Single-user timing estimation in DS-CDMA mobile communication systems using a receiving antenna array

The synchronization of a desired user transmitting a known training sequence in a direct-sequence asynchronous code-division multiple-access (DS-CDMA) system is addressed. This is an essential issue in mobile communication systems because of two reasons. First, it has been shown that the ability to achieve synchronization in a near-far environment limits the capacity of those systems. In the second place, most multiuser detectors require precise knowledge of the users ' timings, powers and carrier phases in order to work properly. We propose a synchronization technique that makes eÆcient use of the structure of the signals in both the space and time domains, employing usual lengths of the training sequence. Finally, it is shown that the use of space-time diversity in the receiver is indispensable for the correct synchronization in heavily loaded systems and in the presence of external interference. 1