On the Performance of Cooperative IoT Using NOMA With Indoor–Outdoor Device Deployment

This work studies applying power-domain downlink nonorthogonal multiple accesses (NOMA) to connect devices in urban environments to nearby Internet of Things (IoT). Therefore, attenuation caused by walls and other obstacles is exploited to treat indoor devices akin to far users in conventional NOMA. The system model considered incorporates a mobile relay, such as unmanned aerial vehicle, to support the link between the base station and IoT devices, highlighting its unique advantages in optimizing the communication link, addressing dynamic challenges, and improving the IoT connectivity experience in urban settings. To capture a wide range of small-scale fading scenarios, the outdoor channel is modeled using the generalized $\kappa$ - $\mu$ fading. The performance of this system is analytically evaluated by deriving accurate closed-form expressions for the outage probability, erodic capacity, throughput, and energy efficiency. The obtained results, corroborated by Monte Carlo simulation, show that outdoor–indoor pairing is an efficient pairing approach given that the power allocated to the paired users is appropriately selected.