On the Analysis and Design of Practical Quantization for Opportunistic Beamforming

We propose a closed-loop scheme that combines opportunistic beamforming (OBF) and closed-loop (CL) transmit-diversity (TD) techniques. This quantized OBF scheme is compatible with CL TD algorithms, and allows to adaptively control the amount of feedback overhead according to the number of participating users. Closed-form expressions for the SNR gain of the quantized OBF proposal are derived. Important reductions in the amount of feedback overhead are observed without affecting the SNR gain considerably, when compared to CL TD techniques.