Type II Codes over F4

AbstractThe natural analogues of Lee weight and the Gray map over F4 are introduced. Self-dual codes for the Euclidean scalar product with Lee weights multiple of 4 are called Type II. They produce Type II binary codes by the Gray map. All extended Q-codes of length a multiple of 4 are Type II. This includes quadratic residue codes attached to a prime p≡3 (mod8), certain double circulant codes, and some affine invariant codes. A general mass formula is derived, a new upper bound for Euclidean self-dual codes over F4 is given, and the first extremal self-dual [92, 46, 16] binary code is built

Different aspects of q-ary images of codes

This paper is a survey on results concerning q-ary images of codes over Fq m mainly about cyclic codes, doubly even binary self dual codes and applications to decoding.Cet article fait le point sur des résultats obtenus concernant la démultiplication des codes sur F qm (image q-aire) principalement à propos des codes cycliques, de codes autoduaux binaires à poids multiples de quatre et d'applications au décodage