Maximal length sequences for QPSK

Abstract

Nonbinary m-sequences are developed for direct use in QPSK. These quaternary maximal-length sequences, which can be directly assigned to the four phases of QPSK, are generated from primitive polynomials whose coefficients are in the Galois field of 2/sup 2/ elements (GF(2/sup 2/)). The autocorrelation function for the quaternary m-sequence is shown to be two-level and the crosscorrelation function for preferred pairs of these quaternary m-sequences is shown to be three- and four-level, similar to the binary cases. A class of quaternary Gold codes for use in spread-spectrum multiple-access communication is developed for sequences whose coefficients are in GF(2/sup 2/).<>