A method is disclosed to calculate combining weight vectors associated with a received composite information signal comprising at least one data stream transmitted from at least four antennae. The method starts with computing a parametric estimate of an impairment covariance matrix including at least a first impairment term associated with common pilots deployed by the antennae. The first impairment term captures effects of interferences of the common pilots. The impairment covariance matrix further includes a data covariance term capturing effects of the at least one data stream and an interference term caused at least partially by contribution of thermal noise of receiver branches. The impairment covariance matrix includes a second impairment term associated with at least one dedicated pilot. Then the method computes the combining weight vector using the computed impairment covariance matrix. A network device performs such method is also disclosed.