Almost Perfect 16-QAM Sequences for Spreading-Spectrum Communication Systems Using 16-QAM Constellation

A sequence with several nonzero nontrivial autocorrelation values is referred to as an almost perfect sequence, which is widely applied to communications, radar, and so forth. In this paper, such sequences over the 16-QAM constellation are investigated and their construction methods are presented. By making use of differently proposed methods, the numbers of nonzero nontrivial autocorrelation values of the resultant sequences are 1, 2, and 4, respectively. Finally, a given example shows the validity of the proposed methods.