Statistical studies of fading in underwater wireless optical channels in the presence of air bubble, temperature, and salinity random variations

Mohammad Vahid Jamali, Ali Mirani, Alireza Parsay, Bahman Abolhassani, Pooya Nabavi, Ata Chizari, Pirazh Khorramshahi, Sajjad Abdollahramezani, Jawad A. Salehi*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

70 Citations (Scopus)

Abstract

Optical signal propagation through underwater channels is affected by three main degrading phenomena, namely, absorption, scattering, and fading. In this paper, we experimentally study the statistical distribution of intensity fluctuations in underwater wireless optical channels with random temperature and salinity variations, as well as the presence of air bubbles. In particular, we define different scenarios to produce random fluctuations on the water refractive index across the propagation path and, then, examine the accuracy of various statistical distributions in terms of their goodness of fit to the experimental data. We also obtain the channel coherence time to address the average period of fading temporal variations. The scenarios under consideration cover a wide range of scintillation index from weak to strong turbulence. Moreover, the effects of beam-expander-and-collimator (BEC) at the transmitter side and aperture averaging lens (AAL) at the receiver side are experimentally investigated. We show that the use of a transmitter BEC and/or a receiver AAL suits single-lobe distributions, such that the generalized Gamma and exponentiated Weibull distributions can excellently match the histograms of the acquired data. Our experimental results further reveal that the channel coherence time is on the order of 10-3 s and larger which implies to the slow fading turbulent channels.

Original languageEnglish
Article number8370053
Pages (from-to)4706-4723
Number of pages18
JournalIEEE Transactions on Communications
Volume66
Issue number10
DOIs
Publication statusPublished - Oct 2018

Keywords

  • air bubbles
  • coherence time
  • fading statistical distribution
  • goodness of fit
  • salinity variation
  • temperature-induced turbulence
  • Underwater wireless optical communications

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