Cooperative-NOMA Assisted by Relay With Sensing and Transmission Capabilities in Underlay Cognitive Hybrid Satellite-Terrestrial Networks

This paper proposes a spectrum sharing scheme for an underlay cognitive hybrid satellite-terrestrial network. The primary network, consisting of a satellite source and its terrestrial receiver, shares spectrum bands with a secondary terrestrial network that comprises two secondary transmitters and their mutual receiver, which employ a cooperative non-orthogonal multiple access (NOMA) scheme. The strong NOMA-user adopts a relaying strategy to enhance the far-away weak NOMA-user's performance. Furthermore, the relay is equipped with sensing and transmission capabilities and operates them alternately. By real-time sensing and identifying the idle spectrum resources of the terrestrial network, an appropriate form for its transmission signal is accordingly selected, thereby realizing efficient utilization of spectrum and power resources. Through exploiting mutual interference and calculating the transmit powers of secondary transmitters for a predetermined outage constraint, we analyze the performance based on the calculated transmit powers at secondary transmitters for a predetermined outage constraint at the primary receiver. Finally, a simulation comparison is conducted to verify the superior performance of our proposed scheme.