Semi-blind channel covariance estimation for MIMO precoding

A method for estimating channel covariance from the uplink received signal power for downlink transmit precoding in multiple-input multiple-output (MIMO) frequency division duplex (FDD) wireless systems is proposed. Unlike other MIMO precoding schemes, the proposed scheme does not require a feedback channel or pilot symbols, i.e. knowledge of the channel covariance is made available at the downlink transmitter through direct estimation from the uplink received signal power. This leads to low complexity and improved system efficiency. It is shown that the proposed scheme performs better or on par with other practical schemes and only suffers a slight performance degradation when compared with systems with perfect knowledge of the channel covariance