A method and device for sending satellite network data

Abstract

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-size antenna terminals, the present invention discloses a satellite network data sending method and device. The present invention 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 a physical layer signaling with sufficient length. In this way, by increasing the length of the frame header, the signal-to-noise ratio of the entire data frame is improved, so that it can also be detected and recognized by small-size antenna terminals under the condition of a lower 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 for 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 m to 1.4 m, 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 -2 dB to 16 dB. For example, when it was 16 dB ( 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), 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 terminal application scenarios for small-sized antennas. Among them, the 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 -10 dB. However, the normal satellite frame format receiver could not complete frame capture and data demodulation under the ultra-low signal-to-noise ratio condition. Therefore, it could not meet the communication requirements of small-sized antenna terminals. Thus, due to the aforementioned deficiencies, how to provide a satellite network data sending method that can perform satellite network data frame capture and data demodulation in the 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 that in the ultra-low signal-to-noise ratio mode in the prior art, frame capture and data demodulation cannot be completed, 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:

[0007] In the first aspect, a satellite network data sending method is provided, including:

[0008] Obtain a satellite payload data packet, and perform encapsulation processing on the satellite payload data packet to obtain a first frame body;

[0009] 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, 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;

[0010] 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;

[0011] 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.

[0012] 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 physical layer signaling field has a length of 64 bits, the first unique code field has a length of 206 or 26 bits, and the second unique code field has a length of 900 bits. Thus, the length of the first frame header exceeds 1000 bits, that is, the present invention is equivalent to increasing the length of the frame header to improve the signal-to-noise ratio of the entire data frame (i.e., the detection ability under low signal-to-noise ratio), 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.

[0013] In a possible design, constructing the first frame header corresponding to the satellite payload data packet includes:

[0014] Randomly generate a number of base sequences, where the length of the base sequence is 16 bits or 8 bits;

[0015] Use a number of base sequences to construct 10 first sequences, where the length of the first sequence is 112 bits;

[0016] Extract the first 2 out of 10 first sequences, and generate a second sequence with a length of 224 bits by using the extracted first 2 first sequences;

[0017] Remove the last 18 bits of data from the second sequence to obtain an initial first unique code domain;

[0018] Generate a third sequence with a length of 896 bits by using the remaining 8 first sequences out of 10 first sequences, and equally divide the third sequence into 8 parts to obtain 8 PN sequences;

[0019] Obtain a Walsh sequence, where 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 represent the coding rate and spreading factor of the satellite payload data packet;

[0020] 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;

[0021] Generate a fourth sequence by using the 8 processed PN sequences, and respectively add 2 target characters at 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;

[0022] Perform a pseudo-random check process 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 a pseudo-random sequence with a length of 206 bits after the pseudo-random check passes.

[0023] In a possible design, performing a pseudo-random check process on the initial first unique code domain and the initial second unique code domain includes:

[0024] Statistically calculate the difference between the number of bit 0 and bit 1 in the target sequence to obtain a difference value, where the target sequence is a combined sequence of the initial first unique code domain and the initial second unique code domain;

[0025] Judge whether the difference value is less than a first threshold;

[0026] If so, perform a modulation check process on the initial first unique code domain and the initial second unique code domain, and judge whether the modulation check passes;

[0027] If so, perform an autocorrelation check process on the initial first unique code domain and the initial second unique code domain, and judge whether the autocorrelation check process passes;

[0028] 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.

[0029] In a possible design, 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, including:

[0030] Use 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;

[0031] 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;

[0032] Determine whether the first maximum symbol count is less than a second threshold;

[0033] 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;

[0034] Determine whether the second maximum symbol count is less than a third threshold;

[0035] 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.

[0036] 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:

[0037] Perform autocorrelation processing on the initial first unique code domain and the initial second unique code domain to obtain an autocorrelation function;

[0038] Based on the autocorrelation function, calculate the maximum normalized sidelobe of the autocorrelation function;

[0039] Determine whether the maximum normalized sidelobe is less than a fourth threshold;

[0040] 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.

[0041] In a possible design, when the first unique code field is the pseudo-random sequence with a length of 206 bits, the first unique code field is:

[0042] 3D42ABA709B03263C78947897D4287897D42B739F263C9B009B0, and the 896 bits in the second unique code field are:

[0043] 26C01E25DCE726C04758DCE7AE9C

[0044] 4758AE9CF50AF50ADCE7AE9CC98F

[0045] 26C0DCE74758F50AAE9C1E254758

[0046] 1E25C98FDCE747581E25F50A4758

[0047] C98FAE9CF50ADCE726C01E254758

[0048] AE9C1E25AE9CC98FAE9CF50AC98F

[0049] C98F47584758C98FDCE7475826C0

[0050] F50A26C01E25DCE7AE9CC98FDCE7; or

[0051] The first unique code field is: 209D6AC85E97C6A21963E1D4E09D6AC8609D5963E09D46A2327F, and the 896 bits in the second unique code field are:

[0052] 7A5F1A8882751A88658F7A5F7A5F

[0053] 7A5F1A881A88AB21AB211A888753

[0054] 8753AB21658FC9FC8275C9FC658F

[0055] 8753658F1A88C9FCC9FC8753C9FC

[0056] 8275658F7A5F87538753C9FC8753

[0057] AB21AB21AB217A5F82757A5F1A88

[0058] C9FC658FC9FCC9FC8275AB211A88

[0059] AB218753658F658F82757A5F8753。

[0060] In a possible design, the satellite payload data packet is encapsulated to obtain a first frame body, including:

[0061] The satellite payload data packet is subjected to constellation diagram modulation processing to obtain a data symbol set;

[0062] 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;

[0063] A pilot block is added to the tail of the initial frame body to obtain the first frame body after 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.

[0064] In a possible design, the length of the physical layer signaling field is 64 bits, and the physical layer signaling field includes physical layer signals 0 to 31. Among them, when the first unique code field is a pseudo-random sequence with a length of 206 bits, physical layer signals 0 to 28 are normal frame signals, physical layer signals 29 and 30 are ultra-low signal-to-noise ratio frame signals, and when the first unique code field is a fixed sequence with a length of 26 bits, physical layer signals 11 and 23 are ultra-low signal-to-noise ratio frame signals, and the remaining physical layer signals are normal frame signals.

[0065] In a possible design, the method further includes:

[0066] The satellite payload data packet is encapsulated to obtain a second frame body;

[0067] A second frame header corresponding to the satellite payload data packet is constructed, wherein the second frame header includes the first unique code field and the physical layer signaling field;

[0068] According to the second frame header and the second frame body, a normal data frame corresponding to the satellite payload data packet is generated;

[0069] Using the time division multiple access method and according to a preset time slot ratio, the normal data frame and the ultra-low signal-to-noise ratio data frame are broadcast to the user terminal.

[0070] Beneficial effects:

[0071] (1)The present invention provides a method for sending satellite network data. By constructing a forward ultra-low signal-to-noise ratio data frame, the communication requirements of small-size antenna terminals are met. 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, by increasing the length of the frame header, the signal-to-noise ratio of the entire data frame is improved, enabling it to be detected and recognized by small-size antenna terminals even under low signal-to-noise ratio conditions; based on this, the communication requirements of small-size antenna terminals can be satisfied.

[0072] (2)The physical layer signaling domain provided by the present invention includes normal frame signaling and ultra-low signal-to-noise ratio frame signaling, which can indicate normal frames and ultra-low signal-to-noise ratio frames. Therefore, in the normal satellite frame mode, the satellite far end can also identify the ultra-low signal-to-noise ratio data frame based on the physical layer signaling domain, and thus skip receiving this frame; thereby, the ultra-low signal-to-noise ratio data frame can also be recognized by a normal signal-to-noise ratio receiver. In this way, the adaptability of use is improved.

[0073] (3)The present invention also supports a mixed transmission mode of normal frames and ultra-low signal-to-noise ratio frames, that is, a second frame body is generated using the satellite payload data packet, and a corresponding second frame header is constructed. Among them, the second frame header only contains the physical layer signaling domain and the first unique code domain, 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 a 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 satisfies the fast capture and data demodulation of data frames at ultra-low signal-to-noise ratio operating 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] Figure 1 is a schematic flow chart of the steps of the satellite network data sending method provided by the embodiment of the present invention;

[0075] Figure 2 is a schematic structural diagram of the format1 ultra-low signal-to-noise ratio data frame provided by the embodiment of the present invention;

[0076] Figure 3 is a schematic structural diagram of the format2 ultra-low signal-to-noise ratio data frame provided by the embodiment of the present invention;

[0077] Figure 4 is a schematic structural diagram of the first unique code domain provided by the embodiment of the present invention;

[0078] Figure 5The coding and modulation scheme mapping table for the physical layer signaling domain provided by the embodiments of the present invention;

[0079] Figure 6 The structural schematic diagram of the second unique code domain provided by the embodiments of the present invention;

[0080] Figure 7 The corresponding relationship between the Walsh sequence, code rate, and spreading factor provided by the embodiments of the present invention;

[0081] 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 the embodiments of the present invention;

[0082] 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 the embodiments of the present invention;

[0083] 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 the embodiments of the present invention;

[0084] 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 the embodiments of the present invention;

[0085] Figure 12 The self-correlation characteristic schematic diagram 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 the embodiments of the present invention;

[0086] Figure 13 The structural schematic diagram of the normal data frame provided by the embodiments of the present invention;

[0087] Figure 14 The schematic diagram of the mixed transmission of the normal data frame and the ultra-low signal-to-noise ratio data frame over the air interface provided by the embodiments of the present invention;

[0088] Figure 15 The performance schematic diagram of the normal frame receiver capturing the ultra-low signal-to-noise ratio data frame provided by the embodiments of the present invention;

[0089] Figure 16 The performance schematic diagram of the ultra-low signal-to-noise ratio frame receiver capturing the ultra-low signal-to-noise ratio data frame provided by the embodiments of the present invention;

[0090] Figure 17 The structural schematic diagram of the satellite network data sending device provided by the embodiments of the present invention;

[0091] Figure 18Schematic diagram of the structure of the electronic device provided by the embodiment of the present invention. Detailed implementation manners

[0092] Embodiment:

[0093] See Figure 1 As shown, the satellite network data sending method provided in this embodiment meets the communication requirements of small-sized 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 physical layer signaling with 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-sized antenna terminals under the condition of low signal-to-noise ratio; based on this, the communication requirements of small-sized 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 entity 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 those shown in the following steps S1 to S4.

[0094] S1. Obtain the satellite payload data packet, and perform encapsulation processing on the satellite payload data packet to obtain the first frame body; in specific implementation, the first frame body has different structures according to different first frame headers, which will be described 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 carried out, and the process is as shown in the following step S2.

[0095] S2. 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, and the second unique code field is a pseudo-random sequence with a length of 900 bits. The physical layer signaling field includes normal frame signaling and 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 the pi / 2 BPSK constellation diagram; for example, a bit sequence with a length of 206 becomes a symbol with a length of 206.

[0096] In this embodiment, when different-length sequences are used in the first unique code field in 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 construction method of a frame body), that is, insert a pilot block with a length of 36 symbols every 720 data symbols (i.e.,

[0097] 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.

[0098] 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 Figure (a) and (b) shown in Figure 3 Figure (a) and (b) shown in Figure 3 Figure (a) in [[ID=2']] Figure 3 Figure (b) represents another structure in the ultra-low signal-to-noise ratio frame of format2. The difference between the two lies in the frame body structure), that is, it is composed of 42 data symbol blocks + 42 pilot blocks, or composed of 20 data symbol blocks + 20 pilot blocks. That is, due to the different lengths of the first frame header, the lengths of the adjusted data symbol sets are different; at the same time, different modulation methods can also obtain different data symbol sets. Therefore, the first frame body has different structures, but the overall construction method is the same, that is, insert a pilot block every several data symbol blocks.

[0099] Among them, constellation diagram modulation is a common technology for satellite payload data packet processing, and its principle will not be elaborated here one by one.

[0100] Furthermore, the structure of the first frame header is described below as follows:

[0101] In this embodiment, referring 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, while 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.

[0102] Referring 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.

[0103] Referring 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, while the physical layer signaling domain (i.e., Figure 3The PLSC in it) occupies 64 bits; the physical layer signaling field contains 5-bit physical layer signaling 0 to 31. For format2, physical layer signaling 11 and physical layer signaling 23 are used to indicate ultra-low signal-to-noise ratio frames, and other physical layer signaling is normal frame signaling.

[0104] See Figure 4 As shown, in the format1 ultra-low signal-to-noise ratio data frame, UW1 is obtained by truncating the 18-bit tail of two PN sequences with a length of 112 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 obtained 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 exclusive-OR operated 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 process of UW1 and UW2 will be elaborated in detail below.

[0105] 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 of 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.

[0106] Furthermore, Figure 8 is an example of selecting UW1 and UW2 by this method. Among them, Figure 8 Figure (a) in it corresponds to an example of UW1, Figure 8 Figure (b) in it corresponds to an example of UW2; in actual application, 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 this completely correlated long sequence 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.

[0107] 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.

[0108] After obtaining a number of base sequences, sequence combination can be performed, and the process is as shown in the following step S22.

[0109] 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 the following steps S23 to S28.

[0110] 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 combining 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 the following step S24.

[0111] S24. Remove the last 18-bit data from the second sequence to obtain the initial first unique code domain.

[0112] After obtaining the initial first unique code domain, the remaining 8 first sequences can be used to combine to obtain a third sequence of 896 bits, 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.

[0113] S25. Use the remaining 8 first sequences among the 10 first sequences to generate a third sequence with a length of 896 bits, and divide the third sequence into 8 equal parts to obtain 8 PN sequences.

[0114] 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.

[0115] S26. Obtain the Walsh sequence. The length of the Walsh sequence is 8 chips. 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 characterize the coding 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 rate and spreading factor. Among them, different Walsh sequences correspond to different coding rates and spreading factors, and the corresponding relationship can be seen in Figure 7 as shown. Thus, by performing an 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.

[0116] After obtaining the Walsh sequence, an exclusive OR operation can be performed with the 8 PN sequences, and the process is as shown in the following step S27.

[0117] S27. Perform an exclusive OR operation on the 8 PN sequences and the corresponding data bits in the Walsh sequence to obtain 8 processed PN sequences after the exclusive OR operation; among them, the corresponding relationship between the 8 PN sequences and each data bit in the Walsh sequence can be seen in Figure 6 as shown, and the Walsh sequence can be any Walsh sequence.

[0118] After completing the exclusive OR operation of the 8 PN sequences and the Walsh sequence, an initial second unique code domain can be generated based on this, and the process is as shown in the following step S28.

[0119] S28. Use the 8 processed PN sequences to generate a fourth sequence, and respectively add 2 target characters at the head and tail of the fourth sequence to obtain an initial second unique code domain after adding the target characters, where the target character is 0; after adding 2 0s at the head and tail of the fourth sequence, an initial second unique code domain can be obtained.

[0120] After obtaining the initial first unique code domain and the initial second unique code domain, they 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 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.

[0121] S29. Perform a pseudo-random check process on the initial first unique code domain and the initial second unique code domain. After the pseudo-random check passes, obtain the second unique code domain and the first unique code domain of a pseudo-random sequence with a length of 206 bits. In specific implementation, the six check conditions that need to be satisfied for the pseudo-random check are respectively the check of the difference in the number of bit 0 and bit 1 in the sequence after combining the two initial sequences, the check of the maximum symbol times after their modulation (this needs to be checked separately, so it is equivalent to two conditions), the check of the maximum normalized sidelobe of the autocorrelation function of their combined sequence, 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 their combined sequence under ultra-low signal-to-noise ratio conditions. Thus, only after passing the aforementioned 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.

[0122] Optionally, the specific check process can be but is not limited to the steps shown in the following S29a to S29e.

[0123] S29a. Statistically calculate the difference in the number of bit 0 and bit 1 in the target sequence to obtain the number difference. Here, 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. 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 check of the number difference can be performed, and the process is as shown in the following step S29b.

[0124] 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. If it is less than, then the check of the difference in the number of bit 0 and bit 1 passes, and then the following step S29c is executed. Otherwise, it is necessary to re-execute the aforementioned step S21, that is, randomly generate several base sequences again, and then re-execute the aforementioned steps S22 to S28 to generate a new initial first unique code domain and a new initial second unique code domain.

[0125] S29c. If so, perform a modulation check process on the initial first unique code domain and the initial second unique code domain, and determine whether the modulation check passes. In this embodiment, the modulation check process is as follows:

[0126] First, adopt the π / 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. Then, 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. Next, 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 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. Finally, determine whether the second maximum symbol count is less than the third threshold (for example, its value is 900 / 4 + 10). 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.

[0127] In this way, the modulation verification 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. If both of the above conditions are met, proceed to the next step (i.e., execute the following step S29d). If either of the above conditions is not met, it is necessary to re-execute the previous step S21. The step S29d is as follows.

[0128] S29d. If so, 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. In specific implementation, first perform autocorrelation processing on the initial first unique code domain and the initial second unique code domain to obtain the 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 the fourth threshold. If so, it is determined 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.

[0129] In specific implementation, the sequence composed of the initial first unique code domain and the initial second unique code domain can be recorded as: , and its corresponding π / 2 BPSK modulation symbol is Z. Therefore, the autocorrelation function of the two is defined as:

[0130] (1)

[0131] In formula (1), represents the autocorrelation function, represents the i-th symbol after sequence 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.

[0132] Thus, the calculation formula for the maximum normalized sidelobe of the autocorrelation function is:

[0133] (2)

[0134] 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.

[0135] Thus, it is necessary to determine whether the maximum normalized sidelobe of the autocorrelation function is less than 0.15; among them, if it is less, it passes the modulation check, and then the following step S29e is executed; otherwise, the previous step S21 needs to be executed again; among them, the execution process of step S29e is as follows.

[0136] S29e. If so, perform 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.

[0137] In specific applications, the single-frame capture check processing process can be but is not limited to the following first step to seventh step.

[0138] The first step: Under the preset signal-to-noise ratio condition, calculate the correlation peak gain of the initial first unique code domain, where 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. Among them, for example, it can be but is not limited to using 10×log10(h) 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 its calculation process is as shown in the following second step.

[0139] Step 2: Calculate the first correlation peak signal-to-noise ratio of the initial first unique code domain according to the said 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 the single-frame capture verification under the subsequent ultra-low signal-to-noise ratio condition according to the judgment result. The judgment process is as shown in the following step 3.

[0140] Step 3: 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 of the normal frame is passed. Otherwise, the previous step S21 needs to be executed again.

[0141] 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.

[0142] Among them, after passing 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 step 4 to step 7.

[0143] Step 4: 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.

[0144] 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 step 5.

[0145] Step 5: Calculate the second correlation peak signal-to-noise ratio of the combined sequence under the preset ultra-low signal-to-noise ratio condition. 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 -10dB.

[0146] Thus, the relevant peak gain of the combined sequence can be calculated according to the foregoing 10×log10(h) formula, and then adding (-10dB) to obtain the second relevant peak signal-to-noise ratio, which is 20dB. Thus, it is possible to continue to determine whether the second relevant 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 determination result, determine 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.

[0147] Step 6: Determine whether the second relevant peak signal-to-noise ratio meets the single-frame capture condition; in specific implementation, the single-frame capture condition for this step is a preset second relevant peak signal-to-noise ratio threshold. Among them, if it is greater than the second relevant peak signal-to-noise ratio threshold, it can be determined that the single-frame capture verification of the initial first unique code domain and the initial second unique code domain passes. At this time, the initial first unique code domain can be used as the foregoing first unique code domain, and the initial second unique code domain can be used as the foregoing second unique code domain; otherwise, it is necessary to re-execute the foregoing step S21; the foregoing process can be seen as shown in the following seventh step.

[0148] Step 7: If so, determine that the single-frame capture verification of the initial first unique code domain and the initial second unique code domain passes; otherwise, randomly generate several base sequences again.

[0149] In this embodiment, frame header detection is obtained through simulation, as shown in Figure 16 That is, perform frame header sliding correlation detection on the alternative uw1 and uw2, so as to determine 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.

[0150] 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, and then, in combination with the foregoing physical layer signaling domain, the first frame header can be combined.

[0151] Among them, the following gives an example of the first unique code domain and the second unique code domain corresponding to format1 (that is, when the first unique code domain is a 206-bit pseudo-random sequence), and the 206-bit pseudo-random sequence is: 3D42ABA709B03263C78947897D4287897D42B739F263C9B009B0.

[0152] And the 896 bits in the second unique code domain are:

[0153] 26C01E25DCE726C04758DCE7AE9C

[0154] 4758AE9CF50AF50ADCE7AE9CC98F

[0155] 26C0DCE74758F50AAE9C1E254758

[0156] 1E25C98FDCE747581E25F50A4758

[0157] C98FAE9CF50ADCE726C01E254758

[0158] AE9C1E25AE9CC98FAE9CF50AC98F

[0159] C98F47584758C98FDCE7475826C0

[0160] F50A26C01E25DCE7AE9CC98FDCE7。

[0161] Furthermore, this embodiment gives another example of the format1 corresponding to the first unique code domain and the second unique code domain, that is:

[0162] The first unique code domain is: 209D6AC85E97C6A21963E1D4E09D6AC8609D5963E09D46A2327F, and the 896 bits in the second unique code domain are:

[0163] 7A5F1A8882751A88658F7A5F7A5F

[0164] 7A5F1A881A88AB21AB211A888753

[0165] 8753AB21658FC9FC8275C9FC658F

[0166] 8753658F1A88C9FCC9FC8753C9FC

[0167] 8275658F7A5F87538753C9FC8753

[0168] AB21AB21AB217A5F82757A5F1A88

[0169] C9FC658FC9FCC9FC8275AB211A88

[0170] AB218753658F658F82757A5F8753。

[0171] 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.

[0172] Further, this embodiment gives examples of the foregoing first unique code domain and second unique code domain; refer to 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 figure (a) of , it is the sequence corresponding to one of the UW1s (i.e., the first unique code domain), Figure 9 In figure (b) of , it is the sequence corresponding to UW2 (i.e., the second unique code domain); similarly, Figure 10 In figure (a) of , it is the sequence corresponding to UW1 in another pseudo-random sequence, Figure 10 In figure (b) of , it is the sequence corresponding to its UW2; at the same time, this embodiment gives a schematic diagram of the autocorrelation characteristics of the foregoing combined sequence, which can be referred to Figure 12 as shown, from Figure 12 it can be seen that its maximum normalized sidelobe is less than 0.15, meeting the autocorrelation characteristics.

[0173] 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 referred to Figure 11 as shown.

[0174] 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.

[0175] 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, add the first frame header to the head of the first frame body, and 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.

[0176] 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.

[0177] 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:

[0178] (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 every 8 time slots in the data symbol set. 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. The schematic structural diagram can be seen in Figure 13 as shown.

[0179] Then, the corresponding second frame header can be constructed, and the process is as follows.

[0180] (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.

[0181] (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 adopted, 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.

[0182] (4) 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 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.

[0183] Through the above 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.

[0184] Optionally, the process of the user terminal capturing an ultra-low signal-to-noise ratio data frame is disclosed as follows:

[0185] In this embodiment, it has been previously described that the physical layer signaling domain is expanded to support the working conditions of format1 ultra-low signal-to-noise ratio data frames, 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 the normal frame receiver decoding the physical layer signaling domain 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, format1 ultra-low signal-to-noise ratio data frames have only two lengths: 35190 and 18198, corresponding to two settings with spreading factors 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 normal frame receiver decodes MODCOD as 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.

[0186] Furthermore, 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 coding method in the physical layer signaling domain respectively indicates MODCOD 0 to 28. When the MODCOD is consistent with the LDPC code length indication, it is determined that the received data frame is 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 domain, when the 5-bit modulation 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, 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.

[0187] Specifically, for a normal frame receiver (i.e., operating under signal-to-noise ratio conditions of -2dB to 16dB), a receiving antenna with a larger aperture is adopted. 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 domain 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 as a normal frame. For format2, when the MODCOD is consistent with the LDPC code length indication, it can be determined as 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 domain decoding is 29 or 30 in the format1 mode, or inconsistent with the LDPC code length indication in the format2 mode, it is determined that the frame is 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.

[0188] 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 as low as -10 dB. At this time, through the joint detection of UW1 and UW2 sequences (that is, merging 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 Figure 7 each Walsh sequence in

[0189] 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.

[0190] 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 detections on UW1 sequence and UW2 sequence. Specifically, if a correlation peak also appears in UW1 sequence but 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 the search for the ultra-low SNR frame header continues.

[0191] 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. See Figure 15 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:

[0192]

[0193] From Figure 15 it can be seen that when is -2 dB, the false detection rate drops to Magnitude, that is, when the terminal receiving the normal frame receives an ultra-low signal-to-noise ratio frame, it locks the boundary of the ultra-low signal-to-noise ratio forward frame with just one frame, and obtains 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 the normal frame can skip the demodulation process of the current ultra-low signal-to-noise ratio frame and enter the search window of the next frame.

[0194] Meanwhile, this embodiment also gives a performance schematic diagram of the ultra-low signal-to-noise ratio frame receiver capturing the ultra-low signal-to-noise ratio data frame. See Figure 16 as shown. When is -11.5 dB, the frame header misdetection rate drops to far less than 10 -4 Magnitude. That is, when the terminal receiving the ultra-low signal-to-noise ratio data frame receives the ultra-low signal-to-noise ratio data frame, it locks the boundary of the ultra-low signal-to-noise ratio data frame with just one frame, and determines the frame format according to the walsh sequence information carried in UW2, so as to perform demodulation and decoding.

[0195] 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 signal-to-noise ratio working points, also support the mixed sending mode of normal frames and ultra-low signal-to-noise ratio frames, meeting the flexible configuration of the system. Thus, it not only meets the high-speed communication requirements of users, but also covers the requirements of connecting networks of small antenna size terminals. Therefore, it is very suitable for large-scale application and promotion.

[0196] 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:

[0197] A frame body encapsulation unit, configured to obtain the satellite payload data packet and perform encapsulation processing on the satellite payload data packet to obtain a first frame body.

[0198] 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 a normal frame signaling and an ultra-low signal-to-noise ratio frame signaling.

[0199] 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.

[0200] 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.

[0201] For the working process, working details and technical effects of the device provided in this embodiment, reference may be made to the first aspect of the embodiment, which will not be elaborated herein.

[0202] 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. Among them, 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.

[0203] For the working process, working details and technical effects of the electronic device provided in this embodiment, reference may be made to the first aspect of the embodiment, which will not be elaborated herein.

[0204] 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. When the instructions run on a computer, the satellite network data sending method described in the first aspect of the embodiment is executed.

[0205] For the working process, working details and technical effects of the storage medium provided in this embodiment, reference may be made to the first aspect of the embodiment, which will not be elaborated herein.

[0206] In the fifth aspect of this embodiment, a computer program product including instructions is provided. When the instructions run on a computer, the computer is made to execute the satellite network data sending method 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.

[0207] 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 method for sending satellite network data, characterized in that, Including: Obtain a satellite payload data packet, and perform encapsulation processing on the satellite payload data packet to obtain a first frame body; 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, 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 a very low signal-to-noise ratio frame signaling; Generate a very 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 very low signal-to-noise ratio data frame to a user terminal, so that the user terminal decodes the very 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; Among them, 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 an initial first unique code field; Use the remaining 8 first sequences among the 10 first sequences to generate a third sequence with a length of 896 bits, and divide the third sequence into 8 equal parts to obtain 8 PN sequences; Obtain a Walsh sequence, where the length of the Walsh sequence is 8 chips, and the 8 PN sequences respectively correspond to one data bit in the Walsh sequence, and the Walsh sequence is used to represent the coding 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 to obtain 8 processed PN sequences after the exclusive OR operation; Use the 8 processed PN sequences to generate a fourth sequence, and add 2 target characters to the head and tail of the fourth sequence respectively to obtain an initial second unique code field after adding the target characters, where the target character is 0; Perform pseudo-random verification processing on the initial first unique code field and the initial second unique code field, and obtain the second unique code field and the first unique code field of the pseudo-random sequence with a length of 206 bits after the pseudo-random verification passes; Performing pseudo-random verification processing on the initial first unique code field and the initial second unique code field 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 field and the initial second unique code field; Judge whether the number difference is less than a first threshold; If so, perform modulation verification processing on the initial first unique code field and the initial second unique code field, and judge whether the modulation verification passes; If so, 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; If so, perform single-frame capture verification processing on the initial first unique code domain and the initial second unique code domain. 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; Among them, the single-frame capture verification processing includes: Under the preset signal-to-noise ratio condition, calculate the correlation peak gain of the initial first unique code domain, where the preset signal-to-noise ratio condition includes -2 dB; According to the correlation peak gain, calculate the first correlation peak signal-to-noise ratio of the initial first unique code domain; Determine whether the first correlation peak signal-to-noise ratio meets the single-frame capture condition. 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 of the normal frame passes; After passing 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 performed, including: Combine the initial first unique code domain and the initial second unique code domain to obtain a combined sequence; Under the preset ultra-low signal-to-noise ratio condition, calculate the second correlation peak signal-to-noise ratio of the combined sequence; the ultra-low signal-to-noise ratio condition includes -10 dB; Determine whether the second correlation peak signal-to-noise ratio meets the single-frame capture condition; If so, determine that the single-frame capture verification of the initial first unique code domain and the initial second unique code domain passes. Otherwise, randomly generate several base sequences again.

2. The method according to claim 1, wherein 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, including: Using the pi / 2 BPSK modulation method, 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; 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; Determine whether the first maximum symbol count is less than the second threshold; 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; Determine whether the second maximum symbol count is less than the 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.

3. The method according to claim 1, characterized in that, 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 the 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.

4. The method according to claim 1, wherein 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 896 bits in the second unique code domain are: 26C01E25DCE726C04758DCE7AE9C 4758AE9CF50AF50ADCE7AE9CC98F 26C0DCE74758F50AAE9C1E254758 1E25C98FDCE747581E25F50A4758 C98FAE9CF50ADCE726C01E254758 AE9C1E25AE9CC98FAE9CF50AC98F C98F47584758C98FDCE7475826C0 F50A26C01E25DCE7AE9CC98FDCE7; or The first unique code domain is: 209D6AC85E97C6A21963E1D4E09D6AC8609D5963E09D46A2327F, and the 896 bits of the second unique code domain are: 7A5F1A8882751A88658F7A5F7A5F 7A5F1A881A88AB21AB211A888753 8753AB21658FC9FC8275C9FC658F 8753658F1A88C9FCC9FC8753C9FC 8275658F7A5F87538753C9FC8753 AB21AB21AB217A5F82757A5F1A88 C9FC658FC9FCC9FC8275AB211A88 AB218753658F658F82757A5F8753.

5. The method according to claim 1, wherein Perform encapsulation processing on the satellite payload data packet to obtain a first frame body, including: Perform constellation map modulation processing on the satellite payload data packet to obtain a data symbol set; In the data symbol set, insert a pilot block every 720 data symbols to obtain an initial frame body after polling all data symbols; Add a pilot block to the tail of the initial frame body to obtain the first frame body after addition, where when the first unique code domain in the first frame header adopts sequences of different lengths, the length of the first frame body is different.

6. The method according to claim 1, characterized in that, The length of the physical layer signaling field is 64 bits. 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, and physical layer signaling 29 and physical layer signaling 30 are very low signal-to-noise ratio frame signaling.

7. The method according to claim 1, characterized in that, The method further includes: Encapsulating the satellite payload data packet to obtain a second frame body; Constructing 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; Generating a normal data frame corresponding to the satellite payload data packet according to the second frame header and the second frame body; Using time division multiple access and broadcasting the normal data frame and the very low signal-to-noise ratio data frame to the user terminal according to a preset time slot ratio.

8. A satellite network data sending device for implementing the satellite network data sending method according to any one of claims 1-7, characterized in that Including: A frame body encapsulation unit, configured to obtain a satellite payload data packet and encapsulate the satellite payload data packet to obtain a first frame body; 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 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, 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 very low signal-to-noise ratio frame signaling; A data frame generation unit, configured to generate a very 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; A sending unit, configured to send the very low signal-to-noise ratio data frame to the user terminal, so that the user terminal decodes the very 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.

Images