A satellite relay communication signal processing system

Abstract

The present invention belongs to the field of satellite relay communication, and particularly relates to a satellite relay communication signal processing system deployed on a sea surface buoy, which conducts two-way communication with a ship-based or shore-based station through a relay satellite link. The signal processing system supports two communication modes, namely data service and short message service. The system includes: a receiving signal processing module for receiving forward satellite signals, demodulating, decoding, and descrambling them, and then transmitting them to a data protocol processing module; a transmitting signal processing module for receiving the observation data processed by the data protocol processing module, performing channel coding, scrambling, and modulation processing on it, and then outputting a return satellite signal; a data protocol processing module for parsing control instructions from the forward satellite signals processed by the receiving signal processing module, switching communication links or performing corresponding data processing according to the content of the control instructions; and also for receiving the observation data from the sea surface buoy, packetizing it, and then transmitting it to the transmitting signal processing module.

Description

Technical Field

[0001] The present invention belongs to the field of satellite relay communication, and particularly relates to a satellite relay communication signal processing system. Background Art

[0002] At present, scientific data obtained by deep-sea exploration buoys at home and abroad mainly uses space-based satellites as relay means to realize real-time data transmission to remote ship-based or shore-based data centers. With the continuous in-depth development of deep-sea exploration and scientific research activities, the requirement of real-time transmission of a large amount of data obtained by underwater payloads to the shore-based data center is very urgent, bringing new challenges to the data transmission capacity between the sea surface and the shore base. At the present stage, the data transmission between deep-sea exploration buoys in China and the shore base mainly relies on Iridium satellite networks, Argos satellite networks, and Beidou satellite networks, etc. Among them, the transmission rates of the VHF (Very high frequency) band sea surface satellite communication terminals based on the Argos satellite network and the L-band sea surface satellite communication terminals based on the Iridium satellite network are both lower than 10 kbps, and the transmitted data has to pass through foreign data processing centers first, and then be distributed to domestic users after processing, so the security of the data is difficult to be guaranteed. Although the Beidou satellite network can ensure the security of data, its communication rate is only 77 byte / min, which is difficult to meet the demand for large-capacity data transmission, and it only supports one communication mode, cannot flexibly adjust the transmission strategy according to sea conditions, and cannot balance the data transmission rate and communication stability.

[0003] In 2022, China completed the construction of the relay satellite SMA (S-band Multiple Access) network. The signals of the relay satellite SMA network can cover the whole world, can support multiple terminals to access simultaneously, and a single terminal has a data transmission capacity of 1 - 50 kbps, and supports two communication modes: data service and short message service, but it has not been applied to the field of sea surface buoys. There is an urgent need for a satellite relay communication signal processing system in the field of sea surface buoy technology. Summary of the Invention

[0004] The purpose of the present invention is to overcome the defects of the prior art and propose a satellite relay communication signal processing system.

[0005] In view of this, the present invention proposes a satellite relay communication signal processing system, which is deployed on a sea surface buoy and conducts two-way communication with a ship-based or shore-based base through a relay satellite link. The signal processing system supports two communication modes: data service and short message service. The signal processing system includes: a received signal processing module, a transmitted signal processing module, and a data protocol processing module, wherein,

[0006] The receiving signal processing module is configured to receive forward satellite signals, and after demodulation, decoding, and descrambling, transmit them to the data protocol processing module;

[0007] The transmitting signal processing module is configured to receive the observation data processed by the data protocol processing module, and after channel coding, scrambling, and modulation, output reverse satellite signals;

[0008] The data protocol processing module is configured to parse control instructions from the forward satellite signals processed by the receiving signal processing module, and perform communication link switching or corresponding data processing according to the content of the control instructions; it is also configured to receive observation data from sea surface buoys, packetize them, and transmit them to the transmitting signal processing module.

[0009] Preferably, the data service adopts a spread spectrum technology and a convolutional coding scheme, and the maximum data transmission rate reaches 50 kbps; the short message service adopts a spread spectrum technology and a polarization coding scheme, and the maximum data transmission rate reaches 1.74 kbps.

[0010] Preferably, the processing process of the receiving signal processing module includes: receiving forward satellite signals and down-converting them to the baseband, and successively performing sampling, acquisition, tracking, Viterbi decoding, and descrambling on the baseband signals; among them,

[0011] The acquisition process includes: generating a pseudo-code consistent with the spreading code locally, using the characteristic of high auto-correlation of the pseudo-code, calculating the cross-correlation value between the local pseudo-code and the pseudo-code of the received signal, detecting the result, and searching for the maximum correlation peak to complete signal acquisition;

[0012] The tracking process includes: completing the synchronization of the carrier phase and the code phase through a carrier loop and a code loop, and then completing bit synchronization;

[0013] The Viterbi decoding process includes: performing convolutional decoding on the data after bit synchronization to restore the original data.

[0014] Preferably, the processing process of the transmitting signal processing module includes:

[0015] Receiving the observation data processed by the data protocol processing module;

[0016] Performing a frame synchronization process;

[0017] Parsing the data packet and identifying the working mode identifier to perform a working mode decision:

[0018] If the current working mode is the data service mode, convolutional coding, scrambling, spread spectrum modulation, and up-conversion will be performed in sequence to output reverse data service signals;

[0019] If the current working mode is the short message service mode, polar coding, spreading modulation, and up-conversion are performed in sequence, and the reverse short message signal is output.

[0020] Preferably, the convolutional coding is implemented by performing a convolutional operation on the input information sequence and two generating polynomials, specifically including: for each received 1-bit input information bit, 2-bit coded bits are calculated and output based on the generating polynomial, and the 2-bit coded bits are interleaved and arranged in a set order to finally form a complete convolutional codeword sequence.

[0021] Preferably, the processing process of the polar coding includes:

[0022] Construct an N×N generating matrix G through Kronecker product operation with the basic kernel matrix F = [1 0; 1 1];

[0023] During coding, the data to be coded is placed at the reliable position, and 0 is filled at the frozen position to obtain a vector u of length N;

[0024] Multiply the vector u by the generating matrix G to obtain the coded word x after polar coding, and perform modulo-2 processing on the obtained coded word to generate a polar code sequence.

[0025] Preferably, the processing process of the data protocol processing module includes:

[0026] Parse the received control instruction data:

[0027] If it is a buoy control instruction, packetize the buoy control instruction according to the specified data format and transmit it to the sea surface buoy platform;

[0028] If it is a reverse link switching instruction, update the working mode identifier, and packetize the observation data of the sea surface buoy and the updated working mode identifier according to the updated reverse link data frame format, and transmit them to the transmit signal processing module through the serial port interface;

[0029] If the reverse link switching instruction is not received, maintain the current working mode, packetize the observation data of the sea surface buoy and the current working mode identifier, and transmit them to the transmit signal processing module.

[0030] Preferably, the strategy for communication link switching includes:

[0031] Step 1) The shore-based terminal monitors the signal-to-noise ratio and bit error rate of the relay satellite received signal in real time. When the signal-to-noise ratio reaches the preset trigger threshold SNR_TH, trigger the switching process and enter Step 2);

[0032] Step 2) The shore-based terminal adopts a SNR-based hierarchical mechanism, divides the SNR into two level intervals, corresponding to high-quality channels and low-quality channels respectively. When the SNR is in the high-quality channel, the data service mode is adopted; when the SNR is in the low-quality channel, it is further judged according to the bit error rate. If it is greater than the set threshold, it switches to the short message mode; otherwise, it still maintains the data service mode;

[0033] Step 3) The shore-based terminal uploads a mode switching request instruction to the relay satellite;

[0034] Step 4) The relay satellite sends a switching command to the signal processing system to notify the target switching link;

[0035] Step 5) The signal processing system identifies the working mode identifier in the switching command and switches to the corresponding mode;

[0036] Step 6) The shore-based terminal receives the mode data after switching, the link access is successful, and the switching execution phase ends.

[0037] Compared with the prior art, the advantages of the present invention are as follows:

[0038] 1. The present invention completes the link data transmission task of the marine buoy-relay satellite-shore-based equipment, and the whole link is reliable and stable.

[0039] 2. The present invention obtains a larger link margin for the system by reducing the channel bandwidth and adopting a better polar code coding method, which is beneficial to the communication link stability under harsh sea conditions.

[0040] 3. The present invention adopts a strategy of switching multiple mode links, effectively balancing the transmission efficiency and reliability of the system. Description of the Drawings

[0041] Figure 1 is a schematic diagram of the relay communication link;

[0042] Figure 2 is a block diagram of the composition of the satellite relay communication signal processing system;

[0043] Figure 3 is a flowchart of the received signal processing;

[0044] Figure 4 is a flowchart of the transmitted signal processing;

[0045] Figure 5 is a flowchart of the working process of the data protocol processing module;

[0046] Figure 6 is a flowchart of the communication link switching. Detailed Embodiments

[0047] In response to the technical requirements for high-speed, stable, and secure data transmission, the present invention proposes a satellite relay communication signal processing system applicable to sea surface buoys, which can support autonomous access of sea surface satellite communication terminals to China's relay satellite SMA network for data transmission, achieving a data transmission rate of up to 50 kbps, providing a new technical approach for high-speed, stable, and secure data transmission to remote ship-based or shore-based data centers.

[0048] It mainly consists of a received signal processing module, a transmitted signal processing module, and a data protocol processing module. The received signal processing module mainly realizes functions such as satellite signal demodulation, decoding, and descrambling. The transmitted signal processing module mainly realizes functions such as channel coding, scrambling, and modulation. The data protocol processing module mainly realizes functions such as data processing and communication link switching.

[0049] As a further improvement of the present invention, the satellite relay communication signal processing system can support autonomous access of sea surface satellite communication terminals to China's relay satellite SMA network for data transmission, and supports two communication modes: data service and short message. The forward link (shore-based / ship-based data center → relay satellite → buoy) adopts the data service mode, and the data transmission rate is 2 kbps. The return link (buoy → relay satellite → shore-based / ship-based data center) can be flexibly switched according to the channel conditions. The data service mode adopts spread spectrum modulation technology and convolutional code coding technology, which can achieve high-speed data transmission, and the maximum transmission rate is 50 kbps. The short message mode adopts spread spectrum modulation technology and polar code coding technology, which is suitable for harsh channel environments, and the maximum transmission rate is 1.74 kbps.

[0050] As a further improvement of the present invention, the satellite relay communication signal processing system has a dynamic switching function for the return link communication mode. The ship-based or shore-based data center can realize adaptive adjustment of the communication mode by monitoring the signal-to-noise ratio of the return link and sending control commands. The return link switching strategy adopts a hierarchical mechanism based on the signal-to-noise ratio, dividing the signal-to-noise ratio into two grade intervals: good and poor, [SNR_TH, +∞) and (-∞, SNR_TH), corresponding to high-quality and low-quality channels respectively. When the signal-to-noise ratio is in the poor interval, the bit error rate is used as an auxiliary criterion, and a bit error rate threshold BER_TH is introduced for secondary judgment. If the bit error rate of the data service mode is higher than BER_TH, the satellite relay communication signal processing system switches to the short message mode. If the bit error rate of the data mode is lower than BER_TH, the data service mode is still maintained. When the signal-to-noise ratio is in the good interval, the satellite relay communication signal processing system selects the data service mode. This link switching strategy can effectively avoid data loss caused by frequent switching when the communication link is in a critical state, taking into account both the data transmission rate and communication stability.

[0051] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0052] Embodiment

[0053] As Figure 1 shown, an embodiment of the present invention provides a satellite relay communication signal processing system (hereinafter referred to as "signal processing system") carried on a sea surface buoy (hereinafter referred to as "buoy"). The signal processing system communicates bidirectionally with a ship-based or shore-based data center through a relay satellite link, supporting two communication modes: data service and short message. The data service mode adopts spread spectrum technology and convolutional coding scheme, and the maximum data transmission rate can reach 50 kbps, which can support high-speed backhaul of large-capacity data in a good channel environment. To cope with complex sea conditions, the signal processing system also designs a short message mode with a data transmission rate of 1.74 kbps. The short message selects polar codes with high coding gain as the channel coding scheme, enhancing the stability of the communication link. The forward link is the link through which the shore-based / ship-based data center (hereinafter referred to as "data center") transmits data to the buoy via a relay satellite. It adopts the data service mode with a transmission rate of 2 kbps, mainly used for transmitting control instructions, including the reverse link working mode control instruction and the buoy control instruction. The reverse link is the link through which the buoy transmits data to the data center via a relay satellite. It adopts the data service mode and short message, with transmission rates of 50 kbps and 1.74 kbps respectively, mainly transmitting ocean observation data.

[0054] As Figure 2 shown, the signal processing system mainly consists of a received signal processing module, a transmitted signal processing module, a data protocol processing module, etc.

[0055] The received signal processing module realizes functions such as demodulation, decoding, and descrambling of forward satellite signals. The received signal processing flow is as Figure 3 shown. The received signal processing module receives the forward satellite signal and down-converts it to the baseband, samples the baseband signal, and the sampled signal is sent to the acquisition unit. The acquisition unit first generates a pseudo-code consistent with the spread spectrum code locally, calculates the cross-correlation value between the local pseudo-code and the received signal pseudo-code using the high auto-correlation characteristic of the pseudo-code, detects the result, searches for the maximum correlation peak, and completes signal acquisition. The tracking unit completes the synchronization of the carrier phase and code phase through the carrier loop and code loop, and finally completes bit synchronization. The Viterbi decoding unit performs convolutional decoding on the synchronized data, restores the original data, then descrambles the data, and finally sends it to the data protocol processing module for control instruction parsing.

[0056] The transmitted signal processing module realizes functions such as channel coding, scrambling, and modulation. The transmitted signal processing flow is as Figure 4As shown in the figure. After the transmission signal processing module receives the data packet from the main control circuit, it first performs the frame synchronization process, then parses the data packet and identifies the working mode identifier to complete the working mode decision. If the current working mode is the data service mode, the data will sequentially go through convolutional coding, scrambling, spreading modulation, and upconversion, and output the reverse data service signal. If the current working mode is the short message service mode, the data will sequentially go through polar coding, spreading modulation, and upconversion, and output the reverse short message signal.

[0057] In the transmission signal processing module, convolutional coding is achieved by performing a convolutional operation on the input information sequence and two generating polynomials. During the coding process, for each received 1-bit input information bit, the encoder calculates and outputs 2-bit coding bits based on the generating polynomials. These two parallel coding outputs are interleaved and arranged in a specific order to finally form a complete convolutional codeword sequence.

[0058] In the transmission signal processing module, polar coding first performs a Kronecker product operation through the basic kernel matrix F = [1 0; 1 1] to construct an N×N generating matrix G. During coding, the data to be coded is placed at reliable positions, and 0 is filled at the frozen positions to obtain a vector u of length N. Finally, multiplying the vector u by the generating matrix G, the coded word x = uG of the polar code can be obtained. Performing a modulo-2 operation on the obtained coded word x generates the polar code sequence. The reliable positions and frozen positions are specified in the protocol.

[0059] The data protocol processing module mainly realizes functions such as communication link switching and data processing. The data protocol processing module is responsible for receiving and parsing the control instructions from the receiving signal processing module and packetizing and transmitting them to the buoy. At the same time, it also receives the observation data from the buoy, packetizes it, and transmits it to the transmission signal processing module. The working process of the data protocol processing module is as Figure 5 shown. When receiving the buoy control instruction, the data protocol processing module packetizes the buoy control instruction according to the specified data format and transmits it to the buoy platform; when receiving the reverse link switching instruction, it updates the working mode identifier, and according to the updated reverse link data frame format, packetizes the observation data of the buoy and the updated working mode identifier, and then transmits it to the transmission signal processing module through the serial port interface; if the reverse link switching instruction is not received, it maintains the current working mode, packetizes the observation data of the buoy and the current working mode identifier and transmits it to the transmission signal processing module.

[0060] To improve communication reliability, the signal processing system adopts a link switching strategy. The link switching process is as Figure 6 shown, specifically including:

[0061] Step 1 monitors the signal-to-noise ratio (SNR) and bit error rate (BER) of the received signal by the relay satellite in real time through the data center. When the SNR reaches the preset trigger threshold SNR_TH, specifically, the SNR threshold is set to 5 dB, the handover process is triggered.

[0062] Step 2 The data center makes a handover decision and selects the target handover link. A hierarchical mechanism based on SNR is adopted. The SNR is divided into two grade intervals of good and poor, [SNR_TH, +∞) and (-∞, SNR_TH), corresponding to high-quality signals and low-quality channels respectively. When the SNR is in the poor interval, the BER is used as an auxiliary criterion, and a BER threshold BER_TH is introduced for secondary decision-making. Specifically, the BER threshold is set to 10 -1 , if the BER of the data service mode is higher than BER_TH, it is switched to the short message. If the BER of the data mode is lower than BER_TH, the data service mode is still maintained to avoid frequent handovers when the link is in the boundary state. When the SNR is in the good interval, the data service mode is selected.

[0063] Step 3 After the data center completes the decision, the data center uploads a handover request instruction to the relay satellite, requesting the relay satellite to make preparations for switching resources in advance.

[0064] Step 4 The relay satellite sends a handover command to the signal processing system.

[0065] Step 5 The signal processing system identifies the working mode identifier in the handover instruction and switches to the corresponding mode. When the data service identifier is recognized, the signal processing system switches to the data service transmission link to ensure high-speed data transmission. When the short message service identifier is recognized, data is transmitted through the short message link to ensure reliable data transmission in harsh environments.

[0066] Step 6 The data center receives the data of the switched link, the link access is successful, and the handover execution stage ends.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the embodiments, those of ordinary skill in the art should understand that any modification or equivalent replacement of the technical solutions of the present invention does not depart from the spirit and scope of the technical solutions of the present invention, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A satellite relay communication signal processing system is deployed on a sea surface buoy and conducts two-way communication with ship-based or shore-based through a relay satellite link. It is characterized in that The signal processing system supports two communication modes, namely data service and short message service. The signal processing system includes: a receiving signal processing module, a transmitting signal processing module, and a data protocol processing module. Among them, The receiving signal processing module is used to receive the forward satellite signal, and after demodulation, decoding, and descrambling processing, it is transmitted to the data protocol processing module; The transmitting signal processing module is used to receive the observation data processed by the data protocol processing module, and after channel coding, scrambling, and modulation processing, it outputs the return satellite signal; The data protocol processing module is used to parse the control instructions from the forward satellite signal processed by the receiving signal processing module, and perform communication link switching or corresponding data processing according to the content of the control instructions; it is also used to receive the observation data from the sea surface buoy, and after packetizing, it is transmitted to the transmitting signal processing module; The data service adopts spread spectrum technology and convolutional coding scheme, and the maximum data transmission rate reaches 50 kbps; the short message service adopts spread spectrum technology and polarization coding scheme, and the maximum data transmission rate reaches 1.74 kbps; The strategy for the communication link switching includes: Step 1: The shore-based terminal monitors the signal-to-noise ratio (SNR) and bit error rate (BER) of the received signal of the relay satellite in real time. When the SNR reaches the preset trigger threshold SNR_TH, the switching process is triggered, and it enters Step 2; Step 2: The shore-based terminal adopts a SNR-based hierarchical mechanism to divide the SNR into two grade intervals, corresponding to high-quality channels and low-quality channels respectively. When the SNR is in the high-quality channel, the data service mode is adopted; when the SNR is in the low-quality channel, it is further judged according to the BER. If it is greater than the set threshold, it is switched to the short message service mode, otherwise, the data service mode is still maintained; Step 3: The shore-based terminal uploads a mode switching request instruction to the relay satellite; Step 4: The relay satellite sends a switching command to the signal processing system to notify the target switching link; Step 5: The signal processing system identifies the working mode identifier in the switching command and switches to the corresponding mode; Step 6: The shore-based terminal receives the mode data after switching, the link access is successful, and the switching execution stage ends.

2. The satellite relay communication signal processing system according to claim 1, wherein, The processing process of the receiving signal processing module includes: receiving the forward satellite signal and down-converting it to the baseband, and sequentially performing sampling, acquisition, tracking, Viterbi decoding, and descrambling on the baseband signal; among them, The process of acquisition includes: generating a pseudo-code consistent with the spreading code locally, using the characteristic of high auto-correlation of the pseudo-code, calculating the cross-correlation value between the local pseudo-code and the received signal pseudo-code, detecting the result, and searching for the maximum correlation peak to complete signal acquisition; The process of tracking includes: completing the synchronization of the carrier phase and code phase through the carrier loop and code loop, and then completing bit synchronization; The process of Viterbi decoding includes: performing convolutional decoding on the data after bit synchronization to restore the original data.

3. The satellite relay communication signal processing system according to claim 1, wherein The processing process of the transmitting signal processing module includes: Receiving the observation data processed by the data protocol processing module; Performing frame synchronization process; Parsing the data packet and identifying the working mode identifier to perform working mode decision: If the current working mode is the data service mode, convolutional coding, scrambling, spreading modulation, and up-conversion are performed in sequence, and a reverse data service signal is output. If the current working mode is the short message service mode, polarization coding, spreading modulation, and up-conversion are performed in sequence, and a reverse short message signal is output.

4. The satellite relay communication signal processing system according to claim 3, wherein, The convolutional coding is implemented by performing a convolutional operation on the input information sequence and two generating polynomials, specifically including: for each received 1-bit input information bit, 2-bit coded bits are calculated and output based on the generating polynomial, and the 2-bit coded bits are interleaved and arranged in a set order to finally form a complete convolutional codeword sequence.

5. The satellite relay communication signal processing system according to claim 3, wherein The processing process of the polarization coding includes: A Kronecker product operation is performed through the basic kernel matrix F = [1 0; 1 1] to construct an N×N generating matrix G. During coding, the data to be coded is placed at reliable positions, and 0 is filled at the frozen positions to obtain a vector u of length N. The vector u is multiplied by the generating matrix G to obtain the coded word x after polarization coding, and the obtained coded word x is processed modulo 2 to generate a polarization code sequence.

6. The satellite relay communication signal processing system according to claim 3, characterized in that, The processing process of the data protocol processing module includes: Parsing the received control instruction data: If it is a buoy control instruction, the buoy control instruction is packetized according to the specified data format and transmitted to the sea surface buoy. If it is a reverse link switching instruction, the working mode identifier is updated, and the observation data of the sea surface buoy and the updated working mode identifier are packetized according to the updated reverse link data frame format and transmitted to the transmit signal processing module through the serial port interface. If the reverse link switching instruction is not received, the current working mode is maintained, and the observation data of the sea surface buoy and the current working mode identifier are packetized and transmitted to the transmit signal processing module.

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