  This paper considers three aspects of Massive MIMO (multiple-input
multiple-output) communication networks that have received little attention in
previous works, but are important to understand when designing and implementing
this promising wireless technology. First, we analyze how bursty data traffic
behaviors affect the system. Using a probabilistic model for intermittent user
activity, we show that the spectral efficiency (SE) scales gracefully with
reduced user activity. Then, we make an analytic comparison between synchronous
and asynchronous pilot signaling, and prove that the choice between these has
no impact on the SE. Finally, we provide an analytical and numerical study of
the SE achieved with random network deployment.
