PD-sets for (nonlinear) Hadamard Z₄-linear codes

Publicació amb motiu de la 21st Conference on Applications of Computer Algebra (July 20-24, 2015, Kalamata, Greece

Partial permutation decoding for binary linear Hadamard codes

Permutation decoding is a technique which involves finding a subset S, called PD-set, of the permutation automorphism group PAut(C) of a code C in order to assist in decoding. A method to obtain s-PD-sets of size s + 1 for partial permutation decoding for the binary linear Hadamard codes H m of length 2 m , for all m ≥ 4 and 1 < s ≤ (2 m − m − 1)/(1 + m) , is described. Moreover, a recursive construction to obtain s-PD-sets of size s + 1 for H m+1 of length 2 m+1 , from a given s-PD-set of the same size for the Hadamard code of half length H m is also established

PD-sets for Z₄-linear codes : Hadamard and Kerdock codes

Permutation decoding is a technique that strongly depends on the existence of a special subset, called PD-set, of the permutation automorphism group of a code. In this paper, a general criterion to obtain s-PD-sets of size s+1, which enable correction up to s errors, for Z₄-linear codes is provided. Furthermore, some explicit constructions of s-PD-sets of size s+1 for important families of (nonlinear) Z₄-linear codes such as Hadamard and Kerdock codes are given

Z2Z4-additive codes

Altres ajuts: UAB PNL2006-13The Combinatoric, Coding and Security Group (CCSG) is a research group in the Department of Information and Communications Engineering (DEIC) at the Universitat Aut'onoma de Barcelona (UAB). The research group CCSG has been uninterruptedly working since 1987 in several projects and research activities on Information Theory, Communications, Coding Theory, Source Coding, Cryptography, Electronic Voting, Network Coding, etc. The members of the group have been producing mainly results on optimal coding. Specifically, the research has been focused on uniformly-packed codes; perfect codes in the Hamming space; perfect codes in distance-regular graphs; the classification of optimal codes of a given length; and codes which are close to optimal codes by some properties, for example, Reed-Muller codes, Preparata codes, Kerdock codes and Hadamard codes. Part of the research developed by CCSG deals with Z2Z4-linear codes. There are no symbolic software to work with these codes, so the members of CCSG have been developing this new package that supports the basic facilities for Z2Z4-additive codes. Specifically, this Magma package generalizes most of the known functions for codes over the ring Z4, which are subgroups of Zn4, to Z2Z4-additive codes, which are subgroups of Zγ2 × Zδ4, maintaining all the functionality for codes over Z4 and adding new functions which, not only generalize the previous ones, but introduce new variants when it is needed. A beta version of this new package for Z2Z4-additive codes and this manual with the description of all functions can be downloaded from the web page http://ccsg.uab.cat. For any comment or further information about this package, you can send an e-mail to [email protected]. The authors would like to thank Lorena Ronquillo, Jaume Pernas, Roger Ten-Valls, and Cristina Diéguez for their contributions developing some parts of this Magma package

Z2Z4-additive codes

Altres ajuts: UAB PNL2006-13The Combinatoric, Coding and Security Group (CCSG) is a research group in the Department of Information and Communications Engineering (DEIC) at the Universitat Aut'onoma de Barcelona (UAB). The research group CCSG has been uninterruptedly working since 1987 in several projects and research activities on Information Theory, Communications, Coding Theory, Source Coding, Cryptography, Electronic Voting, Network Coding, etc. The members of the group have been producing mainly results on optimal coding. Specifically, the research has been focused on uniformly-packed codes; perfect codes in the Hamming space; perfect codes in distance-regular graphs; the classification of optimal codes of a given length; and codes which are close to optimal codes by some properties, for example, Reed-Muller codes, Preparata codes, Kerdock codes and Hadamard codes. Part of the research developed by CCSG deals with Z2Z4-linear codes. There are no symbolic software to work with these codes, so the members of CCSG have been developing this new package that supports the basic facilities for Z2Z4-additive codes. Specifically, this Magma package generalizes most of the known functions for codes over the ring Z4, which are subgroups of Zn4, to Z2Z4-additive codes, which are subgroups of Zγ2 × Zδ4, maintaining all the functionality for codes over Z4 and adding new functions which, not only generalize the previous ones, but introduce new variants when it is needed. A beta version of this new package for Z2Z4-additive codes and this manual with the description of all functions can be downloaded from the web page http://ccsg.uab.cat. For any comment or further information about this package, you can send an e-mail to [email protected]. The authors would like to thank Lorena Ronquillo, Jaume Pernas, Roger Ten-Valls, and Cristina Diéguez for their contributions developing some parts of this Magma package

Binary codes : binary codes databases

Combinatorics, Coding and Security Group (CCSG).The research group CCSG (Combinatorics, Coding and Security Group) is one of the research groups in the dEIC (Department of Information and Communications Engineering) at the UAB (Universitat Autònoma de Barcelona) in Spain. From 1987 the team CCSG has been uninterruptedly working in several projects and research activities on Information Theory, Communications, Coding Theory, Source Coding, Teledetection, Cryptography, Electronic Voting, e-Auctions, Mobile Agents, etc. The more important know-how of CCSG is about algorithms for forward error correction (FEC), such as Golay codes, Hamming product codes, Reed-Solomon codes, Preparata and Preparata-like codes, (extended) nonlinear 1-perfect codes, Z4-linear codes, Z2Z4-linear codes, etc.; computations of the rank and the dimension of the kernel for nonlinear codes as binary 1-perfect codes, q-ary 1-perfect codes, Preparata codes, Hadamard codes, Kerdock codes, quaternary Reed-Muller codes, etc.; the existence and structural properties for 1-perfect codes, uniformly packed codes, completely regular codes, completely transitive codes, etc..