Polar Code Decoder Scoring to Limit Error Propagation
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Solution Overview
Problem
Existing mechanisms for decoding polar codes are prone to error propagation due to the successive decoding procedure, which can lead to decoding errors, and require significant processing to determine candidate scores, often ignoring the impact of bits to come later.
Innovation Solution
A method and information decoder that traverse a polar code diagram, determining bit score terms and adding an adjustment term to form candidate scores for each potential decoding decision, repeating the process until all bits are decoded, and discarding all but one candidate sequence to produce a single decoded sequence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If successive decoding procedure is used to decode polar codes, then decoding can be performed in bit-order, but error propagation occurs and decoding reliability deteriorates
Solution Approach 1:
The patent segments the decoding process into multiple independent candidate paths instead of following a single successive decoding path. By maintaining multiple candidate sequences and evaluating them independently, the method prevents error propagation from affecting the entire decoding process, thus improving reliability while maintaining decoding efficiency.
Solution Approach 2:
The patent performs preliminary evaluation of multiple candidate decoded sequences before final selection. By calculating adjustment terms and candidate scores in advance for all possible paths, the decoder can select the most reliable sequence without propagating errors from early decisions, thereby resolving the contradiction between decoding speed and accuracy.
2Productivity
If candidate scores are calculated based on bits processed so far, then decoding can proceed sequentially, but the impact of future bits is ignored leading to suboptimal decoding decisions
Solution Approach 1:
The patent introduces feedback by calculating adjustment terms that incorporate information from future bits. The candidate score is updated by adding an adjustment term that reflects the impact of yet-to-be-decoded bits, allowing the decoder to make more accurate decisions while maintaining sequential processing efficiency.
Solution Approach 2:
The patent performs preliminary calculation of adjustment terms that anticipate the impact of future bits on candidate scores. This allows the decoder to consider future bit impacts in advance without waiting for actual decoding, improving score accuracy while maintaining decoding speed.
3Reliability
If list decoding with multiple candidate branches is used, then decoding reliability improves, but processing complexity increases significantly
Solution Approach 1:
The patent extracts only the essential adjustment term calculation from the full candidate evaluation process. By focusing on calculating and adding adjustment terms to existing candidate scores rather than performing complete re-evaluation, the method maintains improved reliability through multiple candidates while significantly reducing processing complexity.
Solution Approach 2:
The patent changes the parameter representation by using adjustment terms that can be added to existing candidate scores. This incremental update approach allows maintaining multiple candidate paths for improved reliability while reducing the computational burden compared to complete re-evaluation, thus lowering processing complexity.
Data Source
AI summary
There is provided mechanisms for decoding an encoded sequence into a decoded sequence. A method is performed by an information decoder. The method comprises obtaining a channel output. The channel output represents the encoded sequence as passed through a communications channel. The encoded sequence has been encoded using a polar code. The polar code is representable by a code diagram. The method comprises successively decoding the channel output into the decoded sequence by traversing the code diagram. The method comprises, whilst traversing the code diagram, determining a bit score term for each potential decoding decision on one or more bits being decoded. The method comprises, whilst traversing the code diagram, adding an adjustment term to each bit score term to form a candidate score for said each potential decoding decision. The successive decoding is repeated until all bits of the channel output have been decoded, resulting in at least two candidate decoded sequences. The method comprises discarding all but one of the at least two candidate decoded sequences, resulting in one single decoded sequence.