MAC Rate Region of Low Resolution ADC Digital and Hybrid Beamforming Massive MIMO UL

For 5G it will be important to leverage the available
millimeter wave spectrum. To achieve an approximately omnidi-
rectional coverage with a similar effective antenna aperture, an
antenna array is required at both the mobile and basestation.
Due to the large bandwidth and inefficient amplifiers available
in CMOS for mmWave, the analog front-end of the transceiver
with a large number of antennas is especially power hungry. Two
main solutions exist to reduce the power consumption: Hybrid
BeamForming (HBF) and Digital BeamForming (DBF) with low
resolution ADC. This work compares the uplink rate region for
both systems assuming a basestation with a large number of
antennas. We show, that in the low SNR regime, the performance
of DBF even with about 1-2 bits of resolution outperforms the one
of HBF in terms of the achievable sum rate. The higher the SNR,
the higher also the required resolution of the ADC to achieve a
similar performance compared to HBF. If there is a large spread
in receive power of the signal from different users, systems with
very low resolution (1-3 bit) suffer from a performance loss