Polar Code HARQ Retransmission With Bit Index Mapping
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Solution Overview
Problem
Polar codes in current wireless communication systems do not support Hybrid Automatic Repeat reQuest (HARQ) for data transmission, particularly in the 6G system, due to issues with codeword generation and bit channel index allocation, leading to inefficiencies in system performance.
Innovation Solution
A method for generating and transmitting codewords based on polar codes, where the size of the second polar code is 2n times the size of the first polar code, with specific bit channel index allocation strategies to ensure compatibility and reliability for Incremental Redundancy (IR) HARQ, including copy operations to maintain codeword integrity during retransmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the size of the polar code for retransmission is made different from the size of the polar code for first transmission, then the code rate can be adjusted to match channel conditions, but the data bits are allocated to bit channel indices determined in an order according to the reliability of the polar encoder, causing the codeword generated for first transmission to not be included in the codeword generated for the retransmission
Solution Approach 1:
The patent changes the parameter of bit channel index allocation by introducing a mapping relationship between bit channel indices of different code rates. When the code rate changes between first transmission and retransmission, the patent establishes a correspondence between the bit channel indices of the original code rate and the new code rate, ensuring that data bits are allocated to the same logical positions despite the parameter change. This allows the codeword from first transmission to be properly included in the retransmission codeword for IR-HARQ combining.
2Quantity of substance
If a shortening operation is applied to codeword generation for initial transmission, then the codeword size is reduced to match available resources, but the allocation of data bits to the bit channel index of the polar encoder becomes different between initial transmission and retransmission, making IR-HARQ unsupported
Solution Approach 1:
The patent performs preliminary allocation of bit channel indices before the shortening operation is applied. By determining the mapping relationship between bit channel indices in advance, before the codeword size is reduced, the patent ensures that the same data bits are allocated to consistent logical positions even after the shortening operation changes the physical codeword size. This preliminary action enables IR-HARQ to function properly despite the subsequent size reduction.
3Measurement precision
If the bit channel index allocation is determined in an order according to the reliability of the polar encoder, then the decoding performance is optimized, but the codeword generated for first transmission is not included in the codeword generated for the retransmission when code rates differ
Solution Approach 1:
The patent introduces a bit channel index mapping relationship as an intermediary layer between the polar encoder's reliability-based allocation and the actual codeword generation. This mapping acts as a mediator that translates the reliability-optimized bit channel indices from the first transmission to the corresponding indices in the retransmission, even when code rates differ. This intermediary mapping preserves the decoding performance optimization while enabling proper codeword inclusion for HARQ.
Data Source
AI summary
A method by which a first wireless device transmits a signal on the basis of a hybrid automatic repeat request (HARQ) in a wireless communication system, according to one embodiment of the present specification, comprises the steps of: generating a first codeword on the basis of a first polar code; transmitting the first codeword; generating a second codeword on the basis of a second polar code; and transmitting the second codeword.