1. A method of calculating combining weight vectors associated with a received composite information signal comprising at least one data stream transmitted from at least a first antenna, a second antenna, a third antenna, and a fourth antenna, the calculated combining weight vectors being used to demodulate the at least one data stream transmitted through a transmission channel, the method comprising: computing a parametric estimate of an impairment covariance matrix including at least a first impairment term associated with common pilots deployed by the first antenna, the second antenna, the third antenna, and the fourth antenna respectively, wherein the common pilots are pilots without being precoded or beam-formed, wherein the first impairment term captures effects of interferences of the common pilots, and wherein the computed 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; computing the impairment covariance matrix including a second impairment term associated with at least one dedicated pilot, wherein the dedicated pilot is a pilot being precoded or beam-formed, and wherein the second impairment term captures effects of interferences caused by the at least one dedicated pilot; and computing a combining weight vector using the computed impairment covariance matrix.