Search results for "Free Space Optic"

Rateless codes mitigation technique in a turbulent indoor Free Space Optics link

2014

Free Space Optics (FSO) links are affected by several impairments and, among them, optical turbulence is the most important factor that can degrade the link quality. Due to the presence of this phenomenon, the signal irradiance detected by the receiver fluctuates, thus causing erasure errors and fading events. In this work, we present an indoor Free Space Optics link, in which several turbulence conditions are generated by using two heating elements. We show that the generated turbulence causes erasure errors and packet losses during the data transmission, and we also compare the statistical distribution of the samples with the theoretical models. Moreover, we demonstrate how the applicatio…

Optical wireless GEO satellite-to-ground downlinks: rateless codes as solution for scintillation fading

2013

Scintillation fading can corrupt a satellite-to-ground optical wireless links with burst errors. Rateless codes, suitable for erasure channel, are able to eliminate or to reduce these communication errors. We analyzed the performances of three different rateless codes in a simulated Geo satellite-to-ground downlink.

Packet loss recovery in an indoor Free Space Optics link using rateless codes

2014

Free Space Optics (FSO) systems present some important advantages if compared to Radio Frequency links, but they can be affected by several impairments that degrade the link quality and availability. In particular, due to temporary interruptions of the line-of-sight condition between the transmitter and the receiver, packet loss can occur during data transmission. In this work, we present an indoor Free Space Optics link, in which we have systematically generated interruptions of the beam. We demonstrate how the application of the most recent rateless codes, i.e., RaptorQ codes, can strongly improve the link quality by reducing packet loss. In particular, results show that the Packet Error …

Optical turbulence measurements and channel modeling of an indoor Free Space Optics link (Abstract)

2014

Performance Investigation of Fountaine Codes on a Simulated Terrestrial Free Space Optical Channel

2012

Rateless codes implementation, optimization and application to Free Space Optics links affected by optical turbulence

In this work, I have implemented, optimized and tested the most advanced rateless codes available up to now, i.e., RaptorQ codes. In detail, a multiplatform data transmission software has been appositely developed in order to verify the effectiveness of the above-mentioned codes to decrease packet loss and hence to improve the link quality, under different network and channel conditions. Several simulative and experimental investigations have been carried out to evaluate the performance of the encoding and decoding schemes and the relative recovery capabilities under different test scenarios. In particular, I have applied the software embedding RaptorQ codes to Free Space Optics communicati…

Contribution à l'étude des liaisons optiques atmosphériques : propagation, disponibilité et fiabilité.

2005

In this work we study the fog attenuation in the visible and infrared spectral band related to Free Space Optics (FSO). Based on the Mie scattering theory, fog extinction coefficients for different particle size distributions as a function of wavelength were derived. A simple analytical model allowing the prediction of atmospheric transmission for the 0.69 - 1.55 µm spectral band was developed. This model is valid for advection and convection fog and for visibility range between 50 to 1000 m. This model, implemented into software developed at FT R&D, allows the prediction of the Quality of Service of FSO links. Finally, we performed an experimental study to compare the fog effect on two FSO…

Correlated channel model for terrestrial Free Space Optics: performance analysis of rateless codes

2012

We describe a novel correlated channel model able to predict random temporal fluctuations of optical signal irradiance caused by scintillation. With regards to the same channel, we also report simulation results on the error mitigation performance of Luby-Transform and Raptor codes.

Correlated Channel Model for terrestrial Free Space Optics and project specifications evaluation of LT code in OOK modulation

2011

Free Space Optics is a wireless line-of-sight communication system able to offer good bandwidth performance as well as straightforward installation and relocation. So that it represents a modern technology that allow to realize large bandwidth communication particularly when it is not possible to employ physical cable or radio technologies. Examples of FSO applications are: wireless backaul, fiber backup, temporary links, metro network extension and last mile access[1]. FSO is based on optical signals propagation in air and that is why it suffers of impairments which depend on atmospheric conditions. In detail, FSO suffers of scattering (i. e. Rayleigh and Mie) losses, absorption and scinti…

Model Analysis of Hydrometeor Scattering Effects on Free Space Near-Infrared Links

2012

A promising technology for peer-to-peer connections and urban area networks is represented by wireless communications through free space using optical carrier (Free Space Optics, FSO). This technology ensures high data rates, with relatively low error rates, low power consumption and inherent security. Nevertheless FSO links are quite sensitive to atmospheric condition. Fog droplets, but also raindrops and snowflakes, may introduce severe path attenuation which drastically reduces the channel availability. A parametric model to simulate droplets scattering effects over the FSO link in terms of extinction coefficient, albedo factor and asymmetry coefficient as function of the particle water …