Hybrid precoding design with AoD estimation for millimeter wave MIMO systems

Millimeter Wave (mmWave) wireless communications is considered an enabling technology to allow fifth generation (5G) cellular networks to achieve extremely higher data rates for future mobile applications. Compared to conventional multiple- input-multiple-output (MIMO) systems, in mmWave MIMO systems, precoding cannot be performed only at baseband due to high cost and power consumption of signal mixers and analog-to-digital converters (ADCs). Alternatively, the hybrid analog-digital architecture at transceiver is considered as a cost-effective solution. In this paper, a maximum likelihood (ML) fixed weight beamforming technique is added to the precoder, by approximating the signal's direction of departure in the presence of random noise. Moreover, a low-cost Maximum Likelihood Orthogonality Based Matching Pursuit MLOBMP algorithm is then designed, with predefined layered radio frequency (RF) orthogonal codebook as a candidate matrix, which approximates the BS beamforming vectors in more accurate transmit directions. Simulation results show an acceptable performance of the reduced complexity proposed hybrid pre- coding compared with optimal full-digital precoder.