Electrical & Electronics Engineering

Permanent URI for this collectionhttps://hdl.handle.net/10679/44

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Now showing 1 - 8 of 8

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Diversity-multiplexing trade-off in coherent free-space optical systems with multiple receivers
(IEEE, 2010-12) Aghajanzadeh, S. M.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat
In this paper, from an information theory point of view, we investigate the performance of a coherent freespace optical (FSO) communication system with multiple receive apertures over atmospheric turbulence channels. Our study builds on a recently introduced statistical model that characterizes the combined effects of turbulence-induced wavefront distortion and amplitude fluctuation in coherent receivers with phase compensation. We investigate the link reliability as quantified by “diversity gain” and the relationship between the link reliability and the spectral efficiency as quantified by “diversity–multiplexing trade-off (DMT).” Our results provide insight into the performance mechanisms of coherent FSO systems and demonstrate significant performance gains that can be obtained through the deployment of multiple receive apertures and phase compensation techniques.
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DMT analysis of coherent free-space optical systems over atmospheric turbulence channels
(IEEE, 2010) Aghajanzadeh, S. M.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat
In this paper, we investigate the diversity-multiplexing tradeoff (DMT) performance of a coherent free-space optical (FSO) communication system with multiple receive apertures over atmospheric turbulence channels. Our study builds on the recently introduced statistical model that characterizes the combined effects of turbulence-induced wavefront distortion and amplitude fluctuation in coherent receivers with phase compensation. Our results provide insight into performance mechanisms of coherent FSO systems and demonstrate significant performance gains that can be obtained through the deployment of multiple receive apertures and phase compensation techniques.
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DMT analysis of multi-hop coherent FSO communication over atmospheric channels
(IEEE, 2011) Aghajanzadeh, S. M.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat
In this paper, we investigate the diversity-multiplexing tradeoff (DMT) of a multi-hop coherent free-space optical (FSO) system over atmospheric channels. We consider a relay-assisted FSO system with decode-and-forward relay nodes and multiple heterodyne receivers with modal compensation. Based on a recently introduced statistical characterization for the combined effects of turbulence-induced amplitude fluctuations and phase aberrations, we quantify the potential performance improvements through the derivation of DMT. Our results demonstrate significant performance gains that can be achieved by multi-hop transmission in coherent FSO systems.
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Information theoretic analysis of hybrid-ARQ protocols in coherent free-space optical systems
(IEEE, 2012-05) Aghajanzadeh, S. M.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat
Automatic retransmission request (ARQ) is a feedback-based data link layer technique which enhances the reliability of communication in fading channels. In this paper, we investigate the performance of hybrid-ARQ (H-ARQ) techniques in coherent free-space optical (FSO) communication systems over atmospheric turbulence-induced fading channels. Under the assumption of a Gamma-Gamma statistical fading channel model, we derive outage probability and throughput expressions for three H-ARQ protocols. We further characterize the outage performance at high values of signal-to-noise-ratio (SNR) through diversity and coding gains. Our results provide insight into the performance mechanisms of different H-ARQ protocols in coherent FSO systems and demonstrate that significant performance gains can be achieved through the deployment of H-ARQ particularly in the strong turbulence regime.
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Multi-hop coherent free-space optical communications over atmospheric turbulence channels
(IEEE, 2011) Aghajanzadeh, S. M.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat
In this paper, we investigate multi-hop relaying as an efficient fading mitigation tool for coherent free-space optical (FSO) systems over atmospheric turbulence channels. We consider an FSO relaying system with decode-and-forward relay nodes and multiple heterodyne receivers with modal compensation. Based on a recently introduced statistical characterization for the combined effects of log-normal turbulence fading and modal compensation, we derive the outage probability and quantify the potential performance improvements through the derivation of diversity multiplexing tradeoff (DMT) and diversity gain. Our outage analysis yields impressive power savings for multi-hop relaying even with a single-relay. In addition, the DMT analysis in practical signal-to-noise ratio (SNR) ranges demonstrates that multi-hop transmission scheme improves finite-SNR diversity gain throughout the range of the multiplexing gain.
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Outage analysis of Hybrid-ARQ protocols in coherent free-space optical communications
(IEEE, 2011) Aghajanzadeh, S. M.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat
In this paper, we investigate the performance of automatic retransmission request (ARQ) protocols in coherent free-space optical (FSO) communications. Specifically, we study the outage performance of three different Hybrid-ARQ (H-ARQ) protocols and characterize their performance at large values of signal-to-noise ratio (SNR) through diversity and coding gains. Our results demonstrate that significant performance gains can be achieved by the deployment of H-ARQ in coherent FSO communications especially in strong turbulence regime. Our asymptotic outage analysis further demonstrates that all protocols provide the same diversity order (which is the product of the maximum number of ARQ rounds and the minimum of the channel parameters) while they provide different coding gains.
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Outage performance and DMT analysis of DF parallel relaying in FSO IM/DD communications
(IEEE, 2012) Aghajanzadeh, S. M.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat
In this paper, we investigate the performance of cooperative diversity transmission in free-space optical (FSO) communications. We consider an FSO cooperative diversity system with a single decode-and-forward relay and a line-of sight link between the source and the destination. Focusing on high signal-to-noise ratio (SNR) regime, we develop performance characterizations in terms of outage probability, outage diversity and coding gains, and diversity-multiplexing tradeoff (DMT). Our results demonstrate that cooperative diversity improves the performance of FSO communications by bringing diversity advantages.
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Performance analysis of parallel relaying in free-space optical systems
(IEEE, 2015-11) Aghajanzadeh, S. M.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat
In this paper, we investigate the information theoretic performance of parallel relaying in free-space optical (FSO) communications over Gamma-Gamma fading channels. We consider an intensity modulation/direct-detection (IM/DD) FSO system with a single relay and a line-of-sight link between the source and the destination. Considering both amplify-and-forward and decode-and-forward relaying, we develop performance characterizations of each relaying mode in terms of outage probability, diversity gain, coding gain, and diversity-multiplexing tradeoff (DMT). Our results demonstrate that parallel relaying improves the performance of FSO systems by bringing diversity advantages. In addition, both relaying modes achieve the same DMT and diversity gain while their coding gains can be different depending on underlying channels' characteristics.

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