A note on bounds for q-ary covering codes

Abstract

Two strongly seminormal codes over Z/sub 5/ are constructed to prove a conjecture of Ostergard (see ibid., vol.37, no.3, p.660-4, 1991). It is shown that a result of Honkala (see ibid., vol.37, no.4, p.1203-6, 1991) on (k,t)-subnormal codes holds also under weaker assumptions. A lower bound and an upper bound on K/sub q/(n, R), the minimal cardinality of a q-ary code of length n with covering radius R are obtained. These give improvements in seven upper bounds and twelve lower bounds by Ostergard for K/sub q/(n, R) for q=3, 4, and 5.