Polar Code Construction for IR-HARQ Reliability
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Solution Overview
Problem
In wireless communications, polar code construction for incremental redundancy hybrid automatic repeat request (IR-HARQ) schemes faces challenges due to discrepancies in channel metrics across codewords of different lengths, affecting the reliability of information bit indices and decoding operations.
Innovation Solution
An adjusted information bit index set is determined based on comparisons between reference bit index sets for various mother codeword lengths, selecting common and difference bit indices to improve the reliability of codeword decoding across retransmissions, using a flexible code construction that balances initial transmission performance with subsequent retransmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sequential transmissions of encoded bits with different puncturing configurations are used in IR-HARQ scheme, then redundancy is provided to improve decodability, but discrepancies in channel metrics across different codeword lengths affect the reliability of information bit indices
Solution Approach 1:
The patent applies parameter changes by adjusting the information bit index selection based on the codeword length. Different information bit indices are selected for different mother codeword lengths (M, 2M, 4M, etc.) to account for the changing channel metrics. This ensures that the most reliable bits are always used for decoding regardless of the transmission size, thereby maintaining decoding reliability across incremental redundancy transmissions.
Solution Approach 2:
The patent implements dynamics by making the information bit index set adaptive rather than fixed. The selected information bit indices dynamically change based on the current transmission's mother codeword length and the accumulated redundancy from previous transmissions. This dynamic adaptation allows the system to optimize decoding performance for each specific transmission scenario in the IR-HARQ sequence.
2Ease of operation
If polar code construction uses fixed information bit indices for all codeword lengths, then implementation is simplified, but decoding performance deteriorates due to mismatched reliability assumptions
Solution Approach 1:
The patent changes the parameter of information bit index selection from fixed to variable based on codeword length. For each mother codeword length (M, 2M, 4M, etc.), different information bit indices are selected to match the channel metrics characteristics. This ensures that the selected bits have consistent reliability across different transmission sizes, improving decoding performance without significantly complicating the implementation through the use of pre-defined index sets.
Data Source
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AI summary
A device may identify that an incremental redundancy hybrid automatic repeat request (IR-HARQ) scheme is used in association with sequential transmissions of an information bit vector to or from another wireless device, where each transmission in the scheme is associated with a resource size. The device may identify a mother code length for a polar code based at least in part on an aggregate resource size associated with the sequential transmissions. The device may identify an adjusted bit index set for the polar code based at least in part on the IR-HARQ scheme. The device may transmit (or receive), for each transmission of the information bit vector, a respective subset of encoded bits generated by mapping the information bit vector to a set of polarized bit channels of the polar code in accordance with the bit index set.