CN114221748A - Deep space low code rate data frame backtracking method - Google Patents
Deep space low code rate data frame backtracking method Download PDFInfo
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- CN114221748A CN114221748A CN202111440179.9A CN202111440179A CN114221748A CN 114221748 A CN114221748 A CN 114221748A CN 202111440179 A CN202111440179 A CN 202111440179A CN 114221748 A CN114221748 A CN 114221748A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L7/00—Arrangements for synchronising receiver with transmitter
- H04L7/0079—Receiver details
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
- H04L1/0056—Systems characterized by the type of code used
- H04L1/0057—Block codes
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
- Y02D30/00—Reducing energy consumption in communication networks
- Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks
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Abstract
The application provides a deep space low code rate data frame backtracking method, a method for backtracking data before frame synchronization, comprising: the judgment of a search state, a check state and a locking state is completed through frame synchronization processing, after the locking state is entered, frame synchronization is completed, and a frame synchronization state indication is output; recording the initial position of the first frame synchronization code group in the register after the frame synchronization code group is switched into the locking state; determining a backtracking initial position according to the frame length, the search frame number and the check frame number; and enabling the read pointer to point to the backtracking starting position to start backtracking data.
Description
Technical Field
The application relates to a deep space measurement and control communication method, in particular to a deep space low-code-rate data frame backtracking method.
Background
The deep space measurement and control communication system is the only means for the information interaction between the heaven and the earth of the deep space exploration task, the uplink communication link carries information transmission tasks such as remote control instructions, tracking navigation and attitude and orbit control, and the downlink communication link carries information transmission tasks such as scientific data, files, sounds and images, and is one of important guarantees for the success of the deep space exploration task. And the distance of the deep space target is too far, the signal path attenuation of different targets is very large, and for the solar system marginal target, the relative geosynchronous stationary orbit satellite path attenuation reaches 112 dB. Due to the limitations of weight, energy and power consumption of the spacecraft, signals transmitted by deep space spacecraft beyond billions of kilometers reach deep space ground stations and are very weak when the signals are received.
Because the energy of the downlink signal is very low, the high code rate cannot be transmitted, and only the data transmission with the extremely low code rate can be supported, and the minimum rate is only 8 bits/s. High code rate data cannot be transmitted in the track control and safety mode. Travelers No. 1 and No. 2 supported the lowest telemetry bit rate of 10bit/s, and the Mars Science Laboratory (MSL) supported the lowest telemetry bit rate of 10 bit/s. In order to increase the stability and the anti-interference capability of data receiving and demodulating, the correlation between information code words is enhanced by adopting channel coding. Under the condition of extremely low code rate, the data demodulation performance is deteriorated by the phase noise of the carrier root and the dynamic error of a phase-locked loop under the condition of weak signals. By adopting different channel codes, the efficiency can be improved, the overhead can be reduced, but the carrier capture, the data synchronization and the demodulation all need to consume longer time, the received data is limited, and each bit of data is very precious.
Disclosure of Invention
In view of the above situation, the present application provides a frame backtracking method under a deep space and extremely low code rate condition, which utilizes frame synchronization state information to backtrack related data before frame synchronization, and can maximally obtain valid data.
The application provides a method for backtracking data before frame synchronization, which comprises the following steps:
s1: the judgment of a search state, a check state and a locking state is completed through frame synchronization processing, after the locking state is entered, frame synchronization is completed, and a frame synchronization state indication is output;
s2: recording the initial position of the first frame synchronization code group in the register after the frame synchronization code group is switched into the locking state;
s3: determining a backtracking initial position according to the frame length, the search frame number and the check frame number;
s4: and enabling the read pointer to point to the backtracking starting position to start backtracking data.
In step S3, assuming that the starting position of the first frame synchronization code group after the transition to the locked state in the register is M, the frame length is L, the number of search frames is P, and the number of check frames is Q, the trace-back starting position is M- (P + Q) × L.
According to the method provided by an embodiment of the present application, in step S5, data with a length of L is sequentially read in sequence, and the total number of times is P + Q, so as to obtain a (P + Q) frame trace back and complete data output.
According to an embodiment of the present application, there is provided the method, wherein the step S5 further includes: and backtracking the data to obtain the data in the search frame and the check frame.
According to the method provided by an embodiment of the present application, the coding mode is RS + convolutional coding, the number of search frames is 1, and the number of check frames is 1.
According to the method provided by one embodiment of the application, the encoding mode is LDPC encoding, the number of search frames is 1, and the number of check frames is 3.
The present application also provides a computer readable storage medium having stored thereon software instructions, which when executed, implement the above-described method.
The application also provides a system for backtracking data before frame synchronization, which is used for executing the method.
The invention has the following effective effects:
1. the number of frames of the acquired valid data increases. In a Mars detection task, the method is successfully applied to telemetering data reception under the conditions of a surround device and a Mars vehicle with extremely low code rate, and the number of received effective data frames is 2-4 more than that of the received effective data frames in a traditional mode.
2. The efficiency of data transmission is improved. In a Mars detection task, the method is successfully applied to telemetering data reception under the condition of extremely low code rate of the surround device and the Mars vehicle, and the transmission efficiency is improved by 13-40% compared with that of the traditional method.
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The above features, technical features, advantages and modes of realisation of the present application will be further described in the following detailed description of preferred embodiments in a clearly understandable manner, in conjunction with the accompanying drawings. The drawings are only for purposes of illustrating and explaining the present application and are not to be construed as limiting the scope of the present application. Wherein:
fig. 1 shows a schematic diagram of tri-state logic conversion and output of a conventional frame synchronizer.
Fig. 2 is a schematic diagram of tri-state logic conversion and output after frame backtracking is introduced.
Fig. 3 is a backtracking frame data output flow.
Detailed Description
In order to more clearly understand the technical features, objects, and effects of the present application, embodiments of the present application will now be described with reference to the accompanying drawings.
An important objective of the present application is to utilize the valid frame synchronization status information to trace back the data before frame synchronization, so as to obtain the valid data to the maximum extent.
Under the condition of deep space and extremely low code rate, the total data receiving amount is limited, and each bit of data is very precious. Aiming at the problems that in the traditional frame synchronization processing process, carrier capture, data synchronization and demodulation all need to consume longer time and the data acquisition amount is small, the method for backtracking the data frame during tristate logic conversion in the frame synchronization process by using effective frame synchronization locking state information is provided, multi-frame reliable telemetering data can be effectively acquired, the method is particularly suitable for receiving deep space low code rate data, and has wide practical engineering application prospect in subsequent asteroid, Jupiter and solar system marginal detection tasks.
The invention is based on the principle that: on the basis of traditional frame synchronization, after the tristate logic converter finishes frame synchronization judgment, data in the tristate logic conversion process is traced back by using reliable frame synchronization state indication, and a corresponding effective traced back data frame is obtained.
The invention provides a method for backtracking data before frame synchronization by using effective frame synchronization state information, wherein a schematic diagram of three-state logic conversion and output is shown in fig. 2, and a backtracking frame data output flow is shown in fig. 3.
As shown in fig. 2 and 3, a method for backtracking data before frame synchronization according to an embodiment of the present application includes:
s1: and setting parameters such as a current frame Synchronization code set (ASM), a frame length, a fault-tolerant frame number, a checking frame number and the like.
The parameters are necessary for frame synchronization processing, and subsequent frame synchronization can be performed after the parameters are set.
S2: and acquiring the frame synchronization state indication after the three-state logic conversion of the synchronizer.
In this step, the existing frame synchronization processing method is adopted, and after the frame synchronization work is started, the judgment of the search state, the check state and the locking state is completed according to the relevant states. After entering the locking state, the frame synchronization is completed, and a frame synchronization state indication is output. Reference may be made to CCDSS 130.1-G-3. TM Synchronization and Channel Coding-Summary of Concept and ratio.
S3: the first ASM after the record synchronizer has shifted to the lock state has its home position in the register recorded as M.
S4: and determining the backtracking initial position according to the frame length, the search frame number and the check frame number.
Assuming that the frame length is L, the number of search frames is P, and the number of check frames is Q, the backtracking start position is M- (P + Q) × L.
S5: and enabling the read pointer to point to a backtracking starting position M- (P + Q) × L and starting backtracking data.
And sequentially reading the data with the length of L according to the sequence, counting for P + Q times, obtaining the (P + Q) frame backtracking, and finishing data output.
Because the frame synchronization is completed, a frame introduces a backtracking mechanism to backtrack data in the frame synchronization process, correct frame synchronization code groups can be backtracked to obtain effective data, and therefore search frames and check frames in the frame synchronization process are converted into effective data frames, and the number of the effective data frames is increased to the maximum extent.
The following describes the method for backtracking data before frame synchronization according to the present invention in detail with reference to specific examples.
In a certain task, two detectors are respectively a detector 1 and a detector 2, a frame synchronization code group is 1ACFFCID (H), the coding mode can be RS + convolutional coding or LDPC coding, and the telemetering or data transmission code rate is 32 bit/s.
When RS + convolutional coding is adopted, the optimal search frame number and the check frame number are set to be (1, 1), wherein the search frame 1 and the check frame 1 are adopted, and the effective data frames output by the backtracking method are 2 more than the effective data frames output by the traditional method.
When LDPC coding is adopted, the optimal search frame number and check frame number are set to be (1, 3), wherein the search frame 1 and the check frame 3 are set, and the effective data frames output by the backtracking method are 4 more than the effective data frames output by the traditional method.
The time of the detector 1 before and after orbit control is considered according to 30min (15 frames), the effective observation arc length of the detector 1 to the ground under a safety mode is considered according to 24min (12 frames), and the working time of the detector 2 is considered according to 20min (10 frames) due to energy balance. Under the condition of extremely weak signal level, the carrier capture and bit synchronization consumption are considered according to 2 frames of time, and under the conditions, the data receiving situation of the ground adopting a traditional mode and a backtracking frame mode is shown in table 1.
Table 1 application of the frame backtracking method in a mars detection task
Therefore, under the condition of the same coding mode, the number of effective receiving frames is obviously increased after a backtracking mechanism is introduced. For different encoding modes, due to the difference of frame parameter settings, the number of effective frame receptions is different. Under the working condition, after a backtracking mechanism is introduced, the effective frame receiving ratio is improved by 40%. It should be noted that if the transmission time is short and frame synchronization cannot be completed, the valid data frame cannot be obtained by using the conventional mechanism and the trace-back mechanism.
It should be understood that although the present description has been described in terms of various embodiments, not every embodiment includes only a single embodiment, and such description is for clarity purposes only, and those skilled in the art will recognize that the embodiments described herein may be combined as suitable to form other embodiments, as will be appreciated by those skilled in the art.
The above description is only illustrative of the present invention and is not intended to limit the scope of the present invention. Any equivalent alterations, modifications and combinations that may be made by those skilled in the art without departing from the spirit and principles of this application shall fall within the scope of this application.
Claims (8)
1. A method of backtracking data prior to frame synchronization, comprising:
s1: the judgment of a search state, a check state and a locking state is completed through frame synchronization processing, after the locking state is entered, frame synchronization is completed, and a frame synchronization state indication is output;
s2: recording the initial position of the first frame synchronization code group in the register after the frame synchronization code group is switched into the locking state;
s3: determining a backtracking initial position according to the frame length, the search frame number and the check frame number;
s4: and enabling the read pointer to point to the backtracking starting position to start backtracking data.
2. The method according to claim 1, wherein in step S3, assuming that the start position of the first frame sync code group after shifting to the locked state in the register is M, the frame length is L, the number of search frames is P, and the number of check frames is Q, the trace-back start position is M- (P + Q) × L.
3. The method according to claim 2, wherein in step S5, data with length L are sequentially read in sequence, and the total number of times is P + Q, and a (P + Q) frame backtrack is obtained to complete data output.
4. The method of claim 1, wherein step S5 further comprises: and backtracking the data to obtain the data in the search frame and the check frame.
5. The method of claim 1, wherein the coding scheme is RS + convolutional coding, the number of search frames is 1, and the number of check frames is 1.
6. The method of claim 1, wherein the encoding mode is LDPC encoding, the number of search frames is 1, and the number of check frames is 3.
7. A computer readable storage medium having stored thereon software instructions that, when executed, implement the method of any of claims 1-6.
8. A system for backtracking data prior to frame synchronization, for performing the method according to any one of claims 1-6.
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