Communications in cyber-physical systems : semantic-functional approach, vulnerability, and physical layer performance

Abstract

This doctoral dissertation explores semantic knowledge to minimize the use of explicit communication and proposes a tailor-made design for a multiuser network in a cyberphysical system (CPS). A new perspective for radio access and physical media sharing is introduced for multiuser communication; this approach jointly considers (i) the meaning of the transmitted message and (ii) its function at the end user. By suggesting a semanticfunctional approach to the CPS, this doctoral dissertation leverages implicit communication while guaranteeing the functionality and performance of the system. More specifically, semantic-functional communication can reduce the use of physical radio resources to a system of sensors that communicate alarm messages to a central node. The proposed semantic-functional approach is successfully tested for a swarm of drones. Furthermore, the successful joint operation of the semantic-functional communication with the radiofrequency-based energy harvesting is demonstrated.

Other aspects of communication in multiuser systems are also covered. The privacy of dynamic directional modulation regarding information leakage is evaluated. Dynamic directional modulation can enhance broadcast transmission security by randomly selecting an antenna from an array as the transmitter and applying a suitable correction to the transmitted signal phase. The phase correction enables the legitimate receiver to decode the message. This doctoral dissertation derives some privacy boundaries inherent to dynamic directional modulation and evaluates how an eavesdropper could extract the maximum information from a dynamic directional modulation signal. Based on the optimal case for the eavesdropper, some guidelines that aim to maximize security are proposed for antenna array design. In addition, the information leakage of a dynamic directional modulation system operating with a uniform circular monopole antenna array and an equiprobable transmitting antenna is evaluated.

Finally, the partially-coherent M-psk performance over κ-μ Extreme fading is evaluated. Coherent detection assumes a perfect carrier recovering on the receiver side; however, this assumption is somewhat unsound, at least for more realistic scenarios. In fact, disturbances inherent to the channel lead to an imperfect phase estimation. Assuming a partially-coherent detection whose mismatch phase follows a Gaussian distribution and κ-μ Extreme fading, analytical expressions for the upper bound on the average symbol error probability are derived. The theoretical results are valid for arbitrary values of the κ-μ Extreme distribution and are corroborated by Monte Carlo simulations. In the high signal-to-noise ratio regime, the asymptotic behavior of the average symbol error rate is present.