Satellite network data sending method and device

Abstract

The invention discloses a satellite network data sending method and a satellite network data sending device in order to solve the problem that in the prior art, in an ultra-low signal-to-noise ratio mode, frame capture and data demodulation cannot be completed, and therefore the communication requirement of a small-size antenna terminal cannot be met. The frame body part is generated based on the to-be-transmitted satellite load data packet, and the frame header part comprises a pseudorandom sequence and a physical layer signaling which are sufficient in length, so that the signal-to-noise ratio of the whole data frame is improved by increasing the length of the frame header, and the communication performance of the antenna terminal is improved. Therefore, the antenna can be detected and identified by a small-size antenna terminal under the condition of a low signal-to-noise ratio.

Description

Technical Field

[0001] The present invention belongs to the technical field of satellite network communication, and particularly relates to a satellite network data sending method and device. Background Art

[0002] The goal of satellite network communication is to provide services and applications for user terminals. The user terminals access the satellite network through satellites, and the gateway system provides services such as synchronization and routing for the satellite network, enabling the terminals to access the network to achieve communication. The data flow direction from the network to the remote terminal is called the forward direction, and the direction from the remote terminal to the network is called the reverse direction. In the forward direction, multiple user terminals can share the same channel through time division multiplexing and statistical multiplexing.

[0003] Previous satellite remote stations often used aperture antennas with a diameter of 0.3 meters to 1.4 meters, which worked in the normal satellite frame mode. Among them, there were 28 coding and modulation schemes for normal frames, and they worked under the condition of signal-to-noise ratio of -2dB to 16dB. For example, when it was 16dB ( defining the signal-to-noise ratio at the symbol level, representing the average energy of the symbol, representing the one-sided power spectral density of the noise), then a modulation method with high spectral efficiency of 32APSK was used for transmission.

[0004] Currently, with the advancement of broadband satellite Internet, there are more and more application scenarios for terminals with small-sized antennas. Among them, small-sized antennas have a small gain and need to work in an ultra-low signal-to-noise ratio mode. For example, when it was -10dB. However, a normal satellite frame format receiver could not complete frame capture and data demodulation under ultra-low signal-to-noise ratio conditions. Therefore, it could not meet the communication requirements of small-sized antenna terminals. Thus, based on the above deficiencies, how to provide a satellite network data sending method that can perform satellite network data frame capture and data demodulation in an ultra-low signal-to-noise ratio mode has become an urgent problem to be solved. Summary of the Invention

[0005] The purpose of the present invention is to provide a satellite network data sending method and device to solve the problem in the prior art that frame capture and data demodulation cannot be completed in an ultra-low signal-to-noise ratio mode, thus unable to meet the communication requirements of small-sized antenna terminals.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions: In the first aspect, a satellite network data sending method is provided, including: Obtaining a satellite payload data packet, and performing encapsulation processing on the satellite payload data packet to obtain a first frame body; Construct the first frame header corresponding to the satellite payload data packet, where the first frame header includes a first unique code field, a physical layer signaling field, and a second unique code field. The first unique code field is a pseudo-random sequence with a length of 206 bits or a fixed sequence with a length of 26 bits, the second unique code field is a pseudo-random sequence with a length of 900 bits, and the physical layer signaling field includes a normal frame signaling and an ultra-low signal-to-noise ratio frame signaling; Generate the ultra-low signal-to-noise ratio data frame corresponding to the satellite payload data packet according to the first frame header and the first frame body; Send the ultra-low signal-to-noise ratio data frame to the user terminal, so that the user terminal decodes the ultra-low signal-to-noise ratio data frame according to the physical layer signaling field in the first frame header, or the first unique code field and the second unique code field in the first frame header, to capture and identify the satellite payload data packet.

[0007] Based on the above-disclosed content, the present invention provides a satellite network data sending method, which constructs a new forward ultra-low signal-to-noise ratio data frame to meet the communication requirements of small-size antenna terminals; specifically, the present invention first encapsulates the obtained satellite payload data packet to obtain a first frame body; then, constructs a first frame header including a first unique code field, a physical layer signaling field, and a second unique code field. Finally, combines the first frame header and the first frame body to obtain an ultra-low signal-to-noise ratio data frame, and sends this data frame to the user terminal, then the transmission of the satellite payload data packet can be realized; where the length of the physical layer signaling field is 64 bits, the length of the first unique code field is 206 or 26 bits, and the length of the second unique code field is 900 bits. In this way, the length of the first frame header exceeds 1000 bits, that is, the present invention is equivalent to improving the signal-to-noise ratio of the entire data frame (i.e., the detection ability under low signal-to-noise ratio) by increasing the length of the frame header, so that the data frame can still be quickly captured and data demodulated in the ultra-low signal-to-noise ratio mode. Based on this, the communication requirements of small-size antenna terminals are met. Therefore, the present invention is very suitable for large-scale application and promotion in the field of satellite network communication technology.

[0008] In a possible design, constructing the first frame header corresponding to the satellite payload data packet includes: Randomly generate a number of base sequences, where the length of the base sequence is 16 bits or 8 bits; Use a number of base sequences to construct 10 first sequences, where the length of the first sequence is 112 bits; Extract the first 2 first sequences from the 10 first sequences, and use the extracted first 2 first sequences to generate a second sequence with a length of 224 bits; Remove the last 18 bits of data from the second sequence to obtain the initial first unique code field; Generate a third sequence with a length of 896 bits by using the remaining 8 first sequences among the 10 first sequences, and equally divide the third sequence into 8 parts to obtain 8 PN sequences; Obtain a Walsh sequence, where the length of the Walsh sequence is 8 chips, each of the 8 PN sequences corresponds to one data bit in the Walsh sequence, and the Walsh sequence is used to represent the coding code rate and spreading factor of the satellite payload data packet; Perform an exclusive OR operation on the 8 PN sequences and the corresponding data bits in the Walsh sequence, so as to obtain 8 processed PN sequences after the exclusive OR operation; Generate a fourth sequence by using the 8 processed PN sequences, and respectively add 2 target characters to the head and tail of the fourth sequence, so as to obtain an initial second unique code domain after adding the target characters, where the target character is 0; Perform a pseudo-random check processing on the initial first unique code domain and the initial second unique code domain, and obtain the second unique code domain and the first unique code domain of the pseudo-random sequence with a length of 206 bits after the pseudo-random check passes.

[0009] In a possible design, performing a pseudo-random check processing on the initial first unique code domain and the initial second unique code domain includes: Count the difference between the number of bits 0 and bits 1 in the target sequence to obtain a number difference, where the target sequence is a combined sequence of the initial first unique code domain and the initial second unique code domain; Judge whether the number difference is less than a first threshold; If so, perform a modulation check processing on the initial first unique code domain and the initial second unique code domain, and judge whether the modulation check passes; If so, perform an autocorrelation check processing on the initial first unique code domain and the initial second unique code domain, and judge whether the autocorrelation check processing passes; If so, perform a single-frame capture check processing on the initial first unique code domain and the initial second unique code domain, and after the single-frame capture check passes, use the initial first unique code domain as the first unique code domain and the initial second unique code domain as the second unique code domain.

[0010] In a possible design, performing a modulation check processing on the initial first unique code domain and the initial second unique code domain, and judging whether the modulation check passes includes: Adopt the pi / 2 BPSK modulation method to perform modulation processing on the initial first unique code domain and the initial second unique code domain to obtain the modulated initial first unique code domain and the modulated initial second unique code domain; Statistically count the occurrence frequencies of each π / 2 BPSK symbol in the modulated initial first unique code domain, and select the maximum occurrence frequency as the first maximum symbol count; Determine whether the first maximum symbol count is less than a second threshold; If so, statistically count the occurrence frequencies of each π / 2 BPSK symbol in the modulated initial second unique code domain, and select the maximum occurrence frequency as the second maximum symbol count, otherwise, randomly generate several base sequences again; Determine whether the second maximum symbol count is less than a third threshold; If so, determine that the modulation verification of the initial first unique code domain and the initial second unique code domain passes, otherwise, randomly generate several base sequences again.

[0011] In a possible design, perform autocorrelation verification processing on the initial first unique code domain and the initial second unique code domain, and determine whether the autocorrelation verification processing passes, including: Perform autocorrelation processing on the initial first unique code domain and the initial second unique code domain to obtain an autocorrelation function; Based on the autocorrelation function, calculate the maximum normalized sidelobe of the autocorrelation function; Determine whether the maximum normalized sidelobe is less than a fourth threshold; If so, determine that the autocorrelation verification of the initial first unique code domain and the initial second unique code domain passes, otherwise, randomly generate several base sequences again.

[0012] In a possible design, when the first unique code domain is the pseudo-random sequence with a length of 206 bits, the first unique code domain is: 3D42ABA709B03263C78947897D4287897D42B739F263C9B009B0, and the second unique code domain is: 26C01E25DCE726C04758DCE7AE9C 4758AE9CF50AF50ADCE7AE9CC98F 26C0DCE74758F50AAE9C1E254758 1E25C98FDCE747581E25F50A4758 C98FAE9CF50ADCE726C01E254758 AE9C1E25AE9CC98FAE9CF50AC98F C98F47584758C98FDCE7475826C0 F50A26C01E25DCE7AE9CC98FDCE7; or The first unique code field is: 209D6AC85E97C6A21963E1D4E09D6AC8609D5963E09D46A2327F, and the second unique code field is: 7A5F1A8882751A88658F7A5F7A5F 7A5F1A881A88AB21AB211A888753 8753AB21658FC9FC8275C9FC658F 8753658F1A88C9FCC9FC8753C9FC 8275658F7A5F87538753C9FC8753 AB21AB21AB217A5F82757A5F1A88 C9FC658FC9FCC9FC8275AB211A88 AB218753658F658F82757A5F8753。

[0013] In a possible design, the satellite payload data packet is encapsulated to obtain a first frame body, including: The satellite payload data packet is subjected to constellation diagram modulation processing to obtain a data symbol set; In the data symbol set, a pilot block is inserted every 720 data symbols to obtain an initial frame body after all data symbols are polled; A pilot block is added to the tail of the initial frame body to obtain the first frame body after the addition, wherein when the first unique code field in the first frame header adopts sequences of different lengths, the length of the first frame body is different.

[0014] In a possible design, the length of the physical layer signaling field is 64 bits, and the physical layer signaling field includes physical layer signaling 0 to 31. Among them, when the first unique code field is a pseudo-random sequence with a length of 206 bits, physical layer signaling 0 to 28 are normal frame signaling, physical layer signaling 29 and physical layer signaling 30 are ultra-low signal-to-noise ratio frame signaling. When the first unique code field is a fixed sequence with a length of 26 bits, physical layer signaling 11 and physical layer signaling 23 are ultra-low signal-to-noise ratio frame signaling, and the remaining physical layer signaling is normal frame signaling.

[0015] In a possible design, the method further includes: Encapsulate the satellite payload data packet to obtain a second frame body; Construct a second frame header corresponding to the satellite payload data packet, where the second frame header includes the first unique code field and the physical layer signaling field; Generate a normal data frame corresponding to the satellite payload data packet according to the second frame header and the second frame body; Adopt the time division multiple access method and broadcast the normal data frame and the ultra-low signal-to-noise ratio data frame to the user terminal according to a preset time slot ratio.

[0016] Beneficial effects: (1) The present invention provides a satellite network data sending method, which constructs a forward ultra-low signal-to-noise ratio data frame to meet the communication requirements of small-size antenna terminals. Among them, the frame body part is generated based on the satellite payload data packet to be transmitted, and the frame header part includes a pseudo-random sequence and physical layer signaling of sufficient length. In this way, the present invention improves the signal-to-noise ratio of the entire data frame by increasing the length of the frame header, so that it can be detected and recognized by small-size antenna terminals under the condition of low signal-to-noise ratio; based on this, the communication requirements of small-size antenna terminals can be met.

[0017] (2) The physical layer signaling field provided by the present invention includes a normal frame signaling and an ultra-low signal-to-noise ratio frame signaling, which can indicate the normal frame and the ultra-low signal-to-noise ratio frame. Therefore, in the normal satellite frame mode, the satellite remote end can also identify the ultra-low signal-to-noise ratio data frame based on the physical layer signaling field, so as to skip the reception of this frame; thus, the ultra-low signal-to-noise ratio data frame can also be recognized by a normal signal-to-noise ratio receiver, so that the adaptability of use is improved.

[0018] (3) The present invention also supports the mixed transmission mode of normal frames and ultra-low signal-to-noise ratio frames, that is, a second frame body is generated by using the satellite payload data packet, and a corresponding second frame header is constructed. The second frame header only contains the physical layer signaling field and the first unique code field, and its length is much lower than that of the ultra-low signal-to-noise ratio data frame. Therefore, the normal data frames generated by the two can be captured and recognized by user terminals with normal signal-to-noise ratio; finally, after generating the normal data frame, the present invention adopts the time division multiple access method and broadcasts the normal data frame and the ultra-low signal-to-noise ratio data frame to the user terminal according to a preset time slot ratio. In this way, while the present invention meets the fast capture and data demodulation of data frames at ultra-low signal-to-noise ratio working points, it also supports the mixed transmission mode of normal data frames and ultra-low signal-to-noise ratio data frames. Based on this, the flexible configuration of the system can be satisfied, thereby improving the flexibility of use. Description of the drawings

[0019] Figure 1 It is a schematic flow chart of the steps of the satellite network data sending method provided by the embodiment of the present invention; Figure 2 Schematic diagram of the structure of the format1 ultra-low signal-to-noise ratio data frame provided by an embodiment of the present invention; Figure 3 Schematic diagram of the structure of the format2 ultra-low signal-to-noise ratio data frame provided by an embodiment of the present invention; Figure 4 Schematic diagram of the structure of the first unique code domain provided by an embodiment of the present invention; Figure 5 Coding and modulation scheme mapping table of the physical layer signaling domain provided by an embodiment of the present invention; Figure 6 Schematic diagram of the structure of the second unique code domain provided by an embodiment of the present invention; Figure 7 Corresponding relationship between the Walsh sequence, code rate, and spreading factor provided by an embodiment of the present invention; Figure 8 An example of the first unique code domain and the second unique code domain of the selected format1 ultra-low signal-to-noise ratio data frame provided by an embodiment of the present invention; Figure 9 An example of the first unique code domain and the second unique code domain of the format1 ultra-low signal-to-noise ratio data frame that meets the conditions provided by an embodiment of the present invention; Figure 10 Another example of the first unique code domain and the second unique code domain of the format1 ultra-low signal-to-noise ratio data frame that meets the conditions provided by an embodiment of the present invention; Figure 11 An example of the first unique code domain of the format2 ultra-low signal-to-noise ratio data frame that meets the conditions provided by an embodiment of the present invention; Figure 12 Schematic diagram of the autocorrelation characteristic of the 1106-bit sequence composed of the first unique code domain and the second unique code domain of the format1 ultra-low signal-to-noise ratio data frame provided by an embodiment of the present invention; Figure 13 Schematic diagram of the structure of the normal data frame provided by an embodiment of the present invention; Figure 14 Schematic diagram of the in-air mixed transmission of the normal data frame and the ultra-low signal-to-noise ratio data frame provided by an embodiment of the present invention; Figure 15 Schematic diagram of the performance of the normal frame receiver capturing the ultra-low signal-to-noise ratio data frame provided by an embodiment of the present invention; Figure 16 Schematic diagram of the performance of the ultra-low signal-to-noise ratio frame receiver capturing the ultra-low signal-to-noise ratio data frame provided by an embodiment of the present invention; Figure 17 Schematic diagram of the structure of the satellite network data transmission device provided by an embodiment of the present invention; Figure 18Schematic diagram of the structure of the electronic device provided by the embodiment of the present invention. Detailed implementation manners

[0020] Embodiment: Refer to Figure 1 As shown, the satellite network data sending method provided in this embodiment meets the communication requirements of small-size antenna terminals by constructing a forward ultra-low signal-to-noise ratio data frame. Among them, the frame body part is generated based on the satellite payload data packet to be transmitted, and the frame header part includes a pseudo-random sequence and a physical layer signaling with a sufficient length. In this way, this method improves the signal-to-noise ratio of the entire data frame by increasing the length of the frame header, so that it can be detected and recognized by small-size antenna terminals under the condition of a low signal-to-noise ratio; based on this, the communication requirements of small-size antenna terminals can be met, so it is very suitable for large-scale application and promotion; among them, for example, this method can be but is not limited to running on the satellite remote side. It can be understood that the foregoing execution subject does not constitute a limitation to the embodiments of the present application. Correspondingly, the running steps of this method can be but are not limited to the following steps S1 to S4.

[0021] S1. Obtain a satellite payload data packet, and perform encapsulation processing on the satellite payload data packet to obtain a first frame body; in specific implementation, the first frame body has different structures according to different first frame headers, which will be elaborated in the following step S2 of this embodiment; after generating the construction of the first frame body, the generation of the frame header can be performed, and the process is as shown in the following step S2.

[0022] S2. Construct a first frame header corresponding to the satellite payload data packet, where the first frame header includes a first unique code field, a physical layer signaling field, and a second unique code field. The first unique code field is a pseudo-random sequence with a length of 206 bits or a fixed sequence with a length of 26 bits, and the second unique code field is a pseudo-random sequence with a length of 900 bits. The physical layer signaling field includes a normal frame signaling and an ultra-low signal-to-noise ratio frame signaling. Among them, the pseudo-random sequence is a bit sequence, which becomes a symbol after being modulated by a pi / 2 BPSK constellation diagram; for example, a bit sequence with a length of 206 becomes a symbol with a length of 206.

[0023] In this embodiment, when different-length sequences are used in the first unique code field of the first frame header, the length of the first frame body is different. Specifically, when the first unique code field is a pseudo-random sequence with a length of 206 bits (denoted as format1), the construction method of the first frame body is as follows: First, perform constellation modulation processing on the satellite payload data packet to obtain a data symbol set; then, in the data symbol set, insert a pilot block every 720 data symbols to obtain an initial frame body after polling all data symbols; finally, add a pilot block to the tail of the initial frame body; thus, after adding, the first frame body can be obtained. Based on this, in the frame body part of this embodiment, the insertion rule of pilot symbols is changed, as can be seen in Figure 2 Figure (b) shown in Figure 2 Figure (b) in Figure 2 is one of the construction methods of the frame body), that is: insert a pilot block with a length of 36 symbols every 720 data symbols (i.e.,

[0024] the data symbol block in Figure 2 ), and add an additional pilot block at the end of the frame, thereby generating the first frame body, that is, the first frame body is composed of 45 data symbol blocks and 45 pilot blocks.

[0025] Further, when the first unique code field is a fixed sequence with a length of 26 bits (denoted as format2), the structure of its ultra-low signal-to-noise ratio data frame can be seen in Figure 3 Figures (a) and (b) shown in Figure 3 Figures (a) and (b) shown in Figure 3 Figure (a) in Figure 3 represents one of the structures of the format2 ultra-low signal-to-noise ratio frame,

[0026] Among them, constellation diagram modulation is a common technology for satellite payload data packet processing, and its principle will not be elaborated one by one.

[0027] Furthermore, the structure of the first frame header is described below as follows: In this embodiment, refer to Figure 2 As shown, the first frame header of the format1 ultra-low signal-to-noise ratio data frame (i.e., using a 206-bit pseudo-random sequence as the first unique code domain) is 1170 bits. Among them, the length of the first unique code domain (i.e., UW1) is 206 bits, the length of the second unique code domain (UW2) is 900 symbols, and the total length of the corresponding pseudo-random sequence is 206 + 900 bits. The physical layer signaling domain (i.e., Figure 2 the PLSC in) occupies 64 bits; among them, the physical layer signaling domain includes physical layer signals 0 to 31, and 0 to 28 are normal frame signals, and 29 and 30 are ultra-low signal-to-noise ratio frame signals. The 1170-bit sequence, when physically framed, is modulated by a pi / 2 BPSK constellation diagram and mapped to the first frame header of 1170 symbols.

[0028] Refer to Figure 5 As shown, this embodiment expands the physical layer signaling domain, which includes 28 coding and modulation modes, that is, Figure 5 the coding and modulation modes 0 to 28 in (that is, the coding and modulation modes corresponding to data bits 0 to 28); at the same time, two additional MODCODs are added to indicate the format1 ultra-low signal-to-noise ratio data frame, that is, Figure 5 the coding and modulation modes corresponding to physical layer signal 29 and physical layer signal 30 in; in this way, the ultra-low signal-to-noise ratio data frame can also be recognized by a normal signal-to-noise ratio receiver, so as to skip the reception of this frame, thereby improving the applicability of use; based on this, the physical layer signaling domain supports three working conditions, which will be elaborated in detail in the data frame capture process in step S4 of this embodiment.

[0029] Refer to Figure 3 As shown, when the first unique code domain uses a 26-bit fixed sequence, the first frame header of the format2 ultra-low signal-to-noise ratio data frame is 990 bits. Among them, the length of the first unique code domain (i.e., UW1) is 26 bits, and the bit sequence is 01100011010010111010000010. The length of the second unique code domain (UW2) is 900 symbols, and the total length of the corresponding pseudo-random sequence is 26 + 900 bits. The physical layer signaling domain (i.e., Figure 3 the PLSC in) occupies 64 bits; the physical layer signaling domain includes 5-bit physical layer signals 0 to 31. For format2, physical layer signals 11 and physical layer signal 23 are used to indicate the ultra-low signal-to-noise ratio frame, and other physical layer signals are normal frame signals.

[0030] See Figure 4 As shown, in the format1 ultra-low signal-to-noise ratio data frame, UW1 is obtained by truncating the tails of two PN sequences with a length of 112 bits by 18 bits; similarly, the first 2 bits and the last 2 bits of the UW2 sequence are all 0 bits, and the middle 896 bits are formed by superimposing the PN sequence and the Walsh sequence. See Figure 6 As shown, the length of the Walsh sequence is 8 chips, denoted as , and the superimposing rule of the PN sequence and the Walsh sequence is as follows: The PN sequence is equally divided into 8 parts, each part is a short PN sequence with a length of 112 bits, and each part is respectively XORed with the corresponding chip of the Walsh sequence. In this way, UW2 can be obtained; based on this, the second unique code domain actually contains a signaling indication of an 8-bit walsh code, and this walsh code can be used for subsequent frame format parsing in the ultra-low signal-to-noise ratio mode; of course, the detailed generation processes of UW1 and UW2 will be elaborated in detail below.

[0031] In this embodiment, the sequences of UW1 and UW2 can be two independent sequences. One method of selecting sequences is to independently intercept pseudo-random sequences with relevant lengths from the Gold sequence, that is, intercept a pseudo-random sequence with a length of 206 or 26 as UW1, intercept a pseudo-random sequence with a length of 896, and then add 2 0s to the head and tail of the 896-bit sequence to form a UW2 sequence with a length of 900 bits; among them, the selected UW1 and UW2 sequences need to have good autocorrelation and cross-correlation.

[0032] Furthermore, Figure 8 is an example of selecting UW1 and UW2 by this method, where Figure 8 Figure (a) in corresponds to an example of UW1, Figure 8 Figure (b) in corresponds to an example of UW2; in actual applications, although the method of truncating the Gold sequence can obtain pseudo-random sequences UW1 and UW2 with good autocorrelation and cross-correlation characteristics, however, the implementation of such completely correlated long sequences is relatively complex. In order to simplify the implementation, this embodiment provides a jointly optimized sequence generation method (taking the generation of the first unique code domain with a length of 206 bits and the aforementioned second unique code domain as an example), and its generation process can but is not limited to the following steps S21 to S29.

[0033] S21. Randomly generate a number of base sequences, where the length of the base sequence is 16 bits or 8 bits; in this embodiment, for example, 70 base sequences with a length of 16 bits are generated, and 140 base sequences with a length of 8 bits are generated.

[0034] After obtaining a number of base sequences, sequence combination can be performed, and the process is as shown in the following step S22.

[0035] S22. Use a number of base sequences to construct 10 first sequences, where the length of the first sequence is 112 bits; in this embodiment, 70 16-bit base sequences or 140 8-bit base sequences are used to form 8 sequences with a length of 112 bits. Then, sequence truncation can be performed to generate an initial first unique code domain and an initial second unique code domain, and the process can be referred to as shown in the following steps S23 to S28.

[0036] S23. Extract the first 2 first sequences from the 10 first sequences, and use the extracted first 2 first sequences to generate a second sequence with a length of 224 bits; in this embodiment, it is equivalent to merging the first two first sequences to obtain a 224-bit second sequence. Then, remove 18-bit data at the end of the second sequence to obtain the initial first unique code domain, and the process can be but not limited to as shown in the following step S24.

[0037] S24. Remove the last 18-bit data in the second sequence to obtain the initial first unique code domain.

[0038] After obtaining the initial first unique code domain, the remaining 8 first sequences can be used to combine and obtain an 896-bit third sequence, so as to generate the initial second unique code domain based on the third sequence subsequently, and the process is as shown in the following steps S25 to S28.

[0039] S25. Use the remaining 8 first sequences among the 10 first sequences to generate an 896-bit third sequence, and divide the third sequence into 8 equal parts to obtain 8 PN sequences.

[0040] After the equal division of the third sequence is completed, exclusive OR with the Walsh sequence can be performed, and the process is as shown in the following step S26.

[0041] S26. Obtain the Walsh sequence, where the length of the Walsh sequence is 8 chips, and the 8 PN sequences respectively correspond to one data bit (i.e., one chip) in the Walsh sequence, and the Walsh sequence is used to represent the coding code rate and spreading factor of the satellite payload data packet; in this embodiment, the Walsh sequence is used to indicate the frame format, that is, the coding code rate and spreading factor. Among them, different Walsh sequences correspond to different coding code rates and spreading factors, and the corresponding relationship can be referred to Figure 7 as shown. In this way, by performing exclusive OR operation with the Walsh sequence at the initial stage of sequence generation, it is convenient for the subsequent user terminal to capture the frame and obtain the frame format information based on this.

[0042] After the Walsh sequence is obtained, it can be XORed with the eight PN sequences, and the process is shown in the following step S27.

[0043] S27. The eight PN sequences are XORed with the corresponding data bits in the Walsh sequence to obtain eight processed PN sequences after the XOR operation; wherein the corresponding relationship between the eight PN sequences and the data bits in the Walsh sequence can be found in Figure 6 As shown, the Walsh sequence can be any Walsh sequence.

[0044] After the XOR operation of the eight PN sequences and the Walsh sequence is completed, an initial second unique code field can be generated based on this, and the process is shown in the following step S28.

[0045] S28. Generate a fourth sequence using the eight processed PN sequences, and add two target characters to the head and tail of the fourth sequence respectively, so as to obtain an initial second unique code domain after adding the target characters, wherein the target character is 0; after adding two 0s to the head and tail of the fourth sequence respectively, the initial second unique code domain can be obtained.

[0046] After obtaining the initial first unique code domain and the initial second unique code domain, they still need to be verified. They need to meet the following six conditions. Only after meeting the following six conditions can they be used as the final first unique code domain and the second unique code domain; among them, the verification process of the initial first unique code domain and the initial second unique code domain can be seen in the following step S29.

[0047] S29. Perform pseudo-random check processing on the initial first unique code domain and the initial second unique code domain, and after the pseudo-random check passes, obtain the second unique code domain and the first unique code domain of the pseudo-random sequence with a length of 206 bits; in the specific implementation, the six check conditions that need to be satisfied by the pseudo-random check are respectively the check of the difference between the number of bits 0 and bit 1 in the sequence after the two initial sequences are combined, the check of the maximum number of symbols after the two sequences are modulated (separate checks are required here, so it is equivalent to two conditions), the check of the maximum normalized sidelobe of the autocorrelation function of the combined sequence of the two sequences, the single-frame capture check of the initial first unique code domain under normal signal-to-noise ratio conditions, and the single-frame capture check of the combined sequence of the two sequences under ultra-low signal-to-noise ratio conditions; in this way, only after passing the above six checks, can the initial first unique code domain and the initial second unique code domain be used as the first unique code domain and the second unique code domain.

[0048] Optionally, the specific verification process may be but is not limited to the following steps S29a to S29e.

[0049] S29a. Calculate the difference between the number of bit 0 and bit 1 in the target sequence to obtain the number difference, where the target sequence is the combined sequence of the initial first unique code domain and the initial second unique code domain; in this embodiment, it is equivalent to splicing the initial first unique code domain and the initial second unique code domain to obtain the target sequence, and then, the number of 0s and 1s in the target sequence can be counted, and the difference between the two can be obtained to get the number difference; finally, the verification of the number difference can be performed, and the process is as shown in the following step S29b.

[0050] S29b. Determine whether the number difference is less than the first threshold; in specific implementation, for example, the first threshold (for format1 ultra-low signal-to-noise ratio data frames) can be but is not limited to (900 + 206) / 20, and for format2, it is set to (900 + 26) / 20; where, if it is less than, the verification of the difference between the number of bit 0 and bit 1 is passed, and then the following step S29c is executed, otherwise, the previous step S21 needs to be re-executed, that is, several base sequences are randomly generated again, and then, the previous steps S22 - S28 are re-executed to generate a new initial first unique code domain and a new initial second unique code domain.

[0051] S29c. If so, perform modulation verification processing on the initial first unique code domain and the initial second unique code domain, and determine whether the modulation verification passes; in this embodiment, the modulation verification processing process is as follows: First, use the pi / 2 BPSK modulation method to modulate the initial first unique code domain and the initial second unique code domain to obtain the modulated initial first unique code domain and the modulated initial second unique code domain; then, count the occurrence frequencies of each pi / 2 BPSK symbol in the modulated initial first unique code domain, and select the maximum occurrence frequency as the first maximum symbol count; then, determine whether the first maximum symbol count is less than the second threshold (for example, the second threshold is 206 / 4 + 5, and similarly, it is for format1); if so, count the occurrence frequencies of each pi / 2 BPSK symbol in the modulated initial second unique code domain, and select the maximum occurrence frequency as the second maximum symbol count, otherwise, randomly generate several base sequences again; finally, determine whether the second maximum symbol count is less than the third threshold (for example, its value is 900 / 4 + 10); where, if so, it is determined that the modulation verification of the initial first unique code domain and the initial second unique code domain passes, otherwise, randomly generate several base sequences again.

[0052] Thus, the modulation check is equivalent to determining whether the maximum number of the same symbol in the π / 2 BPSK symbols mapped by the UW1 sequence is less than or equal to 206 / 4 + 5, and determining whether the maximum number of the same symbol in the π / 2 BPSK symbols mapped by the UW2 sequence is less than or equal to 900 / 4 + 10; wherein, if the above two conditions are satisfied, then proceed to the next step (i.e., execute the following step S29d), if either of the above conditions is not satisfied, then the previous step S21 needs to be re-executed; wherein, step S29d is as follows.

[0053] S29d. If so, perform autocorrelation check processing on the initial first unique code domain and the initial second unique code domain, and determine whether the autocorrelation check processing passes; in specific implementation, first perform autocorrelation processing on the initial first unique code domain and the initial second unique code domain to obtain an autocorrelation function; then, based on the autocorrelation function, calculate the maximum normalized sidelobe of the autocorrelation function; finally, determine whether the maximum normalized sidelobe is less than a fourth threshold, wherein, if so, it is determined that the autocorrelation check of the initial first unique code domain and the initial second unique code domain passes, otherwise, several base sequences need to be randomly generated again.

[0054] In specific implementation, the sequence composed of the initial first unique code domain and the initial second unique code domain can be denoted as: , and its corresponding π / 2 BPSK modulation symbol is Z. Therefore, the autocorrelation function of the two is defined as: (1) In formula (1), represents the autocorrelation function, represents the i-th symbol after modulation of the sequence composed of the initial first unique code domain and the initial second unique code domain, represents the autocorrelation delay, represents the conjugate operation.

[0055] Thus, the calculation formula of the maximum normalized sidelobe of the autocorrelation function is: (2) In the above formula (2), represents the maximum normalized sidelobe of the autocorrelation function, represents the value of the autocorrelation function when k takes 0.

[0056] Thus, it is necessary to determine whether the maximum normalized sidelobe of the autocorrelation function is less than 0.15; wherein, if it is less, the modulation check passes, and then the following step S29e is executed; otherwise, the previous step S21 needs to be re-executed; the execution process of step S29e is as follows.

[0057] S29e. If so, perform single-frame capture verification processing on the initial first unique code domain and the initial second unique code domain, and after the single-frame capture verification passes, use the initial first unique code domain as the first unique code domain and the initial second unique code domain as the second unique code domain.

[0058] In specific applications, the single-frame capture verification processing procedure can be but is not limited to the following first step to the seventh step.

[0059] First step: Under the preset signal-to-noise ratio condition, calculate the correlation peak gain of the initial first unique code domain. The preset signal-to-noise ratio condition includes -2dB. In this embodiment, the preset signal-to-noise ratio condition includes -2dB, which is equivalent to verifying whether it can be single-frame captured in the case of a normal frame. For example, but not limited to, 10×log10(h) can be used to calculate the correlation peak gain of the aforementioned initial first unique code domain, where h represents the length of the initial first unique code domain. Based on this, the correlation peak gain of the initial first unique code domain can be calculated as 23dB. Then, the corresponding first correlation peak signal-to-noise ratio can be determined according to the correlation peak gain, and the calculation process is shown in the following second step.

[0060] Second step: Calculate the first correlation peak signal-to-noise ratio of the initial first unique code domain according to the correlation peak gain. In this embodiment, the correlation peak signal-to-noise ratio (dB) = signal signal-to-noise ratio (dB) + correlation peak gain (dB), and the signal signal-to-noise ratio is the preset signal-to-noise ratio condition, that is, -2dB. Therefore, the first correlation peak signal-to-noise ratio is 20dB. Then, it can be judged whether the first correlation peak signal-to-noise ratio meets the single-frame capture condition, so as to perform subsequent single-frame capture verification under ultra-low signal-to-noise ratio conditions according to the judgment result. The judgment process is shown in the following third step.

[0061] Third step: Judge whether the first correlation peak signal-to-noise ratio meets the single-frame capture condition. In this embodiment, the correlation peak signal-to-noise ratio needs to be high enough to reliably detect the signal in the noise. Therefore, the single-frame capture condition can be set as the first correlation peak signal-to-noise ratio threshold. Therefore, when the first correlation peak signal-to-noise ratio is greater than the first correlation peak signal-to-noise ratio threshold, it is considered that the single-frame capture verification in the normal frame passes; otherwise, the previous step S21 needs to be executed again.

[0062] In actual use, the curve as shown in Figure 15 can be obtained through the simulation of the UW1 frame header under the AWGN channel condition to judge whether single-frame capture is possible, that is, when the signal-to-noise ratio is -2dB, the probability of frame header error detection is less than , and it can be considered that single-frame capture is achieved.

[0063] Among them, after the single-frame capture verification of the normal frame, the single-frame capture verification under the ultra-low signal-to-noise ratio condition can be carried out, and the process is as shown in the following fourth to seventh steps. Fourth step: If so, combine the initial first unique code domain and the initial second unique code domain to obtain a combined sequence; in this embodiment, the combined sequence is the same as the target sequence, and both are obtained by splicing the two.

[0064] After obtaining the combined sequence, the second correlation signal-to-noise ratio of the combined sequence can be calculated, and the process is as shown in the following fifth step.

[0065] Fifth step: Under the preset ultra-low signal-to-noise ratio condition, calculate the second correlation peak signal-to-noise ratio of the combined sequence; in this embodiment, the calculation process of the second correlation peak signal-to-noise ratio of the combined sequence is the same as that of the first correlation peak signal-to-noise ratio, and will not be elaborated here; at the same time, an example of the preset ultra-low signal-to-noise ratio condition is that the signal-to-noise ratio is set to -10 dB.

[0066] In this way, according to the aforementioned 10×log10(h) formula, the correlation peak gain of the combined sequence can be calculated, and then adding (-10 dB), the second correlation peak signal-to-noise ratio is obtained, which is 20 dB. In this way, it can be continued to judge whether the second correlation peak signal-to-noise ratio meets the single-frame capture condition under the ultra-low signal-to-noise ratio condition, and thus, according to the judgment result, it can be determined whether the initial first unique code domain and the initial second unique code domain meet the single-frame verification condition, where the verification process is as shown in the following sixth and seventh steps.

[0067] Sixth step: Judge whether the second correlation peak signal-to-noise ratio meets the single-frame capture condition; in specific implementation, the single-frame capture condition of this step is the preset second correlation peak signal-to-noise ratio threshold. Among them, if it is greater than the second correlation peak signal-to-noise ratio threshold, it can be determined that the initial first unique code domain and the initial second unique code domain pass the single-frame capture verification. At this time, the initial first unique code domain can be used as the aforementioned first unique code domain, and the initial second unique code domain can be used as the aforementioned second unique code domain; otherwise, it is necessary to re-execute the aforementioned step S21; the aforementioned process can be seen as shown in the following seventh step.

[0068] Seventh step: If so, determine that the initial first unique code domain and the initial second unique code domain pass the single-frame capture verification, otherwise, randomly generate several base sequences again.

[0069] In this embodiment, frame header detection is obtained through simulation, as shown in Figure 16 shown, that is, perform frame header sliding correlation detection on the alternative uw1 and uw2, so as to judge whether the single-frame capture verification under the ultra-low signal-to-noise ratio condition can be passed based on the probability of frame header error detection.

[0070] Thus, through the foregoing steps S21 to S29 and their sub-steps, the first unique code domain and the second unique code domain can be generated. Then, in combination with the foregoing physical layer signaling domain, the first frame header can be combined and obtained.

[0071] Among them, the following gives an example of format1 corresponding to the first unique code domain and the second unique code domain (that is, when the first unique code domain is a 206-bit pseudo-random sequence). The 206-bit pseudo-random sequence is: 3D42ABA709B03263C78947897D4287897D42B739F263C9B009B0.

[0072] And the second unique code domain is: 26C01E25DCE726C04758DCE7AE9C 4758AE9CF50AF50ADCE7AE9CC98F 26C0DCE74758F50AAE9C1E254758 1E25C98FDCE747581E25F50A4758 C98FAE9CF50ADCE726C01E254758 AE9C1E25AE9CC98FAE9CF50AC98F C98F47584758C98FDCE7475826C0 F50A26C01E25DCE7AE9CC98FDCE7.

[0073] Furthermore, another example of format1 corresponding to the first unique code domain and the second unique code domain is given in this embodiment, that is: The first unique code domain is: 209D6AC85E97C6A21963E1D4E09D6AC8609D5963E09D46A2327F, and the second unique code domain is: 7A5F1A8882751A88658F7A5F7A5F 7A5F1A881A88AB21AB211A888753 8753AB21658FC9FC8275C9FC658F 8753658F1A88C9FCC9FC8753C9FC 8275658F7A5F87538753C9FC8753 AB21AB21AB217A5F82757A5F1A88 C9FC658FC9FCC9FC8275AB211A88 AB218753658F658F82757A5F8753。

[0074] Of course, the foregoing examples are merely illustrative, and the specific sequences of the foregoing second unique code domain and the first unique code domain of the pseudo-random sequence with a length of 206 bits are not limited thereto.

[0075] Furthermore, this embodiment gives examples of the foregoing first unique code domain and second unique code domain; see Figure 9 and Figure 10 as shown, Figure 9 and Figure 10 are both the first unique code domain and the second unique code domain that meet the foregoing six conditions (both refer to the two unique code domains in the frame header under format1); among them, Figure 9 and Figure 10 The first unique code domain and the second unique code domain shown are both represented in hexadecimal, and the leftmost bit is the high-order bit; Figure 9 In the (a) diagram of Figure 9 is the sequence corresponding to one of the UW1s (i.e., the first unique code domain), Figure 10 In the (b) diagram of Figure 10 is the sequence corresponding to UW2 (i.e., the second unique code domain); similarly, Figure 12 In Figure 12 it can be seen that its maximum normalized sidelobe is less than 0.15, meeting the autocorrelation characteristics.

[0076] At the same time, this embodiment also gives an example of the first unique code domain of the format2 ultra-low signal-to-noise ratio data frame that meets the conditions, which can be seen in Figure 11 as shown.

[0077] In this way, after constructing the first frame header based on the foregoing steps, the first frame body in step S1 can be combined to generate an ultra-low signal-to-noise ratio data frame, and the process is as shown in the following step S3.

[0078] S3. Generate the ultra-low signal-to-noise ratio data frame corresponding to the satellite payload data packet according to the first frame header and the first frame body; in this embodiment, by adding the first frame header to the head of the first frame body, the foregoing ultra-low signal-to-noise ratio data frame can be obtained; then, the ultra-low signal-to-noise ratio data frame can be sent, and the process is as shown in the following step S4.

[0079] S4. Send the ultra-low signal-to-noise ratio data frame to the user terminal, so that the user terminal decodes the ultra-low signal-to-noise ratio data frame according to the physical layer signaling field in the first frame header, or the first unique code field and the second unique code field in the first frame header, to capture and identify the satellite payload data packet; in this embodiment, for example, the ultra-low signal-to-noise ratio data frame can be added to the forward frame queue to form a forward data stream, and then, the forward data stream is sent to the user terminal.

[0080] Furthermore, this embodiment also supports the mixed transmission mode of normal data frames, ultra-low signal-to-noise ratio data frames, or normal data frames and ultra-low signal-to-noise ratio data frames. Specifically, the implementation process is as follows: (1) Encapsulate the satellite payload data packet to obtain a second frame body; in this embodiment, first, the satellite payload data packet is subjected to constellation diagram modulation processing to obtain a data symbol set, and then, a pilot block with a length of 36 symbols is inserted into the data symbol set every 8 time slots. Each time slot contains 90 data symbols. In this way, it is equivalent to inserting a pilot block every 720 symbols ( Figure 13 where P represents the pilot block), so as to generate a second frame body, and its structural schematic diagram can be seen in Figure 13 as shown.

[0081] Then, the corresponding second frame header can be constructed, and the process is as follows.

[0082] (2) Construct the second frame header corresponding to the satellite payload data packet, where the second frame header includes the first unique code field and the physical layer signaling field; in this embodiment, compared with the first frame header, the second frame header reduces the second unique code field. Therefore, its length is much lower than that of the first frame header, and it is only suitable for the capture of normal frame receivers, that is, working under the signal-to-noise ratio conditions of -2dB to 16dB; then, the two can be combined to generate a normal data frame, and the process is as shown in step (3) below.

[0083] (3) Generate the normal data frame corresponding to the satellite payload data packet according to the second frame header and the second frame body; after generating the normal data frame, time division multiple access can be used, and according to the preset time slot ratio, the normal data frame and the aforementioned ultra-low signal-to-noise ratio data frame are mixed and sent, so as to achieve the mixed transmission mode of normal frames and ultra-low signal-to-noise ratio frames, and the process is as shown in step (4) below.

[0084] (4) Use the time division multiple access method and broadcast the normal data frame and the ultra-low signal-to-noise ratio data frame to the user terminal according to the preset time slot ratio; among them, the flexible configuration and mixed transmission process of the normal data frame and the ultra-low signal-to-noise ratio data frame can be seen in Figure 14 as shown.

[0085] Through the foregoing design, while the present invention satisfies the fast capture and data demodulation of data frames at an ultra-low signal-to-noise ratio operating point, it also supports the mixed transmission mode of normal data frames and ultra-low signal-to-noise ratio data frames. Based on this, the flexible configuration of the system can be satisfied, thereby improving the flexibility of use.

[0086] Optionally, the process of the user terminal capturing an ultra-low signal-to-noise ratio data frame is disclosed as follows: In this embodiment, it has been described above that the physical layer signaling domain is expanded to support the working conditions of the format1 ultra-low signal-to-noise ratio data frame, which are respectively: (1) Normal frame mode. In the normal frame mode, the normal frame receiver uses 5-bit modulation and coding mode (MODCOD) 0-28 for demodulation and decoding corresponding to the normal frame. That is, if the MODCOD obtained by decoding the physical layer signaling domain of the normal frame receiver is any one of 0-28, it is determined that the received data frame is a normal data frame; (2) Ultra-low signal-to-noise ratio mode. Among them, the format1 ultra-low signal-to-noise ratio data frame has only two lengths: 35190 and 18198, corresponding to two settings of the spreading factor equal to 2 and 1 respectively; in the physical layer signaling domain, when the 5-bit modulation and coding mode MODCOD = 29, the frame length of the format1 ultra-low signal-to-noise ratio data frame is equal to 35190 symbols; when MODCOD = 30, its frame length is equal to 18198 symbols. Thus, when the MODCOD decoded by the normal frame receiver is 29 or 30, it is determined that the captured data frame is an ultra-low signal-to-noise ratio data frame. At this time, the processing of the current frame can be skipped; (3) Mixed transmission mode of normal frames and ultra-low signal-to-noise ratio frames. The normal frame receiver uses the physical signaling domain indication to distinguish whether the current frame is a normal data frame or an ultra-low signal-to-noise ratio data frame, while the ultra-low signal-to-noise ratio frame receiver obtains the signaling indication through the walsh sequence in UW2.

[0087] Further, in this embodiment, there is also a working condition of the format2 ultra-low signal-to-noise ratio data frame, which are respectively: (1) Normal frame mode. In the normal frame mode, the 5-bit modulation and coding method in the physical layer signaling field respectively indicates MODCOD 0 to 28. When the MODCOD is consistent with the LDPC code length indication, the received data frame is determined to be a normal data frame; (2) Ultra-low signal-to-noise ratio mode. Among them, the format2 ultra-low signal-to-noise ratio data frame has two lengths: 33282 and 16686, corresponding to two settings with spreading factors equal to 2 and 1 respectively; in the physical layer signaling field, when the 5-bit modulation and coding method MODCOD = 11, the frame length of the format2 ultra-low signal-to-noise ratio data frame is equal to 33282 symbols; when MODCOD = 23, the frame length of the format2 ultra-low signal-to-noise ratio data frame is equal to 16686 symbols; thus, when the LDPC code length indication is a short code and the normal frame reception decoding MODCOD is 11 or 23, the captured data frame is determined to be an ultra-low signal-to-noise ratio data frame. At this time, the processing of the current frame can be skipped; (3) Normal frame and ultra-low signal-to-noise ratio frame mixed transmission mode. The normal frame receiver uses the physical signaling field indication to distinguish whether the current frame is a normal data frame or an ultra-low signal-to-noise ratio data frame, while the ultra-low signal-to-noise ratio frame receiver obtains the signaling indication through the walsh sequence in UW2.

[0088] Specifically, for the normal frame receiver (i.e., operating under the signal-to-noise ratio condition of -2dB to 16dB), a receiving antenna with a larger aperture is adopted, and the signal-to-noise ratio of the received air interface signal is relatively high. By detecting the frame header through the UW1 sequence, all frames are visible, that is, when it receives a data frame, it obtains 5-bit MODCOD through physical layer signaling field decoding. If the corresponding data bit range is within 0 to 28, for the format1 ultra-low signal-to-noise ratio data frame, it can be determined to be a normal frame. For format2, when the MODCOD is consistent with the LDPC code length indication, it can be determined to be a normal frame. At this time, the frame boundary of the next frame can be calculated; if the corresponding 5-bit MODCOD obtained through physical layer signaling field decoding is 29 or 30 in the format1 mode, or inconsistent with the LDPC code length indication in the format2 mode, the frame is determined to be an ultra-low signal-to-noise ratio data frame. At this time, the frame boundary of the next frame can also be calculated, and the processing of the current frame can be skipped; thus, even in the case of mixed transmission of ultra-low signal-to-noise ratio frames, chain search can still be used during normal frame reception. Based on this, the reliability of frame synchronization is enhanced.

[0089] For an ultra-low signal-to-noise ratio (SNR) frame receiver, it generally uses a receiving antenna with a smaller aperture. Usually, the SNR of the received air interface signal is relatively low, even -10 dB. At this time, through the joint detection of UW1 and UW2 sequences (that is, combining UW1 and UW2 and detecting whether a correlation peak appears. If so, it is an ultra-low SNR frame), the ultra-low SNR frame is visible, while other normal frames are not visible. That is, when an ultra-low SNR frame is received, it is impossible to reliably obtain the corresponding MODCOD through physical layer signaling domain decoding. Therefore, it is necessary to obtain the walsh sequence carried on UW2 to obtain the frame format information (specifically, perform autocorrelation detection between UW2 and each Walsh sequence in Figure 7 and use the code rate and spreading factor corresponding to the Walsh sequence with the highest autocorrelation as the frame format information of the received data frame). At this time, the capture and recognition of the ultra-low SNR frame can be completed.

[0090] In addition, when the SNR of the air interface signal received by the ultra-low SNR frame receiver is relatively high, making normal data frames also visible, at this time, through the joint detection of UW1 and UW2 sequences, it is determined whether a correlation peak appears. Among them, if so, it is determined that the current frame is an ultra-low SNR data frame; at the same time, it is also necessary to perform separate detection on UW1 sequence and UW2 sequence. Specifically, if a correlation peak also appears in UW1 sequence and no correlation peak appears when UW2 sequence is detected alone, at this time, it is determined that the current frame is a normal frame, which can be ignored, and continue to search for the ultra-low SNR frame header.

[0091] In this way, through the aforementioned frame capture technology method, user terminals with different capabilities can achieve the capture and recognition of normal data frames and ultra-low SNR data frames, thus meeting the communication requirements of different user terminals.

[0092] Furthermore, in this embodiment, a performance diagram of a normal frame receiver capturing an ultra-low SNR data frame when using an ultra-low SNR data frame is given. Refer to Figure 15 as shown. Among them, the performance of the frame synchronization algorithm is measured by the false detection rate under different SNR conditions. The false detection rate is defined as:

[0093] From Figure 15 it can be seen that when is -2 dB, the false detection rate drops to Magnitude, that is to say, when the terminal receiving normal frames receives ultra-low signal-to-noise ratio (SNR) frames, it can lock the boundary of the ultra-low SNR forward frame with just one frame, and obtain the frame length information according to the decoding result of the physical signaling domain. That is, when MODCOD = 29 in format1 mode, the frame length is equal to 35,190 symbols; when MODCOD = 30, the frame length is equal to 18,198 symbols; when MODCOD = 11 in format2 mode, the frame length is equal to 33,282 symbols; when MODCOD = 23, the frame length is equal to 16,686 symbols. Thus, the terminal receiving normal frames can skip the demodulation process of the current ultra-low SNR frame and enter the search window of the next frame.

[0094] Meanwhile, this embodiment also gives a performance schematic diagram of the ultra-low SNR frame receiver capturing ultra-low SNR data frames. Refer to Figure 16 as shown. When is -11.5 dB, the frame header misdetection rate drops to far less than 10 -4 magnitude. That is to say, when the terminal receiving ultra-low SNR data frames receives ultra-low SNR data frames, it can lock the boundary of the ultra-low SNR data frame with just one frame, and determine the frame format according to the walsh sequence information carried in UW2, so as to perform demodulation and decoding.

[0095] It can be seen that the satellite network data sending method provided by the present invention can, while satisfying the fast capture and data demodulation of data frames at ultra-low SNR operating points, also support the mixed transmission mode of normal frames and ultra-low SNR frames, meeting the flexible configuration of the system. Thus, it not only meets the high-speed communication requirements of users, but also covers the connection network requirements of small antenna size terminals. Therefore, it is very suitable for large-scale application and promotion.

[0096] As Figure 17 shown, the second aspect of this embodiment provides a hardware device for implementing the satellite network data sending method described in the first aspect of the embodiment, including: A frame body encapsulation unit, configured to obtain a satellite payload data packet, and perform encapsulation processing on the satellite payload data packet to obtain a first frame body.

[0097] A frame header construction unit, configured to construct a first frame header corresponding to the satellite payload data packet, where the first frame header includes a first unique code domain, a physical layer signaling domain, and a second unique code domain. The first unique code domain is a pseudo-random sequence with a length of 206 bits or a fixed sequence with a length of 26 bits, the second unique code domain is a pseudo-random sequence with a length of 900 bits, and the physical layer signaling domain includes normal frame signaling and ultra-low SNR frame signaling.

[0098] A data frame generation unit, configured to generate an ultra-low signal-to-noise ratio data frame corresponding to the satellite payload data packet according to the first frame header and the first frame body.

[0099] A sending unit, configured to send the ultra-low signal-to-noise ratio data frame to a user terminal, so that the user terminal decodes the ultra-low signal-to-noise ratio data frame according to the physical layer signaling field in the first frame header, or the first unique code field and the second unique code field in the first frame header, to capture and identify the satellite payload data packet.

[0100] For the working process, working details and technical effects of the device provided in this embodiment, reference can be made to the first aspect of the embodiment, which will not be elaborated herein.

[0101] As Figure 18 shown, in the third aspect of this embodiment, another satellite network data sending device is provided. Taking the device as an electronic device as an example, it includes: a memory, a processor and a transceiver that are communicatively connected in sequence, where the memory is used to store a computer program, the transceiver is used to send and receive messages, and the processor is used to read the computer program and execute the satellite network data sending method as described in the first aspect of the embodiment.

[0102] For the working process, working details and technical effects of the electronic device provided in this embodiment, reference can be made to the first aspect of the embodiment, which will not be elaborated herein.

[0103] In the fourth aspect of this embodiment, a storage medium storing instructions including the satellite network data sending method described in the first aspect of the embodiment is provided, that is, instructions are stored on the storage medium, and when the instructions run on a computer, the satellite network data sending method as described in the first aspect of the embodiment is executed.

[0104] For the working process, working details and technical effects of the storage medium provided in this embodiment, reference can be made to the first aspect of the embodiment, which will not be elaborated herein.

[0105] In the fifth aspect of this embodiment, a computer program product including instructions is provided, and when the instructions run on a computer, the computer is made to execute the satellite network data sending method as described in the first aspect of the embodiment, where the computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices.

[0106] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A satellite network data transmission method, characterized in that: include: Acquire a satellite payload data packet, and encapsulate the satellite payload data packet to obtain a first frame body; Constructing a first frame header corresponding to the satellite payload data packet, wherein the first frame header includes a first unique code field, a physical layer signaling field, and a second unique code field, the first unique code field is a pseudo-random sequence with a length of 206 bits or a fixed sequence with a length of 26 bits, the second unique code field is a pseudo-random sequence with a length of 900 bits, and the physical layer signaling field includes normal frame signaling and ultra-low signal-to-noise ratio frame signaling; Generate an ultra-low signal-to-noise ratio data frame corresponding to the satellite payload data packet according to the first frame header and the first frame body; The ultra-low signal-to-noise ratio data frame is sent to a user terminal, so that the user terminal decodes the ultra-low signal-to-noise ratio data frame according to a physical layer signaling field in the first frame header, or a first unique code field and a second unique code field in the first frame header, so as to capture and identify the satellite payload data packet.

2. The method according to claim 1, characterized in that Constructing a first frame header corresponding to the satellite payload data packet, including: Randomly generate a number of base sequences, wherein the length of the base sequence is 16 bits or 8 bits; Using a number of base sequences, 10 first sequences are constructed, wherein the length of the first sequence is 112 bits; Extracting first two first sequences from the 10 first sequences, and using the extracted first two first sequences to generate a second sequence with a length of 224 bits; Removing the last 18 bits of data in the second sequence to obtain an initial first unique code field; Using the remaining 8 first sequences of the 10 first sequences, generating a third sequence with a length of 896 bits, and dividing the third sequence into 8 equal parts to obtain 8 PN sequences; Obtaining a Walsh sequence, wherein the length of the Walsh sequence is 8 chips, the 8 PN sequences respectively correspond to one data bit in the Walsh sequence, and the Walsh sequence is used to characterize the coding rate and spread multiple of the satellite payload data packet; Performing an XOR operation on the eight PN sequences and corresponding data bits in the Walsh sequence to obtain eight processed PN sequences after the XOR operation; Generate a fourth sequence using the eight processed PN sequences, and add two target characters to the head and tail of the fourth sequence respectively, so as to obtain an initial second unique code field after adding the target characters, wherein the target character is 0; The initial first unique code field and the initial second unique code field are subjected to pseudo-random check processing, and after the pseudo-random check passes, the second unique code field and the first unique code field of a pseudo-random sequence with a length of 206 bits are obtained.

3. The method according to claim 2, characterized in that Performing pseudo-random check processing on the initial first unique code field and the initial second unique code field includes: Counting the difference between the number of bit 0 and bit 1 in the target sequence to obtain a number difference value, wherein the target sequence is a combination sequence of the initial first unique code field and the initial second unique code field; Determine whether the number difference is less than a first threshold; If yes, performing modulation check processing on the initial first unique code field and the initial second unique code field, and determining whether the modulation check passes; If yes, then performing an autocorrelation check process on the initial first unique code field and the initial second unique code field, and determining whether the autocorrelation check process passes; If so, a single frame capture check is performed on the initial first unique code field and the initial second unique code field, and after the single frame capture check passes, the initial first unique code field is used as the first unique code field, and the initial second unique code field is used as the second unique code field.

4. The method according to claim 3, characterized in that Performing modulation check processing on the initial first unique code field and the initial second unique code field, and determining whether the modulation check passes, comprises: Using pi / 2 BPSK modulation, the initial first unique code field and the initial second unique code field are modulated to obtain a modulated initial first unique code field and a modulated initial second unique code field; Counting the occurrence frequencies of each pi / 2 BPSK symbol in the modulated initial first unique code field, and selecting the maximum occurrence frequency as the first maximum symbol frequency; Determining whether the first maximum symbol number is less than a second threshold; If yes, then count the occurrence frequencies of each pi / 2 BPSK symbol in the modulated initial second unique code field, and select the maximum occurrence frequency as the second maximum symbol number; otherwise, re-randomly generate a number of base sequences; Determining whether the second maximum symbol number is less than a third threshold; If so, it is determined that the modulation check of the initial first unique code domain and the initial second unique code domain passes; otherwise, a plurality of base sequences are randomly generated again.

5. The method according to claim 3, characterized in that: Performing an autocorrelation check process on the initial first unique code field and the initial second unique code field, and determining whether the autocorrelation check process passes, comprises: Performing autocorrelation processing on the initial first unique code field and the initial second unique code field to obtain an autocorrelation function; Based on the autocorrelation function, calculating a maximum normalized sidelobe of the autocorrelation function; Determining whether the maximum normalized sidelobe is less than a fourth threshold; If so, it is determined that the initial first unique code field and the initial second unique code field have passed the autocorrelation check; otherwise, a number of base sequences are randomly generated again.

6. The method according to claim 3, characterized in that: When the first unique code field is the pseudo-random sequence with a length of 206 bits, the first unique code field is: 3D42ABA709B03263C78947897D4287897D42B739F263C9B009B0, and the second unique code field is: 26C01E25DCE726C04758DCE7AE9C 4758AE9CF50AF50ADCE7AE9CC98F 26C0DCE74758F50AAE9C1E254758 1E25C98FDCE747581E25F50A4758 C98FAE9CF50ADCE726C01E254758 AE9C1E25AE9CC98FAE9CF50AC98F C98F47584758C98FDCE7475826C0 F50A26C01E25DCE7AE9CC98FDCE7; or The first unique code field is: 209D6AC85E97C6A21963E1D4E09D6AC8609D5963E09D46A2327F, and the second unique code field is: 7A5F1A8882751A88658F7A5F7A5F 7A5F1A881A88AB21AB211A888753 8753AB21658FC9FC8275C9FC658F 8753658F1A88C9FCC9FC8753C9FC 8275658F7A5F87538753C9FC8753 AB21AB21AB217A5F82757A5F1A88 C9FC658FC9FCC9FC8275AB211A88 AB218753658F658F82757A5F8753.

7. The method according to claim 1, characterized in that The satellite payload data packet is encapsulated to obtain a first frame body, including: Performing constellation modulation processing on the satellite payload data packet to obtain a data symbol set; In the data symbol set, a pilot block is inserted every 720 data symbols, so as to obtain an initial frame body after all data symbols are polled; A pilot block is added to the end of the initial frame body to obtain the first frame body after the addition, wherein when the first unique code field in the first frame header adopts sequences of different lengths, the lengths of the first frame body are different.

8. The method according to claim 1, characterized in that The length of the physical layer signaling domain is 64 bits, and the physical layer signaling domain includes physical layer signaling 0 to 31, wherein, when the first unique code domain is a pseudo-random sequence with a length of 206 bits, physical layer signaling 0 to 28 is normal frame signaling, physical layer signaling 29 and physical layer signaling 30 are ultra-low signal-to-noise ratio frame signaling, when the first unique code domain is a fixed sequence with a length of 26 bits, physical layer signaling 11 and physical layer signaling 23 are ultra-low signal-to-noise ratio frame signaling, and the remaining physical layer signalings are normal frame signaling.

9. The method according to claim 1, characterized in that: The method further comprises: encapsulating the satellite payload data packet to obtain a second frame body; Constructing a second frame header corresponding to the satellite payload data packet, wherein the second frame header includes the first unique code field and the physical layer signaling field; generating a normal data frame corresponding to the satellite payload data packet according to the second frame header and the second frame body; The normal data frame and the ultra-low signal-to-noise ratio data frame are broadcast to the user terminal using a time division multiple access method and according to a preset time slot ratio.

10. A satellite network data transmission device, characterized in that: include: A frame body encapsulation unit, used for acquiring a satellite payload data packet and encapsulating the satellite payload data packet to obtain a first frame body; A frame header construction unit, used to construct a first frame header corresponding to the satellite payload data packet, wherein the first frame header includes a first unique code field, a physical layer signaling field, and a second unique code field, the first unique code field is a pseudo-random sequence with a length of 206 bits or a fixed sequence with a length of 26 bits, the second unique code field is a pseudo-random sequence with a length of 900 bits, and the physical layer signaling field includes normal frame signaling and ultra-low signal-to-noise ratio frame signaling; A data frame generating unit, configured to generate an ultra-low signal-to-noise ratio data frame corresponding to the satellite payload data packet according to the first frame header and the first frame body; The sending unit is used to send the ultra-low signal-to-noise ratio data frame to a user terminal, so that the user terminal decodes the ultra-low signal-to-noise ratio data frame according to the physical layer signaling field in the first frame header, or the first unique code field and the second unique code field in the first frame header, so as to capture and identify the satellite payload data packet.

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