2 research outputs found
Effects of Eavesdropper on the Performance of Mixed {\eta}-{\mu} and DGG Cooperative Relaying System
Free-space optical (FSO) channel offers line-of-sight wireless communication
with high data rates and high secrecy utilizing unlicensed optical spectrum and
also paves the way to the solution of the last-mile access problem. Since
atmospheric turbulence is a hindrance to an enhanced secrecy performance, the
mixed radio frequency (RF)-FSO system is gaining enormous research interest in
recent days. But conventional FSO models except for the double generalized
Gamma (DGG) model can not demonstrate secrecy performance for all ranges of
turbulence severity. This reason has led us to propose a dual-hop eta-mu and
unified DGG mixed RF-FSO network while considering eavesdropping at both RF and
FSO hops. The security of these proposed scenarios is investigated in terms of
two metrics, i.e., strictly positive secrecy capacity and secure outage
probability. Exploiting these expressions, we further investigate how the
secrecy performance is affected by various system parameters, i.e., fading,
turbulence, and pointing errors. A demonstration is made between heterodyne
detection (HD) and intensity modulation and direct detection (IM/DD) techniques
while exhibiting superior secrecy performance for HD technique over IM/DD
technique. Finally, all analytical results are corroborated via Monte-Carlo
simulations
Physical-Layer Security for Two-Hop Air-to-Underwater Communication Systems With Fixed-Gain Amplify-and-Forward Relaying
We analyze a secure two-hop mixed radio frequency (RF) and underwater
wireless optical communication (UWOC) system using a fixed-gain
amplify-and-forward (AF) relay. The UWOC channel is modeled using a unified
mixture exponential-generalized Gamma distribution to consider the combined
effects of air bubbles and temperature gradients on transmission
characteristics. Both legitimate and eavesdropping RF channels are modeled
using flexible distributions. Specifically, we first derive both
the probability density function (PDF) and cumulative distribution function
(CDF) of the received signal-to-noise ratio (SNR) of the mixed RF and UWOC
system. Based on the PDF and CDF expressions, we derive the closed-form
expressions for the tight lower bound of the secrecy outage probability (SOP)
and the probability of non-zero secrecy capacity (PNZ), which are both
expressed in terms bivariate Fox's -function. To utilize these analytical
expressions, we derive asymptotic expressions of SOP and PNZ using only
elementary functions. Also, we use asymptotic expressions to determine the
optimal transmitting power to maximize energy efficiency. Further, we
thoroughly investigate the effect of levels of air bubbles and temperature
gradients in the UWOC channel, and study nonlinear characteristics of the
transmission medium and the number of multipath clusters of the RF channel on
the secrecy performance. Finally, all analyses are validated using Monte Carlo
simulation