Satellite Link Coding With Redundant Code Blocks for Fewer Retransmissions
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Solution Overview
Problem
Satellite communication systems face challenges in ensuring decoding accuracy and reducing transmission delay due to high altitude and long distances, which are exacerbated by the need for retransmissions in conventional HARQ technologies.
Innovation Solution
The method involves generating a redundant code block based on multiple code blocks of equal length, performing channel coding on these blocks, and transmitting them over a satellite channel, allowing the receiving apparatus to determine a priori log-likelihood ratios and combine them for improved decoding accuracy, thereby reducing the need for retransmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If HARQ retransmission is used to ensure decoding accuracy, then decoding reliability is improved, but transmission delay increases due to long satellite communication distance
Solution Approach 1:
The patent applies preliminary action by generating a redundant code block before transmission based on the original code blocks. This redundant block serves as pre-prepared backup information that can be used immediately if decoding fails, eliminating the need for wait-and-retransmit cycles. The redundant code block is created using XOR operations on the original code blocks, ensuring it contains complementary information that can rescue decoding without requiring retransmission over the long satellite channel.
Solution Approach 2:
The patent implements beforehand cushioning by introducing a redundant code block as a protective buffer against decoding failures. This redundant block acts as a cushion that absorbs potential decoding errors, allowing the receiver to attempt decoding using the redundant information first before resorting to time-consuming retransmissions. The cushioning effect is achieved through the mathematical relationship between original and redundant code blocks, providing a safety net that reduces reliance on retransmission mechanisms.
2Reliability
If redundant code blocks are generated and transmitted, then decoding accuracy is improved, but transmission data volume increases
Solution Approach 1:
The patent applies copying by creating a redundant code block that is mathematically derived from the original code blocks through XOR operations. This redundant block is essentially a calculated copy that contains complementary information rather than being an exact duplicate. The copying process generates a block of the same size as the original, but with different information content that can be used to recover from decoding errors, thus increasing reliability without requiring transmission of multiple full copies of the data.
Data Source
AI summary
This application provides encoding and decoding methods to reduce retransmission in satellite communication. A sending apparatus obtains an information transport block, where the information transport block includes a plurality of code blocks; and generates a redundant code block based on at least two of the plurality of code blocks. The at least two code blocks and the redundant code block are sent over a satellite channel after channel coding. A receiving apparatus receives the to-be-decoded information over the satellite channel, calculates, based on the to-be-decoded information of the at least two code blocks and the redundant code block, an a priori log-likelihood ratio of a to-be-decoded bit, and combines the a priori log-likelihood ratio and a log-likelihood ratio obtained after demodulation, to obtain a diversity gain. Decoding is performed based on the combined log-likelihood ratio. This method improves decoding accuracy and reduces the need for retransmission.