On estimating temporal and spatial channel parameters for DS-CDMA system over multipath Rayleigh fading channels

We develop an approximate maximum likelihood (ML) method for joint estimation of time delays and directions-of-arrivals (DOA) for direct-sequence code-division multiple-access (DS-CDMA) systems over multipath Rayleigh fading channels. In developing the proposed estimation scheme, we model the known training sequence of the desired user as the desired signal and the multiple access interferences (MAI)-plus-AWGN as unknown colored Gaussian noise uncorrelated with the desired signal. To reduce computational complexity, a fast algorithm realization is proposed taking advantage of the ridge structure of the objection function. Analytical and simulation results are presented to illustrate the performance in comparison with the Cramer-Rao bounds (CRB). It is shown that the proposed algorithm is near-far resistant for both time delay and DOA estimations, with almost no performance loss compared with CRB