Open-Loop Beamforming for Frequency-Division Duplex Mobile Wireless Access

An open-loop eigen beamformer is designed for frequency-division duplex (FDD) mobile wireless access. In this approach, the base station transmitter does not need any channel feedback nor does the mobile receiver need knowledge of the channel or the transmit beamforming weights. The transmit beamforming weights in the downlink are generated based on the estimate of the uplink spatial covariance matrix. The base station assigns multiple beamforming weights for transmission in the signal subspace, and the mobile combines signals from multiple dimensions to preserve the received signal strength against fast channel fading. Simulation results show that, when the distance between the uplink and downlink signal subspaces is negligible, the open-loop beamformer can improve the performance of FDD systems without spatial covariance matrix transformation from uplink to downlink frequency.