Modelling RACH Arrivals and Collisions for Human Type Communication

Abstract

The paper proposes an analytical model to evaluate the collision probability on the Random-Access CHannel (RACH) in LTE systems as a function of the number of User Equipments (UEs), the number of available preambles and the Inter-arrival times of the RACH Requests (IRR) of the average user. The model for the IRR of the average user is obtained from real traffic data captured at the eNodeB of a mobile operator, and is derived by emulating the RRC state machine for different Radio Resource Control Inactivity Timer (RRC IT ) settings. The results of the presented study suggest that when RRC IT is set to a few seconds a mixture model is more accurate than the Poisson hypothesis both in modelling the IRR and in estimating the RACH performance.