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Proceedings Paper

Energy efficient rateless codes for high speed data transfer over free space optical channels
Author(s): Geetha Prakash; Muralidhar Kulkarni; U. Sripati Acharya
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Paper Abstract

Terrestrial Free Space Optical (FSO) links transmit information by using the atmosphere (free space) as a medium. In this paper, we have investigated the use of Luby Transform (LT) codes as a means to mitigate the effects of data corruption induced by imperfect channel which usually takes the form of lost or corrupted packets. LT codes, which are a class of Fountain codes, can be used independent of the channel rate and as many code words as required can be generated to recover all the message bits irrespective of the channel performance. Achieving error free high data rates with limited energy resources is possible with FSO systems if error correction codes with minimal overheads on the power can be used. We also employ a combination of Binary Phase Shift Keying (BPSK) with provision for modification of threshold and optimized LT codes with belief propagation for decoding. These techniques provide additional protection even under strong turbulence regimes. Automatic Repeat Request (ARQ) is another method of improving link reliability. Performance of ARQ is limited by the number of retransmissions and the corresponding time delay. We prove through theoretical computations and simulations that LT codes consume less energy per bit. We validate the feasibility of using energy efficient LT codes over ARQ for FSO links to be used in optical wireless sensor networks within the eye safety limits.

Paper Details

Date Published: 16 March 2015
PDF: 15 pages
Proc. SPIE 9354, Free-Space Laser Communication and Atmospheric Propagation XXVII, 93540C (16 March 2015); doi: 10.1117/12.2077961
Show Author Affiliations
Geetha Prakash, PES Institute of Technology (India)
Muralidhar Kulkarni, National Institute of Technology, Karnataka (India)
U. Sripati Acharya, National Institute of Technology, Karnataka (India)


Published in SPIE Proceedings Vol. 9354:
Free-Space Laser Communication and Atmospheric Propagation XXVII
Hamid Hemmati; Don M. Boroson, Editor(s)

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