1. A method implemented in a wireless receiver of estimating impairment covariance associated with a received composite information signal comprising at least a first data stream transmitted from first and second antennas according to a first antenna weighting vector, the method comprising: generating first and second propagation channel estimates in the wireless receiver based on the received composite signal; constructing an impairment model including one or more model terms scaled by corresponding scaling parameters, wherein: a first impairment model term in the impairment model is a function of the first propagation channel estimates corresponding to the first antenna; a second impairment model term in the impairment model is a function of the second propagation channel estimates corresponding to the second antenna; a third impairment model term in the impairment model is a function of both the first and second propagation channel estimates; each of the first, second, and third impairment model terms are independent of the first antenna weighting vector; and the scaling parameters capture effects of the first antenna weighting vector; and computing a parametric estimate of the impairment covariance using the impairment model and the generated propagation channel estimates.