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Proceedings Paper

Pilot-symbol assisted modulation for correlated turbulent free-space optical channels
Author(s): Xiaoming Zhu; Joseph M. Kahn
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Paper Abstract

In free-space optical links using intensity modulation and direct detection, atmospheric turbulence can cause signal fading. Pilot-symbol (PS) assisted modulation (PSAM) can help to mitigate this fading, improving system performance. We periodically insert an On-state PS in front of M-1 information bits and form a M-bit frame. We derive the PS assisted maximum-likelihood (PSA-ML) decision rule under the assumption that the temporal coherence of fading is known, but the instantaneous fading state is not known. We also propose a simpler PS assisted detection scheme with variable threshold (PSA-VT), Although these two techniques will introduce some delay to the detection system, they can help to mitigate the atmospheric turbulence induced fading. We have performed numerical simulations to show this improvement. We also describe how to choose the frame size M to optimize the performance of PSAM systems.

Paper Details

Date Published: 22 January 2002
PDF: 8 pages
Proc. SPIE 4489, Free-Space Laser Communication and Laser Imaging, (22 January 2002); doi: 10.1117/12.453222
Show Author Affiliations
Xiaoming Zhu, Univ. of California/Berkeley (United States)
Joseph M. Kahn, Univ. of California/Berkeley (United States)

Published in SPIE Proceedings Vol. 4489:
Free-Space Laser Communication and Laser Imaging
David G. Voelz; Jennifer C. Ricklin, Editor(s)

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