High-reliability multi-target real-time telemetering system

Abstract

The invention relates to a high-reliability multi-target real-time telemetering system, and belongs to the field of communication. Each target telemetering unit takes the data comprehensive integrated device as a core, is additionally provided with a spread spectrum telemetering unit or a frequency modulation telemetering unit according to respective work task requirements, and selects different frequency point and pseudo code combinations to form respective communication links; the data comprehensive integrated device is provided with a data link port, so that ad-hoc networking among different target telemetering units can be realized; the spread spectrum telemetry unit adopts a PCM-CDMA-BPSK spread spectrum telemetry system, a target address is distinguished through a code pattern, and sent signals are allowed to use the same frequency band at the same time. The frequency modulation telemetry unit adopts a PCM-FM system and TPC coding, and a reliable interval is kept between frequency points and frequency points selected by the spread spectrum telemetry unit. The problems that a traditional spacecraft telemetering system is single, the number of communication units is limited, link interference is large, and the space environment is limited are solved.

Description

Technical Field

[0001] The invention belongs to the field of communications and relates to a high-reliability multi-target real-time telemetry system. Background Art

[0002] In traditional aerospace communication systems, a specific communication system is mainly used to achieve single target tracking telemetry. In recent years, multi-target real-time telemetry technology has received widespread attention. Each target unit can work in parallel and interact with the ground platform in real time. At the same time, each target unit has the ability to form a network and realize data backup telemetry through data sharing within the region. Faced with a new working scenario, the limitations of the traditional telemetry communication mode are highlighted:

[0003] a) The communication system is single and cannot adapt to multiple application scenarios;

[0004] b) Poor scalability and limited number of target units;

[0005] c) Electromagnetic interference is serious, spectrum resources are limited, and when multiple units work at the same time, the communication links interfere with each other greatly, reducing the signal transmission quality;

[0006] d) Affected by the space environment, when interference is introduced into the communication link or the rocket-ground antenna cannot be directly aligned, communication will be temporarily interrupted, and reliability is difficult to guarantee in complex environments. Summary of the invention

[0007] The technical problem solved by the present invention is: to solve the problems of single telemetry system, limited number of communication units, large link interference, restricted space environment, etc. of traditional spacecraft, a high-reliability multi-target real-time telemetry system is proposed.

[0008] The solution of the present invention is:

[0009] A highly reliable multi-target real-time telemetry system, each target telemetry unit takes the data integrated device as the core, and selects different frequency points and pseudo code combinations according to the requirements of their respective work tasks to form their own communication links;

[0010] Data integration device: equipped with data link interface, capable of realizing self-organizing network between different target telemetry units; adding spread spectrum telemetry unit or frequency modulation telemetry unit to realize two telemetry systems; responsible for collecting and summarizing data of each target telemetry unit, and making comprehensive framing according to frame format requirements, and then sending the data to the ground platform through antenna feed wireless after modulation and amplification by frequency modulation telemetry unit and spread spectrum telemetry unit;

[0011] Spread spectrum telemetry unit: PCM-CDMA-BPSK spread spectrum telemetry system is adopted, and the target address is distinguished by code type, allowing the transmitted signals to use the same frequency band at the same time; M typical frequency points are selected in the available frequency band, and N groups of orthogonal pseudo codes are selected for each frequency point, so as to divide a maximum of M×N communication links;

[0012] FM telemetry unit: adopts PCM-FM system and TPC coding; the frequency point maintains a reliable interval with the frequency point selected by the spread spectrum telemetry unit to avoid signal crosstalk; the reliable interval between FM signals is set to no less than 1+a times the signal bandwidth, and the reliable interval between spread spectrum signal frequencies is set to no less than 2 times the pseudo code rate, where a is the modulation index of the FM telemetry unit.

[0013] Preferably, redundant transmission is achieved between target telemetry units via backup links.

[0014] Preferably, during the design, multiple target telemetry units are grouped according to spatial distribution, and internal information multicast communication is realized through data link close-range networking within the group, and communication bandwidth is effectively utilized through TDMA; a network time reference is formed within the group, and time slot division is performed;

[0015] Each group periodically selects an external interaction node to realize data communication between groups; based on the data link network, when a communication link is interfered with or the ground platform fails to capture, the target telemetry unit data will be broadcast to the external interaction node within the group, and then transmitted to other groups with good communication through the external interaction node, and further transmitted to the ground platform to realize data backup link transmission.

[0016] Preferably, the inter-group communication adopts an end-to-end mode.

[0017] Preferably, the time slot includes a synchronization segment, an information segment and a protection segment;

[0018] The synchronization segment is used for frequency hopping synchronization search, the information segment is used to send telemetry data, and the protection segment is used for data encryption field to achieve protected transmission.

[0019] Preferably, the ground receiving station adopts a cross-correlation interference suppression algorithm to first separate the strong signal from the medium-strong signal, and then separate the medium-strong signal from the weak signal, and sequentially receives the strong signal, the medium-strong signal, and the weak signal through three-level demodulation.

[0020] Preferably, the inter-group nodes use a Doppler frequency offset compensation algorithm to ensure reliable synchronization between the data receiving end and the data sending end during link communication. The Doppler frequency offset compensation algorithm is as follows:

[0021] The data receiving end calculates the frequency deviation between the received signal and the set frequency point:

[0022] f mS =f r -f0

[0023] Among them, f mS is the received signal frequency deviation, f r is the carrier frequency of the received signal, f0 is the carrier frequency set for the received signal;

[0024] Adjust the transmission frequency according to the calculated frequency deviation. The adjustment method is: obtain the current carrier Doppler value from the receiving channel, and perform conversion compensation according to the set center frequency of the receiving and transmitting channels:

[0025]

[0026] Among them, f mL is the frequency deviation compensation for the return signal, f1 is the static carrier frequency of the return signal;

[0027] f out =f1-f mL

[0028] Among them, f out It is the actual carrier frequency of the return signal.

[0029] Preferably, for the nodes within the group, on the one hand, a dynamic networking method is designed at the network layer and the data link layer to ensure that the information of each node is transmitted in an orderly manner and has corresponding network entry and exit strategies; on the other hand, coherent frequency hopping technology is used at the physical layer to achieve interference avoidance of high-speed signals and have lower signal merging losses.

[0030] The beneficial effects of the present invention compared with the prior art are:

[0031] The present invention uses CDMA to implement code division multiple access, and can support real-time telemetry of data from multiple target telemetry units at the same time. It supports both spread spectrum and frequency modulation communication systems. Each unit can adapt to high-speed communication requirements and multiple application scenarios by adding a frequency modulation telemetry unit; adding a spread spectrum telemetry unit can enhance anti-interference capabilities and achieve highly reliable communication. When receiving multi-target data on the ground, a cross-correlation interference suppression algorithm is used to isolate strong interference signals and parse out target signals. Self-organizing networks can be realized between target telemetry units, and each target telemetry unit can transmit data to adjacent units to achieve backup telemetry of key data, ensuring high reliability of data transmission in complex environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Schematic diagram of the multi-target telemetry system architecture;

[0033] Figure 2 Block diagram of cross-correlation interference mitigation principle;

[0034] Figure 3 Time Division Multiple Access (TDMA) architecture;

[0035] Figure 4 Schematic diagram of data backup telemetry. DETAILED DESCRIPTION

[0036] The present invention will be further described below in conjunction with the embodiments.

[0037] To solve the above problems, the present invention proposes a highly reliable multi-target real-time telemetry system. With the continuous increase in the number of communication targets, code division multiple access (CDMA) has gradually become the research focus in the field of wireless communications. CDMA can achieve simultaneous multi-target responses under limited frequency band resources, effectively reduce link interference, and greatly increase the number of communication units. At the same time, the use of direct sequence spread spectrum (DSSS) improves the processing gain and enhances the anti-interference ability of communication. In order to adapt to multi-scenario applications, combined with the frequency modulation communication system, short-distance high-speed data transmission is achieved. Units whose communication links are interfered with can complete information forwarding through neighboring units to achieve external real-time communication and have link backup capabilities.

[0038] Figure 1 This is a schematic diagram of the multi-target telemetry system architecture. In the multi-target real-time telemetry system, each target telemetry unit takes the data integration device as the core, and selects different frequency points and pseudo code combinations according to their respective work task requirements to form their own communication links. The data integration device has a data link interface, which can realize self-organizing networking between different telemetry units and transmit key data. Add a spread spectrum telemetry unit or a frequency modulation telemetry unit to realize two telemetry systems. The data integration device is responsible for collecting and summarizing data, and performs comprehensive framing according to the frame format requirements, and then sends it to the ground platform through the antenna feed wirelessly.

[0039] The spread spectrum telemetry unit adopts the PCM-CDMA-BPSK spread spectrum telemetry system. The target address is distinguished by the code type, allowing the transmitted signals to use the same frequency band at the same time, and the synchronization requirements are low. At the same time, the spread spectrum system has strong anti-interference and anti-fading capabilities, which can improve the communication reliability of the system. M typical frequency points are selected in the available frequency band, and N groups of orthogonal pseudo codes are selected for each frequency point to divide up to M×N communication links. Through the division in the frequency domain and the code domain, the interference between the links is reduced, which makes it possible to reliably realize multi-unit real-time communication.

[0040] The frequency modulation telemetry unit adopts the PCM-FM system, the modulation index is a, and TPC coding is used to achieve high-speed communication. The frequency point selection should maintain a reliable interval with the spread spectrum link frequency point to avoid signal crosstalk. The reliable interval between frequency modulation signals is set to no less than 1+a times the signal bandwidth, and the reliable interval between spread spectrum signal frequencies is set to no less than 2 times the pseudo code rate.

[0041] Multi-unit telemetry signals exist simultaneously in space. Due to spatial distribution, the signal strength will be different when transmitted to the same ground receiving station. The out-of-band interference of strong signals will have a certain impact on the reception of weak signals. In order to further enhance the anti-interference ability of signal reception, the ground receiving station adopts a cross-correlation interference suppression algorithm. Algorithm principle: First, the strong signal is separated from the medium-strong signal, and then the medium-strong signal is separated from the weak signal. Then, the strong signal, medium-strong signal, and weak signal can be demodulated through three-level demodulation. The block diagram of the cross-correlation interference mitigation principle is as follows: Figure 2 shown.

[0042] To improve the reliability of data transmission, redundant transmission can be achieved between target telemetry units through backup links to enhance data transmission reliability. The backup links are implemented based on ad hoc network technology.

[0043] A large number of communication units are divided into multiple groups according to spatial distribution during design. The internal information multicast communication is realized through data link close-range networking within the group, and the communication bandwidth is effectively utilized through TDMA (time division multiplexing). A network time base is formed within the network and time slots are divided. The time slot contains synchronization segment, information segment and protection segment. The synchronization segment is used for frequency hopping synchronization search, the information segment is used to send telemetry data, and the protection segment is used for data encryption field to realize protection transmission. Figure 3 shown.

[0044] Each group will periodically select external interaction nodes to achieve data communication between groups, and the communication between groups adopts end-to-end mode. Based on the data link network, when a communication link is interfered or the ground platform fails to capture, the data of the communication unit can still be transmitted to the ground platform through the backup link. Figure 4 For example, the wireless link between the A1 communication unit of group A and the ground platform is disturbed, and the data cannot be telemetered. However, the communication unit will broadcast the key data within the group and further transmit it to group C through the external interaction node. Group C transmits the data to the ground platform through the C6 node with normal communication link to realize data backup transmission.

[0045] The number of nodes in the group is huge and their functions are different, so high-speed networking and reliable communication need to be achieved at a higher information rate. On the one hand, it is necessary to design intelligent communication protocols and dynamic networking methods at the network layer and data link layer to ensure that the information of each node is transmitted in an orderly manner and has corresponding network entry and exit strategies; on the other hand, coherent frequency hopping technology is used at the physical layer to achieve interference avoidance of high-speed signals and have lower signal merging losses.

[0046] The dynamic networking methods are as follows:

[0047] After each node joins the network, it periodically queries the communication status of surrounding nodes and elects external interaction nodes. Based on the information interaction between nodes, each node calculates the shortest communication link to reach other nodes in the group to achieve data communication within the network. The time division multiplexing algorithm is used for communication scheduling. The external interaction node can automatically adjust the time slot occupancy status of each node according to the business volume, thereby improving the time slot utilization of the entire system. As the spatial link changes, the group can elect to dynamically replace the external interaction node and update the communication link between the nodes in the group to ensure the reliability of data interaction.

[0048] For inter-group nodes, which have the characteristics of long transmission distance and large speed deviation, dynamic Doppler frequency deviation will be generated during signal transmission, affecting the synchronization of signal reception. Inter-group nodes need to use Doppler frequency deviation compensation algorithm to calculate the frequency difference between the received signal and the set frequency point, adjust the transmission frequency according to the calculated frequency deviation, and ensure reliable synchronization between the data receiving end and the sending end during return link communication. The adjustment method is as follows:

[0049] When the nodes in the group communicate, the receiving end obtains the current carrier frequency from the receiving channel when receiving the signal; and obtains the site information of the current signal by analyzing the signal to determine the pre-set carrier frequency of the signal. The Doppler frequency deviation value is obtained by calculation. Then, the conversion compensation is performed according to the pre-set carrier frequency of the received signal and the carrier frequency of the transmitted return signal, that is, the transmitted signal is compensated according to the specified multiple of the Doppler frequency deviation of the received signal to ensure that the return signal can be reliably synchronized and received.

[0050] Specifically, the Doppler frequency offset compensation algorithm is as follows:

[0051] The data receiving end calculates the frequency deviation between the received signal and the set frequency point:

[0052] f mS =f r -f0

[0053] Among them, f mS is the received signal frequency deviation, f r is the carrier frequency of the received signal, f0 is the carrier frequency set for the received signal;

[0054] Adjust the transmission frequency according to the calculated frequency deviation. The adjustment method is: obtain the current carrier Doppler value from the receiving channel, and perform conversion compensation according to the set center frequency of the receiving and transmitting channels:

[0055]

[0056] Among them, f mL is the frequency deviation compensation for the return signal, f1 is the static carrier frequency of the return signal;

[0057] f out=f1-f mL

[0058] Among them, f out It is the actual carrier frequency of the return signal.

[0059] The data integration device includes a data link interface, a spread spectrum telemetry unit, a frequency modulation telemetry unit, a waveguide, a baseband processing module, a data integration module, and a power module. The data link interface can realize networking between target telemetry units and data sharing; the data integration module receives and summarizes the data of each target telemetry unit and other systems, and sends it to the baseband processing module; the baseband processing module compiles the received telemetry data into frequency modulation telemetry frames and spread spectrum telemetry frames, sends the frequency modulation telemetry frames to the frequency modulation telemetry unit, and sends the spread spectrum telemetry frames to the spread spectrum telemetry unit; the frequency modulation telemetry unit and the spread spectrum telemetry unit modulate and amplify the frequency modulation telemetry frames and the spread spectrum telemetry frames, connect the transmitting antenna through the waveguide, and send the telemetry data; the equipment adopts an integrated power distribution design, and the power module is used to power the above modules.

[0060] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A high-reliability multi-target real-time telemetry system, characterized by: Each target telemetry unit takes the data integrated device as the core and selects different frequency points and pseudo code combinations according to the requirements of their respective work tasks to form their own communication links; Data integration device: equipped with data link interface, capable of realizing self-organizing network between different target telemetry units; adding spread spectrum telemetry unit or frequency modulation telemetry unit to realize two telemetry systems; responsible for collecting and summarizing data of each target telemetry unit, and making comprehensive framing according to frame format requirements, and then sending the data to the ground platform through antenna feed wireless after modulation and amplification by frequency modulation telemetry unit and spread spectrum telemetry unit; Spread spectrum telemetry unit: PCM-CDMA-BPSK spread spectrum telemetry system is adopted, and the target address is distinguished by code type, allowing the transmitted signals to use the same frequency band at the same time; M typical frequency points are selected in the available frequency band, and N groups of orthogonal pseudo codes are selected for each frequency point, so as to divide a maximum of M×N communication links; FM telemetry unit: adopts PCM-FM system and TPC coding; The frequency point maintains a reliable interval with the frequency point selected by the spread spectrum telemetry unit to avoid signal crosstalk; the reliable interval between frequency modulation signals is set to be no less than 1+a times the signal bandwidth, and the reliable interval between spread spectrum signal frequency points is set to be no less than 2 times the pseudo code rate, where a is the modulation index of the frequency modulation telemetry unit.

2. A high-reliability multi-target real-time telemetry system according to claim 1, characterized in that: Redundant transmission is achieved between each target telemetry unit through a backup link.

3. The high-reliability multi-target real-time telemetry system according to claim 1, characterized in that: During the design, multiple target telemetry units are grouped according to spatial distribution, and the internal information multicast communication is realized through data link close-range networking within the group, and the communication bandwidth is effectively utilized through TDMA; A network time reference is formed within the group and time slots are divided; Each group periodically elects external interaction nodes to achieve data communication between groups; Based on the data link network, when a communication link is interfered with or the ground platform fails to capture, the target telemetry unit data will be broadcast to the external interaction node within the group, and then transmitted to other groups with good communication through the external interaction node, and further transmitted to the ground platform to realize data backup link transmission.

4. A high-reliability multi-target real-time telemetry system according to claim 3, characterized in that: Inter-group communication adopts end-to-end mode.

5. The high-reliability multi-target real-time telemetry system according to claim 3 is characterized by: The time slot contains synchronization segment, information segment and protection segment; The synchronization segment is used for frequency hopping synchronization search, the information segment is used to send telemetry data, and the protection segment is used for data encryption field to achieve protected transmission.

6. A high-reliability multi-target real-time telemetry system according to claim 1, characterized in that: The ground receiving station adopts a cross-correlation interference suppression algorithm to first separate the strong signal from the medium-strong signal, and then separate the medium-strong signal from the weak signal. Through three-level demodulation, the strong signal, medium-strong signal, and weak signal are received in turn.

7. The high-reliability multi-target real-time telemetry system according to claim 1, characterized in that: The inter-group nodes use a Doppler frequency offset compensation algorithm to ensure reliable synchronization between the data receiving end and the data sending end during link communication. The Doppler frequency offset compensation algorithm is as follows: The data receiving end calculates the frequency deviation between the received signal and the set frequency point: f mS =f r -f0 Among them, f mS is the received signal frequency deviation, f r is the carrier frequency of the received signal, f0 is the carrier frequency set for the received signal; Adjust the transmission frequency according to the calculated frequency deviation. The adjustment method is: obtain the current carrier Doppler value from the receiving channel, and perform conversion compensation according to the set center frequency of the receiving and transmitting channels: Among them, f mL is the frequency deviation compensation for the return signal, f1 is the static carrier frequency of the return signal; in out =f1-f mL Among them, f out It is the actual carrier frequency of the return signal.

8. The high-reliability multi-target real-time telemetry system according to claim 1, characterized in that: For the nodes within the group, on the one hand, dynamic networking methods are designed at the network layer and data link layer to ensure that information of each node is transmitted in an orderly manner and has corresponding network entry and exit strategies; on the other hand, coherent frequency hopping technology is used at the physical layer to avoid interference of high-speed signals and has lower signal merging loss.

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