Polar IR-HARQ Retransmission Using Variable-Length Codewords
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Solution Overview
Problem
Current HARQ techniques for polar codes face limitations in achieving optimal coding gain and efficiency, particularly in incremental redundancy re-transmissions, compared to other error correction methods like LDPC codes.
Innovation Solution
Implementing polar encoding with incremental redundancy HARQ re-transmissions by generating multiple codewords of varying lengths, where each re-transmission includes different subsets of information and parity bits, allowing for improved decoding and error correction by overlapping and combining codewords.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polar codes use traditional HARQ re-transmission schemes, then implementation is simpler, but coding gain and transmission reliability are insufficient compared to LDPC codes
Solution Approach 1:
The polar code is segmented into multiple sub-codewords of different lengths. The original codeword is divided into a first sub-codeword and a second sub-codeword, where the first sub-codeword has a shorter length and the second sub-codeword has a longer length. This segmentation allows the encoder to transmit different portions of the code in different time slots, improving transmission reliability through incremental redundancy while managing encoding complexity through structured segmentation.
Solution Approach 2:
The encoding scheme dynamically adapts the codeword length and structure based on transmission conditions. The encoder can switch between transmitting the first sub-codeword alone, or combining it with the second sub-codeword, depending on whether re-transmission is needed. This dynamic adaptation allows the system to achieve LDPC-like reliability while maintaining polar code structure, resolving the contradiction between reliability and complexity.
2Productivity
If polar codes transmit fixed-length codewords, then encoding is straightforward, but efficiency is reduced compared to variable-length schemes
Solution Approach 1:
The fixed-length polar code is segmented into variable-length sub-codewords. The first sub-codeword has length N1 and the second sub-codeword has length N2, where N1 + N2 = N (original code length). This segmentation enables the encoder to transmit only the necessary portion in the first transmission and add redundant information in re-transmissions, improving transmission efficiency without requiring completely new encoding schemes.
Solution Approach 2:
The encoding scheme changes the effective code length parameter dynamically. By transmitting sub-codewords of different lengths (N1, N2) instead of a fixed length N, the system can adapt the transmission efficiency to channel conditions while maintaining the underlying polar code structure. This parameter change approach achieves variable-length efficiency with manageable complexity increases.
Data Source
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AI summary
performing a parity check by comparing the values of the one or more information bits obtained from the second part of the second codeword with parity bits in the first codeword. (17).An apparatus comprising: a processor; and a non-transitory computer readable storage medium storing programming for execution by the processor, the programming including instructions to implement actions in a method in accordance with any one of claims 1 to 16.