-point maximum value.

Optionally, before the truncating the received current frame data with the sliding window, the method further includes:

and preprocessing the current frame data by adopting a three-point smoothing filtering method.

Correspondingly, the present application also provides a symbol synchronization system, including:

the receiving module is used for receiving the current frame data through a receiving antenna;

the correlation operation module is used for truncating the received current frame data by adopting a sliding window, performing correlation operation with the local pilot frequency first end head sequence after each truncation, and obtaining a corresponding absolute correlation value by taking a plurality of modules;

the dynamic threshold module is used for performing 16-point accumulation processing on each obtained absolute correlation value, multiplying the obtained absolute correlation value by a coefficient to perform low-pass filtering to be used as a dynamic threshold of the current absolute correlation value point, and storing the size and the position of the absolute correlation value after judging that the absolute correlation value is greater than the corresponding dynamic threshold value;

the operation judgment module is used for performing operation judgment according to the sizes and the positions of all the stored absolute correlation values while the sliding window continuously completes the correlation operation of the frame data to obtain an operation judgment result;

the correlation peak searching module is used for searching to obtain a first section of correlation peak when the operation judgment result is judged to accord with the operation judgment rule of the preset correlation peak;

and the frame output module is used for carrying out frame synchronization after outputting the target frame according to the first section of correlation peak, and reserving the threshold value finally calculated by the current frame data to the next frame for mean value processing.

The present application further proposes a computer device comprising a memory and a processor, the memory storing a computer program, the processor implementing the steps of the symbol synchronization method according to any one of the above when executing the computer program.

The present application also proposes a computer-readable storage medium having stored thereon a computer program which, when being executed by a processor, carries out the steps of the symbol synchronization method of any one of the above.

The embodiment of the invention has the following beneficial effects:

as described above, the present application provides a symbol synchronization method, system, device and readable storage medium, where the method includes: receiving current frame data through a receiving antenna; truncating the received current frame data by adopting a sliding window, performing correlation operation with a local pilot frequency first end head sequence after each truncation, and performing complex modulus to obtain a corresponding absolute correlation value; carrying out correlation operation on each time to obtain an absolute correlation value, carrying out accumulation processing on the first 16 points by using the absolute correlation value, and multiplying the dynamic threshold value corresponding to the absolute correlation value of the point by a coefficient through low-pass filtering; after the absolute correlation value is judged to be larger than the corresponding dynamic threshold value, the size and the position of the absolute correlation value are stored, and operation judgment is carried out according to the size and the position of all the stored absolute correlation values to obtain an operation judgment result; searching to obtain a first section of correlation peak when the judgment result of the judgment operation accords with the preset correlation peak operation judgment rule; and outputting a target frame according to the first section of correlation peak, then carrying out frame synchronization, if the target frame does not accord with the judgment condition, continuing sliding the window until the first section of correlation peak is searched, carrying out frame synchronization, and keeping the threshold value of the current frame data until the next frame is subjected to mean processing. The symbol synchronization method provided by the application can rapidly and accurately position the frame head to recover the frame information by combining a dynamic threshold detection algorithm and an approximate approximation module calculation method and adopting a processing method of reserving a detection threshold and multi-frame averaging, overcomes the problem that the synchronous false alarm rate and the false alarm rate are increased by times due to uncorrelated fading and multipath interference under a Rayleigh fading channel by a fixed threshold frame synchronization algorithm, can accurately and rapidly perform frame synchronization positioning under a low signal-to-noise ratio or a complex environment, can improve the frame synchronization accuracy while reducing the algorithm complexity, and improves the detection performance and efficiency of the frame synchronization positioning.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and together with the description, serve to explain the principles of the application. In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the description of the embodiments will be briefly described below, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise.

Fig. 1 is a schematic flowchart of a first implementation of a symbol synchronization method provided in an embodiment of the present application;

fig. 2 is a schematic structural diagram of frame data of transmitting antennas provided in an embodiment of the present application;

fig. 3 is a schematic structural diagram of a basic data frame provided in an embodiment of the present application;

FIG. 4 is a schematic diagram of three-point smoothing provided by the embodiment of the present application;

FIG. 5 is a schematic diagram illustrating a sliding window correlation operation according to an embodiment of the present disclosure;

FIG. 6 is a graph of relative error for a high-precision approximation modulo algorithm provided by an embodiment of the present application;

fig. 7 is a flowchart illustrating a second implementation manner of a symbol synchronization method according to an embodiment of the present application;

fig. 8 is a schematic structural diagram of a symbol synchronization system according to an embodiment of the present application;

fig. 9 is a block diagram schematically illustrating a structure of a computer device according to an embodiment of the present disclosure.

The implementation, functional features and advantages of the objectives of the present application will be further explained with reference to the accompanying drawings. Specific embodiments of the present application have been shown by way of example in the drawings and will be described in more detail below. These drawings and written description are not intended to limit the scope of the inventive concepts in any manner, but rather to illustrate the inventive concepts to those skilled in the art by reference to specific embodiments.

Detailed Description

Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations described in the following exemplary examples do not represent all implementations consistent with the present application. Rather, they are merely examples of systems and methods consistent with certain aspects of the present application, as detailed in the appended claims.

It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, the statement that an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in the processes, methods, articles, or apparatuses that comprise the element, and that elements, features, or elements having the same designation in different embodiments of the application may or may not have the same meaning as that of the other elements in the embodiment illustrated and/or described in further detail in connection with the context of that embodiment.

It should be understood that although the terms first, second, third, etc. may be used herein to describe various information, such information should not be limited to these terms. These terms are only used to distinguish one type of information from another. For example, first information may also be referred to as second information, and similarly, second information may also be referred to as first information, without departing from the scope herein. The word "if," as used herein, may be interpreted as "at … …" or "when … …" or "in response to a determination," depending on the context. Also, as used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context indicates otherwise. It will be further understood that the terms "comprises," "comprising," "includes" and/or "including," when used in this specification, specify the presence of stated features, steps, operations, elements, components, items, species, and/or groups, but do not preclude the presence, or addition of one or more other features, steps, operations, elements, components, items, species, and/or groups thereof. The terms "or," "and/or," "including at least one of the following," and the like, as used herein, are to be construed as inclusive or mean any one or any combination. For example, "includes at least one of: A. b, C "means" any of the following: a; b; c; a and B; a and C; b and C; a and B and C ", again for example," A, B or C "or" A, B and/or C "means" any of the following: a; b; c; a and B; a and C; b and C; a and B and C'. An exception to this definition will occur only when a combination of elements, functions, steps or operations are inherently mutually exclusive in some way.

It should be understood that, although the steps in the flowcharts in the embodiments of the present application are shown in sequence as indicated by the arrows, the steps are not necessarily performed in sequence as indicated by the arrows. The steps are not performed in the exact order shown and may be performed in other orders unless otherwise indicated herein. Moreover, at least some of the steps in the figures may include multiple sub-steps or multiple stages that are not necessarily performed at the same time, but may be performed at different times, in different orders, and may be performed alternately or at least partially with respect to other steps or sub-steps of other steps.

The words "if", as used herein, may be interpreted as "at … …" or "at … …" or "in response to a determination" or "in response to a detection", depending on the context. Similarly, the phrases "if determined" or "if detected (a stated condition or event)" may be interpreted as "when determined" or "in response to a determination" or "when detected (a stated condition or event)" or "in response to a detection (a stated condition or event)", depending on the context.

It should be noted that step numbers such as S10 and S20 are used herein for the purpose of more clearly and briefly describing the corresponding contents, and do not constitute a substantial limitation on the sequence, and those skilled in the art may perform S20 first and then perform S10 in the specific implementation, which should be within the scope of the present application.

It should be understood that the specific embodiments described herein are merely illustrative of and not restrictive on the broad application.

In the following description, suffixes such as "module", "component", or "unit" used to indicate elements are used only for facilitating the description of the present application, and have no particular meaning in themselves. Thus, "module", "component" or "unit" may be used mixedly.

First, an application scenario that can be provided by the present application is introduced, for example, a symbol synchronization method, a system, a device and a readable storage medium are provided, which aims to solve the problem that a synchronization false alarm rate and a false alarm rate are increased by times due to uncorrelated fading and multipath interference in a rayleigh fading channel in a fixed threshold frame synchronization algorithm, and overcome the defects that the prior art cannot accurately and quickly perform frame synchronization positioning in a low signal-to-noise ratio or complex environment and the algorithm complexity is high.

Referring to fig. 1, fig. 1 is a schematic flow chart of a symbol synchronization method according to an embodiment of the present application, where the present embodiment provides a symbol synchronization method, and the symbol synchronization method includes the following steps:

and S10, receiving current frame data through a receiving antenna.

Optionally, in some embodiments, after receiving the current frame data through the receiving antenna in step S10, the method may further include:

and if the current frame data sent by the transmitting end is judged to be the multiple interpolation data, performing corresponding multiple extraction processing on the received current frame data.

In addition, in step S10, the current frame data is received through the receiving antenna, and the previous frame retention threshold, the low pass filter coefficient and the dynamic threshold amplification factor are also received.

Specifically, in step S10, the receiving antenna receives data Rxsymbols _ rec of one frame, and if N-fold interpolation is adopted at the transmitting end, N-fold extraction should be performed on the received data of one frame. As shown in fig. 2, the frame structure of the transmitting antenna provided in this embodiment includes a CP, a frame synchronization code, a data prefix, and data, where the frame synchronization code is also called a pilot, and is generated by using an m-sequence, and the shift register is constructed according to different feedback coefficients, so as to generate a corresponding m-sequence, but the pilots used by different antennas are different, and the CP is a cyclic prefix symbol of the pilot sequence (frame synchronization code). By adding cyclic prefix, the length of the cyclic prefix is larger than the maximum delay spread tau of the channel_maxThat is, the time difference between each transmitting antenna and the receiving antenna is not greater than the length of the OFDM cyclic prefix, so that the multipath copies of the previous symbol all fall within the cyclic extension range of the next symbol, thereby eliminating the interference between the previous symbol and the next symbol and effectively preventing ICI. The length of the training sequence is usually larger than the cyclic prefix, so the accuracy is higher, the mutual antenna interference can be better reduced by combining two auxiliary data of the training sequence and the pilot frequency through the cross-correlation performance, and the OFDM symbol synchronization, the subsequent carrier frequency offset estimation and other processing are realized.

In addition, as shown in fig. 3, the coherent frame synchronization code insertion method of the present embodiment has the advantages of easy identification, simple structure, and small system resource occupation, and the frame synchronization code is inserted at the start position of each frame by the method, so that the synchronization can be established quickly. The frame synchronization code is a non-periodic sequence or a finite sequence, and in order to make the receiver easily recognize the frame synchronization code from the received data stream, the frame synchronization code should be selected to satisfy the following two principles: (1) the autocorrelation function of the frame synchronization code has sharp unimodal characteristics; (2) the frame synchronization code is easily distinguished from the information code. The pseudo-random sequence has good autocorrelation properties. In addition, the pseudo-random sequence is a periodic sequence and can be artificially copied and generated. The pseudo-random sequence comprises an m sequence, a Gold code, a Weil code and the like, and the scheme adopts a simple m sequence as a frame synchronization code.

Optionally, before truncating the received current frame data by using a sliding window in step S20, the method may further include:

Specifically, in order to cope with the poor condition of extremely low signal-to-noise ratio, the noise influence can be effectively reduced by adopting three-point smoothing filtering, and a preprocessing link is added at the front end of the demodulator, so that the useful signal and the noise influence can be maximized, and the signal-to-noise ratio of the demodulated input signal can be improved. Smoothing filtering is a technique for reducing the effect of noise that is commonly used in various communication systems, and matched filtering is the best reception technique for suppressing white noise in digital communication systems.

In a specific embodiment, as shown in fig. 4, by performing three-point smoothing filtering on the data stream of sample values, a specific method is implemented by averaging consecutive 3-point sample value data by using a shift register as an output of an intermediate point, where y (n) { x ((n-1)) + x (n) + x ((n +1)) }/3, where x (n) is an input signal and y (n) is an output signal.

And S20, truncating the received current frame data by adopting a sliding window, performing correlation operation with the first end head sequence of the local pilot frequency after each truncation, and performing complex modulus to obtain a corresponding absolute correlation value.

Specifically, for step S20, first, the length of the sliding window is set to 128 points, and the length may be set according to actual requirements, and is not limited to 128 points; and (3) performing sliding value taking on the Rxsymbols _ rec of a received frame for 128 points until the last k is less than the frame length-the sliding window length, aiming at performing correlation calculation on a section of 128 point data and local pilot 128 point data, fixing the first 128 points of the local pilot, and storing the sliding window value 128 points and local pilot (1: 128) to calculate a modulus M1(k) of a correlation value as measurement.

Optionally, in some embodiments, the correlation operation in step S20 may specifically include:

and performing approximation simulation combination operation of complex modulus by adopting a preset piecewise function to obtain an approximate modulus value of a correlation value M1(k) between current frame data truncated by the current sliding window and the first end head sequence of the local pilot frequency.

Specifically, based on the correlation characteristics in the synchronization data, the present embodiment can achieve accurate frame synchronization, the training sequences set by the system generally have better cross-correlation and auto-correlation characteristics, and the cross-correlation values between different training sequences are small. The known training sequence and the received signal are subjected to sliding cross correlation, when the known training sequence is aligned with the received training sequence, a peak value is generated, and accurate timing synchronization can be performed by searching the position of the peak value of the cross correlation.

As shown in fig. 5, when each frame of data received by the receiving end arrives, a search window is cut, and then correlation operation is performed on the received data in the window and the pre-stored synchronization training symbol to obtain a correlation value, which is represented by M1 (k). The specific algorithm is as follows:

wherein r (n) is the received signal, t (n) is the known training sequence, P (d) is the correlation result between the received signal and the known training sequence, R (d) is the energy of the known training sequence, M₁(d) Is a metric that produces a peak when the known training sequence is aligned with the received training sequence,

the position is the positioning position, and the position corresponding to the maximum peak value can be obtained by finding the maximum peak value. In order to reduce the amount of computation, the normalized correlation peak processing is not performed here, but it is understood from the comparison that the computation can be reduced greatly by simplifying the normalization processing.

The embodiment improves the algorithm, and the improved algorithm is as follows:

M₁(d)＝|P(d)|

where r (n) is the received signal and t (n) is the known training sequence, by simplifying M₁(d) The measurement value can be removed from the corresponding division, meanwhile, in order to simplify the operation, the modulus approximation algorithm is adopted for calculation, the conventional complex modulus calculation is nonlinear, the hardware realization is more complex, the output delay is large, and the resource consumption is moreDegree and less resource consumption.

The calculation of the complex number mode is equivalent to the calculation of the hypotenuse of a right-angled triangle, the triangle takes the real part and the imaginary part of the number as right-angled sides, when the two right-angled sides are not equal, the right-angled sides are approximately equal to the sum of the long right-angled sides and half of the short right-angled sides, and the larger the difference of the lengths of the two right-angled sides is, the smaller the error is.

This approach to approximate calculation reduces the amount of calculation at the expense of accuracy, and is not recommended in algorithms requiring high accuracy, but can be adjusted slightly in coefficient at the same time.

Another approximation algorithm is a complex modulus calculation of the concept of right triangles,

based on the above idea of function curve fitting, the present embodiment proposes a new piecewise function to approximate the model calculation:

assuming that a is the long side of the square and b is the short side of the square, 4 functions are proposed to approximate the fitting

y₁＝a+b/18

y₂＝13a/16+19b/32

y₃＝70a/80+39b/80

y₄＝33a/34+8b/34

The error can be reduced by adopting the above formula to calculate the approximate value of the mode, but the ratio of the real part and the imaginary part of the complex number is different, and the error of the result is also different, and in the embodiment, the accurate modulo calculation and the simplified modulo calculation are performed by respectively using different a/b values.

In the simulation process, the inventor of the invention finds that the optimization algorithm is in a/b<1.79 case y₂13a/16+19b/32 is approximately equal to the modulus at 1.79<a/b<At 2.72, the error is large, and the exact value of the modulus at this time is approximately equal to y₃70a/80+39 b/80. At 2.72<a/b<6.15, when the exact value of the modulus is approximately equal to y₄33a/34+8 b/34. So the present example is in a/b>When 6.15 is used y₁The value of a + b/18 is taken as the approximation of the modulus. 4 different fitting functions in different a/b regions, and

approximately equal, and through error analysis, different function curves and

based on the idea that the optimized piecewise function is not provided for substitution

y_max＝max(y₁,y₂,y₃,y₄)

As shown in FIG. 6, after simulation analysis, the curve has a maximum positive relative error of 0.15%, a maximum negative relative error of-0.56%, and a total relative error (a large absolute value of the positive and negative relative errors) of 0.56%. Each section adopts approximate modular equations with different error characteristics, and the approximate modular equations are combined to realize a relative error of not more than 0.56 percent, which is 1.82-4.2 times of other similar algorithms.

And S30, performing 16-point accumulation processing on each obtained absolute correlation value, multiplying the accumulated absolute correlation value by a coefficient, and performing low-pass filtering to obtain a dynamic threshold of the current absolute correlation value point.

Optionally, in some embodiments, for the absolute correlation value obtained after performing the correlation operation in step S30, the first 16 points may be accumulated, and the dynamic threshold corresponding to the point may be obtained through low-pass filtering and multiplying by a threshold amplification factor, which may specifically include:

adopting a 16-point accumulation and low-pass filter for the correlation value, and multiplying the correlation value by a filter coefficient to obtain a dynamic threshold value;

and carrying out average operation on the dynamic threshold value and the threshold value of the previous frame.

Specifically, for step S30, 16-point accumulation is taken for each incoming data M1(K), where M1(K) is the modulus of the correlation value;

..............

the true output average is calculated according to the following formula:

ave_real(1)＝ave_now(1)

ave_real(n)＝b*ave_now(n)+(1-b)*ave_now(n-1)

the obtained average value is multiplied by the coefficient of the low-pass filter to obtain a dynamic Threshold, wherein the coefficient is xs, which is generally 3.5, and the balance between the detection performance and the complexity can be obtained by properly selecting the coefficient.

And S40, after the absolute correlation value is judged to be larger than the corresponding dynamic threshold value, the size and the position of the absolute correlation value are stored.

Specifically, for step S40, if the absolute value correlation value currently extracted exceeds the threshold, the size M1(K) and the position K are saved, and the window is continuously slid by a distance of 1.

And S50, while the sliding window continuously completes the correlation operation of the frame data, performing operation judgment according to the sizes and positions of all the stored absolute correlation values to obtain an operation judgment result.

Optionally, in some embodiments, the performing, in step S50, an operation judgment according to the saved absolute correlation values and the positions thereof to obtain an operation judgment result may specifically include:

Specifically, for step S50, after the sliding window completes all correlation operations of the current frame data, an operation judgment is performed on the amplitude and position of the correlation value saved before, when the point position difference of the adjacent position is detected to be <3 and the number of consecutive points is >2, it is judged that the first segment of correlation peak is detected and the absolute value correlation value M1(K) and the corresponding position K are stored, until the end, the absolute value correlation value M1(K) and the position K near the first segment of correlation peak are saved.

And S60, searching to obtain a first section of correlation peak when the operation judgment result is judged to accord with the operation judgment rule of the preset correlation peak. And if the judgment condition is not met, continuing to slide the window to repeat the operation.

Optionally, in some embodiments, for step S60, when it is determined that the operation determination result meets the operation determination rule of the preset correlation peak, the searching for the first-segment correlation peak may specifically include:

when the judgment operation judgment result accords with a preset correlation peak operation judgment rule, detecting to obtain a first section of correlation peak and storing an absolute correlation value and a position corresponding to the first section of correlation peak;

Specifically, in step S60, after storing the absolute value correlation value M1(K) and the position K in the vicinity of the first-stage correlation peak, a plurality of points are expanded in the left and right direction according to the position range to perform fine search of a single point, and at this time, the absolute value of the correlation value in the range is subjected to maximum search to find the maximum value of the single point and the corresponding position thereof, and data is directly extracted based on the calculated pilot position.

In a specific embodiment, frame synchronization may be subdivided into two parts, namely frame arrival detection and accurate frame start position location, or coarse frame synchronization and fine frame synchronization, carrier frequency offset estimation is required to be performed immediately after an accurate data frame start position is found, and frequency offset compensation is performed on a signal by using an estimation result to ensure orthogonality between incoming symbol subcarriers as much as possible.

The coarse frame synchronization, i.e. frame detection, is to find the starting position of a data symbol and find the ending position of the last synchronization header by detecting the synchronization header. The frame synchronization process is divided into two steps, firstly, coarse synchronization is carried out, the rough starting position of a synchronization head is found, then fine synchronization is carried out, and the starting position of a data symbol is determined on the basis of the coarse synchronization determination range. The fine frame synchronization means that the fine frame synchronization can be performed after the data is subjected to the coarse frame synchronization, and the purpose is to find the accurate starting position of the symbol, namely, the fine frame synchronization is taken at the approximate position determined by the coarse frame synchronization and several nearby sampling points to determine the accurate starting position of the synchronization frame head of each transmitting antenna. And correlating the received signal with the transmission sequence of each antenna.

And S70, outputting a target frame according to the first section of correlation peak, then carrying out frame synchronization, and reserving a threshold value finally calculated by the current frame data until the next frame is subjected to mean processing.

Specifically, for step S70, the target frame is output according to the data extracted from the first segment of correlation peak, and the threshold of the frame is retained to the next frame for continuing to perform the average calculation, and by retaining the threshold for a long time, the erroneous judgment and the missing judgment caused by the over-low threshold can be reduced under certain circumstances.

As shown in fig. 7, in a specific embodiment, the embodiment of the present application further provides a second implementation manner of a symbol synchronization method, and the specific process is as follows: receiving one frame data of an antenna, a previous frame retention threshold, a low-pass filter coefficient and an xs threshold amplification factor, and extracting 128 points (namely the length of a sliding window) from a frame header by N times; judging whether the current position is less than or equal to a frame length of-127 points, if so, truncating the received data by using a sliding window with the length of 128 points, correlating the data with a head sequence 128 point of a first end of a local pilot frequency, performing modulus to obtain M1(k), performing single-time sampling, then performing 16-point accumulation on the M1(k), multiplying the Threshold Threshold by a coefficient (xs) through low-pass filtering (b), averaging the Threshold Threshold with a previous frame Threshold, judging whether M1(k) is greater than the Threshold, if so, storing the point M1(k) and a corresponding position k of the Threshold, and continuing sliding the window, wherein k is k +1, namely, the sliding distance is 1 each time until k is greater than the frame length of-127 points; if M1(k) is not greater than the threshold, the sliding window continues. The method comprises the steps of judging whether a correlation peak at a first end is searched roughly while a sliding window is subjected to correlation operation, judging whether the number of stored correlation values is larger than a preset number, if so, judging whether a point coordinate difference value adjacent to the stored correlation values is smaller than or equal to 3, if so, storing a position k corresponding to the correlation values and calculating data of continuous points, if not, searching for a first section of correlation peak and then performing fine search, expanding a search range of 10 points in front of and behind the position range of the stored first section of correlation peak, searching for a first maximum value and a corresponding position thereof from a continuous single point in a first group of peak value range, setting a flag bit, extracting data, and keeping a threshold finally calculated by a frame to a next frame for mean processing and outputting frame data.

As can be seen from the above, the symbol synchronization method provided in the embodiment of the present application includes: receiving current frame data through a receiving antenna; truncating the received current frame data by adopting a sliding window, performing correlation operation on the current frame data and a local pilot frequency first end head sequence after truncation every time, and performing modulus extraction to obtain a corresponding correlation value; obtaining a corresponding absolute correlation value by carrying out complex number modulus on a correlation value obtained after each correlation operation, calculating the accumulation of the first 16 points by using the absolute correlation value, and obtaining a dynamic threshold by low-pass filtering and threshold coefficient amplification; after the absolute correlation value is judged to be larger than the corresponding dynamic threshold value, the size and the position of the absolute correlation value are saved; when the sliding window is adopted to continuously complete the correlation operation of the current truncated frame data, the operation judgment is carried out according to the sizes and the positions of all the stored absolute correlation values to obtain an operation judgment result; searching to obtain a first section of correlation peak when the judgment result of the judgment operation accords with the preset correlation peak operation judgment rule; and performing frame synchronization after outputting the target frame according to the first section of correlation peak, and reserving the threshold value of the current frame data to the next frame.

To sum up, the symbol synchronization method provided by the embodiment of the present application has the following beneficial effects: in a wireless channel with intersymbol interference and multipath fading, the correct detection rate of frame synchronization can be improved and the average search time of a frame header can be reduced on the premise of not increasing the complexity of the system, and the method is suitable for a high-speed mobile communication system. Under the test of different data bits, the correct initial position can be correctly and effectively positioned under the condition of allowing precision loss; the method can accurately and quickly perform frame synchronization positioning under the condition of low signal-to-noise ratio, has good detection performance, is greatly influenced and weakened by noise on a received signal, and can be applied to complex severe environments; compared with the original frame synchronization algorithm, by reducing the operation amount and improving, hardware development resources such as FPGA and the like can be greatly saved, meanwhile, the operation time can be reduced, and the frame synchronization symbol positioning can be rapidly carried out; by the idea of dynamic threshold, the frame synchronization accuracy can be improved under the condition of reducing the algorithm complexity, and compared with the detection algorithm of fixed threshold, the detection algorithm of self-adaptive dynamic threshold adjustment has the advantages of high detection probability and short correct capture time in the aspect of detecting frame synchronization information.

Correspondingly, the present application further provides a symbol synchronization system, please refer to fig. 8, fig. 8 is a schematic structural diagram of the symbol synchronization system provided in the present application, and specifically, the symbol synchronization system may include a receiving module 100, a correlation operation module 200, a dynamic threshold module 300, an operation determining module 400, a correlation peak searching module 500, and a frame output module 600.

The receiving module 100 is configured to receive current frame data through a receiving antenna.

And the correlation operation module 200 is configured to truncate the received current frame data by using a sliding window, perform correlation operation with the local pilot first end header sequence after each truncation, and obtain a corresponding absolute correlation value by performing complex modulo operation.

The dynamic threshold module 300 is configured to perform 16-point accumulation processing on each obtained absolute correlation value, multiply the result by a coefficient, perform low-pass filtering to obtain a dynamic threshold of the current absolute correlation value point, and store the magnitude and position of the absolute correlation value after determining that the absolute correlation value is greater than the corresponding dynamic threshold value.

And the operation judgment module 400 is configured to perform operation judgment according to the sizes and the positions of all the stored absolute correlation values while the sliding window continuously completes the correlation operation of the frame data, so as to obtain an operation judgment result.

And the correlation peak searching module 500 is configured to search for a first segment of correlation peak when it is determined that the operation determination result meets the operation determination rule of the preset correlation peak, and expand the range in the segment of correlation peak to find the maximum absolute correlation value and the corresponding position thereof.

The frame output module 600 is configured to perform frame synchronization after outputting the target frame according to the first segment correlation peak, and keep the threshold value of the current frame data until the next frame is subjected to mean processing. .

To sum up, the symbol timing synchronization system provided in the embodiment of the present application is configured to receive current frame data through a receiving module 100; the correlation operation module 200 is configured to truncate the received current frame data by using a sliding window, perform correlation operation with the local pilot first end header sequence after each truncation, and obtain a corresponding correlation value by taking a module; the dynamic threshold module 300 is configured to calculate the first 16-point accumulation by using an absolute correlation value, obtain a dynamic threshold after low-pass and coefficient amplification, and store the size and position of the absolute correlation value after determining that the absolute correlation value is greater than a corresponding dynamic threshold value; the operation judgment module 400 is configured to perform operation judgment according to the sizes and positions of all stored absolute correlation values when the sliding window continuously completes the correlation operation of the frame data, so as to obtain an operation judgment result; the correlation peak searching module 500 is configured to search for a first section of correlation peak when it is determined that the operation determination result meets a preset operation determination rule, and otherwise, continue sliding the window to repeat the operation of going up to the user; the frame output module 600 is configured to perform frame synchronization after outputting the target frame according to the first segment correlation peak, and keep the threshold value of the current frame data to the next frame.

By the technical scheme, the frame head can be quickly and accurately positioned by combining a dynamic threshold detection algorithm and an approximate approximation model calculation method and adopting a processing method of reserving a detection threshold and multi-frame averaging so as to recover frame information, the problem that the synchronous false alarm rate and the false alarm rate are increased by times due to uncorrelated fading and multipath interference under a Rayleigh fading channel by a fixed threshold frame synchronization algorithm is solved, the frame synchronization can be accurately and quickly positioned under a low signal-to-noise ratio or complex environment, the frame synchronization accuracy can be improved while the algorithm complexity is reduced, and the detection performance and the efficiency of the frame synchronization positioning are improved.

Referring to fig. 9, an embodiment of the present application further provides a computer device, where the computer device may be a server, and an internal structure of the computer device may be as shown in fig. 9. The computer device includes a processor, a memory, a network interface, and a database connected by a system bus. Wherein the computer designed processor is used to provide computational and control capabilities. The memory of the computer device comprises a nonvolatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program, and a database. The memory provides an environment for the operating system and the running of computer programs in the non-volatile storage medium. The database of the computer device is used for storing data such as symbol synchronization methods and the like. The network interface of the computer device is used for communicating with an external terminal through a network connection. The computer program is executed by a processor to implement a symbol synchronization method. The symbol synchronization method comprises the following steps: receiving current frame data through a receiving antenna; truncating the received current frame data by adopting a sliding window, performing correlation operation with a local pilot frequency first end head sequence after each truncation, and performing modulus extraction to obtain a corresponding correlation value; calculating the accumulation of the first 16 points by using the absolute correlation value of the absolute correlation value obtained after each correlation operation, and obtaining a dynamic threshold through low-pass filtering and threshold coefficient amplification; after the absolute correlation value is judged to be larger than the corresponding dynamic threshold value, the size and the position of the absolute correlation value are stored; when the current sliding window continuously performs the correlation operation of the current frame data, performing operation judgment according to the sizes and positions of all the stored absolute correlation values to obtain an operation judgment result; searching to obtain a first section of correlation peak when the judgment operation judgment result accords with a preset correlation peak operation judgment rule; and outputting a target frame according to the first section of correlation peak, then carrying out frame synchronization, and reserving a threshold value finally calculated by current frame data to the next frame for mean value calculation.

An embodiment of the present application further provides a computer-readable storage medium, on which a computer program is stored, the computer program, when executed by a processor, implementing a symbol synchronization method, including the steps of: receiving current frame data through a receiving antenna; truncating the received current frame data by adopting a sliding window, performing correlation operation with a local pilot frequency first end head sequence after each truncation, and performing modulus extraction to obtain a corresponding absolute correlation value; calculating the accumulation of the first 16 points by using the absolute correlation value of the absolute correlation value obtained after each correlation operation, and obtaining a dynamic threshold through low-pass filtering and threshold coefficient amplification; after the absolute correlation value is judged to be larger than the corresponding dynamic threshold value, the size and the position of the absolute correlation value are stored; when the current sliding window continuously performs the correlation operation of the current frame data, performing operation judgment according to the sizes and positions of all the stored absolute correlation values to obtain an operation judgment result; searching to obtain a first section of correlation peak when the judgment operation judgment result accords with a preset correlation peak operation judgment rule; and outputting a target frame according to the first section of correlation peak, then carrying out frame synchronization, and reserving a threshold value finally calculated by current frame data to the next frame for mean value calculation.

The embodiment of the symbol synchronization method can quickly and accurately position the frame head to recover the frame information by combining a dynamic threshold detection algorithm and an approximate approximation model calculation method and adopting a processing method of reserving a detection threshold and multi-frame averaging, overcomes the problem that the synchronous false alarm rate and the false alarm rate are increased by times due to uncorrelated fading and multipath interference under a Rayleigh fading channel by a fixed threshold frame synchronization algorithm, can accurately and quickly perform frame synchronization positioning under a low signal-to-noise ratio or complex environment, can improve the frame synchronization accuracy while reducing the algorithm complexity, and improves the detection performance and the efficiency of the frame synchronization positioning.

It is to be understood that the foregoing scenarios are only examples, and do not constitute a limitation on application scenarios of the technical solutions provided in the embodiments of the present application, and the technical solutions of the present application may also be applied to other scenarios. For example, as can be known by those skilled in the art, with the evolution of system architecture and the emergence of new service scenarios, the technical solution provided in the embodiments of the present application is also applicable to similar technical problems.

The above-mentioned serial numbers of the embodiments of the present application are merely for description, and do not represent the advantages and disadvantages of the embodiments.

The steps in the method of the embodiment of the application can be sequentially adjusted, combined and deleted according to actual needs.

The units in the device in the embodiment of the application can be merged, divided and deleted according to actual needs.

In the present application, the same or similar term concepts, technical solutions and/or application scenario descriptions will be generally described only in detail at the first occurrence, and when the description is repeated later, the detailed description will not be repeated in general for brevity, and when understanding the technical solutions and the like of the present application, reference may be made to the related detailed description before the description for the same or similar term concepts, technical solutions and/or application scenario descriptions and the like which are not described in detail later.

In the present application, each embodiment is described with emphasis, and reference may be made to the description of other embodiments for parts that are not described or illustrated in any embodiment.

The technical features of the technical solution of the present application may be arbitrarily combined, and for brevity of description, all possible combinations of the technical features in the embodiments are not described, however, as long as there is no contradiction between the combinations of the technical features, the scope of the present application should be considered as being described in the present application.

Through the description of the foregoing embodiments, it is clear to those skilled in the art that the method of the foregoing embodiments may be implemented by software plus a necessary general hardware platform, and certainly may also be implemented by hardware, but in many cases, the former is a better implementation. Based on such understanding, the technical solutions of the present application or portions contributing to the prior art may be embodied in the form of a software product, where the computer software product is stored in a storage medium (such as a ROM/RAM, a magnetic disk, and an optical disk) as above, and includes several instructions to enable a terminal device (which may be a mobile phone, a computer, a server, a controlled terminal, or a network device) to execute the method of each embodiment of the present application.

In the above embodiments, the implementation may be wholly or partially realized by software, hardware, firmware, or any combination thereof. When implemented in software, may be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. The procedures or functions according to the embodiments of the present application are all or partially generated when the computer program instructions are loaded and executed on a computer. The computer may be a general purpose computer, a special purpose computer, a network of computers, or other programmable device. The computer instructions may be stored on a computer readable storage medium or transmitted from one computer readable storage medium to another, for example, the computer instructions may be transmitted from one website, computer, server, or data center to another website, computer, server, or data center by wire (e.g., coaxial cable, fiber optic, digital subscriber line) or wirelessly (e.g., infrared, wireless, microwave, etc.). Computer-readable storage media can be any available media that can be accessed by a computer or a data storage device, such as a server, data center, etc., that includes one or more available media. The usable medium may be a magnetic medium (e.g., floppy Disk, storage Disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., Solid State Disk (SSD)), among others.

The above description is only a preferred embodiment of the present application, and not intended to limit the scope of the present application, and all modifications of equivalent structures and equivalent processes, which are made by the contents of the specification and the drawings of the present application, or which are directly or indirectly applied to other related technical fields, are included in the scope of the present application.

Claims

1. A method for symbol synchronization, comprising the steps of:

receiving current frame data through a receiving antenna;

performing first 16-point accumulation processing on each obtained absolute correlation value, multiplying the obtained absolute correlation value by a coefficient, and performing low-pass filtering to obtain a dynamic threshold of the current absolute correlation value point;

after the absolute correlation value is judged to be larger than the corresponding dynamic threshold value, the size and the position of the absolute correlation value are stored;

and outputting a target frame according to the first section of correlation peak, then carrying out frame synchronization, and reserving a threshold value finally calculated by the current frame data to the next frame for mean processing.

2. The symbol synchronization method of claim 1, wherein after said receiving current frame data via the receive antennas, the method further comprises:

3. The symbol synchronization method according to claim 1, wherein the correlation operation specifically includes:

4. The symbol synchronization method according to claim 1, wherein the first 16 points of the obtained absolute correlation values are accumulated, multiplied by a coefficient, and low-pass filtered to be used as a dynamic threshold of the current absolute correlation value point, and specifically comprises:

5. The symbol synchronization method according to claim 1, wherein the performing operation judgment according to the magnitude and the position of all the stored absolute correlation values to obtain an operation judgment result specifically comprises:

6. The symbol synchronization method according to claim 1, wherein when it is determined that the operation determination result meets an operation determination rule of a preset correlation peak, searching for a first section of correlation peak, specifically comprises:

7. The symbol synchronization method of claim 1, wherein prior to said truncating the received current frame data with a sliding window, the method further comprises:

8. A symbol synchronization system, comprising:

a receiving module, configured to receive current frame data through a receiving antenna;

the correlation operation module is used for truncating the received current frame data by adopting a sliding window, performing correlation operation with the first end head sequence of the local pilot frequency after each truncation, and obtaining a corresponding absolute correlation value by complex modulus taking;

a dynamic threshold module, configured to perform 16-point accumulation processing on each obtained absolute correlation value, multiply the result by a coefficient to perform low-pass filtering to obtain a dynamic threshold of a current absolute correlation value point, and store the magnitude and position of the absolute correlation value after determining that the absolute correlation value is greater than a corresponding dynamic threshold value;

the operation judgment module is used for performing operation judgment according to the sizes and positions of all the stored absolute correlation values while the sliding window continuously completes the correlation operation of the frame data to obtain an operation judgment result;

9. A computer device comprising a memory and a processor, the memory storing a computer program, characterized in that the processor, when executing the computer program, implements the steps of the symbol synchronization method of any of claims 1 to 7.

10. A computer-readable storage medium, on which a computer program is stored, which, when being executed by a processor, carries out the steps of the symbol synchronization method according to any one of claims 1 to 7.