1. A method performed by a communication device to generate sequences used for wireless communication systems, the method comprising following steps: setting initial sequences to a first set of sequences; obtaining a second set of sequences by projecting the first set of sequences to a space of tight frames; obtaining a third set of sequences by projecting each of subsets of the second set of sequences to a space of orthogonal matrices; obtaining a fourth set of sequences by projecting the third set of sequences to a space of circulant matrices; obtaining a fifth set of sequences by projecting the fourth set of sequences to a space of matrices with preferable PAPR; iterating said steps at least once by setting the fifth set of sequences to the first set of sequences; obtaining a sixth set of sequences by projecting each element of the fifth set of sequences after the iterating step has been executed to a nearest quadrature phase-shift keying (QPSK) constellation point; and outputting the sixth set of sequences.