Joint DOA estimation and multi-user detection for WCDMA using DELSA

We propose an algorithm to perform jointly the azimuthal direction-of-arrival (DOA) estimation and multi-user detection (MUD) of signals that impinge an array of antennas. We treat DOA estimation and MUD as an inverse problem of finding specific sets of parameters, viz., {φ_i} and the corresponding {s_i}. We reformulate this nonlinear estimation problem into a highly underdetermined linear system. We solve the resulting least squares problem by employing the well-known conjugate gradients (CG) iterations on the normal equations (NE). From the solution, we recover the DOA and detect the desired user information, thereby achieving joint DOA estimation and multi-user detection. Simulation results for a typical 3GPP WCDMA demonstrate the robustness of our algorithm in the regimes of low signal-to-noise ratios (SNRs), fast fading and closely spaced interferences.