Simulation of impulse response for indoor visible light communications using 3D CAD models

n this article, a tool for simulating the channel impulse response for indoor visible light communications using 3D computer-aided design (CAD) models is presented. The simulation tool is based on a previous Monte Carlo ray-tracing algorithm for indoor infrared channel estimation, but including wavelength response evaluation. The 3D scene, or the simulation environment, can be defined using any CAD software in which the user specifies, in addition to the setting geometry, the reflection characteristics of the surface materials as well as the structures of the emitters and receivers involved in the simulation. Also, in an effort to improve the computational efficiency, two optimizations are proposed. The first one consists of dividing the setting into cubic regions of equal size, which offers a calculation improvement of approximately 50% compared to not dividing the 3D scene into sub-regions. The second one involves the parallelization of the simulation algorithm, which provides a computational speed-up proportional to the number of processors used

Parallelization of a Monte Carlo Ray Tracing Algorithm for Channel Modelling in Underwater Wireless Optical Communications

AbstractIn this paper, an algorithm to calculate the underwater wireless optical impulse response is presented. It is based on a modified Monte Carlo Ray Tracing algorithm and takes into account the most significant phenomena of the underwater channel. In order to reduce the simulation time, two parallelization schemes are proposed, one based on a multiprocessor architecture and other based on the use of GPU (Graphics Processing Unit). Several simulation results are presented, including scenario channel simulations and calculation of time computation complexity for each algorithm implementation

Performance of Spatial Diversity DCO-OFDM in a Weak Turbulence Underwater Visible Light Communication Channel

The performance of underwater visible light communication (UVLC) system is severely affected by absorption, scattering and turbulence. In this article, we study the performance of spectral efficient DC-biased optical orthogonal frequency division multiplexing (DCO-OFDM) in combination with the transceiver spatial diversity in turbulence channel. Based on the approximation of the weighted sum of lognormal random variables (RVs), we derived a theoretical exact bit error rate (BER) for DCO-OFDM systems with spatial diversity. The simulation results are compared with the analytical prediction, confirming the validity of the analysis. It is shown that spatial diversity can effectively reduce the turbulence-induced channel fading. The obtained results can be useful for designing, predicting, and evaluating the DCO-OFDM UVLC system in a weak oceanic turbulence condition

Optical wireless channel characterisation in guided structures (vehicle applications)

The field of automotive electronics is growing exponentially in terms of devices related to safety, driver assistance and a variety of other nodes connected to infotainment systems which become standards with every automobile. Networking protocols connect these systems to provide assistance to drivers. However, the demand of high-bandwidth to serve applications lead to the necessity of a more flexible communication network within the vehicle This thesis proposes using optical wireless links in intra-vehicle applications where different parts of the vehicle can form signal transferring media. A vehicle chassis can be represented as an optical wireless waveguide, where Line-of-sight (LOS) or a diffuse optical wireless link exists. In order to predict the validity of the idea, optical wireless channel characteristics should be determined. This thesis describes the design of a modified Monte Carlo simulation tool for modelling a waveguide optical wireless channel. The simulator has the ability to determine the channel characteristics, and it can also be used more generally for indoor systems. The simulator studies the effect of purely diffuse and purely reflective materials as well as mixed diffuse-specular materials. The program was validated by comparing it with other indoor simulation studies and with a laboratory experiment for straight waveguide. Emphasis was placed on understanding the requirements of LOS and diffusing optical wireless communication links. Results are presented for straight and bent waveguides received power, path loss and bandwidth for a series of receiver areas and fields-of-view. Studying the coupling effect between two waveguides which are different in dimensions has been assessed for series of transmitter directions. All studies have been undertaken for two types of materials (scattered and reflective) and two kinds of transmitters (omnidirectional and directional). The study shows that the waveguides are plausible candidates to convey signals with high bandwidth, but a high power transmitter or an array of Light Emitting Diodes (LEDs) is needed due to power limitations