Physical layer security (PLS) solutions for passive eavesdropping in wireless communication
Abstract
An absolute secured wireless communication is unattainable. Nevertheless, communication models must be secure and unique across each layer of the model. The
physical layer is the easiest layer through which information leaks, due to its broadcast nature. The security in the physical layer, measured as secrecy capacity, is
subdivided into keyed and keyless security models. In practice, the eavesdropper’s
evasive and obscure random wireless channel model makes it difficult to optimise
keyless security measure at the physical layer. Considering this practical challenge,
the objective of this work is to use novel keyless approaches to reduce the ability of
an illegitimate user to access the transmitted message via the physical layer. Physical layer security (PLS) was achieved through the deployment of unmanned aerial
vehicles (UAV), intelligent reflecting surfaces (IRS), and communication sensing as
security enablers in this thesis. The UAV operates with interfering signals while the
IRS and sensing techniques optimise respective inherent properties leading to higher
PLS performance. The thesis presents solutions to the parametric design of UAV,
IRS, and wireless sensing technologies for PLS functionality. Designs and analysis
herein follow from analytical derivations and numerical simulations. Specifically, the
thesis presents a novel average secrecy rate formulation for passive eavesdropping
with a reception rate upper bound by that of the legitimate receiver. The keyless
PLS assessed from the formulations guaranteed positive rates with the design of a
broadcast interfering signal delivered from a UAV. Based on the verification of the
positive secrecy rate with passive eavesdropping, a swarm of UAVs improved the
PLS of the communication system delivering more interfering signals. Furthermore,
the functionalities of the interference driven UAV swarm were miniaturised with a
system of aerial IRS. By harnessing inherent channel dynamics, a novel non-iterative
design of the aerial IRS system was presented as a panacea to PLS requirements.
Finally, the thesis presents the analysis of a legitimate receiver with a novel noise
and interference filter as a sensing mitigation technique. The filter enhanced PLS
by enabling the legitimate receiver to effectively extract desired information.