1. A method comprising: at a wireless communications device, receiving signals at an antenna array and generating a first interference spatial signature from an interference signal matrix derived from interference signals received by the antenna array; deriving a second interference spatial signature from the first interference spatial signature based on differences between consecutive vectors of the interference signal matrix; calculating a covariance matrix from the second interference spatial signature; and generating a beamforming weighting vector from the covariance matrix, wherein the beamforming weight vector is for use with the antenna array of the wireless communication device to null interference represented by the first interference spatial signature.