Prioritized random access for machine-to-machine communications in OFDMA based systems

In machine-to-machine (M2M) communications, machine nodes perform a random access (RA) to synchronize with the eNodeB in order to transmit their new packets. However, the conventional RA cannot support prioritized accesses during the RA procedure, even though there are a variety of classes with different quality-of-service (QoS). In this paper, we propose a prioritized random access (PRA) scheme, which enables machine nodes to indicate their access priority during the access phase by differentiating their transmission power level. Moreover, we thoroughly analyze the PRA scheme in terms of collision probability and access delay. The performance evaluation shows that the PRA scheme enables the nodes to indicate the access priority according to their QoS during the RA procedure as well as to achieve much lower collision probabilities and shorter access delay.