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Free-space optical networks : fade and interference mitigation and network congestion control

Authors :
Vincent W.S. Chan.
Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science.
Lee, Etty J. (Etty Joanne)
Vincent W.S. Chan.
Massachusetts Institute of Technology. Dept. of Electrical Engineering and Computer Science.
Lee, Etty J. (Etty Joanne)
Publication Year :
2010

Abstract

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2010.<br />Cataloged from PDF version of thesis.<br />Includes bibliographical references (p. 337-341).<br />Optical communication through the atmospheric channel is commonly known as free-space optical (FSO) communication. When communicating through a clear FSO channel, not only is there atmospheric turbulence which results in fading of the received signal, but there may also be interference that scatters into the receiver and deteriorates performance. In this thesis, we consider mitigating the fading and interference with diversity coherent and diversity incoherent detection. We derive the performance of diversity coherent and diversity incoherent receivers in the presence of fading and various worst case interference types. Diversity coherent detection provides significant power gain over diversity direct detection, and most of the benefit can be achieved with a moderate amount of diversity. Moreover, diversity always improves the performance of coherent detection, whereas diversity improves the performance of direct detection only until an optimal diversity value, beyond which it degrades the performance. We also derive the improvement in expected outage length with diversity, and quantify the amount of interference that the system can handle while still achieving a given outage probability. Although signal fades or 'outages' in an FSO link can be mitigated on the Physical Layer, they cannot be completely eliminated. In a free-space optical network, these outages affect the performance and design of the Transport Layer. The effect of outages on the TCP sender is to diminish its throughput significantly due to drastic reduction of its rate when its packets do not get received through the outage. We consider a class of TCP-based protocols that is better suited for free-space optical networks. In particular, the protocols in this class have the sender distinguish whether a packet loss is due to an outage or congestion and not reduce its rate if the loss was due to an outage. We analyze, using an approximate channel model for FSO links, the maximum performance that can be<br />by Etty J. Lee.<br />Ph.D.

Details

Database :
OAIster
Notes :
341 p., application/pdf, English
Publication Type :
Electronic Resource
Accession number :
edsoai.on1140859847
Document Type :
Electronic Resource