Abstract: In order to increase the number of access in the fifth-generation systems, a hybrid multiple random access (RA) scheme is proposed. The proposed scheme allows user equipments to select the orthogonal multiple access (OMA) RA or the non-orthogonal multiple access (NOMA) RA by a predicted signal noise ratio and predefined thresholds. In order to improve the performance of interference cancelation, a power back-off scheme is applied to guarantee the received powers of overlapped signals are diverse. In addition, the access performance of hybrid RA is theoretically analyzed. In the simulation, both numerical results and simulation results in practical systems are provided. Simulation results show that the proposed RA procedure significantly improves the number of successful access compared with single OMA RA or NOMA RA.

Key words: massive connections, hybrid multiple access, random access, power back-off