Lilian Aveneau

Outdoor and indoor channel characterization by a 3D simulation software

This paper presents a 3D simulation software of radiowave propagation for mobile systems in outdoor and indoor environments. The software allows us to predict the coverage zone of a base station and the behaviour of the transmission channel. After a brief recall of the radio channel characteristics for narrowband and wideband signals, the theoretical basis of our model and applications are described. Different results provided by our software are proposed : the evolution of the received power on a mobile route, the delay spread and the correlation bandwidth. To evaluate the capability of our software for the prediction of the previous parameters, measurements in outdoor and indoor environments are considered as a reference.

Exact, robust and efficient full visibility computation in Plücker space

We present a set of new techniques to compute an exact polygon-to-polygon visibility in Plücker space. The contributions are based on the definition of the minimal representation of lines stabbing two convex polygons. The new algorithms are designed to indicate useless computations, which results in more compact visibility data, faster to exploit, and in a reduced computation time. We also define a simple robust and exact solution to handle degeneracies, where previous methods proposed aggressive solutions.

Efficient Simulation of Optical Wireless Channel Application to WBANs with MISO Link

This paper presents a new optimized simulation algorithm of the optical wireless channel. It has a faster convergence for SISO (Single Input Single Output) systems, while it significantly reduces computation time for MISO (Multiple Inputs Single Output) systems, which are the main ones in WBANs (Wireless Body Area Networks). Our algorithm is based on Monte Carlo methods, and uses 3D launched rays. Its main difference with previous solutions relies on reversing the process of propagation of optical waves, to solve efficiently and in real environments the global illumination equation modeling the propagation of light. Experimental results and comparisons with the literature are given in terms of precision and computation time.

Ultra-Wideband Indoor Channel Modelling Using Ray-Tracing Software for through-the-Wall Imaging Radar

This paper presents a new software for design of through-the-wall imaging radars. The first part describes the evolution of a ray tracing simulator, originally designed for propagation of narrowband signals, and then for ultra-wideband signals. This simulator allows to obtain temporal channel response to a wide-band emitter (3 GHz to 10 GHz). An experimental method is also described to identify the propagation paths. Simulation results are compared to propagation experiments under the same conditions. Different configurations are tested and then discussed. Finally, a configuration of through-the-wall imaging radar is proposed, with different antennas patterns and different targets. Simulated images will be helpful for understanding the experiment obtained images.

Deterministic propagation model influence on a wireless digital transmission simulation in real environment

The purpose of This work is to describe the results of a CDMA digital transmission simulation in terms of quality, based on deterministic modeling of the propagation channel. This modeling allows a fast computation of the channel power delay profile (PDP), which is the common input of a digital transmission system. Thus, the harmful impact of the channel is shown under the original form of bit error rate (BER) maps. Such a representation becomes possible because of our propagation model efficiency, particularly compared to a ray tracing one. These maps represent a part of the Poitiers University in France.

Lazy Visibility Evaluation for Exact Soft Shadows

This paper presents a novel approach to compute high quality and noise‐free soft shadows using exact visibility computations. This work relies on a theoretical framework allowing to group lines according to the geometry they intersect. From this study, we derive a new algorithm encoding lazily the visibility from a polygon. Contrary to previous works on from‐polygon visibility, our approach is very robust and straightforward to implement. We apply this algorithm to solve exactly and efficiently the visibility of an area light source from any point in a scene. As a consequence, results are not sensitive to noise, contrary to soft shadows methods based on area light source sampling. We demonstrate the reliability of our approach on different scenes and configurations.

Radio wave propagation in curved rectangular tunnels at 5.8 GHz for metro applications, simulations and measurements

Nowadays, the need for wireless communication systems is increasing in transport domain. These systems have to be operational in every type of environment and particularly tunnels for metro applications. These ones can have rectangular, circular or arch-shaped cross section. Furthermore, they can be straight or curved. This article presents a new method to model the radio wave propagation in straight tunnels with an arch-shaped cross section and in curved tunnels with a rectangular cross section. The method is based on a Ray Launching technique combining the computation of intersection with curved surfaces, an original optimization of paths, a reception sphere, an IMR technique and a last criterion of paths validity. Results obtained with our method are confronted to results of literature in a straight arch-shaped tunnel. Then, comparisons with measurements at 5.8 GHz are performed in a curved rectangular tunnel. Finally, a statistical analysis of fast fading is performed on these results.

Investigation of wireless optical technology for communication between on-body nodes

Interferences in Body Area Networks (BANs) are a great challenge in order to ensure a good quality of service in health monitoring systems. BANs are disturbed by several kinds of wireless communications, as mobile cells or Wi-Fi systems. Thus the wireless optical technology could be considered as a solution to reduce the interference amount. The validity of such a solution is examined in terms of transmitted power and data rate. The novelty of this paper is that this is the first time where diffuse optical wireless technology is considered to achieve “on body” communication, using the multiple reflections of optical beams in the patient room.

Fast and exact direct illumination

Rendering high quality soft shadows from area light sources is necessary to increase the level of realism. Quality soft shadows are closely related to the visibility computation. An accurate visibility information improves the shadows realism. However, this remains a challenging problem since even small visibility approximations can lead to unacceptable errors in a picture. We propose a new approach to this problem, based on an exact visibility pre-computation, done in the Plucker space. It takes advantage of this first step to provide an exact from-point visibility query algorithm. We propose several results in a ray tracing application, where the direct illumination at any given point is provided with a fast computation, and with a high degree of quality.

Impact of receiver orientation and position on Visible Light Communication link performance

In this paper we study the impact of both receiver orientation and position on Visible Light Communication (VLC) performance when it is worn by a moving person in indoor environment. This is the case for example of a tablet or smartphone. Because of person mobility within the environment, there are cases where Line of Sight (LOS) paths from optical light sources at the ceiling cannot be collected by the receiver. In those cases, high order reflections are taken into account for channel modeling purpose. We evaluate the performance in term of outage probability and show that Inter-Symbol Interference (ISI) impact is more important when considering receiver orientation variations and this all the more as the data rate is high. In addition for a given quality of service we determine the minimum transmitted power needed to achieve data rate up to 1 Gbps. We verify that considering at least 3 order reflection constitutes an accurate way to quantify the receiver orientation impact.