Sequential Automorphism Ensemble Decoding with Early Stopping
For channel coding researchers, this provides a practical complexity reduction for automorphism ensemble decoding of polar codes.
The paper proposes a low-complexity sequential automorphism ensemble decoder that uses early stopping based on SC path metrics, reducing average decoding complexity by 6× to 22× with negligible BLER degradation below 10^{-3}.
In this paper, a low-complexity approach for the automorphism ensemble decoder (AED) using successive cancellation (SC) as constituent decoders is proposed. The approach sequentially activates sub-decoders and terminates the decoding process based on pre-optimized parameters, derived from the strong correlation observed between the decoding outcome and the SC path metric. An algorithm is proposed to find a list of early termination thresholds that minimize average decoding complexity subject to a block-error rate (BLER) constraint. For various code parameters and a BLER below $10^{-3}$, simulation results show that average decoding complexity is reduced by a factor of at least $6 \times$, and up to $22 \times$, compared to the original AED complexity, with a negligible degradation in BLER.