In this paper, we consider a direct-sequence code-division multiple-access system operating in downlink. We propose to improve the performances of a conventional delay tracking algorithm, i.e. the early-late algorithm, by means of prefiltering of the received signal. This concept has been studied by D'Andrea and Luise in [1] for the clock recovery scheme proposed by Gardner [2]. Our main contribution is to extend this concept in a multi-user CDMA context. In this extension, we have to treat multiple-access interference and to deal with the two "timing scales", i.e. symbol and chip duration, due to spread spectrum. The analysis shows improved tracking performances in comparison to the standard early-late algorithm.
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