This paper focuses on the recently introduced Successive Cancellation Flip(SCFlip) decoder of polar codes. Our contribution is twofold. First, we proposethe use of an optimized metric to determine the flipping positions within theSCFlip decoder, which improves its ability to find the first error thatoccurred during the initial SC decoding attempt. We also show that the proposedmetric allows closely approaching the performance of an ideal SCFlip decoder.Second, we introduce a generalisation of the SCFlip decoder to a number of$\omega$ nested flips, denoted by SCFlip-$\omega$, using a similar optimizedmetric to determine the positions of the nested flips. We show that theSCFlip-2 decoder yields significant gains in terms of decoding performance andcompetes with the performance of the CRC-aided SC-List decoder with list sizeL=4, while having an average decoding complexity similar to that of thestandard SC decoding, at medium to high signal to noise ratio.
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