Hybrid Precoding/Combining for single-user and Multi-Usersin mm-Wave MIMO systems

Abstract

mm-Wave is one of the potential 5G technology predominant at high frequency. The antenna arrays allows parallel transmission to the multiple users. Due to the constraints in hardware in mm-Wave systems,it is difficult to implement conventional multiuser MIMO precoding techniques at mm-Wave. In this paper initially Hybrid mm-Wave MIMO capacity is compared with conventional MIMOperformance, the simulation results demonstrates that the performance loss is due to assumption of the quantized angle of arrival and departures in dictionary which is very small using OMP algorithm and the capacity approaches the conventional MIMO performance. Then the Hybrid Precoding(HP)at mm-Wave is formulated as a sparse optimization problem in which the hybrid MIMO precoders and combiners are used as the measurement matrices.Here transmit precoding and combining at the receiver is considered with a limited feedback as knowledge of channel may not be practically available.Orthogonal matching Pursuit(OMP) algorithm is used for single-user case and alsoin Multi-user case using simultaneous Orthogonal matching pursuit(SOMP) algorithm. In single user case numerical results are presented which shows that the proposed algorithm approach is closer to their unconstraint performance even after considering hardware constraints. Multi-user precoding results illustrates that the proposed HP method offers higher Spectral efficiency (SE) compared to analog –only beamforming (AB) and is close tothe performance bench mark of optimal digital beamformer