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: A new and generalized statistical model to model the irradiance fluctuations of an unbounded optical wavefront propagating through a turbulent medium under all irradiance fluctuation conditions in homogeneous, isotropic turbulence is completed by including the adverse effect of pointing error losses due to misalignment.
Abstract: Recently, a new and generalized statistical model, called M or Malaga distribution, was proposed to model 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. Malaga distribution was demonstrated to have the advantage of unifying most of the proposed statistical models derived until now in the bibliography in a closed-form expression providing, in addition, an excellent agreement with published plane wave and spherical wave simulation data over a wide range of turbulence conditions (weak to strong). Now, such a model is completed by including the adverse effect of pointing error losses due to misalignment. In this respect, the well-known effects of aperture size, beam width and jitter variance are taken into account. Accordingly, after presenting the analytical expressions for the combined distribution of scintillation and pointing errors, we derive its centered moments of the overall probability distribution. Finally, we obtain the analytical expressions for the average bit error rate performance for the M distribution affected by pointing errors. Numerical results show the impact of misalignment on link performance.
151 citations
"BER of an optically pre-amplified F..." refers background or methods in this paper
...Under the combined effect of M-distributed turbulence and PEs, the joint distribution of the irradiance is written as [12], [13]:...
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...Remark 1: We have assumed β to be a natural number as justified in [12], [13] for improved analytical tractability and obtaining closed-form solutions....
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...IL is the atmospheric path loss determined by Beer-Lambert Law and is assumed to be a constant for long time period, Ao = [erf(ν)](2), ν = √ π/2R/w, ζ(2) = w(2) e/4σ 2 s , R is the radius of the detection aperture, w is the beam waist, we = [ √ π erf(ν)w2/(2νe−ν 2 )] is the equivalent beam width, σ(2) s is the PE displacement variance [12], [24], erf(⋅) denotes the error function, and G p,q (⋅∣ :) is the Meijer-G function defined in [25, Eq....
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TL;DR: The effects of atmospheric turbulence, background light, source extinction ratio, amplified spontaneous emission, and receiver thermal noise are studied in the context of a semiclassical photon-counting approach and results are presented using a conditional Gaussian approximation method.
Abstract: Atmospheric optical communication systems that use optical preamplifiers and diversity reception are addressed. The particular diversity techniques that are investigated include aperture averaging, linear combining, and adaptive optics. On-off keying and binary pulse position modulation are considered. The effects of atmospheric turbulence, background light, source extinction ratio, amplified spontaneous emission, and receiver thermal noise are studied in the context of a semiclassical photon-counting approach. Numerical results are presented using a conditional Gaussian approximation method. By this method, we can measure the power penalty incurred under various operating conditions as well as the link margin improvement due to optical preamplification and diversity reception.
118 citations
Proceedings Article•
15 Jun 2011TL;DR: In this paper, the effect of thermal, shot, background, and transmitter noises on the receiver performance is investigated. And the dominant noise components for the cases of using a PIN or an APD, and compare their performances at the presence or not of background radiations.
Abstract: P-i-N (PIN) diodes and avalanche photo-diodes (APD) are the most commonly used photo-detectors in terrestrial FSO systems. In this paper, we review the photo-detection process for the cases of PIN- and APD-based receivers and provide a comprehensive study of different noise sources that affect signal detection in an FSO system. We present a complete and precise model for the receiver noise by taking different receiver parts into account. In particular, we study the impact of thermal, shot, background, and transmitter noises on the receiver performance by considering practical and realistic case studies. We bring clearance on the impact of the interaction of signal and background noise due to non-linear characteristic of the photo-detector, and on the role of the trans-impedance load resistance. We discuss the dominant noise components for the cases of using a PIN or an APD, and compare their performances at the presence or not of background radiations.
117 citations
"BER of an optically pre-amplified F..." refers background in this paper
...Along with the background radiations, the two main types of noise in FSO systems are thermal noise and background induced shot noise [14]....
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TL;DR: Analysis of the decode-and-forward (DF) protocol in the free space optical (FSO) links following the Gamma-Gamma distribution and average bit error rate of the DF relaying is obtained.
Abstract: We analyze performance of the decode-and-forward (DF) protocol in the free space optical (FSO) links following the Gamma-Gamma distribution. The cumulative distribution function (cdf) and probability density function (pdf) of a random variable containing mixture of the Gamma-Gamma and Gaussian random variables is derived. By using the derived cdf and pdf, average bit error rate of the DF relaying is obtained.
116 citations
"BER of an optically pre-amplified F..." refers background in this paper
...Free space optical (FSO) communications has garnered significant attention of the research community owing to its numerous benefits such as high modulation bandwidth, unlicensed spectrum, low cost of installation and operation, no health hazards due to non-ionizing radiation, and inherently secure transmission [1]–[3]....
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TL;DR: It is shown by simulations that the proposed beamforming scheme, employing one bit feedback based beamforming with error free feedback, achieves full diversity in 2 × 1 FSO system over Gamma-Gamma fading links.
Abstract: In this paper, we study a beamforming scheme for multiple-input single-output (MISO) free space optical (FSO) system over Gamma-Gamma fading channels. The considered beamforming scheme requires feedback of only one information bit from the receiver about the channel state information. If the feedback bit is always received error free, then the beamforming technique reduces to best transmit aperture selection scheme. It is inferred by bit error rate (BER) analysis in a 2 $\times$ 1 FSO system over Gamma-Gamma fading links, that repetition coding is the best of all arbitrary beamforming schemes with non-zero transmit weights. Further, it is also analytically shown that the simple transmit aperture selection scheme (or one bit feedback based beamforming with error free feedback) has a coding gain advantage over repetition coding in 2 $\times$ 1 FSO system over Gamma-Gamma fading links. However, it is shown by analysis that the simple transmit aperture selection based beamforming scheme is very sensitive to errors in the feedback bit and loses diversity gain even for very small error in the feedback. Then we establish conditions under which a 2 $\times$ 1 FSO system, employing one bit based beamforming with erroneous feedback, achieves full diversity. A simplified asymptotic upperbound of BER of the proposed scheme is obtained by using the order statistics and an optimized beamforming vector is found by minimizing this upperbound. We also analyze the BER performance of a general FSO MISO system that employs equal partitioning of transmit apertures for beamforming, based on one bit feedback. It is shown by simulations that the proposed beamforming scheme outperforms repetition coding despite of error in the feedback bit.
88 citations
"BER of an optically pre-amplified F..." refers methods in this paper
...We have provided the values of the key parameters used in Table I, which are adopted from the literature [13], [24]....
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...IL is the atmospheric path loss determined by Beer-Lambert Law and is assumed to be a constant for long time period, Ao = [erf(ν)](2), ν = √ π/2R/w, ζ(2) = w(2) e/4σ 2 s , R is the radius of the detection aperture, w is the beam waist, we = [ √ π erf(ν)w2/(2νe−ν 2 )] is the equivalent beam width, σ(2) s is the PE displacement variance [12], [24], erf(⋅) denotes the error function, and G p,q (⋅∣ :) is the Meijer-G function defined in [25, Eq....
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