Timing estimation of CDMA communication based on MVDR beamforming technique
A new timing estimation algorithm for asynchronous DS/CDMA multiuser communication system is proposed in this paper. The algorithm is based on the Minimum Variance Distortionless Response (MVDR) beamforming technique that minimizes the beamformer's output Dower with the constraint that only the signal with exact timing is distortionlessly passed. Exploiting the characteristics that the MVDR beamformer's output power is severely degraded according to erroneous timing estimation, we develop an efficient algorithm to estimate each user's timing by scanning the beamformer's output power variation. Compared to the maximum a posteriori (MAP) or maximum likelihood (ML) based multiuser timing estimator [1], the complexity is extensively reduced by separating the multidimensional optimization problem into several one-dimensional optimization problems. Further more, the algorithm is computationally feasible than the subspace-based timing estimator [2], [3] since no eigendecomposition (EVD) is required. Moreover, the proposed algorithm is near-far resistant since the MVDR beamformer is inherently energy independent to the interferers.
beamforming ds/cdma minimum variance distortionless response (mvdr) multiuser timing estimator near-far resistant