In this work, we present a unified performance analysis of a free-space optical (FSO) link that accounts for pointing errors and both types of detection techniques (i.e. intensity modulation/direct detection (IM/DD) as well as heterodyne detection). More specifically, we present unified exact closedform expressions for the cumulative distribution function, the probability density function, the moment generating function, and the moments of the end-to-end signal-to-noise ratio (SNR) of a single link FSO transmission system, all in terms of the Meijer's G function except for the moments that is in terms of simple elementary functions. We then capitalize on these unified results to offer unified exact closed-form expressions for various performance metrics of FSO link transmission systems, such as, the outage probability, the scintillation index (SI), the average error rate for binary and M -ary modulation schemes, and the ergodic capacity (except for IM/DD technique, where we present closed-form lower bound results), all in terms of Meijer's G functions except for the SI that is in terms of simple elementary functions. Additionally, we derive the asymptotic results for all the expressions derived earlier in terms of Meijer's G function in the high SNR regime in terms of simple elementary functions via an asymptotic expansion of the Meijer's G function. We also derive new asymptotic expressions for the ergodic capacity in the low as well as high SNR regimes in terms of simple elementary functions via utilizing moments. All the presented results are verified via computer-based Monte-Carlo simulations.Index Terms-Free-space optical (FSO) communications, optical wireless communications, pointing errors, Lognormal turbulence channels, Gamma-Gamma turbulence channels, Málaga (M) turbulence channels, outage probability (OP), binary modulation schemes, bit-error rate (BER), symbol error rate (SER), scintillation index (SI), ergodic capacity, Meijer's G function.are cost-effective relative to the traditional RF links. It is a promising technology as it offers full-duplex Gigabit Ethernet throughput in certain applications and environment offering a huge license-free spectrum, immunity to interference, and high security [1]. These features of FSO communication systems potentially enable solving the issues that the RF communication systems face due to the expensive and scarce spectrum [1]-[10]. Additionally, FSO communications does offer bandwidth as the world record stands at 1.2 Tbps or 1200 Gbps [11]. Besides these nice characteristic features of FSO communication systems, they span over long distances of 1Km or longer. However, the atmospheric turbulence may lead to a significant degradation in the performance of the FSO communication systems [1].Thermal expansion, dynamic wind loads, and weak earthquakes result in the building sway phenomenon that causes vibration of the transmitter beam leading to a misalignment between transmitter and receiver known as pointing error. These pointing errors may lead to significant perfo...

In this paper, we carry out a unified performance analysis of a dual-hop relay system over the asymmetric links composed of both radio-frequency (RF) and unified free-space optical (FSO) links under the effect of pointing errors. Both fixed and variable gain relay systems are studied. The RF link is modeled by the Nakagami-m fading channel and the FSO link by the Gamma-Gamma fading channel subject to both types of detection techniques (i.e., heterodyne detection and intensity modulation with direct detection). In particular, we derive new unified closed-form expressions for the cumulative distribution function, the probability density function, the moment generating function (MGF), and the moments of the end-to-end signal-to-noise ratio (SNR) of these systems in terms of the Meijer's G function. Based on these formulas, we offer exact closed-form expressions for the outage probability (OP), the higher order amount of fading, and the average bit error rate (BER) of a variety of binary modulations in terms of the Meijer's G function. Furthermore, an exact closed-form expression of the end-to-end ergodic capacity is derived in terms of the bivariate G function. Additionally, by using the asymptotic expansion of the Meijer's G function at the high-SNR regime, we derive new asymptotic results for the OP, the MGF, and the average BER in terms of simple elementary functions.

Abstract-In this work, the performance analysis of a dualhop relay transmission system composed of asymmetric radiofrequency (RF)/free-space optical (FSO) links with pointing errors is presented. More specifically, we build on the system model presented in [1] to derive new exact closed-form expressions for the cumulative distribution function, probability density function, moment generating function, and moments of the end-to-end signal-to-noise ratio in terms of the Meijer's G function. We then capitalize on these results to offer new exact closed-form expressions for the higher-order amount of fading, average error rate for binary and M -ary modulation schemes, and the ergodic capacity, all in terms of Meijer's G functions. Our new analytical results were also verified via computer-based MonteCarlo simulation results.

Error performance is one of the main performance measures and derivation of its closed-form expression has proved to be quite involved for certain systems. In this letter, a unified closed-form

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