Browsing by Author "Aminikashani, Mohammadreza"

Now showing 1 - 4 of 4

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All-optical amplify-and-forward relaying system for atmospheric channels
(IEEE, 2012-10) Aminikashani, Mohammadreza; Rad, M. M.; Safari, M.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; Aminikashani, Mohammadreza
In this letter, we investigate the performance of a dual-hop free space optical link with an all-optical amplify-and-forward relay. We employ photon counting methodology and derive closed form expressions for the end-to-end signal-to-noise ratio and the outage probability. In our derivations, we consider either full or partial channel state information (CSI) at the relay and take into account practical limitations such as amplifier noise and filtering effects. Our results indicate significant performance improvements over direct transmission and furthermore demonstrate that semi-blind relaying (which depends only on statistical CSI) provides nearly identical performance to its full-CSI counterpart.
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Optimal relay placement in cooperative free-space optical communication systems
(IEEE, 2012) Aminikashani, Mohammadreza; Safari, M.; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; Aminikashani, Mohammadreza
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 first investigate how to determine optimal relay locations in serial and parallel FSO relaying as to minimize the outage probability and then quantify performance improvements obtained through optimal relay placement.
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Outage performance of FSO multi-hop parallel relaying
(IEEE, 2012) Aminikashani, Mohammadreza; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; Aminikashani, Mohammadreza
In this paper, we investigate the outage performance of relay-assisted free-space optical (FSO) networks which build upon the combinations of serial and parallel relaying. We assume log-normal atmospheric turbulence channels and derive outage probability expressions for multi-hop parallel relaying scheme under consideration. Our outage probability analysis demonstrates substantial performance improvements with respect to both serial and parallel relaying.
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Relaying techniques for free space optical communications
(Institution of Engineering and Technology, 2019-01-01) Aminikashani, Mohammadreza; Uysal, Murat; Electrical & Electronics Engineering; UYSAL, Murat; Aminikashani, Mohammadreza
Despite the major advantages of FSO technology and variety of its application areas, its widespread use has been hampered by its rather disappointing link reliability particularly in long ranges due to atmospheric turbulence-induced fading. Relay-assisted systems have been introduced as an effective method to extend coverage and mitigate the effects of fading in FSO links. In this chapter, we have analyzed and investigated the outage performance of relay-assisted FSO links with AF and DF relays. For serial relaying, it has been demonstrated that the outage probability is minimized when the consecutive nodes are placed equidistant along the path from the source to the destination. For parallel relaying, it has been shown that all of the relays should be located at the same place (along the direct link between the source and the destination) closer to the source and the exact location of this place depends on the system and channel parameters. Multi-hop parallel relaying which is the combined use of serial (multi-hop) and parallel relaying for FSO mesh networks has been also studied. Our analysis yields that multi-hop parallel relaying smartly exploits the distance dependency of the fading variance in FSO systems and bring substantial improvements with respect to standalone uses of multi-hop and parallel relaying. As an alternative way of implementation, all-optical relaying has been also considered. Unlike the earlier relaying schemes, the signals are processed in optical domain and therefore the requirement of OE and EO conversions is avoided. Comparisons between conventional and all-optical relaying demonstrate that the latter presents a favorable trade-off between complexity and performance and can be used as a low-complexity solution.