RF beamforming considering RF characteristics in MIMO system

We propose the multiple-antenna RF beamforming scheme. The proposed scheme adopts the phase shifters and gain controllers in RF domain to compensate the wireless fading channels which is usually operated on the digital domain in the conventional beamforming scheme. Accordingly, the proposed scheme can have only single analog-to-digital/digital-to-analog (ADC/DAC) since the signals from multiple antennas are beamformed in the RF domain. Also, we propose the codebook search algorithm based on the codebook switching for the channel estimation and apply it to the phase shifter and the gain controller for the beamforming in the RF domain. Based on the analysis of output SNR of the proposed scheme and the simulations we show that the deterioration of BER performance compared to the optimal baseband beamforming techniques in MIMO-MRC [2] is not significant, while the power consumption is much reduced and the requirement of the digital hardware for baseband MODEM is much relaxed owing to the single ADC/DAC both at the transmitter and the receiver.