  Machine-to-Machine (M2M) communications are one of the major drivers of the
cellular network evolution towards 5G systems. One of the key challenges is on
how to provide reliability guarantees to each accessing device in a situation
in which there is a massive number of almost-simultaneous arrivals from a large
set of M2M devices. The existing solutions take a reactive approach in dealing
with massive arrivals, such as non-selective barring when a massive arrival
event occurs, which implies that the devices cannot get individual reliability
guarantees. In this paper we propose a proactive approach, based on a standard
operation of the cellular access. The access procedure is divided into two
phases, an estimation phase and a serving phase. In the estimation phase the
number of arrivals is estimated and this information is used to tune the amount
of resources allocated in the serving phase. Our results show that the
proactive approach is instrumental in delivering high access reliability to the
M2M devices.
