RACH Dimensioning for Reliable MTC over Cellular Networks

Successful implementation of massive machine-type communications (MTC) service over cellular networks is an important enabler of Internet of things. As the existing cellular infrastructure has been designed and optimized for moderate traffic, the introduction of MTC in cellular networks results in several key challenges, among them, temporal starvation of initial access resources is of paramount importance. Here, we propose a new traffic model for cellular networks serving machine-type subscribers. This model is subsequently used to derive closed-form expressions for the access rate performance of the system. This closed-form expression are subsequently used for RACH resources planning in the time and frequency domains. Given a target access rate requirement, numerical analysis indicates how and when the required RACH resources in the code/frequency domain, i.e. number of preambles, can be traded with the occurrence frequency of RACH slots in the time domain.