  This paper focuses on modeling and analysis of the temporal performance
variations experienced by a mobile user in a wireless network and its impact on
system level design. We consider a simple stochastic geometry model: the
infrastructure nodes are Poisson distributed while the user's motion is the
simplest possible i.e., constant velocity on a straight line. We first
characterize variations in the SNR process, and associated downlink Shannon
rate, resulting from variations in the infrastructure geometry seen by the
mobile. Specifically, by making a connection between stochastic geometry and
queueing theory the level crossings of the SNR process are shown to form an
alternating renewal process whose distribution can be completely characterized.
For large or small SNR levels, and associated rare events, we further derive
simple distributional (exponential) models. We then characterize the second
major contributor to variation, associated with changes in the number of other
users sharing infrastructure. Combining these two effects, we study what are
the dominant factors (infrastructure geometry or sharing number) given mobile
experiences a very high or low shared rate. These results are then used to
evaluate and optimize the system-level Quality of Service (QoS) and
system-level capacity to support mobile users sharing wireless infrastructure,
including mobile devices streaming video which proactively buffer content to
prevent rebuffering and mobiles which are downloading large files. Finally, we
use simulation to assess the fidelity of this model and its robustness to
factors which are presently taken into account.
