CR-NOMA Aided Aerial Relay With Dual Roles and Hybrid Long-Short-Packet Transmission

Abstract

To tackle the challenges of high spectrum demand from massive Internet of Things (IoT) communications, this paper proposes a uncrewed aerial vehicle-assisted cognitive radio (CR) non-orthogonal multiple access (NOMA) transmission scheme. Specifically, a secondary aerial IoT base station concurrently acts as a relay to assist the transmission of primary network with favorable aerial-ground channels, and in return, IoT devices of the secondary network can utilize the primary network’s spectrum resources for data transmission. To reduce the signaling overhead of the secondary network, we adopt a hybrid long-short-packet transmission strategy, with primary users using long-packet transmission and secondary IoT devices utilizing short-packet transmission. Inspired by the notion of CR-NOMA, we propose two power allocation algorithms to respectively avoid affecting the quality-of-service (QoS) and age-of-information (AoI) of the primary network. For rigorous performance evaluation, we derive the theoretical expressions of outage probability, block error rate, and AoI performance for both power allocation algorithms. Moreover, for analytical tractability, we derive the high signal-to-noise-ratio (SNR) approximation expressions for the peak AoI (PAoI) of secondary users (SUs), by which the transmission blocklength of the SUs is optimized to minimize the PAoI performances. Finally, we present simulation results to validate the correctness of the theoretical expressions. The results further demonstrate that the SUs of the AoI-based approach achieves superior performance in the low SNR region, whereas the QoS-based approach is more favorable in the moderate SNR region.