Asynchronous multicarrier DS-CDMA using mutually orthogonal complementary sets of sequences

The use of sets of multiple spreading sequences per user in multicarrier co de-division multiple-access (CDMA) is investigated. Each user is assumed to have a distinct set of spreading sequences, with a different spreading seq uence for each carrier in each user's set. We show that when these sets of sequences are chosen to be the mutually orthogonal (MO) complementary sets of sequences, multiple-access interference is minimal on a nonfading channe l. iis a result of the autocorrelation sidelobe cancellation properties of the MO complementary sequences, it is possible to pack symbols more closely together on the nonfading channel, resulting in a higher data rate than in multicarrier CDMA using the same spreading sequence for each carrier. The resulting communication system scheme results in an easily parallelized rec eiver architecture that-may be useful in nonfading coherent channels, such as the optical fiber channel or the Rician channel with a strong line-of-si ght component. On the Rayleigh fading channel, the performance of the syste m is identical to that of multicarrier CDMA employing a single spreading se quence per user, with only a minimal increase in receiver complexity.