Performance comparison of hybrid and digital beamforming with transmitter impairments

Leveraging the available millimeter wave spectrum will be important for 5G. This work compares Hybrid Beam-Forming (HBF) and Digital BeamForming (DBF) with low resolution Analog-to-Digital-Converters, while considering a model for transmitter impairments, in terms of spectral efficiency and energy efficiency for a single-user and multi-user scenario with multipath propagation. We show that in the low Signal to Noise Ratio (SNR) regime, the performance of DBF even with 1–2 bits of resolution outperforms, that of HBF in terms of the spectral efficiency, for both the single-user and multi-user case. Already 3–4 bit effective resolution DBF outperforms HBF for the whole considered SNR range from −30 to 30 dB in terms of spectral efficiency and energy efficiency. For a asymmetric receive power multi-user scenario, this effective resolution is also sufficient to cover receive power differences of 20 dB.