Browsing by Author "Kashani, M. A."

Now showing 1 - 4 of 4

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A novel statistical channel model for turbulence-induced fading in free-space optical systems
(IEEE, 2015-06-01) Kashani, M. A.; Uysal, Murat; Kavehrad, M.; Electrical & Electronics Engineering; UYSAL, Murat
In this paper, we propose a new probability distribution function which accurately describes turbulence-induced fading under a wide range of turbulence conditions. The proposed model, termed double-generalized gamma (double GG), is based on a doubly stochastic theory of scintillation and developed via the product of two generalized gamma distributions. The proposed double GG distribution generalizes many existing turbulence channel models and provides an excellent fit to the published plane and spherical waves simulation data. Using this new statistical channel model, we derive closed form expressions for the outage probability and the average bit error as well as corresponding asymptotic expressions of free-space optical communication systems over turbulence channels. We demonstrate that our derived expressions cover many existing results in the literature earlier reported for gamma-gamma, double-Weibull and K channels as special cases.
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A novel statistical model for turbulence-induced fading in free-space optical systems
(IEEE, 2013) Kashani, M. A.; Uysal, Murat; Kavehrad, M.; Electrical & Electronics Engineering; UYSAL, Murat
In this paper, we propose a new probability distribution function which accurately describes turbulence-induced fading under a wide range of turbulence conditions. The proposed model, termed Double GG distribution, is based on a doubly stochastic theory of scintillation and developed via the product of two Generalized Gamma (GG) distributions. The proposed Double GG distribution generalizes many existing turbulence channel models in a closed-form expression and provides an excellent fit to the published plane and spherical waves simulation data. We finally evaluate the performance of a free-space optical system over the Double GG turbulence channel and derive closed-form expressions for the bit error rate, assuming intensity modulation/ direct detection with on-off keying.
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On the performance of MIMO FSO communications over double generalized gamma fading channels
(IEEE, 2015) Kashani, M. A.; Uysal, Murat; Kavehrad, M.; Electrical & Electronics Engineering; UYSAL, Murat
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.
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Optimal relay placement and diversity analysis of relay-assisted free-space optical communication systems
(IEEE, 2013-01) Kashani, M. A.; Safari, M.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat
Relay-assisted free-space optical (FSO) transmission exploits the fact that atmospheric turbulence fading variance is distance dependent and yields significant performance gains by taking advantage of the resulting shorter hops. In this paper, we investigate how to determine optimal relay locations in serial and parallel FSO relaying so as to minimize the outage probability and quantify performance improvements obtained through optimal relay placement. We further present a diversity gain analysis for serial and parallel FSO relaying schemes and quantify their diversity advantages in terms of the number of relays and channel parameters.