CN-122027005-A - Cross-layer reliability constraint system and method for low-orbit satellite

CN122027005ACN 122027005 ACN122027005 ACN 122027005ACN-122027005-A

Abstract

The invention provides a low-orbit satellite cross-layer reliability constraint system and a low-orbit satellite cross-layer reliability constraint method, wherein the system comprises a rate self-adaptive controller, the rate self-adaptive controller comprises a fine granularity rate adjustment module and a reliability constraint decision module which work cooperatively, the fine granularity rate adjustment module is used for realizing fine granularity continuous adjustment of a transmission rate by distributing non-uniform emission probability for constellation symbols and dynamically adjusting forming entropy under fixed basic modulation and coding formats, and the reliability constraint decision module is used for carrying out statistical modeling on physical layer decoding reliability and evaluating statistical confidence according to cumulative distribution functions of decoding success under different modulation and coding schemes. The invention realizes fine granularity continuous adjustment of the transmission rate through a probability shaping technology, and introduces a reliability constraint mechanism based on decoding statistical characteristics, thereby improving the throughput and link stability of the low-orbit satellite-ground communication under a dynamic channel.

Inventors

GAO YUE
CHEN ZHE
ZHANG YING
FENG YIMENG
YUAN PEIHONG

Assignees

复旦大学

Dates

Publication Date: 20260512
Application Date: 20260413

Claims (6)

1. The system is characterized by comprising a rate self-adaptive controller, wherein the rate self-adaptive controller comprises a fine granularity rate adjusting module and a reliability constraint decision module which work cooperatively, the fine granularity rate adjusting module is used for realizing fine granularity continuous adjustment of a transmission rate by distributing non-uniform transmission probability for constellation symbols and dynamically adjusting forming entropy under a fixed basic modulation and coding format, and the reliability constraint decision module is used for carrying out statistical modeling on physical layer decoding reliability and evaluating statistical confidence of the decoding success cumulative distribution function under different modulation and coding schemes.
2. The low-orbit satellite cross-layer reliability constraint system according to claim 1, wherein the fine-granularity rate adjustment module employs amplitude-phase keying modulation suitable for satellite communications and optimally designs a probability mass function of constellation symbols according to maxwell-boltzmann distribution.
3. The system of claim 1, wherein the reliability constraint decision module uses a confidence level not lower than a preset threshold as a hard constraint condition when making a rate adaptive decision, and preferentially selects a mode with highest spectral efficiency from all candidate modes meeting reliability requirements for transmission.
4. A method for cross-layer reliability constraint of a low-orbit satellite, the method comprising the steps of: Designing and deploying a fine granularity rate adjusting module based on probability shaping, and realizing fine granularity continuous adjustment of the transmission rate by distributing non-uniform emission probability for constellation symbols and dynamically adjusting shaping entropy under a fixed basic modulation coding scheme; Constructing and integrating a reliability constraint decision module based on decoding statistical characteristics, performing statistical modeling on the decoding reliability of a physical layer, and evaluating the statistical confidence of the physical layer according to cumulative distribution functions successfully decoded under different modulation and coding schemes; the plug-and-play rate self-adaptive controller is formed and integrated into a low-orbit satellite communication system, so that the link stability and the overall throughput of the system are improved.
5. The method according to claim 4, wherein the step of designing and deploying a fine granularity rate adjustment module based on probability shaping, and by allocating non-uniform transmission probabilities to constellation symbols and dynamically adjusting shaping entropy under a fixed basic modulation coding scheme, the fine granularity continuous adjustment of the transmission rate is realized, specifically comprises the step that the fine granularity rate adjustment function is realized by a probability shaping controller, at a transmitting end, the probability shaping controller is embodied as a probability shaping mapper integrated after the forward error correction coding module and before the constellation mapping module, and the core of the probability shaping mapper is a distribution matcher responsible for mapping uniformly distributed input bit streams into constellation symbol sequences conforming to non-uniform probability distribution.
6. The method for cross-layer reliability constraint of low-orbit satellite according to claim 4, wherein the step of constructing and integrating a reliability constraint decision module based on coding statistics, statistically modeling the reliability of physical layer coding, and evaluating the statistical confidence according to cumulative distribution functions of decoding success under different modulation and coding schemes comprises: and constructing and integrating a reliability constraint decision module based on decoding statistical characteristics, carrying out statistical modeling on the decoding reliability of a physical layer, evaluating the statistical confidence of the physical layer according to accumulated distribution functions of decoding success under different modulation and coding schemes, and when carrying out rate decision, taking the decoding confidence not lower than a preset threshold as a cross-layer constraint condition, and preferentially selecting the highest frequency spectrum efficiency mode meeting the reliability requirement, thereby converting the traditional hard decision switching depending on instantaneous signal to noise ratio into a soft decision based on statistical reliability, and effectively inhibiting frequent switching and system performance jitter of a critical signal to noise ratio region.

Description

Cross-layer reliability constraint system and method for low-orbit satellite Technical Field The invention relates to the technical field of satellite communication, in particular to a low-orbit satellite cross-layer reliability constraint system and method. Background In low-orbit satellite communication systems, in order to cope with rapid channel changes caused by high-speed motion of satellites, adaptive code modulation techniques are generally used to dynamically match channel conditions. MODCOD (modulation and coding scheme) is a core concept of the technology, which defines a combination of a specific modulation scheme and a channel coding scheme adopted for data transmission, and the system switches among a plurality of preset MODCOD levels to balance transmission rate and reliability under different channel quality. Conventional adaptive code modulation methods generally perform table look-up comparison with a preset SNR threshold according to a measurement result of an instantaneous SNR (Signal-to-Noise Ratio) of a forward link, so as to select the MODCOD with the highest spectral efficiency that can be supported under the current channel condition. The method can achieve a desirable balance between throughput efficiency and decoding reliability when channel conditions are relatively stable and instantaneous SNR is far from the switching threshold. However, when the SNR approaches the switching critical point of a certain MODCOD, even if the system determines the ideal SNR and the corresponding MODCOD based on theoretical calculation, significant performance fluctuation still occurs in actual operation. This phenomenon results mainly from the superposition of multiple factors, firstly, errors in the SNR measurement and estimation itself of the system, which are affected by noise interference, multipath fading and receiver non-ideal characteristics, resulting in that the instantaneous SNR estimate used for decision making does not exactly coincide with the true SNR value. Secondly, the high-speed motion of the low-orbit satellite, the rotation of the earth and the change of the shielding environment can lead the instantaneous SNR of the channel to rapidly fluctuate, so that the channel condition frequently crosses the switching threshold value in a short time, thereby repeatedly triggering the MODCOD switching. Furthermore, there are unavoidable processing and control delays for the system from SNR measurement to MODCOD decision-making, to parameter configuration and signaling. During this time the channel continues to change, resulting in the switching action lagging behind the ideal decision timing. Furthermore, the SNR threshold for MODCOD is typically designed based on long-term channel statistics, and each time the system is operated to face instantaneous channel conditions, the mismatch between such statistics and instantaneous conditions further increases the likelihood of performance jitter. Finally, threshold-based switching belongs to hard switching or discrete decision, i.e. SNR switches to another MODCOD level immediately as soon as the threshold is crossed. This non-adaptive switching mechanism can cause the system to repeatedly enter high-order and low-order modes around a threshold, resulting in severe fluctuations in throughput and Bit Error Rate (BER) in a short period of time. Accordingly, there is a need to provide a new method of rate adaptation that enables fine granularity, high stability. Disclosure of Invention Aiming at the defects in the prior art, the invention aims to provide a low-orbit satellite cross-layer reliability constraint system and a low-orbit satellite cross-layer reliability constraint method, which realize fine-granularity continuous adjustment of transmission rate through a probability shaping technology and introduce a reliability constraint mechanism based on decoding statistical characteristics so as to improve throughput and link stability of low-orbit satellite-to-satellite communication under a dynamic channel. In order to solve the problems, the technical scheme of the invention is as follows: The low-orbit satellite cross-layer reliability constraint system comprises a rate self-adaptive controller, wherein the rate self-adaptive controller comprises a fine granularity rate adjusting module and a reliability constraint decision module which work cooperatively, the fine granularity rate adjusting module is used for realizing fine granularity continuous adjustment of a transmission rate by distributing non-uniform transmission probability for constellation symbols and dynamically adjusting forming entropy under fixed basic modulation and coding formats, and the reliability constraint decision module is used for carrying out statistical modeling on physical layer decoding reliability and evaluating statistical confidence of decoding success cumulative distribution functions under different modulation and coding schemes. Preferably, the fine granularit