Throughput Assessment of Priority-based Semi-Grant-Free NOMA Protocol

Motivated by the emergence of next-generation internet-of-things applications, this paper introduces a novel non-orthogonal semi-grant-free multiple access protocol that enables reliable massive connectivity of scheduled and random access devices with varying data rate requirements. Specifically, the protocol divides devices into two classes, namely primary and secondary devices. Primary devices (PDs) have high data rate requirements, while secondary devices (SDs) transmit data at a lower frequency compared to primary devices, and have a lower data rate requirement. The base-station (BS) enables a single PD and two SDs to access the same radio resource block (RRB). The PD uses grant-based (GB) access to the RRB, while the secondary devices use grant-free (GF) access. The BS first decodes the PD signal by treating the SDs signals as interference. Then, it decodes the signal of the SD with the higher channel gain. To assess the performance of the proposed protocol, we carried out simulations and measured the achieved throughput of each device under various parameters, such as power-to-noise gain, signal-to-noise threshold, and transmission probability.