Diversity combining of a fast-varying, correlated multipath fading channel for direct-sequence spread-spectrum systems

Diversity combining of fast-varying, correlated multiple-fading paths is investigated for direct-sequence spread-spectrum (DS-SS) systems. The multiple correlated paths are modeled as a vector autoregressive process, whose parameters are estimated using the expectation maximization (EM) technique. The proposed technique, requiring no derivatives of the log likelihood function, is computationally efficient and able to achieve near-optimum performance.