Priority Random Access and User Barring Design for NOMA-ALOHA in Heterogeneous mMTC

This paper presents a priority random access (PRA) with non-orthogonal multiple access (NOMA)-ALOHA (PRANA) scheme to enable access priority control for machinetype devices (MTDs) with delay-sensitive and delay-tolerant requirements. To enhance the energy efficiency of random access, we also introduce a channel quality-based user barring algorithm (CQ-UBA) that can alleviate the user overload problem and reduce the average transmit power of MTDs. By extending CQ-UBA to the proposed PRA-NA scheme, simulation results demonstrate that the random access performance in terms of access delay and energy efficiency for delay-sensitive MTDs can be significantly improved compared to the conventional NOMA-ALOHA.