Distributed CRC Placement in Polar Codes for Faster Decoding
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Solution Overview
Problem
Polar codes face challenges with finite-length performance and high decoder latency due to serial decoding and energy expenditure on cyclic redundancy check (CRC) encoding, especially for short-to-medium block lengths.
Innovation Solution
The strategic placement of CRC bits within a polar code codeword, using a multi-dimensional interpretation of polar codes, and further encoding with non-polar codes to reduce decoding latency and improve performance, such as by distributing parity checks and inserting CRCs at specific locations based on criteria like channel transition states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard polar code encoding with CRC is used, then error correction capability is provided, but decoder latency increases and energy consumption increases
Solution Approach 1:
The patent segments the single CRC check at the end of decoding into multiple distributed CRC checks placed at intermediate locations within the codeword. This segmentation allows the decoder to verify error correction at multiple points during the decoding process, enabling early termination when errors are detected, thereby reducing overall decoder latency while maintaining error correction capability.
Solution Approach 2:
The patent performs preliminary error detection by placing CRC checks at intermediate locations before the final decoding step is completed. This preliminary action allows the system to detect and handle errors earlier in the decoding process, preventing propagation of errors through the entire decoding chain and reducing the time required for complete decoding.
2Reliability
If CRC encoding is performed for short-to-medium block lengths, then error detection capability is improved, but energy consumption increases
Solution Approach 1:
The patent applies partial CRC encoding by placing CRC checks only at strategically selected intermediate locations within the codeword rather than encoding the entire block with a single comprehensive CRC. This partial action provides sufficient error detection capability for short-to-medium block lengths while reducing the computational energy required compared to full-block CRC encoding.
3Device complexity
If serial decoding is used for polar codes, then decoding complexity is reduced, but decoder latency increases
Solution Approach 1:
The patent segments the serial decoding process into multiple stages with distributed CRC checks at intermediate points. While maintaining the fundamental serial decoding structure for complexity reasons, the segmentation enables early termination of the decoding process when errors are detected at intermediate CRC check points, thereby reducing the effective decoding latency without requiring complex parallel processing structures.
Data Source
AI summary
Certain aspects of the present disclosure relate to techniques and apparatus for improving decoding latency and performance of Polar codes. An exemplary method generally includes generating a codeword by encoding information bits, using a multi-dimensional interpretation of a polar code of length N, determining, based on one or more criteria, a plurality of locations within the codeword to insert error correction codes generating the error correction codes based on corresponding portions of the information bits, inserting the error correction codes at the determined plurality of locations, and transmitting the codeword. Other aspects, embodiments, and features are also claimed and described.