Outage Performance of Cooperative MISO-NOMA Based Satellite-Terrestrial Networks

This paper studies the outage performance of a cooperative multiple-input single-output satellite-terrestrial net-work in which the satellite equipped with multiple antennas simultaneously serves two single antenna terrestrial users in a non-orthogonal manner, called MISO-NOMA. Specifically, the satellite utilizes the maximal-ratio transmission technique while the user with strong channel gain (called the strong user) assists to the user with weak channel gain (called the weak user) by acting as a decode-and-forward relay with prior knowledge of weak user. We assume that channels are subjected to Shadowed-Rician and Nakagami-m fading for the satellite and terrestrial links, respectively. In order to characterize the performance behavior of both users, outage probability expressions are derived. Theoretical results validated by simulations demonstrate that user-cooperation has more impact on the performance improvement of the weak user under heavy shadowing condition which is the most crucial channel effect in satellite-terrestrial environment. In addition, with the increasing number of antennas, the weak and strong users receive the best performance improvement in non-cooperation and user-cooperation cases, respectively.