A Toeplitz displacement method for blind multipath estimation for long code DS/CDMA signals

The problem of blind channel identification for direct-sequence/code-division multiple-access (DS/CDMA) multiuser systems is explored. For wideband DS/CDMA signals, multipath distortion is well modeled by a finite-impulse response filter. In this work, a blind channel identification technique based on second-order statistics is investigated. The method exploits knowledge of the spreading code of the user of interest via matched filtering, as well as properties of spreading codes. The current scheme focuses on a method appropriate for randomized long sequence DS/CDMA. This access scheme poses special challenges as the spreading codes are time varying. An analytical approximation of the mean-squared error is derived using perturbation techniques. The performance of the algorithm is studied via simulation and through the mean-squared error approximation, which is observed to be tight.