Abstract
In this article, we study the physical layer security of free-space optical (FSO) communications under different eavesdropping scenarios. More specifically, the secrecy performance of FSO communication employing intensity modulation/direct detection detection is analyzed for the well-established Málaga channels. Three different realistic scenarios of eavesdropping are considered by assuming different placement locations for the eavesdropper in the paper. Novel expressions for the average secrecy capacity (ASC) and secrecy outage probability (SOP) are derived for the considered scenarios, and useful insights are also provided through asymptotic analysis. The results show: (1) When the eavesdropper is placed near the transmitter, atmospheric condition imposes a less significant impact on secrecy performance; (2) Certain level of correlation can potentially enhance the secrecy performance for FSO communications; (3) The correlation imposes opposite impacts on the ASC and SOP of FSO communications; and the secrecy performance metrics exhibit a non-monotonic impact with the increase of correlation; (5) When the correlation of the FSO links is too small or too large (i.e., the correlation parameter around 0 or 1), the correlation plays a more significant impact on secrecy performance; and (6) The asymptotic slope of the SOP is 0.5 for all eavesdropping scenarios under practical FSO channels.
Highlights
Physical layer security (PLS) has recently been considered as a complementary technique to the conventional encryption schemes to improve the communication secrecy [1]–[3]
The results show: (1) When the eavesdropper is placed near the transmitter, atmospheric condition imposes a less significant impact on secrecy performance; (2) Certain level of correlation can potentially enhance the secrecy performance for free-space optical (FSO) communications; (3) The correlation imposes opposite impacts on the average secrecy capacity (ASC) and secrecy outage probability (SOP) of FSO communications; and the secrecy performance metrics exhibit a non-monotonic impact with the increase of correlation; (5) When the correlation of the FSO links is too small or too large, the correlation plays a more significant impact on secrecy performance; and (6) The asymptotic slope of the SOP is 0.5 for all eavesdropping scenarios under practical FSO channels
We conducted a comprehensive study on the PLS for the FSO communications under three different scenarios
Summary
Physical layer security (PLS) has recently been considered as a complementary technique to the conventional encryption schemes to improve the communication secrecy [1]–[3]. It is demonstrated that communication nodes can exploit the variations in the communication channels to increase the communication security against eavesdropping [3] This observation has attracted an increasing amount of interest in the research community to investigate the physical layer secrecy performance of communication systems under different setups [4]–[10]. The performance of secure FSO communication was studied in [13] by assuming both the main and wiretap links following independent Málaga distributions. Motivated by the latest advances in the PLS analysis on FSO communication and aiming at investigating the PLS performance of FSO communications under more realistic conditions, we study in this paper the secrecy performance of FSO communications under the Wyner’s wiretap model over Málaga fading channels under different realistic scenarios. Eq (2.56)], which can be readily evaluated with Mathematica [20, Table I], U (·, ·, ·) is the Kummer hypergeometric function [18, Eq (9.210)]
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