On the capacity of decode-and-forward dual-hop free space optical communication systems

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 Málaga 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. INDEX TERMS Physical layer security, Generalized Gamma fading, Málaga fading, variable gain relay, average secrecy capacity, strictly positive secrecy capacity, and secrecy outage probability.

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“…The PDF of equivalent SNR at the destination for the dualhop system can be derived by differentiating (8) with respect to Ψ D as [41,Eq. (12)]…”

Section: Pdf and Cdf Of Snr For Dual-hop Rf-fso Linkmentioning

confidence: 99%

On Secrecy Performance of Mixed Generalized Gamma and Málaga RF-FSO Variable Gain Relaying Channel

et al. 2020

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“…From (16) we realize that P out is nothing but the cumulative distribution function (CDF) of γ eq min γ RF , γ eff FSO evaluated at γ out (2 2R − 1), this CDF, and hence P out , can be expressed as [36]…”

Section: Outage Probabilitymentioning

confidence: 99%

Precise Performance Analysis of Dual-Hop Mixed RF/Unified-FSO DF Relaying With Heterodyne Detection and Two IM-DD Channel Models

et al. 2019

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This paper provides precise performance analysis of the dual-hop mixed radio frequency (RF)/unified free space optical (FSO) decode-and-forward (DF) relaying system, in which the heterodyne detection and the intensity modulation-direct detection (IM-DD) are taken into account for FSO detection. To this end, we derive closed-form expressions for the outage probability, average bit error rate (BER), and the ergodic channel capacity of this system. In this analysis, we utilize, for the first time as per our knowledge, a precise channel capacity result for the IM-DD channel. Moreover, this is the first time that not only the (IM-DD input-independent) but also the (IM-DD cost-dependent) additive white Gaussian noise (AWGN) channel is considered in such system analyses. Additionally in this study, we assume that the first hop (RF link) follows Nakagami-m fading, and the second hop (FSO link) follows Málaga (M) turbulence with pointing errors. These fading and turbulence models contain other models (such as Rayleigh and Gamma-Gamma) as special cases, thus, our analyses can be seen as a generalized one from the RF and FSO fading models point of view. Also, in BER derivation, we assume that the modulation schemes in the two hops can be different, since not all modulation schemes are suitable for IM-DD FSO links. In addition, the system performance is investigated asymptotically at high signal to noise ratios. This investigation leads to new nonreported coding gain and diversity order analyses of such system. Interestingly, we find that in the FSO hop, at high transmitted powers, all the considered FSO detectors result in the same diversity order. Furthermore, we provide simulation results that verify the accuracy of the obtained analytical and asymptotic expressions.

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“…Furthermore, FSO systems have the ability to support higher data-rates and use license-free spectrum for operation, thus making them ideally suited for communication applications. Extension of the cooperative communication paradigm to FSO systems has been proposed by Anees and Bhatnagar [33], [34]. These systems employ the subcarrier intensity modulation (SIM) technique for transmission of M -ary PSK modulated optical symbols over FSO links, as described in [35].…”

Section: Fso Based Multi-relay Cooperative Systemsmentioning

confidence: 99%

“…The instantaneous SNRs at each relay r and destination node in the first phase can be expressed as γ RD corresponding to the source-destination, source-relay r, and relay r-destination links, respectively. The PDF of β SD denoted by f βSD (x) can be obtained as [33] …”

Section: (R)mentioning

confidence: 99%

Asymptotic SER Analysis and Optimal Power Sharing for Dual-Phase and Multi-Phase Multiple-Relay Cooperative Systems

2018

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Abstract-The asymptotic high-SNR symbol error rate (SER) performance of selective decode-and-forward (DF) cooperative multiple relay aided wireless systems is derived for M -PSK and M -QAM modulations. The proposed analysis considers both dual-phase and multi-phase relaying protocols. Furthermore, analytical results are also presented for optimal power allocation both at the source and at each of the relays, since it significantly influences the performance of cooperative communication. A novel aspect of the proposed framework is that the SER and optimal power allocation results derived are applicable to diverse fading channels such as η − µ, κ − µ, shadowed-Rician scenarios and each for non-identical fading for the source-destination (SD), source-relay (SR), and relay-destination (RD) links. The applicability of the proposed framework is also demonstrated for diverse PHY layer schemes, such as multiple-input multipleoutput (MIMO)-orthogonal space time block codes (OSTBCs), cooperative beamforming, joint transmit/receive antenna selection, free space optical (FSO) scenarios etc. This high-SNR analysis provides valuable insights into the impact of the diversity orders of the SR and RD links on the end-to-end SER as well as on the optimal power allocation factors both in the dualphase and multi-phase protocols of various fading channels and schemes. Our simulation results verify the analytical results derived.

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On the capacity of decode-and-forward dual-hop free space optical communication systems

Cited by 24 publications

References 12 publications

On Secrecy Performance of Mixed Generalized Gamma and Málaga RF-FSO Variable Gain Relaying Channel

On Secrecy Performance of Mixed Generalized Gamma and Málaga RF-FSO Variable Gain Relaying Channel

Precise Performance Analysis of Dual-Hop Mixed RF/Unified-FSO DF Relaying With Heterodyne Detection and Two IM-DD Channel Models

Asymptotic SER Analysis and Optimal Power Sharing for Dual-Phase and Multi-Phase Multiple-Relay Cooperative Systems

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