Optimal and suboptimal quadriphase sequences derived from maximal length sequences over Z4

Abstract

The families of quadriphase sequences derived from maximal length sequences over Z4 having good correlation properties are presented. Such sequences are of interest in quadriphase modulated code division multiple access communication systems, where it is desirable to have large sets of sequences that possess low value of θmax, the maximum magnitude of the periodic crosscorrelation and out of phase auto-correlation values. The sequences over Z4 are viewed as trace functions of appropriately chosen unit elements of Galois extension rings of Z4. Quadriphase sequences are then obtained from Z4 sequences by a quadriphase mapping. The majority of the families of sequences derived are optimal with ..