A Novel Random Access Scheme Based on Successive Interference Cancellation for 5G Networks

The massive amounts of machine-type user equipments (UEs) will be supported in the future fifth generation (5G) networks. However, the potential large random access (RA) delay calls for a new RA scheme. Motivated by the key idea of non-orthogonal multiple access, the non-orthogonal random access (NORA) scheme is proposed in this paper to alleviate the access congestion problem. Specifically, NORA utilizes the difference of time of arrival to identify multiple UEs with the identical preamble, and enables power domain multiplexing of collided UEs in the following access process, while the base station performs successive interference cancellation (SIC) based on the channel conditions obtained through preamble detection. Our analysis shows that the performance of NORA is superior to the conventional orthogonal random access (ORA) scheme in terms of collision probability and throughput. Simulation results verify our analysis and further show that our NORA scheme can improve the number of the supported UEs by more than 30%. Moreover, the access delay for successfully accessed UEs are also reduced significantly by using the proposed random access scheme.