Abstract：In this paper, joint estimation of the number of active users, active users and their timing in asynchronous CDMA systems are discussed. The subspace based method to oversampling received signal model is applied to identify the number of active users, and at the same time, to estimate active users and their timing while requiring only a priori knowledge of all the registered users’ signature sequences in its cell. The performances of the proposed algorithm are analyzed. This method does not require training sequence. Theoretical analysis ad simulation show that this algorithm is simple in computation, has good performance in joint estimation of active users and their timing, and is asymptotically near far resistant. Finally, simulation also shows that the performances are obviously improved when the received signal is sampled at multiple of the chip rate (oversampling).
2002, Vol. 24 
