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Proceedings Paper

Adaptive and reliably acknowledged FSO communications
Author(s): Michael P. Fitz; Thomas R. Halford; Cenk Kose; Jonathan Cromwell; Steven Gordon
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Paper Abstract

Atmospheric turbulence causes the receive signal intensity on free space optical (FSO) communication links to vary over time. Scintillation fades can stymie connectivity for milliseconds at a time. To approach the information-theoretic limits of communication in such time-varying channels, it necessary to either code across extremely long blocks of data – thereby inducing unacceptable delays – or to vary the code rate according to the instantaneous channel conditions. We describe the design, laboratory testing, and over-the-air testing of an FSO modem that employs a protocol with adaptive coded modulation (ACM) and hybrid automatic repeat request. For links with fixed throughput, this protocol provides a 10dB reduction in the required received signal-to-noise ratio (SNR); for links with fixed range, this protocol provides the greater than a 3x increase in throughput. Independent U.S. Government tests demonstrate that our protocol effectively adapts the code rate to match the instantaneous channel conditions. The modem is able to provide throughputs in excess of 850 Mbps on links with ranges greater than 15 kilometers.

Paper Details

Date Published: 19 May 2015
PDF: 10 pages
Proc. SPIE 9465, Laser Radar Technology and Applications XX; and Atmospheric Propagation XII, 94650Z (19 May 2015); doi: 10.1117/12.2182617
Show Author Affiliations
Michael P. Fitz, TrellisWare Technologies, Inc. (United States)
Thomas R. Halford, TrellisWare Technologies, Inc. (United States)
Cenk Kose, TrellisWare Technologies, Inc. (United States)
Jonathan Cromwell, TrellisWare Technologies, Inc. (United States)
Steven Gordon, TrellisWare Technologies, Inc. (United States)

Published in SPIE Proceedings Vol. 9465:
Laser Radar Technology and Applications XX; and Atmospheric Propagation XII
Monte D. Turner; Linda M. Wasiczko Thomas; Gary W. Kamerman; Earl J. Spillar, Editor(s)

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