Resource Allocation in Non-Orthogonal Random Access for M2M Communications

To address signaling overhead and resource shortage problems of Machine-to-Machine (M2M) communications in cellular networks, we propose a joint non-orthogonal random access (NORA) and data transmission (DT) scheme, i.e. NORA-DT scheme. Considering the fact that most machine-type communication devices (MTCDs) just transmit small-size data, NORA-DT allows MTCDs to schedule the corresponding Physical Uplink Shared Channel (PUSCH) resources after transmitting preambles, and then directly transmit data packets along with the connection setup request message (Msg.3) to simplify the access process. Based on the proposed NORA-DT scheme, we propose a resource allocation scheme which can allocate uplink resources between Physical Random Access Channel (PRACH) and PUSCH reasonably. As a result, the resource allocation can maximize the utilization of throughput and uplink resources. Simulation results show that compared with orthogonal random access and transmission scheme (ORADTP), the proposed scheme can improve resource efficiency by about 30%.