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Iterative Hard Thresholding-based Multiuser Detector for Uplink Grant Free NOMA Systems

It has been justified that non-orthogonal multiple access (NOMA) scheme is the best multiuser-based transmission scheme for 5G wireless networks. Most importantly is its feature to ensure optimum utilization of scarce wireless resource, the bandwidth. In order to exploit all the advantages associated with the NOMA system, it is essential to provide robust signal processing techniques at the receiver of this system. This paper focuses on one of those signal processing requirements for NOMA system, the multiuser detector (MUD) scheme. Specifically, a multiuser detector based on iterative hard thresholding with accelerated step-size (IHT_ASS) is proposed. The proposed IHT_ASS-based MUD is compared with three other MUDs based on compressive sensing algorithms. The computer simulation results indicate that the proposed IHT_ASS-based MUD outperformed the other three MUDs, however with slightly high computational complexity cost in comparison with the two of the other three MUDs considered in this paper.