Vivisecting Beam Management in Operational 5G mmWave Networks

Beam management plays a fundamental role in 5G mmWave networks, due to the highly directional nature of mmWave signals. Despite its importance, beam management procedures and real-world performance in operational deployments remain underexplored. This paper addresses this gap by presenting the first in-depth empirical study of beam management procedures in commercial 5G mmWave networks. Our study is based on an extensive measurement campaign across two major US operators, covering six cities, different base station types, and varying mobility scenarios, including walking and driving. We evaluate key beam management parameters on both the base station and the user equipment side, assessing their impact on network performance. In addition, we examine the interaction between beam management and two other mechanisms critical to performance, rate adaptation and carrier aggregation. Finally, we quantify the beamforming overhead and analyze the effectiveness of beam tracking. Our findings provide novel insights into the real-world performance of beam management in 5G mmWave networks, offering guidance for further optimization.