  Compared with the perfect complementary sequence sets, quasi-complementary
sequence sets (QCSSs) can support more users to work in multicarrier CDMA
communications. A near-optimal periodic QCSS is constructed in this paper by
using an optimal quaternary sequence set and an almost difference set. With the
change of the values of parameters in the almost difference set, the
near-optimal QCSS can become asymptotically optimal and the number of users
supported by the subcarrier channels in CDMA system has an exponential growth.
