Patent ID: 9059750
Filing Date: 2015-06-16
Classification: H04B

Abstract:
1. A method comprising: receiving uplink signals at a plurality of antennas of a first wireless device that are transmitted via a plurality of antennas of a second wireless device, wherein receiving comprises receiving the uplink signals from the second wireless device that comprise a number of spatial streams less than a number of the plurality of antennas of the second wireless device; deriving values at a plurality of subcarriers of the received uplink signals across the plurality of antennas of the first wireless device; receiving a training pattern of known values from the second wireless device; computing downlink beamforming weights based on values at two or more consecutive subcarriers across the plurality of antennas of the first wireless device by computing a covariance matrix at each of the two or more consecutive subcarriers, wherein computing the downlink beamforming weights comprises deriving full spatial information for a wireless channel between the first wireless device and the second wireless device when the second wireless device uses a spatial expansion matrix to transmit the number of spatial streams less than the number of the plurality of antennas of the second wireless device; estimating cyclic shift diversity performed at the second wireless device by computing an average with respect to the received uplink signals and the known values of the training pattern over the plurality of antennas of the first wireless device at the consecutive subcarriers, the estimated cyclic shift diversity used in the computing of the downlink beamforming weights; and applying the downlink beamforming weights at respective subcarriers to the number of spatial streams in a downlink transmission to be transmitted to the second wireless device.