Inequivalent Hadamard Matrices from Near Normal Sequences

llias S. Kotsireas1, Christos Koukouvinos2, Dimitris E. Simos2
1Department of Phys. and Comp. Sci. Wilfrid Laurier University Waterloo ON, N2L 3C5, Canada
2Department of Mathematics National Technical University of Athens Zografou 15773, Athens, Greece

Abstract

In this paper, we construct inequivalent Hadamard matrices based on Yang multiplication methods for base sequences which are obtained from near normal sequences. This has been achieved by employing various Unix tools and sophisticated techniques, such as metaprogramming. In addition, we present a classification for near normal sequences of length \( 4n + 1 \), for \( n \leq 11 \) and some of these for \( n = 12, 13, 14, 15 \), taking into account previously known results. Finally, we improve several constructive lower bounds for inequivalent Hadamard matrices of large orders.

Keywords: Autocorrelation function, classification, Base sequences, Near normal sequences, Yang multiplication methods, Hadamard matrices, T-sequences, T-matrices.