Power Allocation and Performance Evaluation for NOMA-Aided Integrated Satellite-HAP-Terrestrial Networks Under Practical Limitations

Satellite and high-altitude platform (HAP) are considered as the key parts of the next generation networks, and specifically for the Internet-of-Things networks, which are utilized to provide unobstructed connections and massive user access for terrestrial networks. In this article, we investigate the power allocation (PA) and system performance of nonorthogonal multiple access (NOMA)-enabled integrated satellite-HAP-terrestrial systems under practical limitations. Particularly, a practical system model is established by considering the channel estimation errors and imperfect successive interference cancelation at the receiver. To achieve the different quality of service requirements among multiple served users, we propose a novel NOMA-based PA scheme. In addition, the analytical and asymptotic expressions for the outage probability of NOMA users are obtained to verify the proposed scheme as well as the ergodic capacity. Finally, numerical results are corroborated with Monte Carlo simulations, which show the correctness of our analytical results, and the benefits of our proposed scheme. The proposed scheme indicates that the HAP relay link plays a significant role in the system performance.