Patent ID: 8116698

Claim:
A method comprising: at a plurality of antennas of a first device, receiving transmissions sent via less than all of a plurality of antennas of a second device, wherein each transmission comprises a plurality of time-frequency instances; computing a covariance matrix at the plurality of time-frequency instances within a received transmission and computing an instantaneous covariance matrix for a received transmission by averaging the covariance matrices for the plurality of time-frequency instances within a received transmission; computing a long-term average covariance matrix from a sum of instantaneous covariance matrices over a time period comprising multiple transmissions received from the second device at the first device; determining a reliability of the instantaneous covariance matrix for a most recently received transmission from the second device; computing beamforming weights for transmitting one or more signal streams via the plurality of antennas of the first device to the plurality of antennas of the second device based on the reliability of the instantaneous covariance matrix, wherein when it is determined that the instantaneous covariance matrix for the most recently received transmission is reliable, computing the beamforming weights is based on select eigenvectors associated with eigenvalues of the instantaneous covariance matrix for the most recent transmission and of the long-term average covariance matrix depending on whether a number P of signal streams to be transmitted from the first device to the second device and thus the number P of beamforming weights needed is greater than a number K of antennas at the second device used for transmissions to the first device, and when it is determined that the instantaneous covariance matrix for the most recently received transmission is not reliable, computing the beamforming weights based on the long-term average covariance matrix; and applying the beamforming weights to the one or more signal streams to be transmitted via the plurality of antennas of the first device to the plurality of antennas of the second device.