A chip-interleaved synchronous DS-CDMA technique enabling MAI-free and reduced-ISI transmission with low complexity receiving

The capacity of conventional direct-sequence code-division multiaccess (DS-CDMA) systems is limited by multiaccess interference (MAI) that arises from correlation among user signals, especially in multipath channels. While inducing an intersymbol-interference (ISI) problem, chip-interleaved DS-CDMA (CIDS-CDMA) can preserve the orthogonality among user signals and effect MAI-free transmission. We propose a multicode CIDS-CDMA (MCIDS-CDMA) technique which can also remove ISI in addition to MAI when a sufficient number of multicodes are assigned. This design facilitates a low complexity receiver structure. In addition, a low complexity ISI canceller can be used to deal with the residual ISI, should the number of codes be insufficient.