Open AccessCapacity of underwater optical wireless communication systems over salinity-induced oceanic turbulence channels with ISI
Author(s) -
Rubén Boluda-Ruiz,
Pedro Salcedo-Serrano,
Beatriz Castillo-Vázquez,
Antonio García-Zambrana,
José María Garrido-Balsells
Publication year - 2021
Publication title -
optics express
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.394
H-Index - 271
ISSN - 1094-4087
DOI - 10.1364/oe.430200
Subject(s) - channel (broadcasting) , optical wireless , signal to noise ratio (imaging) , channel capacity , intersymbol interference , underwater acoustic communication , computer science , interference (communication) , optics , physics , telecommunications , underwater , wireless , oceanography , geology
Point-to-point underwater optical wireless communication (UOWC) links are mainly impaired by scattering due to impurities and turbidity in the open water, resulting in a significant inter-symbol interference (ISI) that limits seriously both channel capacity and the maximum practical information rate. This paper conducts, for the first time, the channel capacity analysis of UOWC systems in the presence of ISI and salinity-induced oceanic turbulence when the undersea optical channel is accurately modeled by linear discrete-time filtering of the input symbols. In this way, novel upper and lower bounds on channel capacity and mutual information are developed for non-uniform on-off keying (OOK) modulation when different constraints are imposed on the channel input. The results show that the capacity-achieving distribution, which is computed through numerical optimization, is discrete and depends on the optical signal-to-noise-ratio (SNR). Moreover, a non-uniform input distribution significantly improves the channel capacity of such systems affected by ISI and oceanic turbulence, especially at low optical SNR. Monte Carlo techniques are employed to test the developed bounds for different undersea optical channels with one, two and three casual ISI coefficients.