Physical layer security has re-emerged as a focal point of research in
information and communication theory due to the importance of its potential
applications. Building on the pioneering works of Wyner and Csiszár and
Körner, it has been demonstrated that a noisy communication channel offers
opportunities for perfectly secret information exchange as long as a
legitimate user has a Signal-to-Noise Ratio advantage in respect to an
eavesdropper. In particular, it has been shown that in situations where the
eavesdropper’s channel is on average a degraded version of the main channel,
a positive secrecy capacity can be guaranteed. These results have recently
been extended for the wireless fading channel, Multiple- Input
Multiple-Output and cooperative systems using jamming.

Nevertheless, physical layer security is still considered a primarily
theoretical area as only a few practical system proposals have so far come
to light. In this talk, we investigate physical layer security paradigms
aiming to bridge some of the gap between theory and practice. Firstly, we
explore alternatives to achieve perfect secrecy by exploiting topological
and mobility asymmetries between a legitimate user and potential
eavesdroppers. Then, we discuss optimal jamming interfering strategies for
M-QAM and M-PSK systems. Finally, we conclude with investigating the idea of
incorporating secrecy in the Quality of Service metrics of the network.