Impact and compensation of sample clock offset on up-link SC-CDMA

Single-carrier code division multiple access (SC-CDMA), also named cyclic-prefix CDMA in the literature, is a promising air interface for the up-link of the 4G cellular wireless communication systems. It enables the high capacity intrinsically offered by CDMA by making the equalization of the multi-path channels and the mitigation of the resulting interference possible at a low complexity. This paper studies the impact of multi-user sample clock offset on the performance of up-link SC-CDMA and proposes a compensation strategy at the receiver. It is shown that clock offset leads to an unacceptable degradation of the performance if it is not compensated. In a simultaneous multi-user up-link system, the sample clock offset is usually pre-compensated at the transmitters. This paper demonstrates that the compensation can also be done at the receiver. In a first step the optimal linear multi-user joint detector is designed according to the MMSE criterion, taking the effect of clock offset into account. In a second step the MMSE joint detector is simplified to a low complexity detector incurring a negligible loss of performance