  This paper aims to construct optimal Z-complementary code set (ZCCS) with
non-power-of-two (NPT) lengths to enable interference-free multicarrier
code-division multiple access (MC-CDMA) systems. The existing ZCCSs with NPT
lengths, which are constructed from generalized Boolean functions (GBFs), are
sub-optimal only with respect to the set size upper bound. For the first time
in the literature, we advocate the use of pseudo-Boolean functions (PBFs) (each
of which transforms a number of binary variables to a real number as a natural
generalization of GBF) for direct constructions of optimal ZCCSs with NPT
lengths.
