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CN-122027790-A - Efficient coding and decoding and distributing transmission method for satellite image data

CN122027790ACN 122027790 ACN122027790 ACN 122027790ACN-122027790-A

Abstract

The invention relates to the technical field of satellite communication and discloses a high-efficiency coding, decoding and distributing transmission method of satellite image data, which comprises the steps of obtaining satellite epoch parameters and estimating a downlink channel capacity sequence, decomposing the image data into a basic characteristic code stream and a background residual code stream, distributing transmission priority, mapping the basic characteristic code stream to the most significant bit of a modulation symbol, mapping the background residual code stream to the least significant bit of the modulation symbol, and carrying out nonlinear displacement stretching on constellation point coordinates where the modulation symbol is located according to carrier frequency shift variation rate.

Inventors

  • WU HAO
  • LI WANG
  • ZHANG LIN
  • LUO WEN

Assignees

  • 湖南数界科技有限公司

Dates

Publication Date
20260512
Application Date
20260413

Claims (9)

  1. 1. The efficient encoding and decoding and distributing transmission method for satellite image data is characterized by comprising the following steps: Step S1, acquiring satellite epoch parameters of a satellite-borne navigation receiver in real time, inputting the satellite epoch parameters into a preset orbit prediction model, calculating a transient geometric distance and carrier frequency shift of a downlink in a preset communication time window, and calculating a channel capacity sequence representing throughput limit values of each communication time slot based on a space propagation loss model; s2, decomposing satellite image data to be transmitted into a basic characteristic code stream carrying a key topological structure and a background residual code stream carrying detail texture information through airspace pixel gradient distribution calculation; Step S3, coupling scheduling is carried out on transmission time sequences of the basic characteristic code stream and the background residual code stream in a preset communication time window according to the dynamic evolution trend of the channel capacity sequence; S4, establishing an image space conforming to the multi-system quadrature amplitude modulation, mapping a basic feature code stream to the most significant bit of a complex plane quadrant of a modulation symbol, and mapping a background residual error code stream to the least significant bit of a sub-coordinate position of the modulation symbol in the quadrant; Step S5, calculating the derivative of the carrier frequency shift with respect to time at the current moment according to the satellite epoch parameters to obtain the carrier frequency shift variation rate, and carrying out nonlinear displacement stretching on the physical coordinates of constellation points of the modulation symbols in the complex plane according to the carrier frequency shift variation rate so as to increase the minimum Euclidean distance of the most significant bit in the axial direction of the phase judgment; and S6, packaging the satellite image data into a frame structure conforming to a space data link protocol, and transmitting the modulation symbols subjected to nonlinear displacement stretching processing to a ground receiving station in a preset communication time window.
  2. 2. The efficient encoding, decoding and distributing transmission method of satellite image data according to claim 1, wherein the step S2 includes the step S21 of performing pixel neighborhood gradient estimation on the satellite image data to be transmitted, extracting structural components representing a target boundary and encoding the structural components into a basic feature code stream, the step S22 of calculating algebraic residuals between the satellite image data to be transmitted and the structural components to obtain detailed components representing texture density and encoding the detailed components into a background residual code stream, and the step S23 of allocating a first transmission priority to the basic feature code stream and allocating a second transmission priority lower than the first transmission priority to the background residual code stream.
  3. 3. The method for efficient encoding, decoding and distributing transmission of satellite image data according to claim 1, wherein step S3 includes step S31 of monitoring channel state indexes of downlink in real time, wherein the channel state indexes include carrier-to-noise ratio, step S32 of stopping mapping of background residual code stream when the channel state indexes are lower than a first preset threshold value, performing single stream transmission of basic feature code stream only, and step S33 of performing asymmetric multiplexing of the basic feature code stream and the background residual code stream when the channel state indexes are between the first preset threshold value and a second preset threshold value.
  4. 4. The efficient encoding, decoding and distributing transmission method of satellite image data according to claim 1, wherein step S4 includes step S41 of dividing a complex plane coordinate system of a mapping space into four quadrant regions, step S42 of determining a quadrant region to which a modulation symbol belongs according to a bit logic state of a basic feature code stream, and step S43 of determining a specific point position coordinate of the modulation symbol in the quadrant region to which the modulation symbol belongs according to a bit logic state of a background residual code stream.
  5. 5. The method for efficient encoding, decoding and distributing transmission of satellite image data according to claim 1, further comprising, after step S6, step S7 of obtaining a reception parameter returned by a ground receiving station through a feedback link, the reception parameter including an error rate and a phase error variance, step S8 of calculating a bias compensation vector between the reception parameter and a predicted value outputted by a orbit prediction model, and step S9 of correcting a predicted weight of a channel capacity sequence in a subsequent time step by using the bias compensation vector.
  6. 6. The method for efficient encoding, decoding and distributing transmission of satellite image data according to claim 2, wherein step S21 includes step S211 of identifying a target region of interest in the satellite image data to be transmitted by using a saliency detection operator, and step S212 of allocating quantization bits higher than a background region to pixels in the target region of interest, and using the pixel data quantized by high bit width as generation source data of a basic feature code stream.
  7. 7. The method according to claim 1, wherein in step S1, the prediction process of the channel capacity sequence integrates a free space path loss model and symbol timing synchronization deviation constraints generated by rapid carrier frequency drift, and outputs a maximum allowable code rate limit for each coherence time interval within a predetermined communication time window.
  8. 8. The method according to claim 1, wherein in step S5, nonlinear displacement stretching is started when the carrier frequency shift variation exceeds a preset distortion tolerance threshold, and the offset vectors are distributed along the normal direction of the phase decision boundary of the modulation symbol to offset the constellation point coordinate ambiguity caused by the carrier phase fast rotation.
  9. 9. The method according to claim 1, wherein the satellite image data is encapsulated into a protocol frame conforming to CCSDS standard before being transmitted in step S6, and the average transmission power of the modulation symbol is kept constant by synchronously adjusting the modulation amplitude ratio during the nonlinear displacement stretching process.

Description

Efficient coding and decoding and distributing transmission method for satellite image data Technical Field The invention relates to a high-efficiency coding, decoding and distributing transmission method for satellite image data, and belongs to the technical field of satellite communication. Background With the continuous expansion of the constellation scale of the high-resolution earth observation satellite, the image data flow carried by the satellite-earth link shows a growing trend, the related protocol standard of the consultation committee of the space data system is mainly adopted at present, the data return efficiency is tried to be improved in a limited over-the-ground visible window by utilizing the adaptive coding modulation technology, however, because the low-orbit satellite has higher radial acceleration relative to the ground station, severe transient Doppler change rate is generated in key communication time slots such as zenith intersections and the like, the physical phenomenon causes the phase domain distortion of the decision boundary of the high-order modulation symbol in a complex plane, and the conventional channel evaluation mechanism is mainly anchored in the signal-to-noise ratio fluctuation of an energy domain, lacks microscopic perception capability on the phase evolution trend, and causes the system to show vulnerability when facing the phase storm. The traditional modulation and coding control logic has limitations on high dynamic link distortion, for example, china patent application with publication number of CN110138438A discloses a modulation method for improving satellite communication spectrum efficiency, orbital angular momentum OAM is introduced as physical dimension, information mapping is realized by utilizing OAM wave orthogonality to improve spectrum utilization rate, the method relies on precise geometric centering of a wave beam propagation axis and a receiving array in engineering, radial acceleration and Doppler variation rate are generated by low orbit satellite transit to cause wave beam drift and phase jitter, orthogonality induction detection between OAM modes is interfered to lose efficacy, the technology does not touch constellation decision space collapse bottom mechanism, physical layer isolation protection cannot be provided for key semantic data, robustness under phase noise impact does not meet high-fidelity image transmission requirements, when the phase distortion is processed, conventional logic tries to forcedly suppress noise by increasing satellite-borne transmitting power or improving antenna gain of a ground station, but the method not only increases satellite load quality and energy consumption, but also cannot radically correct constellation geometric deformation caused by orbital dynamic characteristics, but returns to low-order thinking mode, the method cannot cause serious bandwidth occupation of key data in the critical communication window to severely occupy the critical bandwidth, and further cause serious resource occupation of the key data to be wasted. Therefore, how to construct a transmission system of deep coupling image semantic topological features and transient channel phase distortion parameters in the process of maintaining efficient distribution of satellite image data realizes logical isolation and anti-destruction guarantee aiming at core observation data at a symbol judgment level, and becomes the technical problem to be solved by the invention. Disclosure of Invention In order to solve the problems in the background technology, the technical scheme of the invention is as follows, a high-efficiency encoding, decoding and distributing transmission method for satellite image data comprises the following steps: Step S1, acquiring satellite epoch parameters of a satellite-borne navigation receiver in real time, inputting the satellite epoch parameters into a preset orbit prediction model, calculating a transient geometric distance and carrier frequency shift of a downlink in a preset communication time window, and calculating a channel capacity sequence representing throughput limit values of each communication time slot based on a space propagation loss model; s2, decomposing satellite image data to be transmitted into a basic characteristic code stream carrying a key topological structure and a background residual code stream carrying detail texture information through airspace pixel gradient distribution calculation; Step S3, coupling scheduling is carried out on transmission time sequences of the basic characteristic code stream and the background residual code stream in a preset communication time window according to the dynamic evolution trend of the channel capacity sequence; S4, establishing an image space conforming to the multi-system quadrature amplitude modulation, mapping a basic feature code stream to the most significant bit of a complex plane quadrant of a modulation symbol, and mapping a background residual