Synchronization method and device based on differential spread spectrum code in UAV and satellite communication

Abstract

The present application provides a synchronization method and device based on differential spread spectrum code in drone and satellite communication, which relates to the field of communication technology, wherein the method includes: generating a first-level PN code and a second-level PN code; using the first-level PN code to differentially encode the synchronization sequence to obtain a first differential sequence; using the second-level PN code to spread each symbol of the first differential sequence respectively to obtain a differential synchronization header; sending the differential signal to the receiving end, so that the receiving end performs despreading and dedifferentiation processing after receiving the differential signal to obtain a first dedifferentiation sequence, and sliding correlation processing is performed on the first-level PN code and the first dedifferentiation sequence to search for a correlation peak point, the differential signal includes a data sequence and a differential synchronization header, and the data sequence is the original sequence carrying information. By using two-level PN code two-level sliding correlation, the correlation peak point can be accurately found, and a good anti-frequency deviation effect can be guaranteed under the condition of large frequency deviation and low signal-to-noise ratio, so as to achieve fast and accurate synchronization.

Description

Technical Field

[0001] The present application relates to the field of communication technology, and in particular to a synchronization method and device based on differential spread spectrum codes in communications between unmanned aerial vehicles and satellites. Background Art

[0002] In drone and satellite communications, the time synchronization of data frames is one of the key technologies in digital communications, that is, the data receiving end determines the time domain starting point of the data frame sent by the sending end, and thus determines the position of each symbol in the data frame according to the agreed frame structure. The synchronization header and valid data extracted at the receiving end are the basis for subsequent signal differential demodulation, which directly affects the signal processing performance of the system.

[0003] Existing frame synchronization algorithms often use a first-level differential spread spectrum code to process signals. When the system frequency deviation is large and the signal-to-noise ratio is low, the amplitude of the correlation peak found after the correlation operation is low, and it is difficult to determine the exact position of the correlation peak, resulting in the inability to complete accurate synchronization under large frequency deviation conditions. Summary of the invention

[0004] The present application provides a synchronization method and device based on differential spread spectrum codes in UAV and satellite communications. In the case of large frequency deviation, two-stage PN code and two-stage sliding correlation are used to accurately find the correlation peak point, thereby achieving fast and accurate synchronization and having good anti-frequency deviation effect.

[0005] In a first aspect, the present application provides a synchronization method based on differential spread spectrum code in UAV and satellite communication, which is applied to a transmitting end, and the method includes:

[0006] Generate a first-level PN code and a second-level PN code;

[0007] Using the first-stage PN code to differentially encode the synchronization sequence to obtain a first differential sequence;

[0008] The second-level PN code is used to spread spectrum each symbol of the first differential sequence to obtain a differential synchronization header; the differential signal is sent to a receiving end, so that the receiving end performs despreading and dedifferentiation processing after receiving the differential signal to obtain a first dedifferentiation sequence, and the first-level PN code and the first dedifferentiation sequence are subjected to sliding correlation processing to search for correlation peak points, the differential signal includes a data sequence and the differential synchronization header, and the data sequence is an original sequence that carries information.

[0009] By adopting the above technical solution, two-stage PN codes are used at the transmitting end to perform differential encoding and spread spectrum on the synchronization header sequence, and two-stage PN code sliding correlation is used at the receiving end to achieve synchronization of the differential signal. This can resist the influence of large system frequency deviation and low signal-to-noise ratio, accurately determine the correlation peak position and complete synchronization, and has good anti-frequency deviation effect and anti-noise ability.

[0010] Optionally, generating the first-level PN code and the second-level PN code includes:

[0011] The symbol length of the second-level PN code is calculated based on the maximum frequency deviation of the system and the chip rate, and the second-level PN code is generated based on the symbol length of the second-level PN code. The calculation formula is as follows:

[0012] PL2=f c / 2maxdetf

[0013] Where PL2 is the symbol length of the second-level PN code;

[0014] f c is the chip rate;

[0015] maxdetf is the maximum frequency deviation of the system;

[0016] The symbol length of the first-order PN code is calculated using a system gain formula, and the first-order PN code is generated based on the symbol length of the first-order PN code. The system gain formula is as follows:

[0017] Gain=10log(PL1*PL2)

[0018] Where, Gain is the system gain;

[0019] PL1 is the symbol length of the first-level PN code.

[0020] By adopting the above technical solution, the length of the PN code can be adjusted according to the actual noise to be resisted, the consumed logic computing resources and the characteristics of the m-sequence, which can improve the anti-frequency deviation effect and save logic computing hardware resources.

[0021] Optionally, the using the first-level PN code to differentially encode the synchronization sequence to obtain a first differential sequence includes:

[0022] Add a 1-value symbol at the front end of the first-level PN code;

[0023] The synchronization sequence is differentially encoded using the first-level PN code after the symbol is added to obtain a first differential sequence.

[0024] By adopting the above technical solution, a symbol with a value of 1 is added at the front end of the first-stage PN code, which is equivalent to the starting value of the first-stage PN code, and differential encoding is performed starting from the starting value.

[0025] Optionally, before sending the differential signal to the receiving end, the method further includes:

[0026] The differential signal is subjected to interpolation and spread spectrum processing, and a square root raised cosine filter is used to filter the spread spectrum differential signal.

[0027] By adopting the above technical solution, the differential signal before transmission is processed by interpolation and spread spectrum, which can increase the sampling rate of the digital baseband waveform, reduce the requirements for analog filtering, and facilitate signal transmission to DAC; the use of a square root raised cosine filter can suppress and adjust the sidelobe power spectrum components of the output signal, thereby suppressing or avoiding adjacent channel interference.

[0028] In a second aspect, the present application provides a synchronization method based on differential spread spectrum code in UAV and satellite communication, which is applied to a receiving end, and the method includes:

[0029] Receive a differential signal, wherein the differential signal includes a differential synchronization header and a data sequence, wherein the differential synchronization header is obtained by differentially encoding the synchronization sequence with a first-level PN code to obtain a first differential sequence, and then spreading each symbol of the first differential sequence with a second-level PN code, and the data sequence is an original sequence carrying information;

[0030] Using the second-stage PN code to perform sliding correlation despreading on the differential signal to obtain a despreading sequence;

[0031] Multiplying adjacent symbols of the despread sequence differentially to obtain a first de-differential sequence;

[0032] The first solution differential sequence is subjected to sliding correlation processing with the first stage PN code to search for a correlation peak point.

[0033] By adopting the above technical solution, two-stage PN code sliding correlation is used at the receiving end, which can meet the requirements for fast and accurate synchronization of differential signals when the system frequency deviation is large, and has good anti-frequency deviation capability.

[0034] Optionally, after receiving the differential signal, the method further includes:

[0035] The received differential signal is filtered using a square root raised cosine filter.

[0036] By adopting the above technical solution, compared with ordinary low-pass filters, the square root raised cosine filter has lower requirements for oversampled digital signal processing, and the demodulation bit error rate is also lower. The same type of filter is matched with the transmitting end, so that the subsequent processing can quickly and accurately obtain the optimal sampling point to achieve synchronization.

[0037] Optionally, the sliding correlation processing of the first de-differentialized sequence and the first-stage PN code includes:

[0038] The first solution differential sequence is multiplied and added with the first-stage PN code by a sliding isolation degree of sampling points, and the sliding isolation degree is the product of the number of sampling points of a symbol and the symbol length of the first-stage PN code.

[0039] By adopting the above technical solution, sliding point by point during sliding correlation, the distance between the first point and the last point of one correlation is the sliding isolation degree sampling points, which can ensure the code chip accuracy of the sliding correlation scan.

[0040] In a third aspect, the present application provides a synchronization device based on differential spread spectrum code in communication between a drone and a satellite, which is applied to a transmitting end, and the device includes:

[0041] A pseudo-random sequence generation module, used for generating a first-level PN code and a second-level PN code;

[0042] A differential encoding module, used to use the first-level PN code to perform differential encoding on the synchronization sequence to obtain a first differential sequence; a spread spectrum module, used to use the second-level PN code to perform spread spectrum on each symbol of the first differential sequence to obtain a differential synchronization header;

[0043] The differential signal synchronization module is used to send the differential signal to the receiving end, so that the receiving end performs despreading and dedifferentiation processing after receiving the differential signal to obtain a first dedifferentiation sequence, and performs sliding correlation processing on the first-level PN code and the first dedifferentiation sequence to search for correlation peak points. The differential signal includes a data sequence and the differential synchronization header, and the data sequence is the original sequence that carries information.

[0044] In a fourth aspect, the present application provides a computer storage medium, wherein the computer storage medium stores a plurality of instructions, wherein the instructions are suitable for being loaded by a processor and executing any one of the above methods.

[0045] In a fifth aspect, the present application provides an electronic device, comprising a processor, a memory and a transceiver, wherein the memory is used to store instructions, the transceiver is used to communicate with other devices, and the processor is used to execute the instructions stored in the memory so that the electronic device performs any one of the above methods.

[0046] In summary, the beneficial effects brought about by the technical solution of the present application include: using two-stage PN codes at the transmitting end to perform differential encoding and spread spectrum processing on the differential synchronization head, and using the same two-stage PN codes at the receiving end to perform two-stage sliding correlation on the differential signal to achieve synchronization. Compared with the one-stage PN code spread spectrum, in the case of large frequency deviation, the two-stage PN code differential correlation can still accurately find the correlation peak point, thereby achieving fast and accurate synchronization, and having a good anti-frequency deviation effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a structural diagram of a direct sequence spread spectrum provided in an embodiment of the present application;

[0048] Figure 2 It is a flowchart of a synchronization method based on differential spread spectrum code in UAV and satellite communication provided by an embodiment of the present application;

[0049] Figure 3 is a schematic diagram of a baseband synchronization header generation process provided by an embodiment of the present application;

[0050] Figure 4 This is a signal eye diagram comparing different filtering processes provided by an embodiment of the present application;

[0051] Figure 5 It is a flow chart of another synchronization method based on differential spread spectrum code in UAV and satellite communication provided by an embodiment of the present application;

[0052] Figure 6 A schematic diagram of a receiving end graphical processing flow provided in an embodiment of the present application;

[0053] Figure 7 This is a simulation comparison diagram of a peak point search when the frequency deviation is large provided in an embodiment of the present application;

[0054] Figure 8 It is a structural schematic diagram of a synchronization device based on differential spread spectrum code in drone and satellite communication provided by an embodiment of the present application;

[0055] Fig. 9 It is a structural schematic diagram of an electronic device provided in an embodiment of the present application.

[0056] Explanation of the accompanying drawings: 10, pseudo-random sequence generation module; 20, differential encoding module; 30, spread spectrum module; 40, differential signal synchronization module; 1000, electronic device; 1001, processor; 1002, communication bus; 1003, user interface; 1004, network interface; 1005, memory. DETAILED DESCRIPTION

[0057] In order to enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of this specification will be clearly and completely described below in conjunction with the drawings in the embodiments of this specification. Obviously, the described embodiments are only part of the embodiments of this application, not all of the embodiments.

[0058] First, a brief introduction to the process of direct sequence spread spectrum communication is given in Figure 1 , which is a structural diagram of a direct sequence spread spectrum provided in an embodiment of the present application. At the transmitting end, a PN code is used to spread the information codeword to be transmitted, and then the information codeword is transmitted to the receiving end through a channel after carrier modulation processing. The receiving end first recovers the synchronized pseudo-random code, multiplies the pseudo-random code and the modulated signal for despreading, and demodulates the information codeword after carrier synchronization.

[0059] In the description of the embodiments of the present application, words such as "illustrative", "for example" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "illustrative", "for example" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "illustrative", "for example" or "for example" is intended to present related concepts in a specific way.

[0060] In the description of the embodiments of the present application, the meaning of the term "multiple" refers to two or more. For example, multiple systems refer to two or more systems, and multiple screen terminals refer to two or more screen terminals. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the indicated technical features. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. The terms "include", "comprise", "have" and their variations all mean "including but not limited to", unless otherwise specifically emphasized.

[0061] See also Figure 2 , which is a flow chart of a synchronization method based on differential spread spectrum code in drone and satellite communication provided in an embodiment of the present application. The method can be implemented by a computer program, can be implemented by a single-chip microcomputer, or can be run on a synchronization device based on differential spread spectrum code in drone and satellite communication based on the von Neumann system. The computer program can be integrated into an application or run as an independent tool application. The embodiment of the present application takes the transmitting end in the system as an example to explain in detail the specific steps of the synchronization method based on differential spread spectrum code in drone and satellite communication.

[0062] S101, generating a first-stage PN code and a second-stage PN code.

[0063] The first-level PN code and the second-level PN code usually use m-sequence or GOLD sequence. Both m-sequence and GOLD sequence are pseudo-random sequences. The m-sequence is also called the longest linear shift register sequence. In the hardware circuit, it can be generated by connecting the feedback shift register of the original polynomial. The GOLD sequence is composed of two m-sequences with equal code length and the same code clock rate, preferably modulo-two addition. The first-level PN code is used for differential encoding, and the second-level PN code is used for spread spectrum. Both levels of PN codes are generated based on the synchronization sequence of the original differential signal, and the length of both levels of PN codes is 2^N-1.

[0064] In one embodiment, the symbol length of the second-order PN code is calculated based on the maximum frequency deviation of the system and the chip rate, and the second-order PN code is generated based on the symbol length of the second-order PN code. The calculation formula is as follows:

[0065] PL2=f c / 2maxdetf

[0066] Where PL2 is the symbol length of the second-level PN code;

[0067] f c is the chip rate;

[0068] maxdetf is the maximum frequency deviation of the system.

[0069] In order to achieve synchronization under large frequency deviation, the embodiment of the present application needs to set the symbol length of the second-level PN code of the spread spectrum according to the maximum frequency deviation of the system. For example, the chip rate f c When the frequency is set to 10MHz and the symbol length of the second-level PN code of the spread spectrum communication is set to 127 symbols, the maximum frequency deviation that synchronization can withstand is 39KHz, while the frequency deviation of a general communication system is around 5KHz, which can fully meet the situation where the frequency deviation of most systems is larger.

[0070] In one embodiment, the symbol length of the first-order PN code is calculated using a system gain formula, and the first-order PN code is generated based on the symbol length of the first-order PN code. The system gain formula is as follows:

[0071] Gain=10log(PL1*PL2)

[0072] Where, Gain is the system gain;

[0073] PL1 is the symbol length of the first-level PN code.

[0074] After determining the symbol length of the second-stage PN code according to the maximum frequency deviation of the system, the larger the symbol length of the two-stage PN code, the more hardware computing resources are consumed, and the stronger the ability to resist noise is. The length of the first-stage PN code is determined by comprehensively considering the noise that needs to be resisted, the consumption of hardware computing resources and the characteristics of the m-sequence.

[0075] In the embodiment of the present application, taking the symbol length of the first-stage PN code as 31 and the symbol length of the second-stage PN code as 127 as an example, the calculated system gain is 36 dB, which has good anti-noise capability.

[0076] S102: Use a first-order PN code to differentially encode a synchronization sequence to obtain a first differential sequence.

[0077] The formula for differential encoding is as follows:

[0078]

[0079] The differentially encoded signal c k is the previous differentially encoded signal c k-1 A superimposed on k The phase is the differential processing of the code element of the first-level PN code and the previous code element in the first differential sequence.

[0080] In one embodiment, a symbol with a value of 1 is added to the front end of the first-stage PN code; the first-stage PN code with the added symbol is used to perform differential encoding on the synchronization sequence to obtain a first differential sequence.

[0081] The 1-value symbol at the front of the first-level PN code is equivalent to the starting value, and the differential encoding starts with a value. Since the length of the first-level PN code is 2^N-1, the length of the first differential sequence after adding the starting value is 2^N, which is convenient for spread spectrum processing.

[0082] S103, use the second-stage PN code to spread spectrum each symbol of the first differential sequence to obtain a differential synchronization header.

[0083] See also Figure 3 , which is a schematic diagram of a baseband synchronization header generation process provided in an embodiment of the present application. The three schematic sequences from top to bottom are respectively the first-level PN code after adding symbols, the first differential sequence, and the differential synchronization header after being spread by the second-level PN code.

[0084] Each symbol of the first differential sequence is spread, the second-level PN code is used to replace the "1" in the first differential sequence, and the inverted second-level PN code is used to replace the "0" in the first differential sequence. A wideband spectrum with a high chip rate is used to spread the first differential sequence with a low chip rate. Using a larger bandwidth to transmit less information can obtain benefits other than communication rate, such as better anti-frequency deviation and anti-noise performance.

[0085] S104, sending the differential signal to the receiving end, so that the receiving end performs despreading and dedifferentiation processing after receiving the differential signal to obtain a first dedifferentiation sequence, and performs sliding correlation processing on the first-level PN code and the first dedifferentiation sequence to search for a correlation peak point. The differential signal includes a data sequence and a differential synchronization header, and the data sequence is the original sequence that carries information.

[0086] After the differential signal is sent to the receiving end, the receiving end performs sliding correlation despreading, differential multiplication de-differentiation, and sliding correlation peak search on the differential signal, and obtains the frequency deviation and synchronization point through the position of the correlation peak point, thereby completing the frequency deviation measurement and timing synchronization, that is, restoring the original signal at the receiving end and finding the differential synchronization head.

[0087] In one embodiment, the differential signal is subjected to interpolation and spread spectrum processing, and a square root raised cosine filter is used to filter the spread spectrum differential signal.

[0088] Interpolation makes one code chip become multiple points. The interpolation factor is the number of interpolation points between each adjacent code chip, which can also be called the interpolation multiple. The symbol after spread spectrum is expanded into many code chips. Due to the different spreading codes before and after, the frequency band is expanded and the signal rate is greatly improved, which is convenient for transmission to DAC.

[0089] In one embodiment, a square root raised cosine filter is used to filter the received differential signal.

[0090] When processing oversampled digital signals, the square root raised cosine filter can ensure that the sampling points are not distorted, thereby improving the spectrum utilization. Figure 4 , which is a signal eye diagram comparing different filtering processing provided in an embodiment of the present application. The upper half of the figure is a signal eye diagram of a square root raised cosine filter, and the lower half of the figure is a signal eye diagram of a common low-pass filter. It can be seen from the figure that compared with using a common low-pass filter at both the transmitting end and the receiving end, using a square root raised cosine filter has a better inhibitory effect on the influence of inter-code crosstalk and noise.

[0091] In the steps of a synchronization method based on differential spread spectrum codes in drone and satellite communications in another embodiment of the present application, a process is described in detail in which, after receiving the processed differential signal, the receiving end uses two-stage PN codes for sliding correlation and searches for the synchronization head to complete signal synchronization, so as to achieve signal synchronization under large frequency deviation conditions.

[0092] See also Figure 5 , which is a flow chart of another synchronization method based on differential spread spectrum codes in drone and satellite communications provided in an embodiment of the present application.

[0093] S201, receiving a differential signal, the differential signal comprising a differential synchronization header and a data sequence, the differential synchronization header is a synchronization sequence obtained by differentially encoding the first differential sequence with a first-level PN code, and then spreading each symbol of the first differential sequence with a second-level PN code, and the data sequence is an original sequence that carries information.

[0094] The steps of obtaining the differential synchronization header have been described in detail in the above embodiment and will not be repeated here.

[0095] S202, use the second-stage PN code to perform sliding correlation despreading on the differential signal to obtain a despreading sequence.

[0096] The differential signal is composed of a differential synchronization header and a data sequence. To complete synchronization, the sequence of the differential synchronization header needs to be found. Use the second-level PN code to perform sliding correlation despreading on the differential signal, and perform correlation operations on the second-level PN code of the differential signal point by point until the peak point of the sliding correlation is found. The peak point here is the despreading peak point.

[0097] The sliding isolation is the number of interpolation factors. Since multiple points are interpolated between each symbol of the differential signal, for the sliding correlation of the differential signal, the interval between each sampling is the number of sampling points of the interpolation factor.

[0098] S203: differentially multiply adjacent symbols of the despread sequence to obtain a first de-differentialized sequence.

[0099] The distance between adjacent symbols of the demodulated signal is the product of the interpolation factor and the length of the second-stage PN code, that is, the number of sampling points delayed by the differential process is the product of the interpolation factor and the length of the second-stage PN code. After differential processing of the demodulated signal, two continuous signal data are obtained. For example, the product of the interpolation factor and the length of the second-stage PN code is LL2=PL2*IPOINT, PL2 is the symbol length of the second-stage PN code, and IPOINT is the interpolation multiple of the interpolation factor. Therefore, the two segments of differentially processed data are (1+LL2:end) and (1:end-LL2), respectively. The data at both ends after differential processing are conjugate multiplied to obtain the first de-differentialized sequence of de-differentiation.

[0100] S204, performing sliding correlation processing on the first solution differential sequence and the first-stage PN code to search for a correlation peak point.

[0101] After despreading and dedifferentializing the received differential signal, the first dedifferentialized sequence obtained is a synchronization sequence and a data sequence, and the differential synchronization header also becomes a synchronization sequence. The synchronization sequence in the first dedifferentialized sequence is found through the first-level PN code to complete synchronization.

[0102] See also Figure 6 , which is a flow chart of a graphical processing of a receiving end provided in an embodiment of the present application. In the figure, the synchronization process of the receiving end is divided into three steps. The first step is the step of sliding correlation despreading, the second step is the step of delayed conjugate multiplication and de-differentiation, and the third step is the step of sliding correlation and searching for the final correlation peak point.

[0103] In one embodiment, the first solution differential sequence is multiplied and added with the first-stage PN code by a sliding isolation degree of sampling points, and the sliding isolation degree is the product of the number of sampling points of a symbol and the symbol length of the first-stage PN code.

[0104] For example, the distance between the first and last points of a correlation is the product of the symbol length of the first-level PN code and the number of sampling points corresponding to one symbol. The sliding correlation method is point-by-point sliding correlation. Each isolated LL2 sampling point is multiplied and added with the compared first-level PN code to search for the peak point. The peak point is determined to meet the peak-to-average ratio and absolute value. After finding the correlation peak point, the frequency deviation value can be obtained by calculating the phase of the peak point, thereby completing the synchronization.

[0105] See also Figure 7 , which is a simulation comparison diagram of peak point search when the frequency deviation is large provided in an embodiment of the present application. It can be seen from the figure that there are multiple related peak points directly related to the traditional first-level PN code. When the frequency deviation is large, the peak point cannot be accurately obtained, and synchronization cannot be completed. The two-level PN code differential sliding correlation of the embodiment of the present application can quickly and accurately obtain the related peak point when the frequency deviation is large, thereby verifying that the method provided by the present application has good anti-frequency deviation characteristics.

[0106] Through the above technical scheme, two-stage PN code two-stage sliding correlation and one-stage differential demodulation device are used to realize the synchronization of the receiving end. When performing despreading in the first step, only the adders corresponding to the number of the second-stage PN code are required, the differential multiplication in the second step requires a complex multiplier, and the sliding correlation in the third step only requires the adders corresponding to the number of the first-stage PN code. The symbol lengths of the first-stage PN code and the second-stage PN code exemplified in the embodiment of the present application are 31 and 127 respectively, so 158 adders are required, while the traditional algorithm requires 127*32=4064 adders. In comparison, the present application can save a lot of hardware resources for logical calculation; at the same time, under the conditions of large frequency deviation and low signal-to-noise ratio, synchronization can be completed quickly and accurately.

[0107] The following is an embodiment of the system of the present application, which can be used to execute the embodiment of the method of the present application. For details not disclosed in the embodiment of the system of the present application, please refer to the embodiment of the method of the application.

[0108] See also Figure 8 , which shows a schematic diagram of the structure of a synchronization device based on differential spread spectrum code in drone and satellite communication provided by an exemplary embodiment of the present application. The device can be implemented as all or part of the device through software, hardware or a combination of both. The device includes a pseudo-random sequence generation module 10, a differential encoding module 20, a spread spectrum module 30 and a differential signal synchronization module 40.

[0109] A pseudo-random sequence generation module 10, used to generate a first-level PN code and a second-level PN code;

[0110] The differential encoding module 20 is used to perform differential encoding on the synchronization sequence using the first-level PN code to obtain a first differential sequence; the spread spectrum module 30 is used to perform spread spectrum on each symbol of the first differential sequence using the second-level PN code to obtain a differential synchronization header;

[0111] The differential signal synchronization module 40 is used to send the differential signal to the receiving end, so that the receiving end performs despreading and dedifferentiation processing after receiving the differential signal to obtain a first dedifferentiation sequence, and performs sliding correlation processing on the first-level PN code and the first dedifferentiation sequence to search for the correlation peak point. The differential signal includes a data sequence and a differential synchronization header, and the data sequence is the original sequence that carries information.

[0112] Optionally, the pseudo-random sequence generation module 10 further includes a pseudo-random sequence symbol length determination unit 11 .

[0113] The pseudo-random sequence symbol length determination unit 11 is used to calculate the symbol length of the second-level PN code based on the system maximum frequency deviation and the code chip rate, and generate the second-level PN code based on the symbol length of the second-level PN code. The calculation formula is as follows:

[0114] PL2=fc / 2maxdetf

[0115] Where PL2 is the symbol length of the second-level PN code;

[0116] f c is the chip rate;

[0117] maxdetf is the maximum frequency deviation of the system;

[0118] The symbol length of the first-order PN code is calculated using the system gain formula, and the first-order PN code is generated based on the symbol length of the first-order PN code. The system gain formula is as follows:

[0119] Gain=10log(PL1*PL2)

[0120] Where, Gain is the system gain;

[0121] PL1 is the symbol length of the first-level PN code.

[0122] Optionally, the differential encoding module 20 further includes a start value adding unit 21 .

[0123] The value adding unit 21 is started to add a 1-value symbol at the front end of the first-stage PN code; the first-stage PN code after adding the symbol is used to perform differential encoding on the synchronization sequence to obtain a first differential sequence.

[0124] The differential signal synchronization module 40 further includes a spread spectrum filtering unit 41 .

[0125] The spread spectrum filtering unit 41 is used to perform interpolation spread spectrum processing on the differential signal, and use a square root raised cosine filter to filter the spread spectrum differential signal.

[0126] The present application also provides a computer storage medium, which can store multiple instructions, and the instructions are suitable for being loaded and executed by a processor as described above. Figure 1-Figure 8 The synchronization method based on differential spread spectrum code in the UAV and satellite communication in the embodiment shown in the figure can be specifically performed in Figure 1-Figure 8 The specific description of the illustrated embodiment will not be repeated here.

[0127] See also Fig. 9 , is a schematic diagram of the structure of an electronic device provided in an embodiment of the present application. Fig. 9 As shown, the electronic device 1000 may include: at least one processor 1001 , at least one network interface 1004 , a user interface 1003 , a memory 1005 , and at least one communication bus 1002 .

[0128] The communication bus 1002 is used to realize the connection and communication between these components.

[0129] The user interface 1003 may include a display screen (Display) and a camera (Camera), and the optional user interface 1003 may also include a standard wired interface and a wireless interface.

[0130] The network interface 1004 may optionally include a standard wired interface or a wireless interface (such as a WI-FI interface).

[0131] Among them, the processor 1001 may include one or more processing cores. The processor 1001 uses various interfaces and lines to connect various parts in the entire server, and executes various functions of the server and processes data by running or executing instructions, programs, code sets or instruction sets stored in the memory 1005, and calling data stored in the memory 1005. Optionally, the processor 1001 can be implemented in at least one hardware form of digital signal processing (Digital Signal Processing, DSP), field programmable gate array (Field-Programmable Gate Array, FPGA), and programmable logic array (Programmable Logic Array, PLA). The processor 1001 can integrate one or more combinations of a central processing unit (Central Processing Unit, CPU), a graphics processing unit (Graphics Processing Unit, GPU) and a modem. Among them, the CPU mainly processes the operating system, user interface and application programs; the GPU is responsible for rendering and drawing the content to be displayed on the display screen; the modem is used to process wireless communications. It can be understood that the above-mentioned modem may not be integrated into the processor 1001, and it can be implemented separately through a chip.

[0132] Among them, the memory 1005 may include a random access memory (Random Access Memory, RAM) and may also include a read-only memory (Read-Only Memory). Optionally, the memory 1005 includes a non-transitory computer-readable storage medium. The memory 1005 can be used to store instructions, programs, codes, code sets or instruction sets. The memory 1005 may include a program storage area and a data storage area, wherein the program storage area may store instructions for implementing an operating system, instructions for at least one function (such as a touch function, a sound playback function, an image playback function, etc.), instructions for implementing the above-mentioned various method embodiments, etc.; the data storage area may store data involved in the above-mentioned various method embodiments, etc. The memory 1005 may optionally be at least one storage device located away from the aforementioned processor 1001. As Fig. 9 As shown, the memory 1005 as a computer storage medium may include an operating system, a network communication module, a user interface module, and an application program for a synchronization method based on differential spread spectrum codes in communication between a drone and a satellite.

[0133] exist Fig. 9 In the electronic device 1000 shown, the user interface 1003 is mainly used to provide an input interface for the user and obtain data input by the user; and the processor 1001 can be used to call an application stored in the memory 1005 for a synchronization method based on differential spread spectrum codes in drone and satellite communications. When executed by one or more processors, the electronic device executes one or more of the methods described in the above embodiments.

[0134] An electronic device readable storage medium stores instructions, which, when executed by one or more processors, enable the electronic device to execute one or more of the methods described in the above embodiments.

[0135] It should be noted that, for the aforementioned method embodiments, for the sake of simplicity, they are all described as a series of action combinations, but those skilled in the art should be aware that the present application is not limited by the order of the actions described, because according to the present application, certain steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily required for the present application.

[0136] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0137] In the several embodiments provided in the present application, it should be understood that the disclosed devices can be implemented in other ways. For example, the device embodiments described above are only schematic, such as the division of the units, which is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some service interfaces, and the indirect coupling or communication connection of devices or units can be electrical or other forms.

[0138] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0139] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0140] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable memory. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product, which is stored in a memory and includes several instructions for a computer device (which can be a personal computer, server or network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present application. The aforementioned memory includes: various media that can store program codes, such as USB flash drives, mobile hard drives, magnetic disks or optical disks.

[0141] The above is only an exemplary embodiment of the present disclosure, and the scope of the present disclosure cannot be limited thereto. That is, any equivalent changes and modifications made according to the teachings of the present disclosure are still within the scope of the present disclosure. After considering the disclosure of the specification and the truth of practice, it will be easy for those skilled in the art to think of other embodiments of the present disclosure. This application is intended to cover any modification, use or adaptation of the present disclosure, which follows the general principles of the present disclosure and includes common knowledge or customary technical means in the technical field that are not recorded in the present disclosure. The description and examples are regarded as exemplary only, and the scope and spirit of the present disclosure are defined by the claims.

Claims

1. A synchronization method based on differential spread spectrum code in UAV and satellite communication, characterized in that: Applied to the sending end, the method includes: Generate a first-level PN code and a second-level PN code; Using the first-stage PN code to differentially encode the synchronization sequence to obtain a first differential sequence; Among them, the formula for differential encoding is: The differentially encoded signal C k is the previous differentially encoded signal C (k-1) A superimposed on k The phase of the first differential sequence is the differential processing of the symbol of the first-level PN code and the previous symbol; the second-level PN code is used to spread each symbol of the first differential sequence to obtain a differential synchronization header; The differential signal is sent to the receiving end, so that the receiving end performs despreading and dedifferentiation processing after receiving the differential signal to obtain a first dedifferentiation sequence, and performs sliding correlation processing on the first-level PN code and the first dedifferentiation sequence to search for correlation peak points, the differential signal includes a data sequence and the differential synchronization header, and the data sequence is the original sequence that carries information.

2. The method according to claim 1, characterized in that The generating of the first-order PN code and the second-order PN code includes: calculating the symbol length of the second-order PN code based on the maximum frequency deviation of the system and the chip rate, and generating the second-order PN code based on the symbol length of the second-order PN code, and the calculation formula is as follows: PL2=f c / 2maxdetf Where PL2 is the symbol length of the second-level PN code; f c is the chip rate; maxdetf is the maximum frequency deviation of the system; The symbol length of the first-order PN code is calculated using a system gain formula, and the first-order PN code is generated based on the symbol length of the first-order PN code. The system gain formula is as follows: Gain=10log(PL1*PL2) Where, Gain is the system gain; PL1 is the symbol length of the first-level PN code.

3. The method according to claim 1, characterized in that The step of using the first-level PN code to differentially encode the synchronization sequence to obtain a first differential sequence includes: Add a 1-value symbol at the front end of the first-level PN code; The synchronization sequence is differentially encoded using the first-level PN code after the symbol is added to obtain a first differential sequence.

4. The method according to claim 1, characterized in that Before sending the differential signal to the receiving end, the method further includes: performing interpolation spread spectrum processing on the differential signal, and using a square root raised cosine filter to filter the spread differential signal.

5. A synchronization method based on differential spread spectrum code in UAV and satellite communication, characterized in that: Applied to the receiving end, the method comprises: Receive a differential signal, wherein the differential signal includes a differential synchronization header and a data sequence, wherein the differential synchronization header is obtained by differentially encoding the synchronization sequence with a first-level PN code to obtain a first differential sequence, and then spreading each symbol of the first differential sequence with a second-level PN code, and the data sequence is an original sequence carrying information; Among them, the formula for differential encoding is: The differentially encoded signal C k is the previous differentially encoded signal C (k-1) A superimposed on k The phase is the differential processing of the code element of the first-order PN code and the previous code element in the first differential sequence; Using the second-stage PN code to perform sliding correlation despreading on the differential signal to obtain a despreading sequence; Multiplying adjacent symbols of the despread sequence differentially to obtain a first de-differential sequence; The first solution differential sequence is subjected to sliding correlation processing with the first stage PN code to search for a correlation peak point.

6. The method according to claim 5, characterized in that After receiving the differential signal, the method further includes: The received differential signal is filtered using a square root raised cosine filter.

7. The method according to claim 5, characterized in that The sliding correlation processing of the first de-differentialized sequence and the first-stage PN code comprises: The first solution differential sequence is multiplied and added with the first-stage PN code by a sliding isolation degree of sampling points, and the sliding isolation degree is the product of the number of sampling points of a symbol and the symbol length of the first-stage PN code.

8. A synchronization device based on differential spread spectrum code in UAV and satellite communication, characterized in that: Applied to a transmitting end, the device comprises: A pseudo-random sequence generation module, used for generating a first-level PN code and a second-level PN code; The differential encoding module is used to use the first-level PN code to perform differential encoding on the synchronization sequence to obtain a first differential sequence; wherein the differential encoding formula is: The differentially encoded signal C k is the previous differentially encoded signal C (k-1) A superimposed on k The phase is the differential processing of the code element of the first-order PN code and the previous code element in the first differential sequence; A spectrum spreading module, configured to use the second-level PN code to spread each symbol of the first differential sequence to obtain a differential synchronization header; The differential signal synchronization module is used to send the differential signal to the receiving end, so that the receiving end performs despreading and dedifferentiation processing after receiving the differential signal to obtain a first dedifferentiation sequence, and performs sliding correlation processing on the first-level PN code and the first dedifferentiation sequence to search for correlation peak points. The differential signal includes a data sequence and the differential synchronization header, and the data sequence is the original sequence that carries information.

9. A computer storage medium, characterized in that The computer storage medium stores a plurality of instructions, and the instructions are suitable for being loaded by a processor and executing the method according to any one of claims 1 to 7.

10. An electronic device, characterized in that: The electronic device comprises a processor, a memory and a transceiver, wherein the memory is used to store instructions, the transceiver is used to communicate with other devices, and the processor is used to execute the instructions stored in the memory so that the electronic device executes the method according to any one of claims 1 to 7.

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