Equidistant frequency permutation arrays and related constant composition codes

This paper introduces and studies the notion of an equidistant frequency permutation array (EFPA). An EFPA of length n = mλ, distance d and size v is defined to be a v×n array T such that 1) each row is a multipermutation on a multiset of m symbols, each repeated with frequency λ, and 2) the Hamming distance between any two distinct rows of T is precisely d. Such an array generalizes the well-studied equidistant permutation array: it corresponds to a special kind of constant composition code (CCC). Bounds and constructions are obtained for EFPAs and related CCCs (many optimal), and links with other combinatorial structures are explored.