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.