Pierre Combeau

Radio Wave Propagation in Arched Cross Section Tunnels – Simulations and Measurements

For several years, wireless communication systems have been developed for train to infrastructure communication needs related to railway or mass transit applications. The systems should be able to operate in specific environments, such as tunnels. In this context, specific radio planning tools have to be developed to optimize system deployment. Realistic tunnels geometries are generally of rectangular cross section or arch-shaped. Furthermore, they are mostly curved. In order to calculate electromagnetic wave propagation in such tunnels, specific models have to be developed. Several works have dealt with retransmission of GSM or UMTS. Few theoretical or experimental works have focused on 2.4 GHz or 5.8 GHz bands. In this paper, we propose an approach to model radio wave propagation in these frequency bands in straight arch-shaped tunnels using tessellation in multi-facets. The model is based on a Ray Tracing tool using the image method. The work reported in this paper shows the propagation loss variations according to the shape of tunnels. A parametric study on the facets size to model the cross section is conducted. The influence of tunnel dimensions and signal frequency is examined. Finally, some measurement results in a straight arch-shaped tunnel are presented and analyzed in terms of slow and fast fading.

Radio wave propagation in curved rectangular tunnels at 5.8 GHz for metro applications

The need for wireless communication systems is increasing in the 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 paper 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.

On the Importance of the MIMO Channel Correlation in Underground Railway Tunnels

This paper deals with MIMO channel modeling according to the correlation level in underground railway tunnels for various antenna configurations for the transmitting and receiving arrays. MIMO channel matrices have been computed with a 3D ray-tracing based software at 2.4 GHz and 5.8 GHz in two different tunnel environments: 1) a 1-track empty tunnel with a square cross section, 2) a 1-track tunnel with a square cross section in which a train is parked between the transmitter and the receiver. In this paper, two different strategies are investigated to model the MIMO channel using the Kronecker and the Weichselberger correlation based channel models. The first one is to model the MIMO channel using a single model over the total tunnel length. The second one takes into account the correlation at the receiving side according to the transmitter-receiver distance. In the latter solution, it is possible to isolate specific areas in the tunnel with specific correlation properties and model them in an independent way to take them into account in a system simulation. In this paper, these two modeling strategies are compared in terms of channel capacity.

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.

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.

Efficient computation of radio coverage zone using a spatial partitionment approach

Previously, we proposed a geometrical approach to the problem of coverage zone computation (Combeau, P. et al., IEEE European Workshop on Integrated Radio Communication Systems, 2002). It is a three step solution. First, the spatial propagation of a wave is computed, using only a geometrical approach. Then, a partitionment is realised, by use of an image segmentation technique. Finally, the evaluation of the coverage zone is computed using external computations for a reduced number of receiver locations. Since the first step of spatial propagation is very time consuming, we now develop an efficient optimization, based on discrete geometric results. Some results are presented showing a very high time reduction.

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.

MIMO propagation channel characteristics in tunnels

This paper deals with MIMO channels modeling in tunnels. A full 3D ray-tracing based simulator is used to simulate the MIMO channel in a 1-track tunnel for various antennas configurations at the transmitter and at the receiver. A parametric study is described. The main purpose consists in determining correlation based MIMO channel statistical models and evaluating their performances in an empty tunnel. Channel models obtained with the Kronecker and the Weichselberger models are compared in terms of envelope of the matrix coefficients distribution and mean channel capacity. The best configurations which model correctly the channel while maximizing its capacity will be given.