Satellite relay communication signal processing system

Abstract

The invention belongs to the field of satellite relay communication, and particularly relates to a satellite relay communication signal processing system, which is deployed on a sea surface buoy, performs two-way communication with a ship base or a shore base through a relay satellite link, supports two communication modes of a data service and a short message service, and comprises a received signal processing module and a signal processing module, the signal receiving module is used for receiving a forward satellite signal and transmitting the signal to the data protocol processing module after demodulation, decoding and descrambling processing; the transmitting signal processing module is used for receiving the observation data processed by the data protocol processing module, and outputting a reverse satellite signal after channel coding, scrambling and modulation processing; the data protocol processing module is used for performing control instruction analysis on the forward satellite signals processed by the received signal processing module, and performing communication link switching or corresponding data processing according to the content of the control instruction; and the data transmission module is also used for receiving observation data from a sea surface buoy and transmitting the data to the emission signal processing module after packaging.

Description

Technical Field

[0001] The invention belongs to the field of satellite relay communication, and in particular 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 use space-based satellites as relay means to achieve real-time data transmission to remote ship-based or shore-based data centers. With the continuous and in-depth development of deep-sea exploration and scientific research activities, the requirement for real-time transmission of a large amount of data obtained by underwater payloads to shore-based data centers is very urgent, which brings new challenges to the data transmission capacity between the sea surface and the shore. At present, the data transmission between my country's deep-sea exploration buoys and shore-based mainly relies on the Iridium network, Argos satellite network and Beidou satellite network. Among them, the transmission rate of the VHF (Very high frequency) band sea surface satellite communication terminal based on the Argos satellite network and the L-band sea surface satellite communication terminal based on the Iridium network are both lower than 10kbps, and the transmitted data must first pass through foreign data processing centers and then be distributed to domestic users after processing, so the security of the data is difficult to guarantee. Although the Beidou satellite network can ensure the security of data, the communication rate is only 77byte / min, which is difficult to meet the needs of large-capacity data transmission, and it only supports one communication mode, and cannot flexibly adjust the transmission strategy according to changes in sea conditions, and cannot take into account both data transmission rate and communication stability.

[0003] In 2022, my country completed the construction of the relay satellite SMA (S-band Multiple Access) network. The relay satellite SMA network signal can cover the entire world and support multiple terminals to access at the same time. A single terminal has a data transmission capacity of 1~50kbps and supports two communication modes: data services and short messages. However, it has not yet been applied to the field of sea surface buoys. The field of sea surface buoy technology urgently needs a satellite relay communication signal processing system. 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 performs two-way communication with a ship-based or shore-based system 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 receiving signal processing module, a transmitting signal processing module and a data protocol processing module, wherein:

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

[0007] The transmission signal processing module is used to receive the observation data processed by the data protocol processing module, and output the return satellite signal after channel coding, scrambling and modulation processing;

[0008] The data protocol processing module is used to parse the control instructions of 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 observation data from the sea surface buoy and transmit it to the transmitting signal processing module after packaging.

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

[0010] Preferably, the processing process of the receiving signal processing module includes: receiving the forward satellite signal and down-converting it to baseband, and sequentially sampling, capturing, tracking, Viterbi decoding and descrambling the baseband signal; wherein,

[0011] The capture process includes: generating a pseudo code that is consistent with the spread spectrum code locally, calculating the cross-correlation value between the local pseudo code and the pseudo code of the received signal by utilizing the high autocorrelation characteristic of the pseudo code, detecting the result, searching for the maximum correlation peak, and completing signal capture;

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

[0013] The Viterbi decoding process includes: performing convolution decoding on the bit-synchronized data to restore the original data.

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

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

[0016] Perform frame synchronization process;

[0017] Parse the data packet and identify the working mode identifier to make working mode decisions:

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

[0019] If the current working mode is the short message service mode, polarization coding, spread spectrum modulation and up-conversion are performed in sequence to output a return short message signal.

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

[0021] Preferably, the polarization coding processing includes:

[0022] Perform Kronecker product operation on the basic kernel matrix F = [1 0; 1 1] to construct an N×N generator matrix G;

[0023] When encoding, the data to be encoded is placed in a reliable position, and the frozen position is filled with 0 to obtain a vector u of length N;

[0024] The vector u is multiplied by the generator matrix G to obtain a codeword x after polar code encoding. The obtained codeword is subjected to modulo 2 processing to generate a polar code sequence.

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

[0026] Parse the received control command data:

[0027] If it is a buoy control command, the buoy control command is packaged and transmitted to the sea surface buoy platform according to the prescribed data format;

[0028] If it is a return 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 packaged according to the updated return link data frame format, and transmitted to the transmission signal processing module through the serial port interface;

[0029] If the return 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 packaged and transmitted to the transmission signal processing module.

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

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

[0032] Step 2) The shore-based end adopts a hierarchical mechanism based on signal-to-noise ratio, dividing the signal-to-noise ratio into two level intervals, corresponding to high-quality channels and low-quality channels respectively. When the signal-to-noise ratio is in a high-quality channel, the data service mode is adopted; when the signal-to-noise ratio is in a low-quality channel, it is further judged based on 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 end sends 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 to switch the 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 end receives the switched mode data, the link access is successful, and the switching execution phase ends.

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

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

[0039] 2. The present invention reduces the channel bandwidth and adopts a better polarization code encoding method, so that the system obtains a larger link margin, which is beneficial to the stability of the communication link under severe sea conditions.

[0040] 3. The present invention adopts a multi-mode link switching strategy to effectively balance the transmission efficiency and reliability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0043] Figure 3 is a received signal processing flow chart;

[0044] Figure 4 is a flow chart of the transmit signal processing;

[0045] Figure 5 It is the workflow diagram of the data protocol processing module;

[0046] Figure 6 It is a communication link switching flow chart. DETAILED DESCRIPTION

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

[0048] It is mainly composed of receiving signal processing module, transmitting signal processing module and data protocol processing module. The receiving signal processing module mainly realizes satellite signal demodulation, decoding and descrambling functions. The transmitting signal processing module mainly realizes channel coding, scrambling and modulation functions. The data protocol processing module mainly realizes data processing and communication link switching functions.

[0049] As a further improvement of the present invention, the satellite relay communication signal processing system can support the sea surface satellite communication terminal to autonomously access my country'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 with a data transmission rate of 2kbps, and the return link (buoy → relay satellite → shore-based / ship-based data center) can be flexibly switched according to channel conditions. The data service mode adopts spread spectrum modulation technology and convolutional code encoding technology to achieve high-speed data transmission with a maximum transmission rate of 50kbps. The short message mode adopts spread spectrum modulation technology and polarization code encoding technology, which is suitable for harsh channel environments with a maximum transmission rate of 1.74kbps.

[0050] As a further improvement of the present invention, the satellite relay communication signal processing system has a dynamic switching function of the return link communication mode. The ship-based or shore-based data center can realize adaptive adjustment of the communication mode by monitoring the return link signal-to-noise ratio and sending control instructions. The return link switching strategy adopts a hierarchical mechanism based on the signal-to-noise ratio, and divides the signal-to-noise ratio into two level intervals of good and poor [SNR_TH, +∞), (-∞, SNR_TH), corresponding to high 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 the 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 data transmission rate and communication stability.

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

[0052] Example

[0053] like Figure 1 As shown, an embodiment of the present invention provides a satellite relay communication signal processing system (hereinafter referred to as "signal processing system") mounted on a sea surface buoy (hereinafter referred to as "buoy"). The signal processing system performs two-way communication with a ship-based or shore-based data center through a relay satellite link, and supports two communication modes: data service and short message. The data service mode adopts spread spectrum technology and convolution coding scheme, and the maximum data transmission rate can reach 50kbps, which can support high-speed return of large-capacity data in a good channel environment. In order to cope with complex sea conditions, the signal processing system also designs a short message mode with a data transmission rate of 1.74kbps. The short message uses polarization code with high coding gain as the channel coding scheme, which enhances the stability of the communication link. The forward link is a link for the shore-based / ship-based data center (hereinafter referred to as "data center") to transmit data to the buoy via a relay satellite. It adopts a data service mode with a transmission rate of 2kbps, and is mainly used to transmit control instructions, including return link working mode control instructions and buoy control instructions. The return link is the link through which the buoy transmits data to the data center via the relay satellite. It adopts the data service mode and short message, with transmission rates of 50kbps and 1.74kbps respectively, and mainly transmits ocean observation data.

[0054] like Figure 2 As shown, the signal processing system is mainly composed of a receiving signal processing module, a transmitting signal processing module, a data protocol processing module, etc.

[0055] The receiving signal processing module realizes the demodulation, decoding, and descrambling functions of the forward satellite signal. The receiving signal processing flow is as follows: Figure 3 As shown. The receiving signal processing module receives the forward satellite signal and down-converts it to baseband, and samples the baseband signal. The sampled signal is sent to the capture unit. The capture unit first generates a pseudo code locally that is consistent with the spread spectrum code, and uses the high autocorrelation characteristics of the pseudo code to calculate the cross-correlation value between the local pseudo code and the received signal pseudo code, detects the result, searches for the maximum correlation peak, and completes signal capture. The tracking unit completes the synchronization of the carrier phase and code phase through the carrier loop and the code loop, and finally completes the bit synchronization. The Viterbi decoding unit performs convolution decoding on the synchronized data to restore the original data, then descrambles the data, and finally sends it to the data protocol processing module for control instruction parsing.

[0056] The transmit signal processing module implements channel coding, scrambling and modulation functions. The transmit signal processing flow is as follows: Figure 4As shown. 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 judgment. If the current working mode is the data service mode, the data will be sequentially subjected to convolution coding, scrambling, spread spectrum modulation and up-conversion, and the return data service signal will be output. If the current working mode is the short message service mode, the data will be sequentially subjected to polarization coding, spread spectrum modulation, up-conversion, and the return short message signal will be output.

[0057] The convolutional code encoding in the transmit signal processing module is realized by convolution operation between the input information sequence and two generating polynomials. During the encoding process, for every 1 input information bit received, the encoder will calculate and output 2 coded bits based on the generating polynomial. The two parallel coded outputs are interleaved in a specific order to finally form a complete convolutional codeword sequence.

[0058] In the transmission signal processing module, the polarization code encoding is first performed through the Kronecker product operation of the basic kernel matrix F = [1 0; 1 1] to construct an N×N generator matrix G. During encoding, the data to be encoded is placed in the reliable position, and the frozen position is filled with 0 to obtain a vector u of length N. Finally, the vector u is multiplied by the generator matrix G to obtain the codeword x = uG after polarization code encoding. The obtained codeword x is processed modulo 2 to generate the polarization code sequence. The reliable position and frozen position are specified in the protocol.

[0059] The data protocol processing module mainly implements 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 assembling and transmitting them to the buoy. It also receives the observation data from the buoy and assembles them and transmits them to the transmitting signal processing module. The workflow of the data protocol processing module is as follows: Figure 5 When receiving a buoy control instruction, the data protocol processing module packages the buoy control instruction according to the specified data format and transmits it to the buoy platform; when receiving a return link switching instruction, the working mode identifier is updated, and the observation data of the buoy and the updated working mode identifier are packaged according to the updated return link data frame format, and then transmitted to the transmission signal processing module through the serial port interface; if the return link switching instruction is not received, the current working mode is maintained, and the observation data of the buoy and the current working mode identifier are packaged and transmitted to the transmission signal processing module.

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

[0061] Step 1: The data center monitors the signal-to-noise ratio and bit error rate of the relay satellite receiving signal in real time. When the signal-to-noise ratio SNR reaches a preset trigger threshold SNR_TH, specifically, the signal-to-noise ratio threshold is set to 5dB, the switching process is triggered.

[0062] Step 2 The data center makes a handover decision and selects the target handover link. A hierarchical mechanism based on signal-to-noise ratio is adopted to divide the signal-to-noise ratio into two level intervals: good and poor [SNR_TH, +∞), (-∞, SNR_TH), corresponding to high-quality signals and low-quality channels, respectively. When the signal-to-noise ratio is in the poor interval, the bit error rate BER is used as an auxiliary criterion, and the bit error rate threshold BER_TH is introduced for secondary decision. Specifically, the bit error rate threshold is set to 10 -1 If the bit error rate of the data service mode is higher than BER_TH, it switches to short messages. If the bit error rate of the data mode is lower than BER_TH, it still maintains the data service mode to avoid frequent switching when the link is in a boundary state. When the signal-to-noise ratio is in a good range, the data service mode is selected.

[0063] Step 3: After the data center makes the decision, it sends a switching request instruction to the relay satellite, requesting the relay satellite to prepare for switching resources in advance.

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

[0065] Step 5 The signal processing system identifies the working mode identifier in the switching instruction and switches to the corresponding mode. When the data service identifier is identified, the signal processing system switches to the data service transmission link to ensure high-speed data transmission. When the short message service identifier is identified, data transmission is sent 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 switching execution phase ends.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention is described in detail with reference to the embodiments, it should be understood by those skilled in the art 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 should be included in the scope of the claims of the present invention.

Claims

1. A satellite relay communication signal processing system, deployed on a sea surface buoy, performs two-way communication with a ship-based or shore-based system via a relay satellite link, characterized in that: The signal processing system supports two communication modes: 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, wherein: The receiving signal processing module is used to receive the forward satellite signal and transmit it to the data protocol processing module after demodulation, decoding and descrambling; The transmission signal processing module is used to receive the observation data processed by the data protocol processing module, and output the return satellite signal after channel coding, scrambling and modulation processing; The data protocol processing module is used to parse the control instructions of 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 observation data from the sea surface buoy and transmit it to the transmitting signal processing module after packaging.

2. The satellite relay communication signal processing system according to claim 1, characterized in that: The data service adopts spread spectrum technology and convolution coding scheme, and the maximum data transmission rate reaches 50kbps; the short message service adopts spread spectrum technology and polarization coding scheme, and the maximum data transmission rate reaches 1.74kbps.

3. The satellite relay communication signal processing system according to claim 1, characterized in that: The processing process of the receiving signal processing module includes: receiving the forward satellite signal and down-converting it to baseband, sampling, capturing, tracking, Viterbi decoding and descrambling the baseband signal in sequence; wherein, The capture process includes: generating a pseudo code that is consistent with the spread spectrum code locally, calculating the cross-correlation value between the local pseudo code and the pseudo code of the received signal by utilizing the high autocorrelation characteristic of the pseudo code, detecting the result, searching for the maximum correlation peak, and completing signal capture; The tracking process includes: completing the synchronization of carrier phase and code phase through a carrier loop and a code loop, and then completing bit synchronization; The Viterbi decoding process includes: performing convolution decoding on the bit-synchronized data to restore the original data.

4. The satellite relay communication signal processing system according to claim 1, characterized in that: The processing process of the transmission signal processing module includes: Receive observation data processed by the data protocol processing module; Perform frame synchronization process; Parse the data packet and identify the working mode identifier to make working mode decisions: If the current working mode is the data service mode, convolution coding, scrambling, spread spectrum modulation and up-conversion will be performed in sequence to output the return data service signal; If the current working mode is the short message service mode, polarization coding, spread spectrum modulation and up-conversion are performed in sequence to output a return short message signal.

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

6. The satellite relay communication signal processing system according to claim 4, characterized in that: The polar coding processing process includes: Perform Kronecker product operation on the basic kernel matrix F = [1 0; 1 1] to construct an N×N generator matrix G; When encoding, the data to be encoded is placed in a reliable position, and the frozen position is filled with 0 to obtain a vector u of length N; The vector u is multiplied by the generator matrix G to obtain a codeword x after polar code encoding. The obtained codeword x is subjected to modulo 2 processing to generate a polar code sequence.

7. The satellite relay communication signal processing system according to claim 4, characterized in that: The processing process of the data protocol processing module includes: Parse the received control command data: If it is a buoy control command, the buoy control command is packaged and transmitted to the sea surface buoy platform according to the prescribed data format; If it is a return 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 packaged according to the updated return link data frame format, and transmitted to the transmission signal processing module through the serial port interface; If the return 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 packaged and transmitted to the transmission signal processing module.

8. The satellite relay communication signal processing system according to claim 7, characterized in that: The communication link switching strategy includes: Step 1: The shore-based end monitors the signal-to-noise ratio and bit error rate of the signal received by the relay satellite in real time. When the signal-to-noise ratio reaches the preset trigger threshold SNR_TH, the switching process is triggered and enters step 2; Step 2: The shore-based end adopts a hierarchical mechanism based on signal-to-noise ratio, dividing the signal-to-noise ratio into two level intervals, corresponding to high-quality channels and low-quality channels respectively. When the signal-to-noise ratio is in a high-quality channel, the data service mode is adopted; when the signal-to-noise ratio is in a low-quality channel, it is further judged based on 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; Step 3: The shore-based end sends a mode switching request command to the relay satellite; Step 4: The relay satellite sends a switching command to the signal processing system to notify the target to switch the 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 end receives the switched mode data, the link access is successful, and the switching execution phase ends.

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