Chip synchronization of M-PSK signals on nonselective fading channels for bandlimited DS/SS CDMA systems

Abstract

Derives four maximum-likelihood (ML) oriented chip synchronization algorithms for bandlimited direct-sequence spread spectrum (DS/SS) M-PSK signals subjected to nonselective Rician fading. The authors distinguish between these algorithms depending on whether they are decision/data-aided (DA) or not (NDA) and whether they are channel-aided (CA) or not (NCA). The authors also investigate their tracking performance in the presence of multi-user interference in a code-division multiple access (CDMA) system where the received signals from the various users may have unequal power levels. The fading bandwidth influences none of the algorithms, but only the NDA NCA and the DA CA algorithm have a performance that is independent of the carrier-to-multipath ratio of the fading. Furthermore, the DA NCA algorithm is the only algorithm affected by a carrier frequency offset.