This letter presents an efficient blind carrier frequency offset (CFO) estimate approach for multicarrier-code division multiple access (MC-CDMA) system. It can reduce the searching grids required and improve the CFO estimating accuracy compared with conventional searching-based algorithms. Simulation results are provided for illustrating the effectiveness of the proposed blind estimate approach.

This letter deals with adaptive array beamforming based on a minimum variance distortionless response (MVDR) technique with robust capabilities for code-division multiple access signals. It has been shown that the MVDR beamformer suffers from the drawback of being very sensitive to pointing error over the eigenspace-based beamformers. For the purpose of efficient estimation and calibration, a highly efficient approach has been proposed that is implemented on polynomial rooting rather than spectral searching. However, this rooting method is suboptimal in the presence of the noise and multiple access interference (MAI). In this letter, we propose an improved polynomial rooting calibration method that is robust in both of the low signal-to-noise ratio and large MAI scenarios. Several computer simulations are provided for illustrating the effectiveness of the proposed method.

In this letter, two types of blind adaptive frequency offset estimator for multicarrier code division multiple access systems are proposed that do not need any specific training sequence. It can not only accurately estimate the frequency offset, but also improve the revision capability and convergence rate. Several computer simulations confirm the effectiveness of the blind estimate approaches.

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 power 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, the complexity is extensively reduced by separating the multi-dimensional optimization problem into several one-dimensional optimization problems. Furthermore, the algorithm is computationally feasible than the subspace-based timing estimator 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.