Chip interleaving in direct sequence CDMA systems

Abstract

Direct sequence code division multiple access (CDMA) systems are considered, in a multipath environment. We address the problem of estimating each user's signature waveform without requiring training sequences. We show that the problem is considerably simplified if a novel transmission strategy is adopted, which combines spreading and interleaving. In this setup, chip sequences corresponding to successive bits are interleaved before transmission. Novel channel estimation algorithms are developed in this chip interleaving framework and their performance is analyzed. Adaptive implementations are derived and some illustrative simulations are presented.