Channel estimation of long-code CDMA systems utilizing transmission induced cyclostationarity

For long code DS-CDMA systems, where the spreading codes are aperiodic and extending over a large number of data symbols, chip-rate sampled signals and MUI (multiuser interferences) are generally modeled as time-varying vector processes. This complicates the application of traditional blind multiuser detectors, since consistent estimation of the needed signal statistics can not be obtained by time-averaging over received data record. In this paper, we propose an equivalent time-invariant system model for long code CDMA, in which the received signals and MUI are modeled as cyclostationary processes with modulation introduced cyclostationarity. Based on knowledge of the desired user's code sequences, channel estimation is carried out using a frequency domain subspace method.