A method of generating a pair of orthogonal sets with a spreading factor N for a direct sequence spread spectrum communication system, includes selecting a two-level autocorrelation sequence of a period of N−1, the two-level autocorrelation sequence including elements, each of which includes a value of 1 or 0, and obtaining binary sequences based on the two-level autocorrelation sequence. The method further includes obtaining quasi-orthogonal sets based on the two-level autocorrelation sequence and the binary sequences, and generating the pair of the orthogonal sets based on the quasi-orthogonal sets.