A method for communication includes receiving signals at a receiver from multiple sources, including a target signal transmitted by a given transmitter, and estimating a channel response from the given transmitter to the receiver. A filter response is computed by taking a sum including a first autocorrelation of the received signals with a second autocorrelation of the channel response, and applying the sum to the estimated channel response. The filter response is applied to the received signals in order to recover the target signal.