Abstract
The emergence of an array of new wireless networks has led researchers to evaluate the prospect of utilizing the physical properties of the wireless medium in order to design secure systems. In this paper, the physical layer secrecy performance of a mixed radio frequency-free space optical (RF-FSO) system with variable gain relaying scheme is investigated in the presence of an eavesdropper. We assume that the eavesdropper can wiretap the transmitted confidential data from the RF link only. It is further assumed that the main and eavesdropper RF links are modeled as generalized Gamma (GG) fading channel, and the free space optical (FSO) link experiences Malaga turbulence with pointing error impairment. Our primary concern is to protect this confidential information from being wiretapped. Besides pointing error, the atmospheric turbulence and two types of detection techniques (i.e. heterodyne detection and intensity modulation with direct detection) are also taken into consideration. Utilizing amplify-and-forward (AF) scheme, the novel mathematical closed-form expressions for average secrecy capacity, lower bound of secrecy outage probability, and strictly positive secrecy capacity are derived. As both the links (RF and FSO) undergo generalized fading channels, the derived expressions are also general. We present a unification of some existing works utilizing the proposed model to better clarify the novelty of this work. Finally, all the derived expressions are justified via Monte-Carlo simulations.
Highlights
INTRODUCTIONFixed gain and channel state information (CSI) assisted relaying technique was considered by the authors in [10] for a dual hop mixed radio frequency-free space optical (RF-Free space optical (FSO)) system
We present some numerical outcomes based on the derived expressions of average secrecy capacity (ASC), secure OP (SOP), and strictly positive secrecy capacity (SPSC)
NUMERICAL RESULTS This section illustrates the analytical results corresponding to the closed-form expressions of ASC, SPSC, and SOP
Summary
Fixed gain and channel state information (CSI) assisted relaying technique was considered by the authors in [10] for a dual hop mixed RF-FSO system They examined the channels’ performance by acquiring the closed-form expressions for OP and bit-error rate (BER). Considering variable gain relaying technique for both HD and IM/DD techniques, the authors of [24] derived the exact closed-form expression for average secrecy capacity (ASC) over Nakagami-m-Málaga fading model. We present some numerical outcomes based on the derived expressions of ASC, SOP, and SPSC As both of our channels (RF and FSO) are generalized fading channels, the performance of our dual-hop mixed RFFSO system unifies the secrecy performance of several existing models in the existing literature [35], [36].
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