  This paper investigates the impact of realistic propagation conditions on the
achievable secrecy performance of multiple-input multiple-output systems in the
presence of an eavesdropper. Specifically, we concentrate on the $\kappa$-$\mu$
shadowed fading model because its physical underpinnings capture a wide range
of propagation conditions, while, at the same time, it allows for much better
tractability than other state-of-the-art fading models. By considering transmit
antenna selection and maximal ratio combining reception at the legitimate and
eavesdropper's receiver sides, we study two relevant scenarios $(i)$ the
transmitter does not know the eavesdropper's channel state information (CSI),
and $(ii)$ the transmitter has knowledge of the CSI of the eavesdropper link.
For this purpose, we first obtain novel and tractable expressions for the
statistics of the maximum of independent and identically distributed (i.i.d.)
variates related to the legitimate path. Based on these results, we derive
novel closed-form expressions for the secrecy outage probability (SOP) and the
average secrecy capacity (ASC) to assess the secrecy performance in passive and
active eavesdropping scenarios, respectively. Moreover, we develop analytical
asymptotic expressions of the SOP and ASC at the high signal-to-noise ratio
regime. In all instances, secrecy performance metrics are characterized in
closed-form, without requiring the evaluation of Meijer or Fox functions. Some
useful insights on how the different propagation conditions and the number of
antennas impact the secrecy performance are also provided.
