On Secrecy Analysis of Underlay Cognitive UAV-Aided NOMA Systems With TAS/MRC

This article investigates the secrecy performance for an unmanned aerial vehicle (UAV)-aided nonorthogonal multiple access (NOMA) network in the context of an underlay cognitive radio. Specifically, a multiantenna secondary source (
$S$
) transmits a mixed signal incorporated with NOMA to two multiantenna secondary destinations (
$D_{i}$
) via a UAV-enabled decode-and-forward relay in the presence of an eavesdropper (
$E$
). In addition, both a transmit antenna selection scheme at
$S$
and a maximal ratio combining protocol at
${D_{i}}$
and
$E$
are taken into account. Considering all the links undergo Nakagami-
$m$
fading with path loss, we analyze the secrecy performance in terms of secrecy outage probability for both users. Moreover, we also use Monte-Carlo simulations to verify the accuracy of those derived expressions.