  The extensive deployment of Low Earth Orbit (LEO) satellites introduces
significant security challenges for communication security issues in Internet
of Things (IoT) networks. With the rising number of satellites potentially
acting as eavesdroppers, integrating Physical Layer Security (PLS) into
satellite communications has become increasingly critical. However, these
studies are facing challenges such as dealing with dynamic topology
difficulties, limitations in interference analysis, and the high complexity of
performance evaluation. To address these challenges, for the first time, we
investigate PLS strategies in satellite communications using the Stochastic
Geometry (SG) analytical framework. We consider the uplink communication
scenario in an LEO-enabled IoT network, where multi-tier satellites from
different operators respectively serve as legitimate receivers and
eavesdroppers. In this scenario, we derive low-complexity analytical
expressions for the security performance metrics, namely availability
probability, successful communication probability, and secure communication
probability. By introducing the power allocation parameters, we incorporate the
Artificial Noise (AN) technique, which is an important PLS strategy, into this
analytical framework and evaluate the gains it brings to secure transmission.
In addition to the AN technique, we also analyze the impact of constellation
configuration, physical layer parameters, and network layer parameters on the
aforementioned metrics.
