Cognitive IoT relaying NOMA networks with user clustering and imperfect SIC

To implement machine type communications (MTCs) in next generation mobile networks, Narrowband-Internet of Things (NB-IoT) need be studied. Such NB-IoT has been released by the third generation partnership project (3GPP) as a promising method to exhibit extended coverage and low energy consumption, especially for cheap MTC devices. However, the existing NB-IoT using orthogonal multiple access (OMA) scheme which cannot provide connectivity for a massive MTC devices. In this paper, we consider NB-IoT using non-orthogonal multiple access (NOMA). We find that power allocation factors for devices in clustering users as main enabler to exhibit differences in term of performance of devices. The worse situation of imperfect successive interference cancellation (SIC) is further studied due to main reason regarding degraded system performance. We derive closed-form expressions of outage probability for devices in a cluster to highlight main parameters affecting quality of devices. We verify our mathematical analysis via Monte-Carlo simulations.