Parameter Estimation and Multiuser Detection for Bandlimited Long-Code CDMA Systems

This paper considers the problem of parameter estimation and data detection in multiuser bandlimited long-code DS/CDMA systems. Centralized (i.e., multiuser) and decentralized (i.e., single-user) estimation procedures for the delay, amplitude and phase offset of the users´ CDMA received signals are derived. The proposed estimation procedures may be devised as two-steps ones: indeed, first a composite channel impulse response is estimated and, then, such an estimate is further processed in order to obtain the parameter estimates. Closed-form formulas for the Cramer-Rao Lower Bound (CRLB) are derived, and the performance of the proposed estimators is numerically contrasted to that of the CRLB and of competing alternatives. The problem of multiuser detection is also considered, and indeed we report the performance of some relevant multiuser detectors built upon the estimates provided by the proposed estimation algorithms. We are thus able to assess the impact that the proposed estimation algorithms have on the bit error rate performance of the system.