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Turbo-Coded MC-CDMA Communication Link over Strong Turbulence Fading Limited FSO Channel with Receiver Space Diversity  [PDF]
MD. Zoheb Hassan,Tanveer Ahmed Bhuiyan,S. M. Shahrear Tanzil,S. P. Majumder
ISRN Communications and Networking , 2011, DOI: 10.5402/2011/701670
Abstract: This paper demonstrates an analytical approach on the bit error rate (BER) performance evaluation of a multi- carrier code division multiple access (MC-CDMA) communication link operating over terrestrial free space optical (FSO) channel considering effect of atmospheric turbulence The turbulence induced intensity fading is statistically modeled by Gamma-Gamma PDF (probability density function). Bit error rate performance improvement is proposed using photo detector spatial diversity with Equal Gain Combining (EGC) and Turbo Coding. Analysis is carried out with different bandwidth efficient phase shift keying (PSK) based sub-carrier intensity modulation (SIM) with direct detection. Numerical simulation results of proposed analytical model indicate that, sub-carrier intensity modulation scheme; number of receiver photo detectors, turbo coding parameter and link length should be optimally engineered for ensuring system reliability. It can be inferred from the simulation that, a reliable communication link ( 1 0 ? 1 0 ?BER) can be established over a link length of 4?Km in strong turbulence fading condition using an array of 4 PIN photo detectors, 8-ary PSK based sub-carrier intensity modulation scheme and appropriate turbo coding parameter with an average 10.2?dB CINR (Carrier to Interference and Noise Ratio) requirement per photo detector. Besides, more than 130?dB average CINR gain is also confirmed from BPSK modulated, un-coded SISO (single input-single output) system for maintaining targeted BER ( 1 0 ? 1 0 ) in presence of strong turbulence fading. 1. Introduction Free space optical communication (FSO) also known as wireless optical communication technique is a point to point to communication link in which two optical transceivers communicate via infrared laser light propagated through atmospheric channel. FSO recently has become a promising technology both for commercial as well as military application that can replete the gap between end user and backbone fiber optic infrastructure addressing the “last-mile” or “bottleneck” problem [1]. In metropolitan area network or local area network, end user is connected to the optical fiber network by means of existing DSL (digital subscriber line) having data speed in the range of Mbit/sec while FSO provides data rate in the rage of giga?bit/sec. Besides addressing “bottle-neck” problem, FSO is also promising for transmitting RF signal over free space by means of subcarrier multiplexing (SCM). The present technology of transmission of radio signal over optical fiber link is multiplexing of several carriers in
On the Performance of MIMO FSO Communications over Double Generalized Gamma Fading Channels  [PDF]
Mohmmadreza Aminikashani,Murat Uysal,Mohsen Kavehrad
Mathematics , 2015,
Abstract: A major performance degrading factor in free space optical communication (FSO) systems is atmospheric turbulence. Spatial diversity techniques provide a promising approach to mitigate turbulence-induced fading. In this paper, we study the error rate performance of FSO links with spatial diversity over atmospheric turbulence channels described by the Double Generalized Gamma distribution which is a new generic statistical model covering all turbulence conditions. We assume intensity modulation/direct detection with on-off keying and present the BER performance of single-input multiple-output (SIMO), multiple-input single-output (MISO) and multiple-input multiple-output (MIMO) FSO systems over this new channel model.
Error Performance Analysis of FSO Links with Equal Gain Diversity Receivers over Double Generalized Gamma Fading Channels  [PDF]
Mohammadreza Aminikashani,Mohsen Kavehrad
Mathematics , 2015,
Abstract: Free space optical (FSO) communication has been receiving increasing attention in recent years with its ability to achieve ultra-high data rates over unlicensed optical spectrum. A major performance limiting factor in FSO systems is atmospheric turbulence which severely degrades the system performance. To address this issue, multiple transmit and/or receive apertures can be employed, and the performance can be improved via diversity gain. In this paper, we investigate the bit error rate (BER) performance of FSO systems with transmit diversity or receive diversity with equal gain combining (EGC) over atmospheric turbulence channels described by the Double Generalized Gamma (Double GG) distribution. The Double GG distribution, recently proposed, generalizes many existing turbulence models in a closed-form expression and covers all turbulence conditions. Since the distribution function of a sum of Double GG random variables (RVs) appears in BER expression, we first derive a closed-form upper bound for the distribution of the sum of Double GG distributed RVs. A novel union upper bound for the average BER as well as corresponding asymptotic expression is then derived and evaluated in terms of Meijer's G-functions.
On the Capacity of FSO Links over Gamma-Gamma Atmospheric Turbulence Channels Using OOK Signaling  [cached]
Antonio García-Zambrana,Carmen Castillo-Vázquez,Beatriz Castillo-Vázquez
EURASIP Journal on Wireless Communications and Networking , 2010, DOI: 10.1155/2010/127657
Abstract: A new upper bound on the capacity of power- and bandwidth-constrained optical wireless links over gamma-gamma atmospheric turbulence channels with intensity modulation and direct detection is derived when on-off keying (OOK) formats are used. In this free-space optical (FSO) scenario, unlike previous capacity bounds derived from the classic capacity of the well-known additive white Gaussian noise (AWGN) channel with uniform input distribution, a new closed-form upper bound on the capacity is found by bounding the mutual information subject to an average optical power constraint and not only to an average electrical power constraint, showing the fact that the input distribution that maximizes the mutual information varies with the turbulence strength and the signal-to-noise ratio (SNR). Additionally, it is shown that an increase of the peak-to-average optical power ratio (PAOPR) provides higher capacity values. Simulation results for the mutual information are further demonstrated to confirm the analytical results under several turbulence conditions.
On the Capacity of FSO Links over Gamma-Gamma Atmospheric Turbulence Channels Using OOK Signaling  [cached]
García-Zambrana Antonio,Castillo-Vázquez Carmen,Castillo-Vázquez Beatriz
EURASIP Journal on Wireless Communications and Networking , 2010,
Abstract: A new upper bound on the capacity of power- and bandwidth-constrained optical wireless links over gamma-gamma atmospheric turbulence channels with intensity modulation and direct detection is derived when on-off keying (OOK) formats are used. In this free-space optical (FSO) scenario, unlike previous capacity bounds derived from the classic capacity of the well-known additive white Gaussian noise (AWGN) channel with uniform input distribution, a new closed-form upper bound on the capacity is found by bounding the mutual information subject to an average optical power constraint and not only to an average electrical power constraint, showing the fact that the input distribution that maximizes the mutual information varies with the turbulence strength and the signal-to-noise ratio (SNR). Additionally, it is shown that an increase of the peak-to-average optical power ratio (PAOPR) provides higher capacity values. Simulation results for the mutual information are further demonstrated to confirm the analytical results under several turbulence conditions.
Performance analysis of bit error rate for free space optical communication with tip-tilt compensation based on gamma–gamma distribution  [PDF]
Hanling Wu,Haixing Yan,Xinyang Li
Optica Applicata , 2009,
Abstract: In this paper, the gamma – gamma probability distribution is used to model turbulent channels. The bit error rate (BER) performance of free space optical (FSO) communication systems employing on-off keying (OOK) or subcarrier binary phase-shift keying (BPSK) modulation format is derived. A tip-tilt adaptive optics system is also incorporated with a FSO system using the above modulation formats. The tip-tilt compensation can alleviate effects of atmospheric turbulence and thereby improve the BER performance. The improvement is different for different turbulence strengths and modulation formats. In addition, the BER performance of communication systems employing subcarrier BPSK modulation is much better than that of compatible systems employing OOK modulation with or without tip-tilt compensation.
Axicons in FSO Systems  [PDF]
Leonardo A. Ambrosio,Michel Zamboni-Rached,Hugo E. Hernández-Figueroa
Physics , 2010,
Abstract: This paper studies the possibility of using axicons in Free Space Optics (FSO) systems. The behavior of the pseudo- Bessel beams generated by "logarithmic" and "linear" axicons, with or without stops, was analyzed through the Huygens-Fresnel integral of diffraction in cylindrical coordinates. We also show that GRIN (Gradient Index) axicons, when well designed, could be used in order to choose the intensity pattern along the propagation axis, which could be a new technique for the alignment equipment.
BER and Availability Measured on FSO Link
R. Kvicala,V. Kvicera,M. Grabner,O. Fiser
Radioengineering , 2007,
Abstract: The BER and the availability belong among the basic qualitative parameters of free space optical (FSO) links. The BER parameter is usually mentioned by FSO manufacturers, but it is not defined what conditions a certain value of BER stands for. This article deals with problems of measuring the BER of free space optical link and with questions how to determine the probability of unavailability of a certain link. The implementation of bit error rate tester with the E1 interface system is presented. In the article the statistics of the meteorological optical range for the year 2006 are shown. Using these data one can determine the probability of a certain value of atmospheric attenuation that influences the link unavailability.
Modeling of 830 nm FSO Link Attenuation in Fog or Wind Turbulence
J. Pesek,O. Fiser,J. Svoboda,V. Schejbal
Radioengineering , 2010,
Abstract: This study is focused on the experimental research of the atmosphere impact on FSO link attenuation. Experiment is performed on a mountain observatory Milesovka of severe weather conditions. The empirical relationships on 830 nm only between FSO attenuation A on one hand and atmospheric visibility V or wind turbulent energy ET on the other hand are presented and discussed. In the fog case it was found A= 401.4V-0.5738- 1.462 dB/60m (V in meters) while for the attenuation due to the wind turbulence ET it holds A = 2.112 - 2.213 exp(-0.2867ET) dB/60m (ET in m2s-2, it was derived for 830 nm wave length). A discussion concerning problems of the “clear air attenuation,” atmospheric turbulences and sun shine impact, which was observed as a maximum 2 dB attenuation for a few minutes with a period of 24 hours is added.
On the Performance of FSO Communications Links under Sandstorm Conditions  [PDF]
Zabih Ghassemlooy,Joaquin Perez,Erich Leitgeb
Physics , 2015,
Abstract: In this paper we focus in the analysis of the FSO link performance under sandstorms conditions. The sandstorms are characterized by the size of the particles and the necessary wind speed in order to blowing them up during a minimum period of time. Sandstorm is a well know problem in many parts of the world and different reports has been presented regarding the impairments that sandstorms produces on outdoor link communications. The paper first focuses on the indoor laboratory sandstorms chamber and that is being used to investigate the performance on an FSO link. We propose an improvement to chamber with a dedicated customised structure where wind speed, sand blowing and turbulence can be generated, controlled and maintained over a much longer time period. This study would help in the deployment of a stable state of the art sandstorm environment for assessing FSO communication links.
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