Patent ID: 8638871

Claim:
A method comprising: receiving an uplink channel sounding (ULCS) signal comprising ULCS subcarriers; determining, at a base station, one or more of an uplink channel estimation and a covariance matrix based on the uplink channel sounding (ULCS) signal; forming, at the base station, a first weight vector with one complex element per transmit antenna based on the one or more of the uplink channel estimation and the covariance matrix, wherein the forming the first weight vector comprises: producing a downlink (DL) equivalent received signal from the ULCS signal and a set of reciprocity calibration coefficients, partitioning an antenna array into two sub-arrays wherein for each ULCS subcarrier, the DL equivalent received signal is partitioned into two sub-vectors; computing a spatial covariance matrix for each sub-array using the two sub-vectors; and selecting a largest eigenvector in the spatial covariance matrix for said each sub-array as the first weight vector; forming, at the base station, a second weight vector from the first weight vector, where each complex element of the second weight vector is equal to a normalized version of a corresponding complex element of the first weight vector; and transmitting a multiple input, multiple output (MIMO) signal using the second weight vector, wherein the second weight vector is partitioned into two or more sub-vectors prior to the transmitting and further, wherein the transmitting includes transmitting the MIMO signal over the two or more sub-vectors.