RACH Performance Analysis for Large-Scale Cellular IoT Applications

Providing energy efficient and delay-aware access is essential to many anticipated cellular Internet of Things (IoT) applications. In cellular networks, before devices transmit their data, they use a contention-based association protocol, known as random access channel (RACH), which introduces extensive access delays and energy wastage as the number of contending devices increases. Modeling the performance of the RACH protocol is a challenging task due to the complexity of uplink transmission that exhibits a wide range of interference components; nonetheless, it is an essential process that will help determine the applicability of cellular IoT communication paradigm. This paper presents a novel mathematical framework based on stochastic geometry to analyze the RACH protocol and identify its limitations in the context of cellular IoT applications with a massive number of devices. To do so, we study the traditional cellular association process and derive a mathematical model for its association success probability. The derived model accounts for device density, spatial characteristics of the network, power control employed, and mutual interference among the devices. Our analysis and results highlight the shortcomings of the RACH protocol and give insights into the potentials brought on by employing power control techniques. The developed framework can be applied to evaluate the performance of other contention-based access schemes by incorporating their unique operational principles.