Improving the decoding performance of CA-polar codes

TL;DR

This paper enhances CA-polar code decoding by integrating code-agnostic decoders to improve error rates and control undetected errors, achieving significant performance gains in 5G standards.

Contribution

It introduces a method to convert CA-SCL decoders into complete decoders using code-agnostic techniques, improving decoding success and error control.

Findings

Up to 0.2 dB gain in block error rate for standard CA-Polar codes.

Improved gain of 0.2 to 1 dB with systematic encoding.

Ability to control undetected error rate with recent soft output methods.

Abstract

We investigate the use of modern code-agnostic decoders to convert CA-SCL from an incomplete decoder to a complete one. When CA-SCL fails to identify a codeword that passes the CRC check, we apply a code-agnostic decoder that identifies a codeword that satisfies the CRC. We establish that this approach gives gains of up to 0.2 dB in block error rate for CA-Polar codes from the 5G New Radio standard. If, instead, the message had been encoded in a systematic CA-polar code, the gain improves to 0.2 ~ 1dB. Leveraging recent developments in blockwise soft output, we additionally establish that it is possible to control the undetected error rate even when using the CRC for error correction.