Binary duadic code[1]


Member of a pair of cyclic linear binary codes that satisfy certain relations, depending on whether the pair is even-like or odd-like duadic. Duadic codes exist for lengths \(n\) that are products of powers of primes, with each prime being \(\pm 1\) modulo \(8\) [2].

Duadic codes come in two pairs, an even-like duadic pair and an odd-like duadic pair. All codewords in the respective pairs are even-like, i.e., \(\sum_i c_i = 0\), or odd-like, i.e., \(\sum_i c_i = 1\). A code with all even-like (odd-like) codewords is called even-like (odd-like).

Duadic code pairs can be defined in terms of their idempotent generators (see Cyclic-to-polynomial correspondence). A pair of even-like codes \(C_1\) and \(C_2\) with respective idempotents \(e_1\) and \(e_2\) is an even-like duadic pair if (1) \(e_1(x)+e_2(x)=1-\frac{1}{n}(1+x+x^2+\cdots+x^{n-1})\) and (2) there exists a multiplier \(\mu\) such that \(C_1 \mu=C_2\) and \(C_2 \mu=C_1\).

There is an odd-like duadic pair \(\{D_1,D_2\}\) associated with the even-like pair \(\{C_1, C_2\}\), where \(1-e_2(x)\) generates \(D_1\) and \(1-e_1(x)\) generates \(D_2\). The even-pair codes are \([n,\frac{n-1}{2}]\) codes while the odd-pair codes are \([n,\frac{n+1}{2}]\) codes.


Since duadic codes are cyclic, the BCH bound can be used to determine their minimum distance.


Reviews of duadic codes [2][3].





J. Leon, J. Masley, and V. Pless, “Duadic Codes”, IEEE Transactions on Information Theory 30, 709 (1984). DOI
V. Pless, “Duadic Codes and Generalizations”, Eurocode ’92 3 (1993). DOI
W. C. Huffman and V. Pless, Fundamentals of Error-correcting Codes (Cambridge University Press, 2003). DOI

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“Binary duadic code”, The Error Correction Zoo (V. V. Albert & P. Faist, eds.), 2022.
@incollection{eczoo_binary_duadic, title={Binary duadic code}, booktitle={The Error Correction Zoo}, year={2022}, editor={Albert, Victor V. and Faist, Philippe}, url={} }
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“Binary duadic code”, The Error Correction Zoo (V. V. Albert & P. Faist, eds.), 2022.