  The location of active users is an important factor in the performance
analysis of mobile multicell networks, but it is difficult to quantify due to
the wide variety of user mobility and session patterns. In particular, the
channel holding times in each cell may be arbitrarily distributed and dependent
on those in other cells. In this work, we study the stationary distribution of
users by modeling the system as a multi-route queueing network with Poisson
inputs. We consider arbitrary routing and arbitrary joint probability
distributions for the channel holding times in each route. Using a
decomposition-composition approach, we show that the user distribution (1) is
insensitive to the user movement patterns, (2) is insensitive to general and
dependently distributed channel holding times, (3) depends only on the average
arrival rate and average channel holding time at each cell, and (4) is
completely characterized by an open network with M/M/infinity queues. This
result is validated by experiments with the Dartmouth user mobility traces.
