It is shown that the residue code of a self-dual ℤ4 -code of length 24k (resp. 24k + 8) and minimum Lee weight 8k + 4 or 8k + 2 (resp. 8k + 8 or 8k + 6) is a binary extremal doubly even self-dual code for every positive integer k. A number of new self-dual ℤ4 -codes of length 24 and minimum Lee weight 10 are constructed using the above characterization. These codes are Type I ℤ4 -codes having the largest minimum Lee weight and the largest Euclidean weight among all Type I ℤ4 -codes of that length. In addition, new extremal Type II ℤ4 -codes of length 56 are found.
ASJC Scopus subject areas
- コンピュータ ネットワークおよび通信