On Random Access Channel Performance and M2M Support in Standalone LTE Unlicensed

Next generation telecommunication systems are required to efficiently support orders of magnitude larger amount of devices per cell than the current LTE networks. This requirement is causing major design challenges for the Random Access Channel (RACH), especially for Machine-to-Machine (M2M) applications. On the other hand, due to the increasing spectrum demands, LTE vendors are exploring unlicensed spectrum. For example, MulteFire has been recently standardized as an LTE-based technology for standalone deployment in unlicensed 5GHz frequency bands. It is reasonable to expect that the coexistence with Wi-Fi and standalone LTE in the unlicensed spectrum, will amplify Random Access problem and worsen RACH performance. Henceforth, in this paper, we quantify the Wi-Fi-LTE coexistence and its impact on the RACH performance. We consider a synchronized activation of a large amount of UEs in an MulteFire/LTE unlicensed cell, and analyze the time it takes to connect all of them to the base station. Our results confirm that the presence of Wi-Fi substantially degrades RACH performance, with an increase of almost 50% per additional Wi-Fi station. Furthermore, we illustrate applications of our evaluation for RACH resource dimensioning and network planning.