  Millimeter wave (mmWave) holds promise as a carrier frequency for fifth
generation cellular networks. Because mmWave signals are sensitive to blockage,
prior models for cellular networks operated in the ultra high frequency (UHF)
band do not apply to analyze mmWave cellular networks directly. Leveraging
concepts from stochastic geometry, this paper proposes a general framework to
evaluate the coverage and rate performance in mmWave cellular networks. Using a
distance-dependent line-of-site (LOS) probability function, the locations of
the LOS and non-LOS base stations are modeled as two independent
non-homogeneous Poisson point processes, to which different path loss laws are
applied. Based on the proposed framework, expressions for the
signal-to-noise-and-interference ratio (SINR) and rate coverage probability are
derived. The mmWave coverage and rate performance are examined as a function of
the antenna geometry and base station density. The case of dense networks is
further analyzed by applying a simplified system model, in which the LOS region
of a user is approximated as a fixed LOS ball. The results show that dense
mmWave networks can achieve comparable coverage and much higher data rates than
conventional UHF cellular systems, despite the presence of blockages. The
results suggest that the cell size to achieve the optimal SINR scales with the
average size of the area that is LOS to a user.
