A Frame Structure Design Method and Frame Synchronization Method under a Dynamic Occlusion Channel

Abstract

The present invention relates to a frame structure design method and a frame synchronization method under a dynamic occlusion channel, belonging to the technical field of wireless communication. It includes a frame structure design method and a frame synchronization method. The frame structure design method determines the data frame structure and sub-frame structure according to the occlusion period of the dynamic occlusion channel. The sub-frame structure includes a synchronization sequence, a verification sequence, and data. The frame synchronization method includes the synchronization, verification, and positioning of the data frame, and finally extracts the data from the synchronized data frame. Through the frame structure composed of multiple sub-frames with consistent formats and different lengths, the present invention effectively solves the problem of missed capture under the dynamic occlusion channel. Moreover, each sub-frame contains a synchronization sequence and a verification sequence, which can accurately capture the data frame, reduce the probability of false capture in synchronization capture, achieve reliable communication under the dynamic occlusion channel, and improve the performance of the communication system.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless communication, and particularly relates to a frame structure design method and a frame synchronization method under a dynamically occluded channel. Background Art

[0002] In a wireless communication system, in order to correctly demodulate information, it is necessary to achieve synchronization between the receiving end and the transmitting end. However, in a dynamically occluded channel, the signal will be dynamically and periodically occluded, affecting signal synchronization. Currently, the most widely used communication technology for dealing with dynamic occlusion is the physical layer channel coding technology. By utilizing the powerful error correction ability of error control coding, the code length or code rate of the error control coding is designed for the occlusion situation, and then interleaving is combined to overcome the influence of occlusion on the signal. The physical layer channel coding technology is easy to combine with methods such as spreading spectrum and multi - ary modulation to meet different actual usage requirements, and its bandwidth efficiency is stable, making it easy for resource allocation and management. However, the disadvantage of this technology is that ordinary frame structures will still have false captures and missed captures under dynamic occlusion, and cannot correctly synchronize the signal.

[0003] In helicopter - satellite communication, due to the influence of the helicopter's mechanical structure, the satellite antenna is installed on the helicopter's head or tail beam. This structure causes the on - board antenna to be periodically occluded by the rotor when the helicopter is flying in the air, and the occlusion situation corresponding to different rotor speeds is dynamically changing. For example, the invention patent with the publication number CN105656831A proposes a helicopter - satellite communication transmission and reception method. The frame structure of the burst spread - spectrum signal consists of a unique code and the data to be carried, and only the unique code is used as the preamble sequence of the burst frame. Among them, the burst signal receiving method based on FFT can simultaneously complete tasks such as spreading code acquisition, frequency offset estimation, and frame synchronization detection. Although this method reduces the average acquisition time in a low - signal - to - noise ratio environment and short - time burst mode, and improves the system transmission efficiency, there are still problems of high false capture and missed capture probabilities and low communication system performance.

[0004] Another example is the invention patent with the publication number CN108023681A, which proposes an error control method based on punctured interleaving mapping. This method performs error - correction coding on the transmitted information at the ground station, obtains the data after error coding, sends it into the punctured interleaver for interleaving mapping and then transmits it, which can better solve the influence of rotor occlusion on error control in the reverse link of helicopter - satellite communication, has good stability and is easy to implement. However, the design of the frame structure of this method needs to be designed according to a certain helicopter occlusion pattern or the equivalent minimum occlusion duty cycle of a certain group of helicopters.

[0005] In summary, the ordinary frame structure design needs to be designed for a fixed occlusion pattern or the equivalent minimum occlusion duty cycle. Under dynamic occlusion, there will still be false captures and missed captures, and it is impossible to achieve synchronization between the receiving end and the sending end, and it is impossible to correctly demodulate the information, resulting in a problem of low performance of the communication system. Therefore, there is an urgent need to provide a reasonable frame structure to overcome dynamic occlusion, achieve signal synchronization under different dynamic occlusion channels, and efficiently and accurately demodulate the information. Summary of the Invention

[0006] To solve the above problems existing in the prior art, the present invention provides a frame structure design method and a frame synchronization method under a dynamic occlusion channel. The frame structure composed of multiple sub-frames with the same format and different lengths effectively solves the problem of missed capture under the dynamic occlusion channel. And each sub-frame contains a synchronization sequence and a verification sequence, which can accurately capture the data frame, reduce the probability of false capture in synchronization capture, achieve reliable communication under the dynamic occlusion channel, and improve the performance of the communication system.

[0007] The object of the present invention can be achieved by the following technical solutions:

[0008] The present invention provides a frame structure design method under a dynamic occlusion channel. The frame structure includes N sub-frames. Define i as the sub-frame number, and the value range is 0 to N - 1. The sub-frame includes a synchronization sequence, a verification sequence, and data. The frame structure design method specifically includes the following steps:

[0009] S11. Determine the occlusion period range T of the dynamic occlusion channel min ~T max where T min is the minimum value of the occlusion period of the dynamic occlusion channel, and T max is the maximum value of the occlusion period of the dynamic occlusion channel;

[0010] S12. Determine the frame length and structure of the data frame according to the occlusion period range of the dynamic occlusion channel;

[0011] S13. Determine the length L of each sub-frame i i ;

[0012] S14. Generate a pseudo-random synchronization sequence and a verification sequence with a length of K, where K is a positive integer;

[0013] S15. Determine the number M of verification sequences in the sub-frame, where M is a positive integer;

[0014] S16. Add the length of the sub-frame except the synchronization sequence and the verification sequence to the data;

[0015] S17. Combine the synchronization sequence, the verification sequence, and the data into a complete sub-frame;

[0016] S18. Generate each sub-frame and combine all sub-frames into a complete data frame.

[0017] Further, the structure of the frame specifically includes N sub-frames: sub-frame 0, sub-frame 1, sub-frame 2, …, sub-frame N-1, and the length of the data frame where L i is the length of sub-frame i;

[0018] The format of sub-frame i is as follows:

[0019] PN 1 、PN 2 、PN 3 、PN 4 、…PN M+1 、Data i

[0020] where, PN 1 represents a synchronization sequence with a length of K, PN 2 、PN 3 、PN 4 、…PN M+1 represent M verification sequences each with a length of K, and Data i represents the modulated data with a length of L i -(1 + M)×K. The calculation formula for M is:

[0021]

[0022] In the above formula, the symbol represents rounding up, and A is the number of different PN sequences.

[0023] Further, the verification sequences are used to verify and identify the sub-frame positions; each sub-frame has M verification sequences. In the case of having A different PN sequences, there are A M different verification sequence combinations for verification and identification, and each verification sequence combination uniquely identifies sub-frame i.

[0024] Further, the length L s of the data frame is an integer multiple of the maximum value T max of the dynamic occlusion channel occlusion period.

[0025] Further, the lengths L i of sub-frame i are different from each other. The determination of the sub-frame length L i is related to the minimum value T min of the dynamic occlusion channel occlusion period, and the length of each sub-frame is greater than T min .

[0026] The present invention also provides a frame synchronization method under a dynamic occlusion channel. The frame is obtained based on the frame structure design method. The frame synchronization method includes the following steps:

[0027] S21. Data input: Parallelly input data into A parallel synchronization devices for operation, where A is the number of different PN sequences in the data frame structure;

[0028] S22. Obtain a synchronization sequence: A synchronization or verification sequence acquirer selects a K-length sequence from the input data as the synchronization sequence;

[0029] S23. Segment the synchronization sequence: Divide the synchronization sequence into H segments, and the length of each segment is K / H;

[0030] S24. FFT operation: Respectively perform a correlation operation between the synchronization sequences of H correlators and the local reference sequence, sum the results, perform an FFT operation, and then take the modulus value;

[0031] S25. Select the maximum signal for decision-making:

[0032] Take the maximum value in the FFT output result as the correlation peak, record the position of the maximum value, perform a threshold decision on the obtained correlation peak using an adaptive decision method. If the threshold requirement is met, start the peak confirmation mechanism to confirm the peak position, and use the confirmed peak position as the capture position; if not, slide the next sample into the correlator group and execute step S22;

[0033] S26. Verify the capture position: Take the capture position obtained in step S25 as the starting point, intercept a K-length sequence of the signal, and repeat steps S23 to S25 for verification; if it is successfully verified M times, it is determined that the synchronization capture is successful and the current position is output as the final synchronization position, where M is the number of verification sequences in the sub-frame; if not, slide the next sample into the correlator group and execute step S22;

[0034] S27. Extract data: According to the verification sequence, obtain the sub-frame number i to which the synchronization position belongs, and output data from the i-th FIFO in the FIFO group; intercept useful data from the output data according to the frame format.

[0035] Further, the number of the correlator groups is A, where A is the number of different PN sequences in the data frame structure, and each input data is sent to A correlator groups for parallel operation.

[0036] Further, the FIFO group is serially composed of N FIFOs, where N is the number of sub-frames in the data frame, and the length of the i-th FIFO is equal to the frame length L of sub-frame i i is equal.

[0037] The beneficial effects of the present invention are:

[0038] (1) The data frame structure designed by the present invention is composed of multiple sub-frames with the same format but different lengths. A synchronization sequence and a verification sequence are inserted before the data in each sub-frame. This frame structure can effectively solve the problem of missed capture in a dynamically occluded channel, thereby accurately capturing the data frame, overcoming the drawback of the prior art that it is difficult to cope with the dynamic changes of the occluded channel, and enabling reliable communication in a dynamically occluded channel.

[0039] (2) The present invention includes a synchronization sequence and a verification sequence in each sub-frame. The success of synchronization capture is determined by one capture and multiple verifications, reducing the probability of false capture in synchronization capture, making the communication system have the advantage of a high correct synchronization capture probability, and improving the performance of the communication system. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] For the convenience of those skilled in the art to understand, the present invention will be further described below with reference to the accompanying drawings.

[0041] Figure 1 is a schematic structural diagram of the data frame of the present invention;

[0042] Figure 2 is a schematic structural diagram of a sub-frame in the data frame of the present invention;

[0043] Figure 3 is a schematic flow diagram of the frame structure design method of the present invention;

[0044] Figure 4 is a schematic structural diagram of the synchronization device of the present invention;

[0045] Figure 5 is a schematic structural diagram of the data extraction module of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0046] To further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following will describe in detail the specific implementation manners, structures, features, and effects of the present invention with reference to the accompanying drawings and preferred embodiments.

[0047] Embodiment 1

[0048] As Figure 1 shown, the data frame of the present invention is composed of N sub-frames including sub-frame 0, sub-frame 1, sub-frame 2,..., sub-frame N-1. The length of the data frame is an integer multiple of the maximum value T max of the occlusion period of the dynamically occluded channel.

[0049] It should be noted that L i is the length of sub-frame i, and the values of L i are different. The determination of the sub-frame length and the minimum value T of the occlusion period of the dynamically occluded channelmin is related, and the length of each sub-frame needs to be greater than T min .

[0050] As Figure 2 shown, the format of sub-frame i is as follows:

[0051] PN 1 , PN 2 , PN 3 , PN 4 , …PN M+1 , Data i

[0052] Among them, PN 1 represents a synchronization sequence with a length of K, PN 2 , PN 3 , PN 4 , …PN M+1 represents M verification sequences each with a length of K, Data i represents the modulated data with a length of L i -(1 + M)×K, and the calculation formula for M is:

[0053]

[0054] In the above formula, the symbol represents rounding up, and A is the number of different PN sequences.

[0055] It should be noted that the verification sequence is used for both verification and identifying the position of the sub-frame. Each sub-frame has M verification sequences. In the case of having A different PN sequences, there are A M different verification sequence combinations that can be used for verification and identification, and each verification sequence combination can uniquely identify sub-frame i.

[0056] The design method of the frame structure in the present invention is as Figure 3 shown, and includes the following steps:

[0057] S11. Determine the occlusion period range T min ~T max .

[0058] S12. Determine the frame length and structure of the data frame according to the occlusion period range of the dynamic occlusion channel. The frame length is an integer multiple of T max , as Figure 1 shown, the frame structure is composed of multiple sub-frames with the same format and different lengths.

[0059] S13. Determine the length L i of each sub-frame. The length of each sub-frame needs to be greater than T min , and the frame length L iThe calculation formula is as follows:

[0060]

[0061] where x is a random number between 0 and 1, L s is the data frame length, and N is the number of sub - frames.

[0062] S14. Generate a pseudo - random synchronization sequence and a verification sequence of length K: Determine the number A of different PN sequences to be used in the frame structure.

[0063] It can be understood that each PN sequence consumes certain resources during synchronization, and the number of PN sequences should not be too large.

[0064] S15. Determine the number M of verification sequences in the sub - frame. The specific value of M is obtained by calculation.

[0065] It should be noted that the symbol represents rounding up, and A is the number of different PN sequences.

[0066] S16. Add the length of the sub - frame except for the synchronization sequence and the verification sequence to the data.

[0067] S17. Combine the synchronization sequence, the verification sequence, and the data into a complete sub - frame i.

[0068] S18. Generate each sub - frame and combine all sub - frames into a complete data frame.

[0069] A frame synchronization method under a dynamic occlusion channel includes the following steps:

[0070] S21. Data input: Input the data in parallel into A parallel synchronization devices for operation.

[0071] It should be noted that this synchronization method uses A parallel synchronization devices, where A is the number of different PN sequences in the data frame structure, and the data will be input in parallel into the A parallel synchronization devices as shown in Figure 4 for operation.

[0072] S22. Obtain the synchronization sequence: The synchronization or verification sequence acquirer selects a sequence of length K from the input data as the synchronization sequence.

[0073] S23. Segment the synchronization sequence: Divide the synchronization sequence into H segments, and the length of each segment is K / H.

[0074] Also divide the local reference sequence of length K into H segments according to the above - mentioned segmentation method, with the length of each segment being K / H, and store the segmented local reference sequence in the corresponding correlator.

[0075] S24, FFT operation: Perform correlation operations on the synchronization sequences of H correlators and the local reference sequence respectively, sum the results, perform a Fast Fourier Transform (FFT) operation, and then take the modulus value to obtain the FFT output result.

[0076] S25, Select the maximum signal for decision-making:

[0077] Take the maximum value in the FFT output result as the correlation peak, record the position of the maximum value, and perform threshold decision on the obtained correlation peak using an adaptive decision-making method. If the threshold requirement is met, start the peak confirmation mechanism to confirm the peak position, and use the confirmed peak position as the capture position; if not, slide the next sample point into the correlator group and execute step S22.

[0078] S26, Capture position verification: Use the capture position obtained in step S25 as the starting point, intercept a sequence of length K from the signal, and repeat steps S23 - S25.

[0079] It can be understood that the method in step S25 is used to verify whether the capture position can be determined. If it cannot be confirmed, the synchronous capture fails, slide the next sample point of the signal into the correlator group, and go to step S22; if it can be confirmed, the verification is successful, use the obtained capture position as the starting point, intercept a sequence of length K from the signal, repeat steps S23 - S25, and verify again; if the verification is successful M times, it is determined that the synchronous capture is successful and the current position is output as the final synchronous position; if not, slide the next sample point into the correlator group and execute step S22; where M is the number of verification sequences in the subframe.

[0080] It should be noted that as Figure 4 shown, there is a correlator group in each synchronization device, and there are a total of A parallel synchronization devices. A correlator group contains H correlators.

[0081] S27, Extract data: Obtain the subframe number i to which the synchronization position belongs according to the verification sequence, and output data from the i-th FIFO in the FIFO group; intercept useful data from the output data according to the frame format.

[0082] It should be noted that the FIFO group in the present invention contains N FIFO components and a selection device. As Figure 5 shown, the input data is connected to the input end of FIFO component 1. The output end of FIFO component 1 is respectively connected to the input end of FIFO component 2 and the input end of the selection device. The output end of FIFO component 2 is connected to the input end of the next FIFO component and the input end of the selection device. The output end of FIFO component N is connected to the input end of the selection device.

[0083] Where N is the number of sub - frames in the data frame, and the length of the i - th FIFO is equal to the frame length L of sub - frame i. i Equal.

[0084] It can be understood that if the frame where the finally determined capture position in step S26 is sub - frame i, the data output from the i - th FIFO can be selected, and then the data can be intercepted according to the frame format.

[0085] Embodiment 2

[0086] The difference between this embodiment and Embodiment 1 lies in determining the length L of each sub - frame i Calculated by the following formula:

[0087]

[0088] Where x is a random number between 0 and 1, L s Is the data - frame length, N is the number of sub - frames, T max Is the maximum value of the occlusion period of the dynamic occlusion channel, T min Is the minimum value of the occlusion period of the dynamic occlusion channel.

[0089] The data - frame structure designed by the present invention is composed of multiple sub - frames with the same format but different lengths. A synchronization sequence and a verification sequence are inserted before the data in each sub - frame. This frame structure can effectively solve the problem of missed capture in a dynamic occlusion channel, so that the data frame can be accurately captured, overcoming the shortcoming that the prior art is difficult to cope with the dynamic changes of the occlusion channel, and can achieve reliable communication in a dynamic occlusion channel.

[0090] The present invention includes a synchronization sequence and a verification sequence in each sub - frame. The success of synchronous capture is determined by one capture and multiple verifications, reducing the probability of false capture in synchronous capture, making the communication system have the advantage of a high correct synchronous capture probability, and improving the performance of the communication system.

[0091] The verification sequence in the data frame generated by the present invention is used for both verification and identification of sub - frames. The number of verification sequences owned by each sub - frame is M. In the case of having A different PN sequences, there are A M Different verification - sequence combinations that can be used for verification and identification. Each verification - sequence combination can uniquely identify sub - frame i, making full use of the data - frame resources and improving the frame efficiency.

[0092] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Although the present invention has been disclosed above with the preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments with equivalent changes within the scope of the technical solution of the present invention. However, as long as it does not depart from the content of the technical solution of the present invention, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for designing a frame structure under a dynamic occlusion channel, characterized in that: The frame structure includes N sub-frames. Define i as the sub-frame number, with a value range of 0 to N - 1. The sub-frame includes a synchronization sequence, a verification sequence, and data. The method for designing the frame structure specifically includes the following steps: S11. Determine the occlusion period range T of the dynamic occlusion channel min ~T max , where T min is the minimum occlusion period of the dynamic occlusion channel, and T max is the maximum occlusion period of the dynamic occlusion channel; S12. Determine the frame length and structure of the data frame according to the occlusion period range of the dynamic occlusion channel; S13. Determine the length L of each subframe i i ; S14. Generate a pseudo-random synchronization sequence and a verification sequence with a length of K, where K is a positive integer; S15. Determine the number M of verification sequences in the sub-frame, where M is a positive integer; S16. Add the length of the sub-frame except for the synchronization sequence and the verification sequence to the data; S17. Combine the synchronization sequence, the verification sequence, and the data into a complete sub-frame; S18. Generate each sub-frame and combine all sub-frames into a complete data frame.

2. A method for designing a frame structure under a dynamic occlusion channel according to claim 1, characterized in that: The structure of the frame specifically includes N sub-frames, namely sub-frame 0, sub-frame 1, sub-frame 2, …, sub-frame N-1, and the length of the data frame where L i is the length of sub-frame i; The format of the sub-frame i is as follows: PN 1 、PN 2 、PN 3 、PN 4 、…PN M+1 、Data i Among them, PN 1 represents a synchronization sequence of length K, and PN 2 , PN 3 , PN 4 , … PN M+1 represent M verification sequences each of length K, and Data i represents the modulated data of length L i -(1 + M)×K, and the calculation formula for M is: In the above formula, the symbol represents rounding up, and A is the number of different PN sequences.

3. A method for designing a frame structure under a dynamic occlusion channel according to claim 2, characterized in that: The verification sequence is used to verify and identify the subframe position; the number of verification sequences owned by each subframe is M. In the case of having A different PN sequences, there are A M different verification sequence combinations for verification and identification, and each verification sequence combination has a unique identifier for subframe i.

4. A method for designing a frame structure under a dynamic occlusion channel according to claim 3, characterized in that: The length L of the data frame s is an integer multiple of the maximum value T of the occlusion period of the dynamic occlusion channel max .

5. A method for designing a frame structure under a dynamic occlusion channel according to claim 1, characterized in that: The length L of the subframe i i has different values, and the subframe length L i is determined in relation to the minimum value T of the dynamic occlusion channel occlusion period min such that the length of each subframe is greater than T min .

6. A frame synchronization method under a dynamic occlusion channel, characterized in that: The frame is obtained based on the frame structure design method described in any one of claims 1 - 5. The frame synchronization method includes the following steps: S21. Data input: Input the data in parallel into A parallel synchronization devices for operation, where A is the number of types of different PN sequences in the data frame structure; S22. Obtain the synchronization sequence: The synchronization or verification sequence acquirer selects a sequence with a length of K from the input data as the synchronization sequence; S23. Segment the synchronization sequence: Divide the synchronization sequence into H segments, and the length of each segment is K / H; S24. FFT operation: Perform correlation operations on the synchronization sequences of H correlators with the local reference sequence respectively, sum them up, perform FFT operation, and then take the modulus value; S25. Select the maximum signal for decision: Take the maximum value in the FFT output result as the correlation peak value, record the position of the maximum value, and perform threshold decision on the obtained correlation peak value using an adaptive decision method. If the threshold requirement is met, start the peak confirmation mechanism to confirm the peak position, and take the confirmed peak position as the capture position; if not, slide the next sample into the correlator group and execute step S22; S26. Verify the capture position: Take the capture position obtained in step S25 as the starting point, intercept a sequence with a length of K from the signal, and repeat steps S23 - S25 for verification; if it is verified successfully M times, it is determined that the synchronization capture is successful and the current position is output as the final synchronization position, where M is the number of verification sequences in the sub-frame; if not, slide the next sample into the correlator group and execute step S22; S27. Extract data: Obtain the subframe number i to which the synchronization position belongs according to the verification sequence, and output data from the i-th FIFO in the FIFO group; intercept useful data from the output data according to the frame format.

7. A frame synchronization method under a dynamic occlusion channel according to claim 6, wherein: the number of the correlator groups is A, where A is the number of different PN sequences in the data frame structure, and each input data is sent to A correlator groups for parallel operation.

8. A frame synchronization method under a dynamic occlusion channel according to claim 6, wherein: The FIFO group consists of N FIFOs in series, where N is the number of sub-frames in the data frame, and the length of the i-th FIFO is equal to the frame length L of sub-frame i i is equal.

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