We present new MAP decoding algorithms for first order Reed-Muller and Hamming codes. The proposed algorithms have complexities proportional to n/spl times/log/sub 2/(n), where n is the code length.
A maximum a posteriori (MAP) probability decoder of a block code minimizes the probability of error for each transmitted symbol separately. The standard way of implementing MAP decoding of a linear code is the Bahl-Cocke-Jelinek-Raviv (BCJR) algorithm, which is based on a trellis representation of the code. The complexity of the BCJR algorithm for the first-order Reed-Muller (RM-1) codes and Hamming codes is proportional to n/sup 2/, where n is the code's length. In this correspondence, we present new MAP decoding algorithms for binary and nonbinary RM-1 and Hamming codes. The proposed algorithms have complexities proportional to q/sup 2/n log/sub q/n, where q is the alphabet size. In particular, for the binary codes this yields complexity of order n log n.
In this paper we are interested in MAP decoding of first order Reed-Muller and Hamming codes. A MAP decoder of a linear code computes a-posteriori probabilities for all values of each transmitted symbol and chooses the maximum one. The standard way of doing this is the BCJR algorithm. This algorithm is based on a trellis representation of a code. Such a representation allows one to reduce the complexity of MAP decoding, though it still remains exponential. The BCJR algorithm for binary first order Reed-Muller and Hamming codes has complexity proportional to n/sup 2/, where n is the code length. In this paper we propose a new MAP decoding algorithm for both RM-1 and Hamming codes with complexity proportional to nlog/sub 2/n.
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.
New soft- and hard decision decoding algorithms are presented for general Reed-Muller codes $\left\{\genfrac{}{}{0pt}{}{m}{r}\right\} $ of length 2m and distance 2m−r. We use Plotkin (u,u+v) construction and decompose code $\left\{\genfrac{}{}{0pt}{}{m}{r}\right\} $ onto subblocks $u\in\left\{\genfrac{}{}{0pt}{}{m-1}{r}\right\} $ and v∈{r−1m−1}. In decoding, we first try to find a subblock v from the better protected code and then proceed with the block u. The likelihoods of the received symbols are recalculated in a way similar to belief propagation. Thus, decoding is relegated to the two constituent codes. We repeat this recursion and execute decoding only at the end nodes $\left\{\genfrac{}{}{0pt}{}{j}{1}\right\} $ and $\left\{\genfrac{}{}{0pt}{}{j}{j-1}\right\} $. The overall complexity has low order of nlogn. It is shown that this decoding substantially outperforms other algorithms of polynomial complexity known for RM codes. In particular, for medium and high code rates, the algorithm corrects most error patterns of weight dlnd/2.
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-/spl epsiv/) given that /spl epsiv/ exceeds n/sup -1/2r/. This improves the asymptotic bounds known for decoding RM codes with nonexponential complexity. To evaluate decoding capability, we develop a probabilistic technique that disintegrates decoding into a sequence of recursive steps. Although dependent, subsequent outputs can be tightly evaluated under the assumption that all preceding decodings are correct. In turn, this allows us to employ second-order analysis and find the error weights for which the decoding error probability vanishes on the entire sequence of decoding steps as the code length n grows.