CN114785653B

CN114785653B - Symbol synchronization method, system, equipment and readable storage medium

Info

Publication number: CN114785653B
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: 2023-08-04
Anticipated expiration: 2042-04-20
Also published as: CN114785653A

Abstract

The application provides a symbol synchronization method, a system, a device and a readable storage medium. The method comprises the following steps: shortening the received current frame data by adopting a sliding window, carrying out each section of correlation operation on the current frame data and the first end head sequence of the local pilot frequency after each shortening, and taking an absolute value after obtaining a correlation value; and performing accumulation processing by using the first 16 points of the absolute correlation values, multiplying the absolute correlation values by coefficients to perform low-pass filtering, detecting the occurrence of a correlation peak, after judging that each absolute correlation value is greater than a corresponding dynamic threshold value, storing the magnitude and the position of the absolute correlation value to perform operation judgment, obtaining an operation judgment result, searching to obtain a first section of correlation peak when judging that the operation judgment result accords with an operation judgment rule of a preset correlation peak, performing output target frame and finishing frame synchronization, and reserving the finally obtained dynamic threshold to the next frame to perform average processing. The method and the device for detecting the frame synchronization improve the search timing speed and the detection performance during the frame synchronization by combining a dynamic threshold detection algorithm and an approximate approximation modulo algorithm, and effectively reduce the operation quantity.

Description

Symbol synchronization method, system, equipment and readable storage medium

Technical Field

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

Background

With the development of the scientific society and the arrival of the mobile communication age, more and more diversified multimedia service demands are put forward, and the requirements on the speed and quality of wireless communication are higher and higher. The conventional broadband wireless access technology generally comprises four major types of wireless personal area networks, wireless local area networks, wireless metropolitan area networks and wireless wide area networks, a network architecture of broadband wireless access is formed together, an operator can provide more flexible access service for users through broadband unlimited access, and multi-demand service of the users is met.

In a wireless transmission environment, signals are transmitted through different paths, and then the signals are accumulated through multiple paths with different attenuation amplitude and phase delay, because the signals can undergo reflection, scattering, refraction and other processes when traveling in free space. Multipath effects can cause intersymbol interference to occur such that the received signal is either very weak or is drowned out by various types of noise. In order to detect useful signals under low signal-to-noise ratio conditions, a simple and easy-to-implement synchronization technique is particularly important. The mainstream of the present technology is OFDMA, which is an OFDM multiple access method, and is an access system of a multi-user communication system using OFDM in combination with TDMA, FDMA or CDMA multiple access technology. The sensitivity of OFDM synchronization performance is one of the most serious factors affecting the overall communication system performance, and OFDM frame synchronization deviation not only causes intersymbol interference, but also causes phase linear rotation of the fft output data, thereby degrading system performance. The existing timing synchronization technology of the downlink of the OFDMA system can be solved by using the timing synchronization scheme of the traditional system, and can be roughly divided into three categories: based on the synchronization of the training sequence, the synchronization is blind estimated based on the synchronization of the cyclic prefix. These three classes of algorithms are typically the Schmidl & cox (SC) algorithm, the Maximum Likelihood (ML) algorithm, and the MUSIC algorithm, respectively.

However, in the course of research and practice of the prior art, the inventors of the present invention found that the prior art had the following drawbacks: the performance of the blind estimation algorithm is not ideal, the algorithm complexity is very high, and the estimation accuracy is not as good as that of the training sequence estimation algorithm; while the training sequence algorithm has higher estimation accuracy, the training sequence needs to occupy extra system resources; and the traditional frame synchronization method is easily affected by a wireless channel when receiving signals, and bit synchronization based on a 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 does not necessarily constitute 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 operand.

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

receiving current frame data through a receiving antenna;

the received current frame data is truncated by adopting a sliding window, correlation operation is carried out on the current frame data and the first end head sequence of the local pilot frequency after each time of truncation, and a corresponding absolute correlation value is obtained by complex number modulo;

Taking the first 16 points of accumulation processing for 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 judging that the absolute correlation value is larger than the corresponding dynamic threshold value, storing the absolute correlation value and the position thereof;

performing operation judgment according to all the stored absolute correlation values and the positions thereof while continuously completing correlation operation of frame data in the sliding window to obtain an operation judgment result;

searching to obtain a first section of correlation peak when the operation judgment result accords 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 calculated finally from the current frame data to the next frame for average value processing.

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

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

Optionally, the correlation operation specifically includes:

and performing approximation analog synthesis operation by adopting a preset piecewise function to obtain the approximate modulus value of the correlation value after performing correlation operation on the current frame data truncated by the current sliding window and the first end head sequence of the local pilot frequency, and obtaining the absolute correlation value.

Optionally, the adding the first 16 points to 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, which specifically includes:

the absolute correlation value is subjected to low-pass filtering by a 16-point accumulation filter multiplied by a filter coefficient to obtain a dynamic threshold value;

and reserving the dynamic threshold value obtained by the final calculation to the threshold value of the next frame to perform mean value operation.

Optionally, the calculating and judging are performed according to the magnitude and the position of all the stored absolute correlation values to obtain a calculating and judging result, which specifically includes:

and detecting whether the adjacent position difference value corresponding to any absolute correlation value is smaller than a first threshold value and the number of continuous points is larger than a second threshold value until all absolute correlation values are detected.

Optionally, when the operation judgment result accords with an operation judgment rule of a preset correlation peak, searching to obtain a first section of correlation peak specifically includes:

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

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

According to the maximum absolute correlation value, the corresponding single point maximum value and the position thereof, and calculating to obtain the 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 comprises:

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

Correspondingly, the application also provides a symbol synchronization system, which comprises:

a receiving module for receiving 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, carrying out correlation operation on the current frame data and the first end head sequence of the local pilot frequency after truncating each time, and obtaining a corresponding absolute correlation value by complex modulus;

the dynamic threshold module is used for taking the first 16 points of accumulation processing of each obtained absolute correlation value, multiplying the obtained absolute correlation value by a coefficient to carry out low-pass filtering to serve as a dynamic threshold of a current absolute correlation value point, and storing the magnitude and the position of the absolute correlation value after judging that the absolute correlation value is larger than the corresponding dynamic threshold;

the operation judging module is used for carrying out operation judgment according to all the stored absolute correlation values and the positions thereof while the sliding window continuously completes the correlation operation of the frame data, so as to obtain an operation judging result;

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

and the frame output module is used for synchronizing frames after outputting the target frames according to the first section of correlation peak, and preserving the threshold value calculated finally from the current frame data to the next frame for average processing.

The application also proposes a computer device comprising a memory storing a computer program and a processor implementing the steps of the symbol synchronization method of any of the above, when the processor executes the computer program.

The present application also proposes a computer readable storage medium having stored thereon a computer program which, when executed by a processor, implements the steps of the symbol synchronization method of any 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; the current frame data received by the sliding window is truncated, and after each time of truncation, the current frame data and the first end head sequence of the local pilot frequency are subjected to correlation operation, and complex modulus is carried out to obtain a corresponding absolute correlation value; the absolute correlation value obtained after each correlation operation is subjected to accumulation processing of the first 16 points by utilizing the absolute correlation value, and the dynamic threshold value corresponding to the absolute correlation value of the point is obtained by multiplying the coefficient through low-pass filtering; after judging that the absolute correlation value is larger than the corresponding dynamic threshold value, saving the magnitude and the position of the absolute correlation value, and carrying out operation judgment according to all the saved magnitude and the position of the absolute correlation value 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 a preset correlation peak operation judgment rule; and outputting the target frame according to the first section of correlation peak, then carrying out frame synchronization, if the target frame does not meet the judgment condition, continuing sliding the window until the first section of correlation peak is searched and carrying out frame synchronization, and reserving the threshold value of the current frame data until the next frame is subjected to mean value processing. The symbol synchronization method provided by the application can quickly and accurately position the frame head by combining a dynamic threshold detection algorithm and an approximate approximation mode calculation method and adopting a processing method for reserving a detection threshold and multi-frame average so as to recover frame information, overcomes the problem that the synchronous false alarm rate and the false alarm rate of a fixed threshold frame synchronization algorithm are multiplied by uncorrelated fading and multipath interference under a Rayleigh fading channel, can accurately and quickly perform frame synchronization positioning under a low signal-to-noise ratio or complex environment, and can improve the frame synchronization accuracy and the detection performance and efficiency of the frame synchronization positioning while reducing the complexity of the algorithm.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the 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 that are needed in the description of the embodiments will be briefly described below, and it will be obvious to those skilled in the art that other drawings can be obtained from these drawings without inventive effort.

Fig. 1 is a schematic flow chart 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 a transmitting antenna according to 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 filtering provided in an embodiment of the present application;

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

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

fig. 7 is a schematic flow chart of a second implementation of the symbol synchronization method provided in the 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 schematic block diagram of a structure of a computer device provided in an embodiment of the present application.

The realization, functional characteristics and advantages of the present application will be further described with reference to the embodiments, referring to the attached drawings. Specific embodiments thereof have been shown by way of example in the drawings and will herein be described in more detail. These drawings and the written description are not intended to limit the scope of the inventive concepts in any way, but to illustrate the concepts of the present application to those skilled in the art by reference to specific embodiments.

Detailed Description

Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, the same numbers in different drawings refer to the same or similar elements, unless otherwise indicated. The implementations described in the following exemplary examples are not representative of all implementations consistent with the present application. Rather, they are merely examples of systems and methods that are consistent with aspects of the present application as detailed in the accompanying 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 element defined by the phrase "comprising one … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element, and furthermore, elements having the same name in different embodiments of the present application may have the same meaning or may have different meanings, a particular meaning of which is to be determined by its interpretation in this particular embodiment or by further combining the context of this particular embodiment.

It should be understood that although the terms first, second, third, etc. may be used herein to describe various information, these information should not be limited by 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 "at … …" or "responsive to a determination", depending on the context. Furthermore, 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" specify the presence of stated features, steps, operations, elements, components, items, categories, and/or groups, but do not preclude the presence, presence or addition of one or more other features, steps, operations, elements, components, items, categories, and/or groups. The terms "or," "and/or," "including at least one of," and the like, as used herein, may be construed as inclusive, or meaning any one or any combination. For example, "including at least one of: A. b, C "means" any one of the following: a, A is as follows; b, a step of preparing a composite material; c, performing operation; a and B; a and C; b and C; a and B and C ", again as examples," A, B or C "or" A, B and/or C "means" any of the following: a, A is as follows; b, a step of preparing a composite material; c, performing operation; 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 in some way inherently mutually exclusive.

It should be understood that, although the steps in the flowcharts in the embodiments of the present application are shown in order as indicated by the arrows, these steps are not necessarily performed in order as indicated by the arrows. The steps are not strictly limited in order and may be performed in other orders, unless explicitly stated herein. Moreover, at least some of the steps in the figures may include multiple sub-steps or stages that are not necessarily performed at the same time, but may be performed at different times, the order of their execution not necessarily occurring in sequence, but may be performed alternately or alternately with other steps or at least a portion of the other steps or stages.

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 phrase "if determined" or "if detected (stated condition or event)" may be interpreted as "when determined" or "in response to determination" or "when detected (stated condition or event)" or "in response to detection (stated condition or event), depending on the context.

It should be noted that, in this document, step numbers such as S10 and S20 are adopted, and the purpose of the present invention is to more clearly and briefly describe the corresponding content, and not to constitute a substantial limitation on the sequence, and those skilled in the art may execute S20 first and then execute S10 when implementing the present invention, which is within the scope of protection of the present application.

It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the present application.

In the following description, suffixes such as "module", "component", or "unit" for representing elements are used only for facilitating the description of the present application, and are not of specific significance per se. Thus, "module," "component," or "unit" may be used in combination.

Firstly, an application scenario provided by the application, such as providing a symbol synchronization method, a system, a device and a readable storage medium, aims to solve the problem that the synchronous false alarm rate and the false alarm rate are multiplied by uncorrelated fading and multipath interference caused by a fixed threshold frame synchronization algorithm under a Rayleigh fading channel, and overcomes the defects that the frame synchronization positioning cannot be accurately and rapidly performed under a low signal-to-noise ratio or complex environment and the algorithm complexity is higher in the prior art.

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

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 specifically further include:

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

Specifically, for step S10,if the receiving antenna receives the data rxsymbols_rec of one frame and N times interpolation is adopted at the transmitting end, the received data of one frame should also be extracted N times. 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 m-sequences, and a shift register is configured according to different feedback coefficients, so that a corresponding m-sequence can be generated, 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 a cyclic prefix, the length of the cyclic prefix is greater than the channel maximum delay spread τ _max That is, the time difference between each transmitting antenna and each receiving antenna is not greater than the length of the OFDM cyclic prefix, so that multipath copies of the previous symbol are all in the cyclic extension range of the next symbol, interference between the previous symbol and the next symbol is eliminated, and ICI can be effectively prevented. The length of the training sequence is generally longer than that of the cyclic prefix, so that the accuracy is higher, two auxiliary data of the training sequence and pilot frequency are combined, mutual antenna interference can be reduced better through cross-correlation performance, and the processing of OFDM symbol synchronization, subsequent carrier frequency offset estimation and the like is realized.

In addition, as shown in fig. 3, the method of inserting the frame synchronization code at the beginning of each frame can realize quick synchronization establishment, and has the advantages of easy identification, simple structure, small occupied system resources and the like. The frame synchronization code is an aperiodic sequence or a finite-length sequence, and in order for the receiver to easily identify the frame synchronization code from the received data stream, the frame synchronization code needs to be selected so as to satisfy the following two principles: (1) The autocorrelation function of the frame synchronization code has sharp unimodal characteristics; (2) frame synchronization codes facilitate distinction from information codes. The pseudo-random sequence has good autocorrelation properties. In addition, the pseudo-random sequence is a periodic sequence and can be artificially reproduced 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 the step S20 truncating the received current frame data using the sliding window, the method may specifically further include:

Specifically, in this example, in order to cope with the severe condition of extremely low signal-to-noise ratio, the noise influence can be effectively reduced by adopting the three-point smoothing filter, and the preprocessing link is added at the front end of the demodulator, so that the useful signal can be maximized and the noise influence can be minimized, and the signal-to-noise ratio of the demodulated input signal can be improved. Smoothing filtering is a technique commonly used in various communication systems to reduce the effects of noise, while matched filtering is the best receiving 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 sampling values, a specific method is implemented by averaging, by a shift register, continuous 3-point sampling value data, 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, as an output of the intermediate point.

S20, shortening the received current frame data by adopting a sliding window, carrying out correlation operation on the current frame data and the first end head sequence of the local pilot frequency after each shortening, and obtaining a corresponding absolute correlation value by complex modulus.

Specifically, for step S20, the length of the sliding window is set to 128 points, where the length can be set according to the actual requirement, and is not limited to 128 points; the sliding value of Rxsymbols_rec of the received data of one frame is 128 points until the last k is less than the frame length-sliding window length, the purpose is to take a section of 128-point data and perform correlation calculation on local pilot 128 point data, the local pilot frequency is fixed at the first 128 points, the sliding window value of 128 points and the local pilot frequency (1:128) are stored, and the module M1 (k) of the correlation value obtained by calculation is taken as a measurement.

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

and performing approximation analog synthesis operation of complex modulo by adopting a preset piecewise function to obtain an approximate modulus value of a correlation value M1 (k) between the 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 characteristic in the synchronous data, the embodiment can realize accurate frame synchronization, the training sequence set by the system generally has better cross correlation and autocorrelation characteristics, and the cross correlation value between different training sequences is small. The known training sequence and the received signal are subjected to sliding cross-correlation, a peak value is generated when the known training sequence and the received training sequence are aligned, and accurate timing synchronization can be performed by searching the peak value position of the cross-correlation.

As shown in fig. 5, a search window is cut when each frame of data received by the receiving end arrives, and then the received data in the window and the pre-stored synchronization training symbol are subjected to correlation operation to obtain a correlation value, and the correlation value is denoted 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 result of correlating the received signal with the known training sequence, R (d) is the energy of the known training sequence, M ₁ (d) Is a metric that produces a peak when the training sequence is known to align with the received training sequence,the position is the location, and by finding the maximum peak value, the position corresponding to the maximum peak value can be obtained in reverse. In order to reduce the amount of computation, the normalization of the correlation peak is not performedBy contrast, it is clear that the normalization process can be simplified to greatly reduce the number of operations.

The algorithm is improved in this embodiment, and the improved algorithm is as follows:

M ₁ (d)＝|P(d)|

where r (n) is the received signal and t (n) is the known training sequence by simplifying M ₁ (d) The corresponding division value can be removed, meanwhile, in order to simplify the operation, a modulo approximation algorithm is adopted for calculation, the conventional complex modulo computation is nonlinear, the hardware implementation is complex, the output delay is large, and the consumption of resources is high.

The calculation of complex modulus is equivalent to calculating the hypotenuse of a right triangle, which uses the real part and the imaginary part of the number as right-angle sides, when the two right-angle sides are unequal, the right-angle sides are approximately equal to the long right-angle side plus half of the short right-angle side, and the larger the difference of the lengths of the two right-angle sides is, the smaller the error is.

This approach to approximation reduces the amount of computation at the expense of accuracy, and in algorithms that require very high computational accuracy, the use of such algorithms is not recommended, but at the same time the coefficients can be slightly adjusted.

Another approximation algorithm is complex modulo calculation of the right triangle idea,

based on the above function curve fitting concept, this embodiment proposes a new piecewise function to approximate the modulo calculation:

assuming a is the long side of the right-angle side and b is the short side of the right-angle side, 4 functions are proposed to approximate the fit

y ₁ ＝a+b/18

y ₂ ＝13a/16+19b/32

y ₃ ＝70a/80+39b/80

y ₄ ＝33a/34+8b/34

The approximation of the modulus calculated by the above equation reduces the error, but the ratio of the real part to the imaginary part of the complex number is different, and the error of the result is also different.

During the simulation, the inventor of the invention finds that the optimization algorithm is in a/b<1.79 in the case of y ₂ =13a/16+19b/32 is approximately equal to the modulus at 1.79 <a/b<2.72, the error is large, and the exact value of the mode is approximately equal to y ₃ =70a/80+39b/80. At 2.72<a/b<6.15, when the exact value of the mode is approximately equal to y ₄ =33a/34+8b/34. The present example is therefore described in a/b>6.15 use y ₁ The value =a+b/18 is taken as the approximation of the modulus. 4 different fitting functions in different a/b regions, andapproximately equal, by error analysis, different function curves and +.>Based on this idea, an optimized piecewise function can be provided instead of +.>

y _max ＝max(y ₁ ,y ₂ ,y ₃ ,y ₄ )

As shown in fig. 6, it was found from simulation analysis that the positive maximum relative error of the curve was 0.15%, the negative maximum relative error was-0.56%, and the total relative error (the absolute value of the positive and negative relative errors was large) was 0.56%. Each section adopts an approximate modulo formula with different error characteristics, and the relative error of not more than 0.56% is realized by combining the approximate modulo formulas, which is 1.82-4.2 times of other approximation algorithms of the same type.

S30, taking the first 16 points of accumulation processing for 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.

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

The correlation value is subjected to 16-point accumulation and a low-pass filter, and a dynamic threshold value is obtained by multiplying the filter coefficient;

and carrying out mean value operation on the dynamic threshold value and the threshold value of the last frame.

Specifically, for step S30, 16-point accumulation is taken for each incoming data M1 (K), where M1 (K) is a 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 dynamic Threshold is obtained by multiplying the obtained average value by the low-pass filter coefficient, where the fixed coefficient is xs, typically 3.5, and properly selecting this coefficient, a balance between detection performance and complexity can be obtained.

S40, after judging that the absolute correlation value is larger than the corresponding dynamic threshold value, storing the absolute correlation value and the position of the absolute correlation value.

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

S50, performing operation judgment according to all the stored absolute correlation values and the positions thereof while continuously completing correlation operation of the frame data in the sliding window, and obtaining an operation judgment result.

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

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

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

Optionally, in some embodiments, when the operation judgment result of the step S60 meets the operation judgment rule of the preset correlation peak, the searching to obtain the first section of correlation peak may specifically include:

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

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

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;

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

In a specific embodiment, the frame synchronization may be subdivided into two parts, namely, frame arrival detection and frame start accurate position location or referred to as coarse frame synchronization and fine frame synchronization, and the carrier frequency offset needs to be estimated immediately after the accurate data frame start position is found, and the signal is subjected to frequency offset compensation by using the estimation result so as to ensure orthogonality among the symbol subcarriers entered as much as possible.

The coarse frame synchronization is to find a start position of a data symbol, and find an end position of a last synchronization header by detecting the synchronization header. The frame synchronization process is performed in two steps, namely coarse synchronization, finding the approximate starting position of the synchronization head, then fine synchronization, and determining the starting position of the data symbol on the basis of the coarse synchronization determination range. The fine frame synchronization is that the data can be subjected to coarse frame synchronization, and the purpose of the fine frame synchronization 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 a plurality of nearby sampling points to determine the accurate starting position of the synchronous frame head of each transmitting antenna. And correlating the received signal with the transmission sequence of each antenna.

S70, outputting a target frame according to the first section of correlation peak, then carrying out frame synchronization, and reserving a threshold value calculated finally from current frame data to the next frame for average processing.

Specifically, for step S70, the target frame is output according to the data extracted from the first section of correlation peak, and the threshold of the target frame is reserved to the next frame to continue to perform average calculation, and erroneous judgment and missed judgment caused by too low threshold can be reduced under certain conditions through long-time threshold reservation.

As shown in fig. 7, in a specific embodiment, the embodiment of the present application further provides a second implementation manner of the symbol synchronization method, which specifically includes the following steps: receiving one frame of data of an antenna, a last frame of reservation threshold, a low-pass filter coefficient and xs threshold amplification factor, and extracting 128 points (namely the length of a sliding window) from the beginning of a frame; judging whether the current position is smaller than or equal to a frame length-127 x N point, if so, shortening the received data by using a sliding window with the length of 128 points, correlating with the first end head sequence 128 points of the local pilot frequency, taking a module to obtain M1 (k), carrying out single sampling, accumulating the M1 (k) by 16 points, multiplying the coefficient (xs) by the low-pass filtering (b) to obtain a Threshold, taking an average value with the Threshold of the last frame, judging whether the M1 (k) is larger than the Threshold, if so, storing the point M1 (k) with the Threshold and the corresponding position k, continuing sliding the window, wherein k=k+1, namely the sliding distance is 1 each time until k is larger than the frame length-127 x N point; if M1 (k) is not greater than the threshold, the sliding window is continued. And when the sliding window performs correlation operation, judging whether the number of the correlation peaks at the first end of the rough search is larger than a preset number, if yes, judging whether the difference value of the coordinates of the points adjacent to the detected and stored correlation values is smaller than or equal to 3, if yes, storing the position k corresponding to the correlation values and calculating the data of continuous points, if not, performing fine search after finding out the first section of the correlation peaks, expanding the search range of 10 points before and after the point range in the stored first section of the correlation peaks, searching the first maximum value and the corresponding position thereof continuously from the first section of the peak range, setting the marker bit, extracting the data, reserving the threshold calculated finally by the frame to the next frame for average value processing, and outputting the frame data.

As can be seen from the above, the symbol synchronization method provided in the embodiments of the present application includes: receiving current frame data through a receiving antenna; the received current frame data is truncated by adopting a sliding window, and after each time of truncation, the current frame data and a first end head sequence of a local pilot frequency are subjected to correlation operation, and a corresponding correlation value is obtained by taking a module; the correlation value obtained after each correlation operation is subjected to complex modulus to obtain a corresponding absolute correlation value, the absolute correlation value is used for calculating the accumulation of the first 16 points, and a dynamic threshold is obtained through low-pass filtering and threshold coefficient amplification; after judging that the absolute correlation value is larger than the corresponding dynamic threshold value, storing the absolute correlation value and the position thereof; when the sliding window is adopted to continuously complete the correlation operation of the current truncated frame data, carrying out operation judgment according to the magnitude 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 a preset correlation peak operation judgment rule; and outputting the target frame according to the first section of correlation peak, then carrying out frame synchronization, and reserving the threshold value of the current frame data to the next frame.

In summary, the symbol synchronization method provided in the embodiment of the present application has the following beneficial effects: in the wireless channel with intersymbol interference and multipath fading, the method can improve the correct detection rate of frame synchronization and reduce the average search time of frame heads on the premise of not increasing the complexity of the system, and is suitable for a high-speed mobile communication system. Under the test of different data bits, the device can be correctly and effectively positioned to a correct starting position under the condition of accuracy loss permission; the method can accurately and rapidly perform frame synchronization positioning under the condition of low signal-to-noise ratio, has good detection performance, and can be applied to complex severe environments due to the influence of noise and excessive attenuation of a received signal; compared with the original frame synchronization algorithm, the method has the advantages that the method can greatly save hardware development resources such as FPGA and the like by reducing the improvement of the operation amount, can reduce the operation time and can rapidly perform frame synchronization symbol positioning; through the thought of dynamic threshold, can also improve the frame synchronization accuracy under the circumstances of reducing algorithm complexity, compare with fixed threshold's detection algorithm, self-adaptation dynamic threshold adjustment's detection algorithm has the advantage that detection probability is high and the correct capture time is short in the aspect of detecting frame synchronization information.

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

Wherein, the receiving module 100 is configured to receive current frame data through a receiving antenna.

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

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

The operation judging module 400 is configured to perform operation judgment according to all the stored absolute correlation values and the positions thereof 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 section of correlation peak when the operation and judgment result accords with the operation and judgment rule of the preset correlation peak, and expand the range in the section of correlation peak to search for the maximum absolute correlation value and the corresponding position thereof.

And the frame output module 600 is configured to output a target frame according to the first correlation peak, perform frame synchronization, and reserve a threshold value of current frame data until a next frame is subjected to mean processing. .

In summary, in the symbol timing synchronization system provided in the embodiments of the present application, the receiving module 100 is configured to receive current frame data through a receiving antenna; the correlation operation module 200 is configured to truncate the received current frame data using a sliding window, perform correlation operation with the first end header sequence of the local pilot after each truncation, and perform modulo extraction to obtain a corresponding correlation value; the dynamic threshold module 300 is configured to calculate the previous 16-point accumulation by using an absolute correlation value, obtain a dynamic threshold after low-pass and coefficient amplification, and store the magnitude and the position of the absolute correlation value after judging that the absolute correlation value is greater than a corresponding dynamic threshold; the operation judging module 400 is configured to perform operation judgment according to all the stored absolute correlation values and the positions thereof when the sliding window continuously completes the correlation operation of the frame data, so as to obtain an operation judging result; the correlation peak searching module 500 is configured to search for a first section of correlation peak when the operation and judgment result meets a preset operation and judgment rule, and if not, continue sliding the window to repeat the prosecution operation; the frame output module 600 is configured to output a target frame according to the first correlation peak, perform frame synchronization, and reserve a threshold value of current frame data to a next frame.

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

Referring to fig. 9, a computer device is further provided in the embodiment of the present application, where the computer device may be a server, and the 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 is configured to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, computer programs, and a database. The memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage media. The database of the computer equipment 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; the received current frame data is truncated by adopting a sliding window, and after each time of truncation, the current frame data and a first end head sequence of a local pilot frequency are subjected to correlation operation, and a corresponding correlation value is obtained by taking a module; calculating the accumulation of the first 16 points by using the absolute correlation value, and obtaining a dynamic threshold through low-pass filtering and threshold coefficient amplification; after judging that the absolute correlation value is larger than the corresponding dynamic threshold value, storing the absolute correlation value and the position thereof; when the current sliding window continuously carries out the correlation operation of the current frame data, carrying out operation judgment according to the stored absolute correlation values and the positions thereof 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 a preset correlation peak operation judgment rule; and outputting the target frame according to the first section of correlation peak, then carrying out frame synchronization, and reserving the last calculated threshold value of the current frame data until the next frame to carry out average value calculation.

An embodiment of the present application further provides a computer readable storage medium having stored thereon a computer program which, when executed by a processor, implements a symbol synchronization method comprising the steps of: receiving current frame data through a receiving antenna; shortening the received current frame data by adopting a sliding window, carrying out correlation operation on the current frame data and a first end head sequence of a local pilot frequency after each shortening, and taking a module to obtain a corresponding absolute correlation value; calculating the accumulation of the first 16 points by using the absolute correlation value, and obtaining a dynamic threshold through low-pass filtering and threshold coefficient amplification; after judging that the absolute correlation value is larger than the corresponding dynamic threshold value, storing the absolute correlation value and the position thereof; when the current sliding window continuously carries out the correlation operation of the current frame data, carrying out operation judgment according to the stored absolute correlation values and the positions thereof 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 a preset correlation peak operation judgment rule; and outputting the target frame according to the first section of correlation peak, then carrying out frame synchronization, and reserving the last calculated threshold value of the current frame data until the next frame to carry out average value calculation.

According to the symbol synchronization method, the dynamic threshold detection algorithm and the approximate approximation mode calculation method are combined, and the frame header can be quickly and accurately positioned by adopting a processing method of reserving a detection threshold and multi-frame average, so that frame information is recovered, the problem that the synchronous false alarm rate and the false alarm rate of a fixed threshold frame synchronization algorithm are multiplied due to uncorrelated fading and multipath interference under a Rayleigh fading channel is solved, frame synchronization positioning can be accurately and quickly performed under a low signal-to-noise ratio or a complex environment, the complexity of the algorithm is reduced, and meanwhile, the frame synchronization accuracy is improved, and the detection performance and efficiency of the frame synchronization positioning are improved.

It can be understood that the above scenario is merely an example, and does not constitute a limitation on the application scenario of the technical solution provided in the embodiments of the present application, and the technical solution of the present application may also be applied to other scenarios. For example, as one of ordinary skill in the art can know, with the evolution of the system architecture and the appearance of new service scenarios, the technical solutions provided in the embodiments of the present application are equally applicable to similar technical problems.

The foregoing embodiment numbers of the present application are merely for describing, and do not represent advantages or 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 of the embodiment of the application can be combined, divided and pruned according to actual needs.

In this application, the same or similar term concept, technical solution, and/or application scenario description will generally be described in detail only when first appearing, and when repeated later, for brevity, will not generally be repeated, and when understanding the content of the technical solution of the present application, etc., reference may be made to the previous related detailed description thereof for the same or similar term concept, technical solution, and/or application scenario description, etc., which are not described in detail later.

In this application, the descriptions of the embodiments are focused on, and the details or descriptions of one embodiment may be found in the related descriptions of other embodiments.

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

From the above description of the embodiments, it will be clear to those skilled in the art that the above-described embodiment method may be implemented by means of software plus a necessary general hardware platform, but of course may also be implemented by means of hardware, but in many cases the former is a preferred embodiment. Based on such understanding, the technical solution of the present application may be embodied essentially or in a part contributing to the prior art in the form of a software product stored in a storage medium (e.g. ROM/RAM, magnetic disk, optical disk) as above, including several instructions for causing a terminal device (which may be a mobile phone, a computer, a server, a controlled terminal, or a network device, etc.) to perform the method of each embodiment of the present application.

In the above embodiments, it may be implemented in whole or in part 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. When the computer program instructions are loaded and executed on a computer, the processes or functions in accordance with embodiments of the present application are produced in whole or in part. The computer may be a general purpose computer, a special purpose computer, a network of computers, or other programmable devices. The computer instructions may be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another computer-readable storage medium, 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 a wired (e.g., coaxial cable, fiber optic, digital subscriber line), or wireless (e.g., infrared, wireless, microwave, etc.). Computer readable storage media can be any available media that can be accessed by a computer or data storage devices, such as servers, data centers, etc., that contain an integration of one or more available media. Usable media may be magnetic media (e.g., floppy disks, storage disks, magnetic tape), optical media (e.g., DVD), or semiconductor media (e.g., solid State Disk (SSD)), among others.

The foregoing description is only of the preferred embodiments of the present application, and is not intended to limit the scope of the claims, and all equivalent structures or equivalent processes using the descriptions and drawings of the present application, or direct or indirect application in other related technical fields are included in the scope of the claims of the present application.

Claims

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

receiving current frame data through a receiving antenna;

2. The symbol synchronization method of claim 1, wherein after the receiving current frame data through a receiving antenna, the method further comprises:

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

4. The symbol synchronization method as claimed in claim 1, wherein the step of taking the first 16 points of accumulation processing for each obtained absolute correlation value, multiplying the obtained absolute correlation value by a coefficient, and performing low-pass filtering as a dynamic threshold of the current absolute correlation value point comprises:

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

6. The symbol synchronization method according to claim 1, wherein when the operation judgment result is judged to conform to an operation judgment rule of a preset correlation peak, searching to obtain a first section of correlation peak specifically includes:

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

8. A symbol synchronization system, comprising:

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

10. A computer readable storage medium having stored thereon a computer program, characterized in that the computer program, when executed by a processor, implements the steps of the symbol synchronization method of any of claims 1 to 7.