I. Introduction
A complete complementary code (CCC) [1] consists of Golay complementary sets (GCSs) and any different constituent GCSs are mutually orthogonal. The autocorrelations of constituent Golay sequences in a GCS sum to zero except at zero shift, and the cross correlations of sequences from two distinct constituent GCSs sum to zero for all shifts. Therefore, CCCs have been applied to multicarrier code division multiple access (MC-CDMA) systems to mitigate the multiple-access interference [2] according to their good correlation properties. However, CCCs cannot support large amount of users since the set size, i.e., the number of users, is limited. It is bounded by the flock size, that is, the number of sequences in a constituent GCS. Recently, to support more users, the concept of zero correlation zone (ZCZ) was exploited by Fan et al. [3] to propose the Z-complementary sequence (ZCS) set, which has ideal autocorrelation and cross-correlation properties within a certain range, i.e., the ZCZ. Compared with conventional CCCs, the set sizes and lengths of ZCS sets are more flexible. Therefore, ZCS sets can have potential applications in MC-CDMA systems and cyclic-prefix-based single-carrier multiantenna systems [4].