DS-CDMA Synchronization in Time-Varying Fading Channels

Herein, the problem of estimating propagation delays of the transmitted signals in a direct-sequence code-division multiple access (DS-CDMA) system operating over fading channels is considered. Even though this study is limited to the case when the propagation delays are xed during the observation interval , the channel gain and phase are allowed to vary in time. Special attention is given to the near-far problem which is catastrophic for the standard acquisition algorithm. A near-far robust estimator based on subspace identiication techniques is proposed, and the Cram er-Rao bound, which serves as an optimality criterion, is derived.