Spectral Efficiency of Millimeter Wave Multiple-Input-Multiple-Output System for Different Precoding Techniques

Multiple-input-multiple-output (MIMO) techniques and effective precoding algorithms are required due to the inherent difficulties of Millimeter-Wave (mmWave) propagation.The challenges include the significant route loss due to high-frequency usage.Further, the sparse channel matrix yields improper channel estimation (CE), resulting in erroneous reception, which limits the implementation of mmWave technology.Therefore, beam formation is required to direct the power in the direction of the user by exploiting the spatial multiplexing of MIMO.The above-stated limitations, along with hardware constraints of using a lesser number of radio frequency (RF) chains, can be mitigated through effective precoding at the transmitter.The efficient utilization of mmWave bandwidth by users is crucial for a spectrally efficient system, as it helps conserve this scarce resource.Hence, this study has examined the spectral efficiency (SE) of mmWave MIMO systems for various precoding strategies, including minimum mean-square estimation (MMSE) precoding, fully digital and hybrid zero-forcing (ZF) precoding, and analog beamforming.The performance in terms of achievable SE has been studied considering variability in the user base and the number of transmit and receive antennas.Simulation results have been presented, showing that the MMSE precoder outperforms the ZF precoder.Furthermore, the dominant fully digital MMSE precoder approaches the SE of single-user MIMO as the number of users increases, compared to the fully digital ZF precoder.