  Beam management is central in the operation of beamformed wireless cellular
systems such as 5G New Radio (NR) networks. Focusing the energy radiated to
mobile terminals (MTs) by increasing the number of beams per cell increases
signal power and decreases interference, and has hence the potential to bring
major improvements on area spectral efficiency (ASE). This paper proposes a
first system-level stochastic geometry model encompassing major aspects of the
beam management problem: frequencies, antenna configurations, and propagation;
physical layer, wireless links, and coding; network geometry, interference, and
resource sharing; sensing, signaling, and mobility management. This model leads
to a simple analytical expression for the effective rate that the typical user
gets in this context. This in turn allows one to find the number of beams per
cell and per MT that maximizes the effective ASE by offering the best tradeoff
between beamforming gains and beam management operational overheads and costs,
for a wide variety of 5G network scenarios including millimeter wave (mmWave)
and sub-6 GHz. As part of the system-level analysis, we define and analyze
several underlying new and fundamental performance metrics that are of
independent interest. The numerical results discuss the effects of different
systemic tradeoffs and performance optimizations of mmWave and sub-6 GHz 5G
deployments.
