Investigation of moderate-to-strong turbulence effects on free space optics &amp;#x2014; A laboratory demonstration

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In this paper, we investigate the performance of a vehicular visible light communications (VVLC) link with a non-collimated and incoherent light source (a light-emitting diode) as the transmitter (Tx), and two different optical receiver (Rx) types (a camera and photodiode (PD)) under atmospheric turbulence (AT) conditions with aperture averaging (AA). First, we present simulation results indicating performance improvements in the signal-to-noise ratio (SNR) under AT with AA with increasing size of the optical concentrator. Experimental investigations demonstrate the potency of AA in mitigating the induced signal fading due to the weak to moderate AT regimes in a VVLC system. The experimental results obtained with AA show that the link’s performance was stable in terms of the average SNR and the peak SNR for the PD and camera-based Rx links, respectively with <1 dB SNR penalty for both Rxs, as the strength of AT increases compared with the link with no AT.

(in m −2/3 ) is most commonly used to describe the strength of AT [ 26 ], which is given by [ 27 ]:

where P represents the pressure in millibars, T is the temperature in Kelvin, and

is the temperature structure parameter, which is related to the universal 2/3 power law of temperature variations given as [ 27 ]:

where

is the separation distance between two points with temperatures of

and

, and the inner and outer scales of the small temperature variations are denoted by

and

, respectively.…”

Section: System Descriptionmentioning

confidence: 99%

Section: System Setupmentioning

confidence: 99%

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Performance of Vehicular Visible Light Communications under the Effects of Atmospheric Turbulence with Aperture Averaging

Eso

Ghassemlooy

Zvánovec

et al. 2021

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“…It typically ranges from 10

or less for weak turbulence, and above 10

for strong turbulence. It is given by [ 43 , 44 , 45 ]:

where P and T are the average values of the air’s pressure in millibar and temperature in Kelvin, respectively.

is the temperature structure parameter, which can be calculated by measuring the temperature of two or more points in the space separated by a distance R .…”

Section: Proposal Of Optical Camera Communication-based Sensor Network Architecturementioning

confidence: 99%

Wireless Sensor Networks Using Sub-Pixel Optical Camera Communications: Advances in Experimental Channel Evaluation

Matus

Guerra

Jurado-Verdú

et al. 2021

Optical wireless communications in outdoor scenarios are challenged by uncontrollable atmospheric conditions that impair the channel quality. In this paper, different optical camera communications (OCC) equipment are experimentally studied in the laboratory and the field, and a sub-pixel architecture is raised as a potential solution for outdoor wireless sensor networks (WSN) applications, considering its achievable data throughput, the spatial division of sources, and the ability of cameras to overcome the attenuation caused by different atmospheric conditions such as rain, turbulence and the presence of aerosols. Sub-pixel OCC shows particularly adequate capabilities for some of the WSN applications presented, also in terms of cost-effectiveness and scalability. The novel topology of sub-pixel projection of multiple transmitters over the receiver using small optical devices is presented as a solution using OCC that re-uses camera equipment for communication purposes on top of video-monitoring.

“…Consequently, this leads to variations of the refractive index of the air, resulting in amplitude and phase fluctuations of the propagating optical beam [33]. For describing the strength of atmospheric turbulence, the parameter most commonly used is the refractive index structure parameter (C 2 n ) (in units of m −2/3 ) [34,35], given by:…”

Section: Meteorological Phenomenamentioning

confidence: 99%

Experimentally Derived Feasibility of Optical Camera Communications under Turbulence and Fog Conditions

Matus

Eso

Teli

et al. 2020

Optical camera communications (OCC) research field has grown recently, aided by ubiquitous digital cameras; however, atmospheric conditions can restrict their feasibility in outdoor scenarios. In this work, we studied an experimental OCC system under environmental phenomena emulated in a laboratory chamber. We found that the heat-induced turbulence does not affect our system significantly, while the attenuation caused by fog does decrease the signal quality. For this reason, a novel strategy is proposed, using the camera’s built-in amplifier to overcome the optical power loss and to decrease the quantization noise induced by the analog-digital converter of the camera. The signal quality has been evaluated using the Pearson’s correlation coefficient with respect to a reference template signal, along with the signal-to-noise ratio that has been empirically evaluated. The amplification mechanism introduced allows our system to receive the OCC signal under heavy fog by gradually increasing the camera gain up to 16 dB, for meteorological visibility values down to 10 m, with a correlation coefficient of 0.9 with respect to clear conditions.