Outage Analysis of Multi-Relay NOMA-Based Hybrid Satellite-Terrestrial Relay Networks

This article investigates the outage performance of a novel two-user multi-relay non-orthogonal multiple access (NOMA)-based hybrid satellite-terrestrial relay network (HSTRN), in which one user has a direct link to the satellite (termed as the direct-link user), while the other user (termed as the relay-aided user) seeks the help of the direct-link user or the
$K$
dedicated decode-and-forward (DF) relays to acquire its desired signal. A relaying protocol and a three-stage relay selection strategy are proposed for minimizing the whole system outage probability (WSOP) and providing full diversity order (DO) for both users. Exact and asymptotic outage probabilities of the considered network are derived, showing that under the proposed relay selection strategy, the relay-aided user, the direct-link user and the whole system each can achieve a DO of
$K + 1$
. Finally, numerical results are presented to verify the theoretical analyses, manifest the impacts of key parameters on the system performance, and demonstrate the advantages of our proposed relay selection scheme over other benchmarks.