Bit Error Rate Performance Study of UWOC System Based on Multiple Degenerate Composite Channels

Underwater Wireless Optical Communication (UWOC) capitalizes on the blue-green segment of the light spectrum which is subject to minimal attenuation in marine environments, thereby rendering it optimal for the conveyance of information. The advantages of UWOC are manifold, it boasts of swift data transmission, negligible latency, and fortified confidentiality. However, UWOC grapples with significant barriers which encompass the limitation of transmission range and the deleterious effects attributable to the intrinsic properties of seawater, as well as marine turbulence-factors like absorption, scattering, bubbles and turbulence that collectively compromise communicative efficiency. To systematically confront these impediments and to gauge the comprehensive influence of the aforementioned factors on UWOC system efficacy, this inquiry has formulated an integrative underwater wireless optical channel model. This archetype not only encapsulates solitary influences but also their concomitant interactions and aggregate impact on signal transmission. By harnessing the Mie scattering theorem, the research meticulously delineates the volume scattering function, the scattering coefficient, and the phase function of microbubble assemblages in seawater-pivotal determinants essential for the assessment of scattering phenomena on the propagation of optical signals. Addressing turbulence, an elaborate channel model featuring a mixed exponential generalized Gamma distribution is employed, defining the statistical behavior of turbulence to faithfully represent the stochastic and unpredictable nature of the channel. This study extends its analysis to include the repercussion of signal attenuation and acoustic noise as a consequence of turbulence, effectively projecting these perturbations onto the optical signals disseminated through the composite channel. Importantly, it elucidates a closed-form expression for the Bit Error Ratio (BER) within the composite channel, employing On-Off Keying (OOK) modulation, thus establishing a theoretical groundwork for the analysis of UWOC system performance. The research delves into the impact of critical determinants such as turbulence strength, bubble density, transmission range, and marine water quality on the BER metrics of UWOC systems. It is discerned that heightened turbulence intensity incrementally necessitates a greater minimum Signal to Noise Ratio (SNR) at the receiver end to maintain a predetermined average BER. Consistent with this SNR, an augmentation in turbulence intensity conspicuously degrades system throughput, inducing a systematic deterioration in BER performance. Within a transparent seawater milieu at a transmission span of 20 m, with a bubble concentration of 3 x 10(6) per cubic volume, the system's mean BER is recorded at 4.57 x 10(-4). As the bubble density escalates to 9 x 10(6) and subsequently to 9 x 10(7) per cubic volume, the average BER correspondingly declines to 5.76 x 10(-4) and 1.19 x 10(-2). In scenarios of turbulence characterized by a scintillation index of 1.932 8, the system is adept at sustaining low BER transmissions. Ensuring dependable communication quality with an average BER falling below 10(-3) across an array of aquatic environments-be it crystalline seawater, littoral waters, or murky harbor waters-the utmost permissible transmission distances with bubble presence(at a density of 1 x 10(7) per cubic volume) are confined to 22.5 m, 10.4 m, and 2.3 m respectively. Absent bubble interference, these distances are extendable to 28.0 m, 13.5 m, and 2.7 m. Given the pronounced absorption and scattering induced by elevated turbidity and suspended particulates, securing long-range communication in silt-laden harbor waters presents a significant hurdle. Additionally, the study substantiates that elevating the link distance precipitates an almost linear augmentation in BER, indicative of a noteworthy degeneration in signal integrity. The outcomes not only underscore the exigency of crafting and fine-tuning UWOC systems attuned to the vicissitudes of the oceanic realm but also accentuate the latent efficacy of modulation methodologies and channel coding strategies as instrumental in amplifying system competence.