CN-122001449-A - Satellite-to-ground laser communication-oriented adaptive modulation switching method

CN122001449ACN 122001449 ACN122001449 ACN 122001449ACN-122001449-A

Abstract

The invention provides a satellite-to-ground laser communication-oriented adaptive modulation switching method, which improves the performance of a communication system by using 16QAM and BPSK modulation adaptive switching. And introducing an atmospheric turbulence estimation module into the receiving end, feeding back the estimated atmospheric channel state information to the transmitting end by using an estimated value of the atmospheric turbulence intensity of the satellite-to-ground laser communication, and switching a modulation mode of the transmitting end according to a threshold value to realize low-delay reliable transmission of the satellite-to-ground laser communication.

Inventors

LIU ZHI
MA XINYU
Du Heqi

Assignees

长春理工大学

Dates

Publication Date: 20260508
Application Date: 20260211

Claims (7)

1. A satellite-to-ground laser communication-oriented adaptive modulation switching method is characterized by comprising the following steps: S1, sending an original information sequence into a CRC encoder, and forming a cyclic redundancy check code word according to a generator polynomial and a generator matrix; s2, inputting the cascade CRC-Poalr code generated in the step S1 into an interleaver, and scrambling an information sequence code element sequence, then selecting a modulation mode according to the turbulence intensity of the current satellite-to-ground laser communication channel, and finally transmitting the modulation mode to a channel of the satellite-to-ground laser communication system; S3, demodulating the information received by the receiving end in the step S2, de-interleaving the demodulated information, and recovering an information sequence; S4, performing cyclic redundancy check operation on the cascade CRC-Poalr codes restored in the step S3 to obtain polarization codes, and recovering the original information sequence through a continuous elimination list decoder.
2. The adaptive modulation switching method for satellite-to-ground laser communication according to claim 1, wherein step S1 comprises: S1.1, calculating information bits according to a CRC polynomial to obtain check bits; S1.2, adding the obtained check bit as a new information bit to the original information to obtain a cyclic redundancy check information sequence; s1.3, taking the obtained cyclic redundancy check information sequence as input information, and performing initial polarization change operation; S1.4, carrying out corresponding mathematical computation on the information sequence and the polarization code generation matrix to obtain a cascade CRC-Poalr code which is sent to the channel.
3. The adaptive modulation switching method for satellite-to-ground laser communication according to claim 1, wherein step S2 comprises: S2.1, the information is affected by atmospheric turbulence in the satellite-to-ground laser communication channel transmission process, the information sequence can generate a long-string error phenomenon, the error correction upper limit can be possibly reached, the error information sequence is continuously transmitted, and the problem of long-string error can be solved by adopting a random interleaver to disturb the information sequence order.
4. The adaptive modulation switching method for satellite-to-ground laser communication according to claim 3, wherein step S2 further comprises: S2.2, transmitting the information sequence randomly interleaved by the interleaver into a modulator for modulation; s2.3, modulating the signals according to different turbulence intensity values transmitted by the receiving end and the modulation modes correspondingly adopted according to the divided different turbulence intensities, and transmitting the modulated signals into a satellite-to-ground channel.
5. The adaptive modulation switching method for satellite-to-ground laser communication according to claim 1, wherein step S3 comprises: S3.1, demodulating the received information sequence through a demodulator, and sending the demodulated information sequence into a de-interleaver; s3.2, the disturbed interleaving is restored into an original sequence by adopting de-interleaving, and the correct de-interleaving sequence is sent to an error correction code decoding module; and S3.3, estimating the atmospheric turbulence intensity information of the channel by adopting a moment method.
6. The adaptive modulation switching method for satellite-to-ground laser communication according to claim 1, wherein step S4 comprises: S4.1, initializing a path list, wherein each path has corresponding probability and decoding state; S4.2, processing each bit ui bit, and carrying out different processing according to whether the bit ui bit is an information bit or a frozen bit, wherein the frozen bit is 0 in all paths, the information bit is divided into two paths, the current bit is 0 or 1 respectively, the probability of each path is calculated, L paths with the maximum probability are reserved after each division, and the rest paths are discarded.
7. The adaptive modulation switching method for satellite-to-ground laser communication according to claim 5, wherein step S4 further comprises S4.3CRC checking assistance, namely obtaining a candidate bit sequence from each path after decoding is completed, performing CRC (cyclic redundancy check) on each candidate sequence, screening out sequences meeting CRC, selecting the path with the best measurement if a plurality of paths pass the CRC, and selecting the path with the best measurement as a final output if the paths do not pass the CRC.

Description

Satellite-to-ground laser communication-oriented adaptive modulation switching method Technical Field The application relates to the technical field of satellite-ground laser communication, in particular to a method for improving system performance by modulating satellite-ground laser communication under atmospheric turbulence disturbance. Background With the rapid development of the information industry, the information transmission requirement in satellite communication is rapidly increased, and higher requirements are placed on performances such as communication capacity and speed. In satellite communication, for large capacity, high speed and high safety which are difficult to realize by traditional microwave communication, a satellite communication technology with higher transmission speed and better communication safety is required to be sought, and the wireless laser communication just can make up for the current shortages of the microwave communication in the satellite communication field. The satellite-ground laser technology is used as a key link of satellite optical communication, is a bridge for connecting a satellite network and a ground optical fiber network, and is an important point of current research. The polarization code has a regular coding structure and a coding and decoding algorithm with low complexity, and has excellent performance and low implementation complexity under the condition of short codes, so that the polarization code has very strong practical application significance in the satellite-to-ground laser communication process. In satellite-to-ground laser communication systems, a single modulation mode is often used, which brings adverse effects of low spectrum utilization rate or high system error rate under medium-intensity turbulence to the system, and the problem is solved by adopting proper modulation switching. Under weak turbulence, the frequency spectrum utilization rate of the communication system can be improved by adopting 16QAM modulation, under medium-strong turbulence, the system robustness can be enhanced by adopting BPSK modulation, and the communication quality of a communication link is ensured, so that the 16QAM-BPSK modulation switching mode has very strong practical application value in a satellite-to-ground communication system. Disclosure of Invention The application introduces a polarization code 16QAM-BPSK modulation switching technology into satellite-to-ground laser communication, adopts 16QAM under the condition of weak turbulence intensity to ensure the spectrum efficiency of the system, reduces the error rate in the satellite-to-ground laser communication system by sacrificing the spectrum efficiency of the system under medium-strong turbulence, improves the capability of the communication system for resisting the interference of atmospheric turbulence, and increases the stability of information transmission of the satellite-to-ground laser communication system. In order to achieve the above object, the present application provides a method for improving system performance by using a polarization code and a 16QAM-BPSK modulation switching technique for satellite-to-ground laser communication under the disturbance of atmospheric turbulence, comprising the steps of: S1, sending an original information sequence into a CRC encoder, and forming a cyclic redundancy check code word according to a generator polynomial and a generator matrix; S2, inputting the cascade CRC-Poalr codes generated in the step S1 into an interleaver, and scrambling the information sequence code element sequence. Then, a modulation mode is selected according to the turbulence intensity of the current satellite-to-ground laser communication channel, and finally the modulation mode is transmitted to a channel of a satellite-to-ground laser communication system; S3, demodulating the information received by the receiving end in the step S2, de-interleaving the demodulated information, and recovering an information sequence; s4, performing cyclic redundancy check operation on the restored cascade CRC-Poalr codes to obtain polarization codes, and recovering original information sequences by using a continuous elimination list decoder; 2. the method for improving system performance by using modulation switching for satellite-to-ground laser communication under atmospheric turbulence as recited in claim 1, wherein step S1, determining the polarization code encoding method comprises: S1.1, calculating information bits according to a CRC polynomial to obtain check bits; S1.2, adding the obtained check bit as a new information bit to the original information to obtain a cyclic redundancy check information sequence; s1.3, taking the obtained cyclic redundancy check information sequence as input information, and performing initial polarization change operation; s1.4, carrying out corresponding mathematical computation on the information sequence and the polarization code generation matrix