BER of an optically pre-amplified FSO system under Málaga turbulence, pointing errors, and ASE noise
01 Oct 2017-pp 1-6
TL;DR: The bit error rate (BER) performance of a FSO system assuming non-return-to-zero on-off keying modulation in the presence of ASE noise under M-turbulence and PEs is evaluated.
Abstract: The performance of a free space optical (FSO) communication system is significantly affected by atmospheric turbulence and pointing errors (PEs) apart from the additive noise which is assumed to be Gaussian. The Malaga or M-distribution encompasses various proposed statistical models for atmospheric turbulence in FSO systems. An optical pre-amplifier is an essential component of FSO systems for improving the receiver (Rx) sensitivity. However, optical pre-amplification results in amplified spontaneous emissions (ASE), which dominate the Rx thermal and shot noises. The square law photodetection process at the Rx in a FSO system necessitates the consideration of Chi-square statistics for the decision variable contrary to the Gaussian approximation that is widely used in the literature. In this paper, we evaluate the bit error rate (BER) performance of a FSO system assuming non-return-to-zero on-off keying modulation in the presence of ASE noise under M-turbulence and PEs. We also derive asymptotic BER expressions for the considered FSO system for large values of signal-to-noise ratio in terms of simple elementary functions. A further insight into the system is provided by performing the diversity analysis.
Citations
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TL;DR: The physical layer secrecy performance of a hybrid satellite and free-space optical (FSO) cooperative system is studied and it is found that with the AF with fixed gain scheme, the secrecy diversity order of the investigated system is only dependent on the channel characteristics of the FSO link and theFSO detection type, whereas the secrecy Diversity is zero when the relay node employs DF or AF with variable-gain schemes.
Abstract: In this paper, we study the physical layer secrecy performance of a hybrid satellite and free-space optical (FSO) cooperative system. The satellite links are assumed to follow the shadowed-Rician fading distribution, and the channel of the terrestrial link between the relay and destination is assumed to experience the gamma-gamma fading. For the FSO communications, the effects of different types of detection techniques (i.e., heterodyne detection and intensity modulation with direct detection) as well as the pointing error are considered. We derive exact analytical expressions for the average secrecy capacity and secrecy outage probability (SOP) for both cases of amplify-and-forward (AF) and decode-and-forward (DF) relaying. The asymptotic analysis for the SOP is also conducted to provide more insights on the impact of FSO and satellite channels on secrecy performance. It is found that with the AF with fixed gain scheme, the secrecy diversity order of the investigated system is only dependent on the channel characteristics of the FSO link and the FSO detection type, whereas the secrecy diversity is zero when the relay node employs DF or AF with variable-gain schemes.
104 citations
Cites methods from "BER of an optically pre-amplified F..."
...Remark 1: It is worth mentioning that another widely used distribution to model the FSO link is the Málaga model [25], [26]....
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TL;DR: It is shown analytically that, both correlation and pre-amplification do not affect the diversity order of the system, however, both factors have contrasting behaviour with respect to coding gain.
Abstract: This paper presents theoretical and experimental bit error rate (BER) results for a free-space optical (FSO) multiple-input-multiple-output system over an arbitrarily correlated turbulence channel. We employ an erbium-doped fiber amplifier at the receiver (Rx), which results in an improved Rx’s sensitivity at the cost of an additional non-Gaussian amplified spontaneous emission noise. Repetition coding is used to combat turbulence and to improve the BER performance of the FSO links. A mathematical framework is provided for the considered FSO system over a correlated non-identically distributed Gamma-Gamma channel; and analytical BER results are derived with and without the pre-amplifier for a comparative study. Moreover, novel closed-form expressions for the asymptotic BER are derived; a comprehensive discussion about the diversity order and coding gain is presented by performing asymptotic analysis at high signal-to-noise ratio (SNR). To verify the analytical results, an experimental set-up of a $2\times 1$ FSO-multiple-input-single-output (MISO) system with pre-amplifier at the Rx is developed. It is shown analytically that, both correlation and pre-amplification do not affect the diversity order of the system, however, both factors have contrasting behaviour with respect to coding gain. Further, to achieve the target forward error correction BER limit of $3.8\times 10^{-3}$ , a $2\times 1$ FSO-MISO system with a pre-amplifier requires 6.5 dB lower SNR compared with the system with no pre-amplifier. Moreover, an SNR penalty of 2.5 dB is incurred at a higher correlation level for the developed $2\times 1$ experimental FSO set-up, which is in agreement with the analytical findings.
10 citations
Cites methods from "BER of an optically pre-amplified F..."
...The authors in [24]–[27] studied the effect of turbulence and pointing error on the BER performance of an optically pre-amplified FSO system by considering different distributions to model the FSO channel....
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TL;DR: Based on the working principle of the photoelectric detector in atmospheric turbulence, an optical communication receiving system based on the detector gain factor regulation control is designed, which calculates the scintillation variance according to the received signal in real-time, establishes the function conversion relationship between the SCI variance and the gain factor, realizes the closed-loop regulation control of the detector, and improves the SNR of the receiving system as discussed by the authors.
Abstract: Space laser communication, with its strong anti-jamming capability, high transmission rate and good adaptability, offers hope for the establishment of 5G mobile networks in areas that are not conducive to the erection of cables, such as islands and remote land areas. Turbulent scintillation effect is one of the important factors affecting the performance of laser communication, which can lead to the increase of communication BER and even communication interruption. Based on the working principle of the photoelectric detector in atmospheric turbulence, an optical communication receiving system based on the detector gain factor regulation control is designed, which calculates the scintillation variance according to the received signal in real time, establishes the function conversion relationship between the scintillation variance and the gain factor, realizes the closed-loop regulation control of the detector gain factor, and improves the SNR of the receiving system. A ground-based 13km static laser communication experiment was set up to test the reception performance, and the test results show that the system reduces the communication BER by more than two orders of magnitude and can be kept at 1E-6 under medium to weak turbulence (discriminated by flash variance) at a communication rate of 2.5Gbps. The technology was applied to the test of laser 5G signal transmission between the airship and the ground, and for the first time, the mobile communication (access network) signal transmission with a downlink speed of 1.230Gbps and an uplink speed of 76.4Mbps is realized, which verified the performance of mobile signal transmission between the mobile base station and the fixed station on the ground.
References
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TL;DR: In this article, the authors derived the bit-error probability for a lightwave communications system using an amplitude-shift-keying (ASK) pulse modulation format and employing optical amplifiers such that amplified spontaneous emission noise dominates all other noise sources.
Abstract: A description is given of a relatively simple derivation of the bit-error probability for a lightwave communications system using an amplitude-shift-keying (ASK) pulse modulation format and employing optical amplifiers such that amplified spontaneous emission noise dominates all other noise sources Mathematically, this noise is represented as a Fourier series expansion with Fourier coefficients that are assumed to be independent Gaussian random variables The bit-error probability is given in a closed analytical form that is derived by the approximate evaluation of several integrals appearing in the analysis The author uses the theory to derive the Gaussian approximation and finds that it overestimates the bit-error rate by one to two orders of magnitude >
359 citations
"BER of an optically pre-amplified F..." refers background in this paper
...) of the decision variable is assumed to follow the non-central Chi-square distribution in the presence of the transmitted signal; whereas the central Chi-square distribution models the decision variable in the absence of the transmitted signal [18]–[20], [22], [23]....
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...where N0 = Nsphf(G− 1) is the noise power spectral density, h is the Planck’s constant, f is the frequency of interest, G is the OPA gain, Nsp is an imperfection factor with value unity, E is the bit energy, 2M is the number of degrees of freedom, and Iν(⋅) is the modified Bessel function of first kind and order ν [18]–[20], [22]....
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...for modeling the received signal statistics has also been highlighted in [18]–[20], [22]....
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TL;DR: In this paper, a new statistical model for the irradiance fluctuations of an unbounded optical wavefront (plane and spherical waves) propagating through a turbulent medium under all irradiance fluctuation conditions in homogeneous, isotropic turbulence was developed.
Abstract: In this paper we develop a new statistical model for the irradiance fluctuations of an unbounded optical wavefront (plane and spherical waves) propagating through a turbulent medium under all irradiance fluctuation conditions in homogeneous, isotropic turbulence. The major advantage of the model is that leads to closed-form and mathematically-tractable expressions for the fundamental channel statistics of an unbounded optical wavefront under all turbulent regimes. Furthermore, it unifies most of the proposed statistical models for the irradiance fluctuations derived in the bibliography providing, in addition, an excellent agreement with the experimental data.
285 citations
"BER of an optically pre-amplified F..." refers background in this paper
...Recently, a new and more generalised model known as M?́?laga turbulence model or the M-distribution has been proposed that covers all the channel conditions from weak to strong turbulence effects [11]–[13]....
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...of M-turbulence is expressed in [11]–[13]....
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TL;DR: In this article, a unified performance analysis of a single-link free-space optical (FSO) link that accounts for pointing errors and both types of detection techniques is presented.
Abstract: 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) and heterodyne detection]. More specifically, we present unified exact closed-form 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.
273 citations
TL;DR: These fading models describe the atmospheric turbulence because of its very good agreement with experimental measurement data and can be used as an alternative to time-consuming Monte-Carlo simulations.
Abstract: Turbulence fading is one of the main impairments affecting the operation of free-space optical (FSO) communication systems. The authors study the performance of FSO communication systems, also known as wireless optical communication systems, over log-normal and gamma-gamma atmospheric turbulence-induced fading channels. These fading models describe the atmospheric turbulence because of its very good agreement with experimental measurement data. Closed-form expressions for the average (ergodic) capacity and the outage probability are derived for both statistical models. Another contribution of this work is a study of how the performance metrics are affected by the atmospheric conditions and other parameters such as the length of the link and the receiver's aperture diameter. The derived analytical expressions are verified by various numerical examples and can be used as an alternative to time-consuming Monte-Carlo simulations.
224 citations
"BER of an optically pre-amplified F..." refers background in this paper
...The atmospheric turbulence in FSO systems is characterized by log-normal [5], [6], Gamma-Gamma [7], [8], and negative exponential distribution [9], [10] for weak, moderate to strong, and very strong turbulence regimes....
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TL;DR: In this work, the performance and the capacity analysis of a fixed-gain amplify-and-forward (AF)-based dual-hop asymmetric radio frequency-free space optical (RF-FSO) communication system is performed and the effects of fading, turbulence, and pointing error are studied on the outage probability, average BER, and the channel capacity.
Abstract: In this work, the performance and the capacity analysis of a fixed-gain amplify-and-forward (AF)-based dual-hop asymmetric radio frequency–free space optical (RF–FSO) communication system is performed. The RF link experiences Nakagami-m fading and the FSO link experiences Gamma–Gamma turbulence. For this mixed RF–FSO cooperative system, novel and finite power series-based mathematical expressions for the cumulative distribution function, probability density function, and moment generating function of the end-to-end signal-to-noise ratio are derived. Using these channel statistics new finite power series-based analytical expressions are obtained for the outage probability, the average bit error rate (BER) for various binary and M-ary modulation techniques, and the average channel capacity of the considered system. The same analysis is also performed for the scenario when the FSO link undergoes significant pointing errors along with the Gamma–Gamma distributed turbulence. As a special case analytical expressions for the outage probability, BER, and channel capacity are also presented for a dual-hop asymmetric RF–FSO system where the RF link is Rayleigh distributed. Simulation results validate the proposed mathematical analysis. The effects of fading, turbulence, and pointing error are studied on the outage probability, average BER, and the channel capacity.
186 citations
"BER of an optically pre-amplified F..." refers background in this paper
...However, the performance of FSO links is greatly affected by the atmospheric conditions including turbulence and pointing errors (PEs) due to building sway induced misalignment in the line of sight (LOS) transmission between the transmitter (Tx) and the receiver (Rx) [4]....
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