CN117544469A - Frame synchronization method, equipment and storage medium based on time-frequency processing technology - Google Patents

Abstract

The invention provides a frame synchronization method based on a time-frequency processing technology, which comprises the following steps: generating constant modulus CAZAC sequence, and taking conjugate of the second half section as transmitting sequence and local sequence; receiving a sending sequence, and performing time domain correlation matching on the receiving sequence and a local sequence; if the matching result has two peaks, performing correlation calculation on the sliding access of the received data and the local sequence in the time domain through a sliding window, performing FFT (fast Fourier transform) on the calculation result, recording the maximum position higher than a second threshold and the position of the corresponding sliding window, and calculating the coarse synchronization position and the frequency offset; if only a single peak value exists, directly calculating a coarse synchronization position and frequency offset; and carrying out frequency offset compensation, carrying out correlation matching on the data subjected to frequency offset compensation and a local sequence in a time domain, carrying out peak value search, and finding out a precise synchronization position according to a correlation peak value. The invention does not need to construct a plurality of synchronous sequences, saves time-frequency resources, and increases the probability and the correctness of synchronous position detection by adopting a double detection mechanism.

Description

A frame synchronization method, equipment and storage medium based on time-frequency processing technology

Technical field

The present invention relates to the field of wireless communication technology, and in particular to a frame synchronization method, equipment and storage medium based on time-frequency processing technology.

Background technique

In burst communications, data-assisted synchronization methods have high synchronization accuracy and low computational complexity, and have received more and more attention. Therefore, OFDM systems usually use data-assisted synchronization methods. However, in OFDM systems, timing and Frequency deviation is particularly sensitive. Small timing or frequency offset errors will have a greater impact on the OFDM system. Therefore, synchronization within a large frequency offset estimation range under low signal-to-noise ratio is the goal pursued by researchers.

In order to obtain better synchronization performance, researchers introduced the CAZAC sequence. The CAZAC sequence has good correlation characteristics. Timing synchronization is obtained by using the local sequence to correlate with the received signal. However, direct correlation is greatly affected by frequency offset during timing estimation. In order to resist the influence of greater frequency offset, it is necessary to divide the received signal into more small segments. Each part is cross-correlated with the local sequence and then the power is summed. However, since the number of relevant sampling points becomes smaller after segmentation, this in turn leads to extreme It is susceptible to the influence of noise. To solve this problem, the only way to solve this problem is to increase the number of symbols of the OFDM synchronization sequence, which will occupy more time-frequency resources. Therefore, in the case of harsh environment and limited resources, these methods have small resistance to frequency offset range and Disadvantages of poor performance.

Contents of the invention

In order to solve the problems existing in the existing technology, a frame synchronization method based on time-frequency processing technology is provided. The constant-module CAZAC sequence is used to construct OFDM synchronization symbols. After dual detection processing in the time-frequency domain, the frame synchronization method is improved in the low signal-to-noise ratio. Frame synchronization capability in frequency offset environment.

The first aspect of the present invention provides a frame synchronization method based on time-frequency processing technology, including:

Step 1. Generate a constant modulus CAZAC sequence and conjugate its second half to obtain the final transmission sequence, which is also used as a local sequence;

Step 2. Receive the transmitted sequence through the antenna to obtain the received sequence, and perform time domain correlation matching between the received sequence and the local sequence;

Step 3. Compare the time domain correlation matching result with the first threshold. If there are two peaks, go to step 4; if there is only a single peak, go to step 5;

Step 4. Based on the positions of the two peaks, calculate the coarse synchronization position and frequency offset of the received data, and proceed to step 8;

Step 5: Open a window at half the sliding length at the single peak position, and perform correlation calculations on the received data sliding count and the local sequence in the time domain;

Step 6: Perform FFT transformation on the relevant calculation results, and record the maximum value position higher than the second threshold and the corresponding sliding window position;

Step 7. Calculate the coarse synchronization position and frequency offset based on the single peak position and the corresponding sliding window position;

Step 8: Taking the coarse synchronization position as the starting point, retrieve the received data backwards and the same length as the local sequence, and perform frequency offset compensation;

Step 9: Correlate the frequency offset compensated data with the local sequence in the time domain;

Step 10: Perform a peak search on the correlation matching results, and find the precise synchronization position based on the correlation peak.

As a preferred solution, in step 1, the transmission sequence generation method is:

Among them, local_seq is the sending sequence, and N is the length of the CAZAC sequence.

As a preferred solution, in step 2, the relevant matching method is:

Among them, rx_corr is the correlation matching calculation result, and rx_seq is the received sequence.

As a preferred solution, in step 4, the rough synchronization position calculation method is:

Cpos＝(pos1+pos2)/2

Among them, Cpos is the coarse synchronization position, pos1 and pos2 are the positions of the two peaks respectively.

As a preferred solution, in step 4, the frequency offset is calculated as:

fre_offset＝Fs/N*(pos1-pos2)/2

Among them, fre_offset is the frequency offset, Fs is the sampling rate of the data, and N is the length of the local sequence.

As a preferred solution, in step 5, the relevant calculation method is:

rx_corr_win(n)=rx_seq(pos3-m+n)*local_seq(n)

Among them, rx_corr_win is the relevant calculation result, pos3 is the single peak position, m is the value of the sliding window, m=-win/2,-win/2+1,...,win/2, win is the data sliding length, n is the sequence No., n=1,2,…,N.

As a preferred solution, in step 7, the rough synchronization position calculation method is:

Cpos＝pos3+m

Among them, Cpos is the coarse synchronization position.

As a preferred solution, in step 7, the frequency offset calculation method is:

fre_offset=Fs/N_FFT*ind

Among them, Fs is the sampling rate of the data, N_FFT is the number of FFT transformation points, and ind is the maximum value position.

A second aspect of the present invention provides an electronic device, including a memory and a processor. The memory stores a computer program that can be loaded by the processor and execute the above frame synchronization method based on time-frequency processing technology.

A third aspect of the present invention provides a computer-readable storage medium on which computer program instructions are stored. When the program instructions are executed by a processor, they are used to implement the process corresponding to the above-mentioned frame synchronization method based on time-frequency processing technology.

Compared with the existing technology, the beneficial effects of adopting the above technical solution are:

1. Based on the time-frequency processing method, the present invention does not need to construct multiple synchronization sequences to occupy multiple OFDM symbols, saving time-frequency resources;

2. The present invention uses the symmetry of the CAZAC sequence to conjugate the second half of the original sequence and transform the sequence characteristics into two peaks after correlation matching in the time domain, and can calculate the frequency offset of the received signal;

3. When the matching of two peaks in the time domain is not obvious, the present invention uses a single peak position to perform FFT transformation on the time domain data, and then performs peak detection in the frequency domain. This dual detection mechanism increases the probability of synchronous position detection and Correctness.

4. After performing time-frequency domain detection, the present invention compensates the received signal according to the calculated frequency offset. After matching with the local sequence again, it can accurately synchronize OFDM timing according to the peak value, reducing the impact of subsequent timing errors on OFDM. The effect of phase rotation.

Description of drawings

Figure 1 is a schematic signal flow diagram of a frame synchronization method based on time-frequency processing technology according to the present invention.

Figure 2 is a diagram of two peaks after correlation matching between the received data and the local sequence according to the present invention.

Figure 3 is a spectrum diagram of the received data after performing FFT after optimal sliding window selection according to the present invention.

Figure 4 is a peak diagram after synchronization matching after frequency offset correction according to the present invention.

Detailed ways

The embodiments of the present application are described in detail below. Examples of the embodiments are shown in the drawings, where the same or similar reference numerals throughout represent the same or similar modules or modules with the same or similar functions. The embodiments described below with reference to the drawings are exemplary and are only used to explain the present application and cannot be understood as limiting the present application. On the contrary, the embodiments of the present application include all changes, modifications and equivalents falling within the spirit and scope of the appended claims.

In order to resist frequency offset in the case of harsh environment and limited resources, the embodiment of the present invention proposes a frame synchronization method based on time-frequency processing technology, taking a transmission sequence with a length of 2048 points as an example, which occupies one OFDM symbols, the specific scheme is as follows:

Step 1. Generate a constant-module CAZAC sequence and conjugate its second half to obtain the final transmission sequence, which is also used as a local sequence. The sending sequence generation method is:

Among them, local_seq is the sending sequence, and N is the length of the CAZAC sequence.

Step 2: Receive the transmitted sequence through the antenna to obtain the received sequence, and perform time domain correlation matching between the received sequence and the local sequence. In this embodiment, the relevant matching method is:

Among them, rx_corr is the correlation matching calculation result, and rx_seq is the received sequence.

Step 3. Compare the time domain correlation matching result with the first threshold. If there are two peaks, as shown in Figure 2, there are two peaks after correlation matching between the received sequence and the local sequence. Go to step 4; if there are only For a single peak, go to step 5.

Step 4. Calculate the coarse synchronization position and frequency offset of the received data based on the positions of the two peaks, and proceed to step 8.

In this embodiment, the rough synchronization position calculation method is:

Cpos＝(pos1+pos2)/2

Among them, Cpos is the coarse synchronization position, pos1 and pos2 are the positions of the two peaks respectively.

The calculation method of frequency offset is:

fre_offset＝Fs/N*(pos1-pos2)/2

Among them, fre_offset is the frequency offset, Fs is the sampling rate of the data, and N is the length of the local sequence.

Step 5: Open the window at the single peak position by retreating to the win/2 point as the starting point, and perform correlation calculations on the sliding number of received data and the local sequence in the time domain.

In this embodiment, the relevant calculation method is:

rx_corr_win(n)=rx_seq(pos3-m+n)*local_seq(n)

Among them, rx_corr_win is the relevant calculation result, pos3 is the single peak position, m is the value of the sliding window, m=-win/2,-win/2+1,...,win/2, win is the data sliding length, n is the sequence No., n=1,2,…,N.

Step 6: Perform FFT transformation on the relevant calculation results, and record the maximum value position higher than the second threshold and the corresponding sliding window position. Please refer to Figure 3, which shows the spectrum diagram of the received data when the FFT is performed on the optimal sliding window and the local sequence correlation calculation, and the frequency domain is higher than the maximum value of the second threshold.

Step 7. Calculate the coarse synchronization position and frequency offset based on the single peak position and the corresponding sliding window position.

In this embodiment, the rough synchronization position calculation method is:

Cpos＝pos3+m

Among them, Cpos is the coarse synchronization position.

The frequency offset calculation method is:

fre_offset=Fs/N_FFT*ind

Among them, Fs is the sampling rate of the data, N_FFT is the number of FFT transformation points, and ind is the maximum value position.

Step 8: Taking the coarse synchronization position as the starting point, retrieve the received data backwards and the same length as the local sequence, and perform frequency offset compensation;

Step 9: Correlate the frequency offset compensated data with the local sequence in the time domain;

Step 10. Please refer to Figure 4 to perform a peak search on the correlation matching results and find the precise synchronization position based on the correlation peak.

At the same time, the present invention provides an electronic device, including a memory and a processor. The memory stores a computer program that can be loaded by the processor and execute the above frame synchronization method based on time-frequency processing technology.

In particular, according to embodiments of the present application, the process described above with reference to the flowchart may be implemented as a computer software program. For example, embodiments of the present application include a computer program product including a computer program carried on a computer-readable medium, the computer program containing program code for performing the method illustrated in the flowchart.

It should be noted that the computer-readable medium shown in the embodiments of the present application may be a computer-readable signal medium or a computer-readable storage medium, or any combination of the above two. The computer-readable storage medium may be, for example, but is not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus or device, or any combination thereof. More specific examples of computer readable storage media may include, but are not limited to: an electrical connection having one or more wires, a portable computer disk, a hard drive, random access memory (RAM), read only memory (ROM), removable Erasable Programmable Read Only Memory (EPROM), flash memory, optical fiber, portable compact disk read-only memory (Compact Disc Read-Only Memory, CD-ROM), optical storage device, magnetic storage device, or any of the above suitable The combination. As used herein, a computer-readable storage medium may be any tangible medium that contains or stores a program for use by or in connection with an instruction execution system, apparatus, or device. In this application, the computer-readable signal medium may include a data signal propagated in baseband or as part of a carrier wave, in which computer-readable program code is carried. Such propagated data signals may take many forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination of the above. A computer-readable signal medium may also be any computer-readable medium other than a computer-readable storage medium that can send, propagate, or transmit a program for use by or in connection with an instruction execution system, apparatus, or device . Program code embodied on a computer-readable medium may be transmitted using any suitable medium, including but not limited to: wireless, wired, etc., or any suitable combination of the above.

The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operations of possible implementations of systems, methods, and computer program products according to various embodiments of the present application. Each block in the flow chart or block diagram may represent a module, program segment, or part of the code. The above-mentioned module, program segment, or part of the code includes one or more executable components for implementing the specified logical function. instruction. It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown one after another may actually execute substantially in parallel, or they may sometimes execute in the reverse order, depending on the functionality involved. It will also be noted that each block in the block diagram or flowchart illustration, and combinations of blocks in the block diagram or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or operations, or may be implemented by special purpose hardware-based systems that perform the specified functions or operations. Achieved by a combination of specialized hardware and computer instructions.

The units involved in the embodiments of this application can be implemented in software or hardware, and the described units can also be provided in a processor. Among them, the names of these units do not constitute a limitation on the unit itself under certain circumstances.

As another aspect, the present application also provides a computer program product or computer program, which computer program product or computer program includes computer instructions, and the computer instructions are stored in a computer-readable storage medium. The processor of the computer device reads the computer instructions from the computer-readable storage medium, and the processor executes the computer instructions, so that the computer device performs the frame synchronization method based on the time-frequency processing technology described in the above embodiment.

As another aspect, this application also provides a computer-readable medium. The computer-readable medium may be included in the electronic device described in the above embodiments; it may also exist independently without being assembled into the electronic device. middle. The computer-readable medium carries one or more programs. When the one or more programs are executed by an electronic device, the electronic device implements the frame synchronization method based on time-frequency processing technology described in the above embodiments.

It should be noted that although several modules or units of equipment for action execution are mentioned in the above detailed description, this division is not mandatory. In fact, according to the embodiments of the present application, the features and functions of two or more modules or units described above may be embodied in one module or unit. Conversely, the features and functions of one module or unit described above may be further divided into being embodied by multiple modules or units.

Through the above description of the embodiments, those skilled in the art can easily understand that the example embodiments described here can be implemented by software, or can be implemented by software combined with necessary hardware. Therefore, the technical solution according to the embodiment of the present application can be embodied in the form of a software product, which can be stored in a non-volatile storage medium (which can be a CD-ROM, U disk, mobile hard disk, etc.) or on the network , including several instructions to cause a computing device (which can be a personal computer, server, touch terminal, or network device, etc.) to execute the method according to the embodiment of the present application.

It should be noted that in the description of the embodiments of the present invention, it should also be noted that, unless otherwise clearly stated and limited, the terms "setting" and "connection" should be understood in a broad sense. For example, it can be a fixed connection, or a fixed connection. It can be detachably connected or integrally connected; it can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood in specific situations; the drawings in the embodiments are used to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, all The described embodiments are some, but not all, of the embodiments of the present invention. The components of the embodiments of the invention generally described and illustrated in the figures herein may be arranged and designed in a variety of different configurations.

Although the embodiments of the present application have been shown and described above, it can be understood that the above-mentioned embodiments are illustrative and cannot be understood as limitations of the present application. Those of ordinary skill in the art can make modifications to the above-mentioned embodiments within the scope of the present application. The embodiments are subject to changes, modifications, substitutions and variations.

Claims (10)

1. A frame synchronization method based on time-frequency processing technology, which is characterized by including: Step 1. Generate a constant modulus CAZAC sequence and conjugate its second half to obtain the final transmission sequence, which is also used as a local sequence; Step 2. Receive the transmitted sequence through the antenna to obtain the received sequence, and perform time domain correlation matching between the received sequence and the local sequence; Step 3. Compare the time domain correlation matching result with the first threshold. If there are two peaks, go to step 4; if there is only a single peak, go to step 5; Step 4. Based on the positions of the two peaks, calculate the coarse synchronization position and frequency offset of the received data, and proceed to step 8; Step 5: Open a window at half the sliding length at the single peak position, and perform correlation calculations on the received data sliding count and the local sequence in the time domain; Step 6: Perform FFT transformation on the relevant calculation results, and record the maximum value position higher than the second threshold and the corresponding sliding window position; Step 7. Calculate the coarse synchronization position and frequency offset based on the single peak position and the corresponding sliding window position; Step 8: Taking the coarse synchronization position as the starting point, retrieve the received data backwards and the same length as the local sequence, and perform frequency offset compensation; Step 9: Correlate the frequency offset compensated data with the local sequence in the time domain; Step 10: Perform a peak search on the correlation matching results, and find the precise synchronization position based on the correlation peak. 2. The frame synchronization method based on time-frequency processing technology according to claim 1, characterized in that, in step 1, the transmission sequence generation method is: Among them, local_seq is the sending sequence, and N is the length of the CAZAC sequence. 3. The frame synchronization method based on time-frequency processing technology according to claim 2, characterized in that, in step 2, the correlation matching method is: Among them, rx_corr is the correlation matching calculation result, and rx_seq is the received sequence. 4. The frame synchronization method based on time-frequency processing technology according to claim 1, characterized in that in step 4, the coarse synchronization position calculation method is: Cpos＝(pos1+pos2)/2 Among them, Cpos is the coarse synchronization position, pos1 and pos2 are the positions of the two peaks respectively. 5. The frame synchronization method based on time-frequency processing technology according to claim 4, characterized in that in step 4, the frequency offset calculation method is: fre_offset＝Fs/N*(pos1-pos2)/2 Among them, fre_offset is the frequency offset, Fs is the sampling rate of the data, and N is the length of the local sequence. 6. The frame synchronization method based on time-frequency processing technology according to claim 1, characterized in that in step 5, the relevant calculation method is: rx_corr_win(n)=rx_seq(pos3-m+n)*local_seq(n) Among them, rx_corr_win is the relevant calculation result, pos3 is the single peak position, m is the value of the sliding window, m=-win/2,-win/2+1,...,win/2, win is the data sliding length, n is the sequence No., n=1,2,…,N. 7. The frame synchronization method based on time-frequency processing technology according to claim 6, characterized in that in step 7, the coarse synchronization position calculation method is: Cpos＝pos3+m Among them, Cpos is the coarse synchronization position. 8. The frame synchronization method based on time-frequency processing technology according to claim 7, characterized in that, in step 7, the frequency offset calculation method is: fre_offset=Fs/N_FFT*ind Among them, Fs is the sampling rate of the data, N_FFT is the number of FFT transformation points, and ind is the maximum value position. 9. An electronic device, characterized in that it includes a memory and a processor, and the memory stores frames that can be loaded by the processor and execute the time-frequency processing technology based on any one of claims 1-8. A computer program corresponding to the synchronization method. 10. A computer-readable storage medium on which computer program instructions are stored, characterized in that, when executed by a processor, the program instructions are used to implement the time-frequency processing according to any one of claims 1-8. The process corresponding to the technical frame synchronization method.