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dc.contributor.advisorNarayan, Prakashen_US
dc.contributor.authorChakraborty, Kaushiken_US
dc.date.accessioned2005-10-11T09:57:26Z
dc.date.available2005-10-11T09:57:26Z
dc.date.issued2005-09-20en_US
dc.identifier.urihttp://hdl.handle.net/1903/2855
dc.description.abstractIn free space optical communication links,atmospheric turbulence causes random fluctuations in the refractive index of air at optical wavelengths, which in turn cause random fluctuations in the intensity and phase of a propagating optical signal. These intensity fluctuations, termed ``fading,'' can lead to an increase in link error probability, thereby degrading communication performance. Two techniques are suggested to combat the detrimental effects of fading, viz., (a) estimation of channel fade and use of these estimates at the transmitter or receiver; and (b) use of multiple transmitter and receiver elements. In this thesis, we consider several key issues concerning reliable transmission over multiple input multiple output (MIMO) optical fading channels. These include the formulation of a block fading channel model that takes into account the slowly varying nature of optical fade; the determination of channel capacity, viz., the maximum achievable rate of reliable communication, when the receiver has perfect fade information while the transmitter is provided with varying degrees of fade information; characterization of good transmitter power control strategies that achieve capacity; and the capacity in the low and high signal-to-noise ratio (SNR) regimes. We consider a shot-noise limited, intensity modulated direct detection optical fading channel model in which the transmitted signals are subject to peak and average power constraints. The fading occurs in blocks of duration $T_{c}$ (seconds) during each of which the channel fade (or channel state) remains constant, and changes across successive such intervals in an independent and identically distributed (i.i.d.) manner. A single-letter characterization of the capacity of this channel is obtained when the receiver is provided with perfect channel state information (CSI) while the transmitter CSI can be imperfect. A two-level signaling scheme (``ON-OFF keying'') with arbitrarily fast intertransition times through each of the transmit apertures is shown to achieve channel capacity. Several interesting properties of the optimum transmission strategies for the transmit apertures are discussed. For the special case of a single input single output (SISO) optical fading channel, the behavior of channel capacity in the high and low signal-to-noise ratio (SNR) regimes is explicitly characterized, and the effects of transmitter CSI on capacity are studied.en_US
dc.format.extent1772259 bytes
dc.format.mimetypeapplication/pdf
dc.language.isoen_US
dc.titleReliable Communication over Optical Fading Channelsen_US
dc.typeDissertationen_US
dc.contributor.publisherDigital Repository at the University of Marylanden_US
dc.contributor.publisherUniversity of Maryland (College Park, Md.)en_US
dc.contributor.departmentElectrical Engineeringen_US
dc.subject.pqcontrolledEngineering, Electronics and Electricalen_US


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