Recursive trellis decoding of polar codes is considered. Polar codes are shown to have much lower recursive trellis decoding complexity compared to similar Reed-Muller codes. Furthermore, a low-latency decoding algorithm, which combines recursive trellis and successive cancellation decoding methods, is presented.
A reduced complexity algorithm is presented for computing the log-likelihood ratios (LLRs) arising in the successive cancellation (SC) decoder for polar codes with large kernels of arbitrary dimension. The proposed algorithm exploits a recursive trellis representation of the codes generated by submatrices of the polarization kernel and enables polar codes based on large kernels to be decoded with lower complexity compared to the codes based on the Arıkan kernel with the same performance. Extensions to the case of non-binary kernels are presented.
Recursive decoding techniques are considered for Reed-Muller (RM) codes of growing length n and fixed order r. An algorithm is designed that has complexity of order nlogn and corrects most error patterns of weight up to n(1/2−ε) given that ε exceeds n−1/2r. This improves the asymptotic bounds known for decoding RM codes with nonexponential complexity.