AF relaying for millimeter wave communication systems with hybrid RF/baseband MIMO processing

Due to the high cost and power consumption of radio frequency (RF) chains, millimeter wave (mm-wave) communication systems equipped with large antenna arrays typically employ less RF chains than the antenna elements. This leads to the use of a hybrid MIMO processor consisting of a RF beamformer and a baseband MIMO processor in mm-wave communications. In this paper, we consider amplify-and-forward (AF) relay-assisted mm-wave systems with the hybrid MIMO processors over frequency-selective channels. We develop an iterative algorithm for jointly designing the receive/transmit (Rx/Tx) RF/baseband processors of the relay based on the orthogonal matching pursuit (OMP) algorithm for sparse approximation, while assuming orthogonal frequency division multiplexing (OFDM) signaling. Simulation results show that the proposed method outperforms the conventional method that designs the baseband processor after steering the RF beams.