  In this era of 5G technology, the ever-increasing demands for high data rates
lead researchers to develop hybrid satellite-terrestrial (HST) networks as a
substitution to the conventional cellular terrestrial systems. Since an HST
network suffers from a masking effect which can be mitigated by adopting the
terrestrial relaying strategy, in this work, we focus on wireless multicasting
through an HST relaying net-work (HSTRN) in which a satellite sends messages to
multiple terrestrial nodes via multiple relays under the wiretapping efforts of
multiple eavesdroppers. Our concern is to protect the multicast messages from
being eavesdropped taking advantage of the well-known opportunistic relaying
technique. We consider the satellite links follow Shadowed Rician fading
whereas the terrestrial links undergo alpha-mu fading. The secrecy performance
of the proposed HSTRN model is accomplished by deriving expressions for the
probability of nonzero secrecy multicast capacity, ergodic secrecy multicast
capacity, and secure outage probability for multicasting in closed-form.
Capitalizing on the derived expressions, we analyze how a perfect secrecy level
can be preserved in spite of harsh channel conditions and also present a
secrecy trade-off in terms of the number of relays, multicast users, and
multiple eavesdroppers. Finally, the numerical analyses are corroborated via
Monte-Carlo simulations.
