TitleHybrid Beamforming Designs for Frequency-Selective mmWave MIMO Systems with Per-RF chain or Per-antenna Power Constraints
Publication TypeJournal Article
Year of PublicationIn Press
AuthorsLópez-Valcarce, R, González-Prelcic, N
JournalIEEE Trans. Wireless Communications
KeywordsmmWave, rodin
Abstract Configuring precoders and combiners is a majorchallenge to deploy practical multiple-input multiple-output(MIMO) millimeter wave (mmWave) communication systemswith large antenna arrays. Most prior work addresses the problemfocusing on a total transmit power constraint. In practicaltransmitters, however, power amplifiers must operate within theirlinear range, so that a power constraint applies to each oneof the input signals to these devices. Therefore, precoder andcombiner designs should incorporate per-antenna or per-radiofrequency (RF) chain transmit power constraints. We focus onsuch problem for frequency-selective channels with multicarriermodulation, and assuming hybrid analog/digital architecturesbased on fully connected analog blocks implemented with finite resolutionphase shifters. We first derive an all-digital solutionwhich aims to maximize spectral efficiency. Then, we develophybrid precoders and combiners by approximately matchingthe corresponding all-digital matrices while still enforcing thepower constraints. Numerical results show that the proposedall-digital design performs close to the upper bound givenby the standard waterfilling-based solution with a total powerconstraint. Additionally, the hybrid designs exhibit a moderateloss even when low-resolution phase shifters are considered.