CRC-Aided Polar Coding to Prevent Circular Shift CRC Ambiguity
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Solution Overview
Problem
Polar codewords in wireless communication systems exhibit repetition, leading to false CRC pass determinations and ambiguity in aggregation levels, which affects communication efficiency and accuracy.
Innovation Solution
An encoder is configured to place CRC bits at the beginning of the polar codeword and set them to non-zero values to reduce repetition, thereby improving the likelihood of non-zero CRC bits and minimizing leading zeros, allowing for implicit signaling and accurate aggregation level determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If polar codewords are transmitted with repetition for implicit signaling, then additional information can be conveyed through circular shifting, but false CRC pass determinations occur and aggregation level ambiguity arises
Solution Approach 1:
The patent applies CRC-aided polar coding before transmission to pre-validate the codeword structure. By performing CRC checking in advance and using the CRC bits to guide the decoding process, the system can distinguish valid codewords from false matches, thereby preventing false CRC pass determinations while maintaining implicit signaling through circular shifting
Solution Approach 2:
The patent introduces CRC bits as an intermediary element between the polar codeword and the validation process. These CRC bits act as a mediator that provides additional verification information, enabling the receiver to accurately determine whether a circularly shifted codeword is valid without ambiguously passing invalid codewords
2Adaptability or versatility
If circular shifting is used for implicit signaling of polar codewords, then transmission flexibility increases, but aggregation level ambiguity occurs
Solution Approach 1:
The patent employs feedback mechanisms where the receiver validates received circularly shifted codewords using CRC checks and reports back to the transmitter. This feedback loop enables the system to identify valid aggregation levels and resolve ambiguities by confirming which circular shifts produce valid CRC results, thereby maintaining transmission flexibility while improving aggregation level determination accuracy
3Device complexity
If polar encoding is performed with standard CRC placement, then encoding simplicity is maintained, but repetition in codewords causes false CRC passes
Solution Approach 1:
The patent segments the polar codeword structure by placing CRC bits at specific positions within the encoded sequence rather than as a separate appendix. This segmentation allows the CRC validation to occur at multiple points during decoding, enabling the system to detect and reject false CRC passes while maintaining relatively simple encoding complexity through structured bit placement
Data Source
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AI summary
Certain aspects of the present disclosure provide techniques for an improved encoder for reducing repetition in polar codewords. An apparatus for wireless communication is provided. The apparatus includes at least one processor. The at least one processor is coupled with a memory. The at least one processor includes at least one encoder circuit configured to encode a set of information bits based on a cyclic redundancy check (CRC)-aided polar code to produce a codeword including polar encoded information bits and CRC bits. The at least one encoder circuit is configured to place one or more of the CRC bits at a start of the codeword and to set a value of the one or more CRC bits to a non-zero value. The apparatus includes a transmitter configured to transmit the codeword in accordance with a wireless technology across a channel via one or more antenna elements situated proximate the transmitter.