Abstract
In this paper, the physical layer security (PLS) challenges for a decode and forward (DF) based dual hop mixed free space optical (FSO) / radio frequency (RF) communication system in the presence of multiple eavesdroppers has been investigated. In order to improve the PLS of the energy efficient co-operative communication system, diversity combining techniques have been introduced at the destination node. In addition to this, collusion and non collusion eavesdropper scenarios are considered to make the system more practical. The FSO and RF links are assumed to experience independent Málaga ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mathcal {M}$</tex-math></inline-formula> ) and Nakagami- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$m$</tex-math></inline-formula> fading distributions, respectively. Additionally, the FSO link model considers the impact of boresigt and non-zero boresight pointing errors and type of optical demodulation scheme. To investigate the security performance, the lower bound for the secrecy outage probability (SOP) and effective secrecy throughput (EST) have been obtained in terms of Meijer’s G function. Thereafter, asymptotic expressions have been derived for the considered system and the numerical results have been verified by the Monte-Carlo simulation method. Finally, we have analyzed the secrecy energy efficiency (SEE) based on secrecy rate ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$R_s$</tex-math></inline-formula> ) of the considered system to provide practical insights into the effect of major parameters on the energy efficient secure transmission design.
Highlights
Theorem 4: The closed-form expression for the lower bound of secrecy outage probability (SOP), SOPLSC, when selection combining (SC) is employed in the presence of multiple eavesdroppers for the considered mixed free space optical (FSO)/radio frequency (RF) decode and forward (DF) relaying system can be obtained as (19)
We have studied the secrecy performance of a DF based dual link mixed FSO/RF system in the presence of multiple eavesdroppers
We have considered the effect of non-zero boresight pointing error in the analysis
Summary
Free space optical (FSO) communication systems have been gaining recognition as valid contender to solve the bandwidth deficiency problem in radio frequency (RF) systems. FSO communication suffer from some inbuilt complications such as: 1) requirement of a line-of-sight (LoS) path, 2) impact of pointing deflection caused due to natural phenomenon such as earthquake, wind flow and thermal expansion of the device etc., 3) sensitive to atmospheric turbulence effects. These aforementioned key problems may lead to link failure. To improve the performance of such systems, researchers focused on the mixed architecture such as parallel and serial combinations of the RF and FSO links These structures are widely studied for single hop as well as for dual hop scenarios [5]-[31]
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