Performance of Hybrid Beamforming for mmW Multi-antenna Systems in Dense Urban Scenarios

Among the many proposals to meet the fifth generation (5G) data rate demands, current spectrum scarcity has motivated the use of millimeter-Wave (mmW) bands for cellular communication. It is well known that mmW communication involves many propagation challenges, which can be compensated through massive multi-antenna techniques. However, implementing fully digital precoding schemes with massive arrays entails huge complexity and costs, which have recently boosted the interest for hybrid beamforming solutions. Although hybrid schemes have shown good performance in simplified setups, their suitability for realistic cellular systems with many interfering base stations and users is still unclear. In this sense, this paper assesses the performance of hybrid beamforming in a dense urban cellular system with a realistic mmW channel model and shows that it can reach the performance of fully digital maximum ratio transmission under line of sight conditions and with a sufficient number of parallel radio-frequency chains. Another important result is that multi-user hybrid beamforming provides a substantial capacity increase with respect to its single-user (SU) counterpart. This finding complements the views on mmW communication usage, which has been so far mainly intended for SU communication to provide high beamforming gains.