  Competing cellular operators aggressively share infrastructure in many major
US markets. If operators also were to share spectrum in next-generation
millimeter-wave (mmWave) networks, intra-cellular interference will become
correlated with inter-cellular interference. We propose a mathematical
framework to model a multi-operator mmWave cellular network with co-located
base-stations (BSs). We then characterize the signal-to-interference-plus-noise
ratio (SINR) distribution for an arbitrary network and derive its coverage
probability. To understand how varying the spatial correlation between
different networks affects coverage probability, we derive special results for
the two-operator scenario, where we construct the operators' individual
networks from a single network via probabilistic coupling. For external
validation, we devise a method to quantify and estimate spatial correlation
from actual base-station deployments. We compare our two-operator model against
an actual macro-cell-dominated network and an actual network primarily
comprising distributed-antenna-system (DAS) nodes. Using the actual deployment
data to set the parameters of our model, we observe that coverage probabilities
for the model and actual deployments not only compare very well to each other,
but also match nearly perfectly for the case of the DAS-node-dominated
deployment. Another interesting observation is that a network that shares
spectrum and infrastructure has a lower rate coverage probability than a
network of the same number of BSs that shares neither spectrum nor
infrastructure, suggesting that the latter is more suitable for low-rate
applications.
