Permuted successive cancellation decoder for polar codes
Harish Vangala, Emanuele Viterbo, Yi Hong · 2014
Abstract—We study a new variant of Arikan’s successive cancellation decoder (SCD) for polar codes. We first propose a new decoding algorithm on a new decoder graph, where the various stages of the graph are permuted. We then observe that, even though the usage of the permuted graph doesn’t affect the encoder, it can significantly affect the decoding performance of a given polar code. The new permuted successive cancellation decoder (PSCD) typically exhibits a performance degradation, since the polar code is optimized for the standard SCD. We then present a new polar code construction rule matched to the PSCD and show in simulations that this can yield BER gains for high code rates. For lower rates we observe that the polar code matched to a given PSCD performs as well as the original polar code with the standard SCD. We also see that a PSCD with a reversal permutation can lead to a natural decoding order, avoiding the standard bit-reversal decoding order in SCD without any loss in performance. Keywords—Successive cancellation decoder, permuted succes-sive cancellation decoder, decoding order, permuted polar code construction, permutation invariance of the polar encoder. I.