A cross-layer approach to mitigate fading on bidirectional free space optical communication links

• Published in: MILCOM 2008 - 2008 IEEE Military Communications Conference pp. 1 - 6
• Main Authors: Milner, S.D., Trisno, S., Davis, C.C., Epple, B., Henniger, H.
• Format: Conference Proceeding
• Language: English; Japanese
• Published: IEEE 01.11.2008
• Subjects: ARQ; Automatic repeat request; coding; Delay; diversity; Fading; Forward error correction; free space optics; Optical buffering; Optical fiber communication; Optical fiber networks; Optical receivers; Optical transmitters; optical wireless communication networks; Protection; protocols
• ISBN: 9781424426768; 1424426766
• ISSN: 2155-7578; 2155-7586
• DOI: 10.1109/MILCOM.2008.4753050

In free-space optical (FSO) communications the transmitted signal is subject to different fading effects. These effects can cause short-term outages of a few milliseconds, caused by atmospheric turbulence-induced fading, and long-term outages up to a few seconds duration caused by line of sight obstructions or pointing errors. To mitigate these effects, several different approaches have been presented in the past. At the physical layer, forward-error correction (FEC), dynamic thresholding, and time-delayed diversity (TDD) have been shown to be reasonable solutions. At higher layers, FEC has also been demonstrated to be a possible solution, but it imposes a penalty on channel throughput. For bidirectional communications, automatic repeat request (ARQ) protocols are proposed to be a more efficient solution. In this paper we will investigate physical layer delay diversity as well as link layer FEC and ARQ.