Subchannel Gain Product based Frequency Selective Hybrid Beamforming with Limited Feedback

Wireless communication in millimeter wave frequency provides a high data rate using a wide bandwidth. However, the large array antenna is necessary to overcome the high path loss, which may result in the high feedback overhead and hardware complexity. Moreover, the characteristics of frequency selective channel should be considered due to the wide bandwidth. To deal with these problems, we propose the orthogonal frequency division modulation (OFDM)-based hybrid beamforming (HBF) scheme with limited feedback. While the conventional OFDM-based HBF schemes are based on minimizing the sum of the Frobenius norm of the differences between digital BF (DBF) and HBF as simple extension of the narrowband systems, our approach is based on the achievable sum rate maximization of all the subcarriers. In particualr, we derive a design criterion to jointly optimize the HBF matrices of the transmitter and receiver. Specifically, we propose a HBF method which designs subchannel gain product based orthogonal matching pursuit. Through this, an analog BF algorithm considering both the transitter and receiver is proposed, while the baseband BF is based on the conventional digital precoding scheme. Simulation results show that the proposed HBF scheme outperforms the conventional ones. Notably, the results show that the proposed HBF scheme is robust to channel estimation error.